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76 Commits

Author SHA1 Message Date
Beman Dawes
6f795dce04 Change +++m_count to ++m_count in three places
[SVN r11217]
2001-09-23 12:31:10 +00:00
Beman Dawes
7496ecbc73 sprintf -> std::sprintf + related workarounds
[SVN r11202]
2001-09-22 13:29:58 +00:00
Beman Dawes
76e80ee4c4 Added std:: to size_t in three places
[SVN r11173]
2001-09-20 18:46:11 +00:00
William E. Kempf
8e2536fc54 Updated for new config system.
[SVN r11168]
2001-09-20 14:52:42 +00:00
William E. Kempf
9bbbfbe6ff Fixed some extern "C" bugs.
[SVN r11153]
2001-09-19 17:52:44 +00:00
Beman Dawes
a2fc9ebfaa Fix broken links and other HTML changes related to new config system
[SVN r11142]
2001-09-18 21:24:51 +00:00
William E. Kempf
16c78b81e2 Fixed bug in pthread implementation.
[SVN r11125]
2001-09-14 17:47:09 +00:00
William E. Kempf
e71b204d10 Cleaned up code on warning level 4.
[SVN r11122]
2001-09-14 15:13:12 +00:00
William E. Kempf
f64208ce7a Third round of changes from the review.
[SVN r11109]
2001-09-12 21:29:42 +00:00
Beman Dawes
3410029cad Changes relating to addition of overview.html
[SVN r11103]
2001-09-12 14:38:03 +00:00
Beman Dawes
25fd0f52e7 Initial commit
[SVN r11102]
2001-09-12 14:36:32 +00:00
William E. Kempf
095f16c4f1 Made the constructors inline.
[SVN r11082]
2001-09-10 02:48:20 +00:00
William E. Kempf
5a4a5f405f Fixed bugs in the implementation found during review.
[SVN r11081]
2001-09-10 02:47:46 +00:00
William E. Kempf
7775aceb86 Third changes during review.
[SVN r11049]
2001-09-06 13:11:34 +00:00
William E. Kempf
29177b34a7 Second round of changes during review.
[SVN r11024]
2001-09-05 01:44:20 +00:00
Beman Dawes
ae1c315e0c Fixes after review of Bill's first batch of changes based on Formal Review comments.
[SVN r11021]
2001-09-04 17:16:22 +00:00
William E. Kempf
3592d8c412 First round of modifications during review.
[SVN r11001]
2001-09-03 18:08:35 +00:00
William E. Kempf
63fdf6ef22 Final modifications before submission.
[SVN r10961]
2001-08-30 00:51:17 +00:00
William E. Kempf
915c2cd206 Changed thread design. Updated code and documentation in preperation of submission.
[SVN r10952]
2001-08-28 20:19:37 +00:00
Beman Dawes
54abba952b Event rationale + minor other cleanups
[SVN r10884]
2001-08-17 12:07:35 +00:00
William E. Kempf
7cee797d2e Maded tss class an implementation detail and added thread_specific_ptr template.
[SVN r10873]
2001-08-15 20:49:42 +00:00
William E. Kempf
a7fb1e73d2 Cleaned up code for tss and once methods. Added unit tests for once methods.
[SVN r10838]
2001-08-10 20:47:02 +00:00
Beman Dawes
6a46149868 Added "share stack objects" Q&A
[SVN r10831]
2001-08-10 13:41:58 +00:00
Beman Dawes
f07d726011 Wording clarifications based on comments by Asger Alstrup Nielsen
[SVN r10830]
2001-08-10 12:22:37 +00:00
William E. Kempf
344ddb5fd2 Added tss cleanup functionality and once methods.
[SVN r10827]
2001-08-09 20:32:52 +00:00
Beman Dawes
537b623b18 Add two new questions
[SVN r10820]
2001-08-08 21:07:43 +00:00
Beman Dawes
ab180e79d1 Clarified Memory visibility between threads
[SVN r10798]
2001-08-07 14:45:35 +00:00
Beman Dawes
089dc81880 Major docs workover; use stylesheet, std doc form, show namespace boost in synopsis, rename locks basic_ -> scoped_, etc.
[SVN r10797]
2001-08-06 20:46:24 +00:00
Beman Dawes
73187a40b6 Initial commit
[SVN r10796]
2001-08-06 20:41:47 +00:00
Beman Dawes
3d06b18e3e Renamed from basic_*.html
[SVN r10795]
2001-08-06 20:41:02 +00:00
Beman Dawes
fd9d19b050 Renamed scoped_*.html
[SVN r10794]
2001-08-06 20:39:53 +00:00
William E. Kempf
692aa0e352 Moved lock types into boost::detail::thread. Renamed the lock types. Added locked() methods to lock types.
[SVN r10725]
2001-07-30 18:29:25 +00:00
Beman Dawes
307bbdc951 Format updated.
[SVN r10707]
2001-07-25 20:10:39 +00:00
Beman Dawes
b460053eda Make format consistent with other pages.
[SVN r10706]
2001-07-25 19:38:47 +00:00
Beman Dawes
df704a5dae "basic_lock" -> "scoped_lock" name changes. Added locked() member.
[SVN r10704]
2001-07-25 15:56:43 +00:00
Beman Dawes
9b76b71b5f Changes links format_thread_definition.html -> definitions.html
[SVN r10672]
2001-07-19 20:42:31 +00:00
Beman Dawes
427a109865 Renamed file; was thread_formal_definitions.html
[SVN r10671]
2001-07-19 20:41:30 +00:00
Beman Dawes
5662e2f6bb Remove prior to adding renamed (definitions.html) file
[SVN r10670]
2001-07-19 20:40:40 +00:00
Beman Dawes
6a6fbd0553 Change spelling "thread safe" to "thread-safe" and link to definition of the term. Fix other minor spelling errors.
[SVN r10669]
2001-07-19 20:24:45 +00:00
William E. Kempf
5084e9ccd2 Changed the documentation of basic_lock to describe proper lock() behavior.
Minor modifications to condition.html style.


[SVN r10668]
2001-07-19 18:36:43 +00:00
Beman Dawes
84cb093ee6 basic_lock and related updates
[SVN r10667]
2001-07-19 17:33:12 +00:00
Beman Dawes
8305cad4f8 Add entry, more uniformly apply citation tag
[SVN r10661]
2001-07-18 19:17:47 +00:00
William E. Kempf
b52c5d45ec Added new FAQ questions and cleaned up some documentation.
[SVN r10659]
2001-07-18 14:15:44 +00:00
Beman Dawes
71103fe1bc make wait and timed_wait formatting consistent
[SVN r10655]
2001-07-18 01:16:35 +00:00
Beman Dawes
57d262d4d6 Recast into stanard Boost.Threads doc form (Beman)
[SVN r10651]
2001-07-17 21:22:21 +00:00
Beman Dawes
acf721b0bd Minor changes
[SVN r10650]
2001-07-17 21:17:56 +00:00
William E. Kempf
3ee4bf04dc Fixed minor code changes.
[SVN r10639]
2001-07-16 20:48:39 +00:00
William E. Kempf
6e4a874880 Fixed minor code bugs and changed Jamfiles according to form suggested by Dave Abrahams.
[SVN r10638]
2001-07-16 20:47:48 +00:00
William E. Kempf
b07d60aa94 Updated tss.html for new documentation style. Fixed minor things in thread.html.
[SVN r10637]
2001-07-16 20:04:31 +00:00
William E. Kempf
fb3aed485c Added reference for POSA2.
[SVN r10636]
2001-07-16 18:45:53 +00:00
William E. Kempf
cbf212f1cd Added styles.css. Updated threads.html documentation for new look and design.
[SVN r10635]
2001-07-16 18:24:07 +00:00
Beman Dawes
562c4583d4 Add bibliography link
[SVN r10632]
2001-07-16 15:47:50 +00:00
Beman Dawes
95053b7516 Move Bibliography to separate page, minor tweeks
[SVN r10631]
2001-07-16 15:47:23 +00:00
Beman Dawes
65d06c138e Initial commit
[SVN r10630]
2001-07-16 15:46:04 +00:00
Dave Abrahams
9e3e80558c Repaired.
[SVN r10627]
2001-07-15 19:48:39 +00:00
William E. Kempf
d27e195ca2 Changed code that included exceptions.h to include exceptions.hpp.
[SVN r10601]
2001-07-12 20:36:04 +00:00
William E. Kempf
0ae839e0bb Applied patches for Unix/GNU toolset.
[SVN r10600]
2001-07-12 20:29:43 +00:00
William E. Kempf
21067cb309 Removed extraneous VC++ project files.
[SVN r10560]
2001-07-06 20:13:08 +00:00
Beman Dawes
5cb2a46ae4 Minor wording improvements, more references added
[SVN r10555]
2001-07-06 19:23:45 +00:00
William E. Kempf
66fa1995cf Fixed coding style to match proposed Boost guidelines.
[SVN r10550]
2001-07-06 18:23:40 +00:00
William E. Kempf
6e83cfdc72 Added a FAQ document.
[SVN r10549]
2001-07-06 18:02:56 +00:00
William E. Kempf
c2930faaec Added thread_group documentation.
[SVN r10544]
2001-07-05 19:29:05 +00:00
William E. Kempf
64ad66034a Updated thread documentation to reflect latest design.
[SVN r10543]
2001-07-05 19:11:07 +00:00
William E. Kempf
101e7cfbda Fixed the title.
[SVN r10541]
2001-07-05 18:40:12 +00:00
William E. Kempf
76de0ff7fd Added rationale documentation.
[SVN r10540]
2001-07-05 18:33:05 +00:00
William E. Kempf
f70b32cc63 Modified boost::thread to use a noncopyable design.
[SVN r10519]
2001-07-03 18:29:18 +00:00
William E. Kempf
8ce4eeca24 Changed boost::thread to use a noncopyable design.
[SVN r10518]
2001-07-03 18:28:10 +00:00
William E. Kempf
2febaf386c Modified to use Boost.Function for the threadproc.
[SVN r10437]
2001-06-26 19:20:11 +00:00
William E. Kempf
1d6f10702d Fixed bug (case sensitive subproject name) in jamfiles that prevented building.
[SVN r10434]
2001-06-26 15:40:59 +00:00
William E. Kempf
ebe3a7beee Update all Jamfiles for new build system. (Note: problem with <lib> pseudo-target)
[SVN r10428]
2001-06-25 21:53:57 +00:00
William E. Kempf
9e38dc5f48 Made WinThreads the default for MSVC, as it should have been to begin with.
[SVN r10427]
2001-06-25 21:52:35 +00:00
William E. Kempf
6dafed21fc First attempt at modifying Jamfiles for latest Boost.Build system.
[SVN r10425]
2001-06-25 18:15:31 +00:00
Beman Dawes
067d2a39f7 Integrate new Formal Definition of "Thread" page
[SVN r10365]
2001-06-20 22:49:44 +00:00
Beman Dawes
d70f46126b Replaced by _atomic.cpp
[SVN r10343]
2001-06-15 15:44:13 +00:00
Beman Dawes
b282e06a90 Initial commit
[SVN r10342]
2001-06-15 15:42:45 +00:00
nobody
abd2e68f8d This commit was manufactured by cvs2svn to create branch
'thread-initial'.

[SVN r10341]
2001-06-15 15:42:44 +00:00
158 changed files with 6125 additions and 13667 deletions

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bin*
*.pdb

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# in all copies. This software is provided "as is" without express or implied
# warranty, and with no claim as to its suitability for any purpose.
#
# Boost.Threads build Jamfile
# Boost.Threads build and test Jamfile
#
# Declares the following targets:
# 1. libboost_thread, a static link library.
# 1a. On Win32 (when PTW32 is not defined), a dynamic link library
# boost_threadmon, which must be used in conjunction with
# libboost_thread. Note that this DLL *must* be used through static
# linking to the import library. Dynamic loading will cause undefined
# behavior.
# Additional configuration variables used:
# 1. PTW32 may be used on Win32 platforms to specify that the pthreads-win32
# library should be used instead of "native" threads. This feature is
# mostly used for testing and it's generally recommended you use the
# native threading libraries instead. PTW32 should be set to be a list
# of two strings, the first specifying the installation path of the
# pthreads-win32 library and the second specifying which library
# variant to link against (see the pthreads-win32 documentation).
# Example: jam -sPTW32="c:\pthreads-win32 pthreadVCE.lib"
# 1a. On Win32, a dynamic link library libboost_threadmon,
# which must be used in conjunction with libboost_thread.
# Declare the location of this subproject relative to the root.
# declare the location of this subproject relative to the root
subproject libs/thread/build ;
# Include threads.jam for Boost.Threads global build information.
# This greatly simplifies the Jam code needed to configure the build
# for the various Win32 build types.
SEARCH on <module@>threads.jam = $(SUBDIR) ;
include <module@>threads.jam ;
template thread_libs
## sources ##
: <template>thread_base
## requirements ##
:
## default build ##
: debug release <runtime-link>static/dynamic
;
#######################
# Conditionally declare the Boost.Threads dynamic link library boost_threadmon.
if $(NT) && ! $(PTW32)
#
# Declare the Boost.Threads static link library.
#
# For Win32 we need to build a special DLL, libboost_threadmon, to handle
# TSS destruction.
if $(NT)
{
dll boost_threadmon : <template>thread_libs ../src/threadmon.cpp ;
dll libboost_threadmon : ../src/threadmon.cpp
# requirements
: <threading>multi
: debug release ;
}
#######################
# Declare the Boost.Threads static link library libboost_thread.
# Base names of the source files for libboost_thread.
# Base names of the source files for libboost_thread
CPP_SOURCES =
condition mutex recursive_mutex thread tss xtime once exceptions thread_pool barrier rw_mutex ;
condition mutex recursive_mutex semaphore thread tss xtime once ;
lib boost_thread : <template>thread_libs ../src/$(CPP_SOURCES).cpp ;
#######################
# Stage the generated targets.
#stage bin-stage
# : <lib>boost_thread $(threadmon)
# : <tag><runtime-link-static>"s"
# <tag><debug>"d"
# : debug release <runtime-link>static/dynamic
#;
lib libboost_thread : ../src/$(CPP_SOURCES).cpp
# requirements
: <include>$(BOOST_ROOT)
<threading>multi
: debug release ;

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# Do some OS-specific setup
threadmon = ;
pthreads-win32 = ;
if $(NT)
{
if $(PTW32)
{
local install-path = $(PTW32[1]) ;
local lib = $(PTW32[2]) ;
pthreads-win32 =
<define>BOOST_HAS_PTHREADS
<define>PtW32NoCatchWarn
<include>$(install-path)/pre-built/include
<library-file>$(install-path)/pre-built/lib/$(lib)
;
}
else
{
threadmon = <dll>../build/boost_threadmon ;
}
}
template thread_base
## sources ##
:
## requirements ##
: <sysinclude>$(BOOST_ROOT) <threading>multi $(pthreads-win32)
## default build ##
:
;

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72
doc/acknowledgements.html Normal file
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Boost.Threads Acknowledgements</title>
</head>
<body bgcolor="#FFFFFF" text="#000000">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Acknowledgements</h2>
</td>
</tr>
</table>
<h2>Acknowledgments</h2>
<p><a href="../../../people/william_kempf.htm">William E. Kempf</a> was the
architect, designer, and implementor of <b>Boost.Threads</b>.</p>
<p>Important contributions were also made by Jeremy Siek (lots of input on
the design and on the implementation), Alexander Terekhov (lots of input on
the Win32 implementation, especially in regards to boost::condition, as well
as a lot of explanation of POSIX behavior), Greg Colvin (lots of input on the
design), and Paul Mclachlan, Thomas Matelich and Iain Hanson (for help in
trying to get the build to work on other platforms).</p>
<p>The documentation was written by William E. Kempf. Beman Dawes provided
additional documentation material and editing.</p>
<p>Discussions on the boost.org mailing list were essential in the development
of <b>Boost.Threads</b>. As of August 1, 2001, participants included Alan Griffiths,
Albrecht Fritzsche, Aleksey Gurtovoy, Alexander Terekhov, Andrew Green, Andy Sawyer,
Asger Alstrup Nielsen, Beman Dawes, Bill Klein, Bill Rutiser, Bill Wade, Branko
Èibej, Brent Verner, Craig Henderson, Csaba Szepesvari, Dale Peakall, Damian
Dixon, Dan Nuffer, Darryl Green, Daryle Walker, David Abrahams, David Allan
Finch, Dejan Jelovic, Dietmar Kuehl, Doug Gregor, Douglas Gregor, Duncan Harris,
Ed Brey, Eric Swanson, Eugene Karpachov, Fabrice Truillot, Frank
Gerlach, Gary Powell, Gernot Neppert, Geurt Vos, Ghazi Ramadan, Greg Colvin,
Gregory Seidman, HYS, Iain Hanson, Ian Bruntlett, J Panzer, Jeff Garland, Jeff
Paquette, Jens Maurer, Jeremy Siek, Jesse Jones, Joe Gottman, John (EBo) David,
John Bandela, John Maddock, John Max Skaller, John Panzer, Jon Jagger , Karl
Nelson, Kevlin Henney, KG Chandrasekhar, Levente Farkas, Lie-Quan Lee, Lois
Goldthwaite, Luis Pedro Coelho, Marc Girod, Mark A. Borgerding, Mark Rodgers,
Marshall Clow, Matthew Austern, Matthew Hurd, Michael D. Crawford, Michael H.
Cox , Mike Haller, Miki Jovanovic, Nathan Myers, Paul Moore, Pavel Cisler, Peter
Dimov, Petr Kocmid, Philip Nash, Rainer Deyke, Reid Sweatman, Ross Smith, Scott
McCaskill, Shalom Reich , Steve Cleary, Steven Kirk, Thomas Holenstein, Thomas
Matelich, Trevor Perrin, Valentin Bonnard, Vesa Karvonen, Wayne Miller, and
William Kempf.</p>
<p>Apologies for anyone inadvertently missed.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->29 August, 2001<!--webbot bot="Timestamp" endspan i-checksum="34360" -->
</p>
<p>©<i> Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Acknowledgments</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Acknowledgments</h2>
</td>
</tr>
</table>
<hr>
<p><a href="../../../people/william_kempf.htm">William E. Kempf</a> was the architect,
designer, and implementor of <b>Boost.Threads</b>.</p>
<p>Mac OS Carbon implementation written by <a href="../../../people/mac_murrett.htm">Mac
Murrett</a>.</p>
<p><a href="mailto:jdmoore99@comcast.net">Dave Moore</a> provided initial submissions
and further comments on the <code>barrier</code>, <code>thread_pool</code>,
<code>rw_mutex</code>, <code>rw_try_mutex</code> and <code>rw_timed_mutex</code>
classes.</p>
<p>Important contributions were also made by Jeremy Siek (lots of input on the
design and on the implementation), Alexander Terekhov (lots of input on the
Win32 implementation, especially in regards to boost::condition, as well as
a lot of explanation of POSIX behavior), Greg Colvin (lots of input on the design),
Paul Mclachlan, Thomas Matelich and Iain Hanson (for help in trying to get the
build to work on other platforms), and Kevin S. Van Horn (for several updates/corrections
to the documentation).</p>
<p>The documentation was written by William E. Kempf. Beman Dawes provided additional
documentation material and editing.</p>
<p>Discussions on the boost.org mailing list were essential in the development
of <b>Boost.Threads</b>. As of August 1, 2001, participants included Alan Griffiths,
Albrecht Fritzsche, Aleksey Gurtovoy, Alexander Terekhov, Andrew Green, Andy
Sawyer, Asger Alstrup Nielsen, Beman Dawes, Bill Klein, Bill Rutiser, Bill Wade,
Branko &Egrave;ibej, Brent Verner, Craig Henderson, Csaba Szepesvari, Dale Peakall,
Damian Dixon, Dan Nuffer, Darryl Green, Daryle Walker, David Abrahams, David
Allan Finch, Dejan Jelovic, Dietmar Kuehl, Doug Gregor, Douglas Gregor, Duncan
Harris, Ed Brey, Eric Swanson, Eugene Karpachov, Fabrice Truillot, Frank Gerlach,
Gary Powell, Gernot Neppert, Geurt Vos, Ghazi Ramadan, Greg Colvin, Gregory
Seidman, HYS, Iain Hanson, Ian Bruntlett, J Panzer, Jeff Garland, Jeff Paquette,
Jens Maurer, Jeremy Siek, Jesse Jones, Joe Gottman, John (EBo) David, John Bandela,
John Maddock, John Max Skaller, John Panzer, Jon Jagger , Karl Nelson, Kevlin
Henney, KG Chandrasekhar, Levente Farkas, Lie-Quan Lee, Lois Goldthwaite, Luis
Pedro Coelho, Marc Girod, Mark A. Borgerding, Mark Rodgers, Marshall Clow, Matthew
Austern, Matthew Hurd, Michael D. Crawford, Michael H. Cox , Mike Haller, Miki
Jovanovic, Nathan Myers, Paul Moore, Pavel Cisler, Peter Dimov, Petr Kocmid,
Philip Nash, Rainer Deyke, Reid Sweatman, Ross Smith, Scott McCaskill, Shalom
Reich , Steve Cleary, Steven Kirk, Thomas Holenstein, Thomas Matelich, Trevor
Perrin, Valentin Bonnard, Vesa Karvonen, Wayne Miller, and William Kempf.</p>
<p>Apologies for anyone inadvertently missed.</p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
</body>
</html>

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@@ -1,168 +0,0 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/barrier.hpp&gt;</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/barrier.hpp">boost/thread/barrier.hpp</a>&gt;</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-barrier">Class <code>barrier</code></a></dt>
<dl class="page-index">
<dt><a href="#class-barrier-synopsis">Class <code>barrier</code> synopsis</a></dt>
<dt><a href="#class-barrier-ctors">Class <code>barrier</code> constructors
and destructor</a></dt>
<dt><a href="#class-barrier-modifiers">Class <code>barrier</code> modifier
functions</a></dt>
</dl>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>Include the header &lt;<a href="../../../boost/thread/barrier.hpp">boost/thread/barrier.hpp</a>&gt;
to define the class <code>boost::barrier</code>.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-barrier"></a>Class <code>barrier</code></h3>
<p>An object of class <code>barrier</code> is a synchronization primitive used
to cause a set of threads to wait until they each perform a certain function
or each reach a particular point in their execution. When a barrier is created,
it is initialized with a thread count "N". The first N-1 calls to wait() will
all cause their threads to be blocked. The Nth call to wait() will allow all
of the waiting threads, including the Nth thread, to be placed in a ready state.
Should an additional thread make an N+1th call to wait() on the barrier, it
will be as though this was the first call to wait(), and the process will be
repeated until another N threads call wait(). This functionality allows the
same set of N threads to re-use a barrier object to synchronize their execution
at multiple points during their execution.</p>
<p>See <A href="definitions.html">Formal Definitions</A> for definitions of thread
states <A href="definitions.html#state">blocked</A> and <A href="definitions.html#state">
ready</A>. Note that "waiting" is a synonym for blocked.</p>
<h4><a name="class-barrier-synopsis"></a>Class <code>barrier</code> synopsis</h4>
<pre>
namespace boost
{
class barrier : private <A href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</A> // Exposition only.
// Class barrier meets the <A href="overview.html#NonCopyable" .. utility.htm#Class? utility>NonCopyable</A> requirement.
{
public:
barrier(size_t count);
~barrier();
bool wait();
};
};
</pre>
<h4><a name="class-barrier-ctors"></a>Class <code>barrier</code> constructors
and destructor</h4>
<pre>
barrier(size_t count);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs a <code>barrier</code> object that will cause
count threads to block on a call to <code>wait()</code>.</dt>
</dl>
<pre>
~barrier();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Destroys <code>*this</code>. If threads are still executing
their <code>wait()</code> operations, the behavior for these threads is undefined.</dt>
</dl>
<h4><a name="class-barrier-modifiers"></a>Class <code>barrier</code> modifier
functions</h4>
<pre>
bool wait();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Wait until N threads call wait(), where N equals the count
provided to the constructor for the barrier object.</dt>
<dt><b>Returns:</b> Exactly one of the N threads will receive a return value
of <code>true</code>, the others will receive a value of <code>false</code>.
Precisely which thread receives the return value of <code>true</code> will
be implementation defined. Applications can use this value to designate one
thread as a leader that will take a certain action, and the other threads
emerging from the barrier can wait for that action to take place.</dt>
<dt><b>Danger:</b> If the barrier is destroyed before <code>wait()</code> can
return, the behavior is undefined.</dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<pre>
#include <a href="../../../boost/thread/condition.hpp">&lt;boost/thread/barrier.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
#include &lt;iostream&gt;
const int N_THREADS = 10;
boost::barrier gen_barrier(N_THREADS);
int global_parameter = 0;
boost::mutex mutex;
static void worker()
{
for (int i = 0; i &lt; 5; ++i)
{
// Simulate 5 cycles of computation...
if (gen_barrier.wait())
{
boost::mutex::scoped_lock lock(mutex);
global_parameter++;
}
}
// Let one worker "report" the results
if (gen_barrier.wait())
{
boost::mutex::scoped_lock lock(lock);
std::cout &lt;&lt; "Global Parameter=" &lt;&lt; global_parameter &lt;&lt; "\n";
}
}
int main(int, char*[])
{
boost::thread_group g;
global_parameter = 0;
for (int i = 0; i &lt; N_THREADS; ++i)
g.create_thread(&amp;worker);
g.join_all();
}
</pre>
<p>The output is:</p>
<pre>
Global Parameter=5
</pre>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:jdmoore99@comcast.net">Dave Moore</a> and <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
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<title>Boost.Threads - Bibliography</title>
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<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
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<h1 align="center">Boost.Threads</h1>
@@ -17,149 +20,126 @@
</td>
</tr>
</table>
<hr>
<table summary="Bibliography" border="0" cellpadding="5" width="777">
<h2>Bibliography</h2>
<table border="0" cellpadding="5" width="777">
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Andrews-83">Andrews 83</a>]</b></td>
<td width="645"> Gregory R. Andrews, Fred B. Schneider, <cite>Concepts and
Notations for Concurrent Programming</cite>, ACM Computing Surveys, Vol.
15, No. 1, March, 1983. <a href=
"http://www.acm.org/pubs/citations/journals/surveys/1983-15-1/p3-andrews/">
http://www.acm.org/pubs/citations/journals/surveys/1983-15-1/p3-andrews/</a>
<p>Good general background reading. Includes descriptions of Path Expressions,
Message Passing, and Remote Procedure Call in addition to the basics.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Boost">Boost</a>]</b></td>
<td width="645"> The <cite>Boost</cite> worldwide web site. <a href=
"http://www.boost.org">http://www.boost.org</a>
<p>Boost.Threads is one of many Boost libraries. The Boost web site includes
a great deal of documentation and general information which applies to
all Boost libraries. Current copies of the libraries including documentation
and test programs may be downloaded from the web site.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Brinch-Hansen-73">Brinch Hansen 73</a>]</b></td>
<td width="645"> Per Brinch Hansen, <cite>Concurrent Programming Concepts</cite>,
ACM Computing Surveys, Vol. 5, No. 4, December, 1973. <a href=
"http://www.acm.org/pubs/articles/journals/surveys/1973-5-4/p223-hansen/p223-hansen.pdf">
http://www.acm.org/pubs/articles/journals/surveys/1973-5-4/p223-hansen/</a>
<p>&quot;This paper describes the evolution of language features for multiprogramming
from event queues and semaphores to critical regions and monitors.&quot;
Includes analysis of why <i>events</i> are considered error-prone. Also
noteworthy because of an introductory quotation from Christopher Alexander;
Brinch Hansen was years ahead of others in recognizing pattern concepts
applied to software too.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>]<a name=
"Butenhof-97">Butenhof 97</a>]</b></td>
<td width="102" valign="top" align="left"><b>[<a name="Andrews-83">Andrews
83</a>]</b></td>
<td width="645">
<p>David R. Butenhof, <cite>Programming with POSIX Threads</cite>, Addison-Wesley
1997, ISBN 0-201-63392-2 <a
href="http://cseng.aw.com/book/0,3828,0201633922,00.html">
http://cseng.aw.com/book/0,3828,0201633922,00.html</a></p>
<p>This is a very readable explanation of threads and how to use them. Many
of the insights given apply to all multithreaded programming, not just
POSIX Threads.</p>
Gregory R. Andrews, Fred B. Schneider, <cite>Concepts and Notations for Concurrent
Programming</cite>, ACM Computing Surveys, Vol. 15, No. 1, March, 1983. <a href="http://www.acm.org/pubs/citations/journals/surveys/1983-15-1/p3-andrews/">http://www.acm.org/pubs/citations/journals/surveys/1983-15-1/p3-andrews/</a>
<p>Good general background reading.&nbsp; Includes descriptions of Path
Expressions, Message Passing, and Remote Procedure Call in addition to the
basics.&nbsp;
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Hoare-74">Hoare 74</a>]</b></td>
<td width="102" valign="top" align="left"><b>[<a name="Boost">Boost</a>]</b></td>
<td width="645">
<p>C.A.R Hoare, <cite>Monitors: An Operating System Structuring Concept</cite>,
Communications of the ACM, Vol. 17, No. 10. October 1974, pp. 549-557
<a href=
"http://www.acm.org/classics/feb96/"> http://www.acm.org/classics/feb96/</a></p>
<p>Hoare and Brinch Hansen&#39;s work on Monitors is the basis for reliable
multithreading patterns. This is one of the most often referenced papers
in all of computer science, and with good reason.</p>
The <cite> Boost</cite> world-wide web site.&nbsp; <a href="http://www.boost.org">http://www.boost.org</a>
<p>Boost.Threads is one of many Boost libraries.&nbsp; The Boost web site
includes a great deal of documentation and general information which applies to
all Boost libraries. Current copies of the libraries including documentation and
test programs may be downloaded from the web site.
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"ISO-98">ISO 98</a>]</b></td>
<td width="102" valign="top" align="left"><b>[<a name="Brinch-Hansen-73">Brinch
Hansen 73</a>]</b></td>
<td width="645">
<p>ISO/IEC 14882:1998(E) <cite>Programming Language C++</cite> <a href="http://www.ansi.org">
http://www.ansi.org</a></p>
<p>This is the official C++ Standards document. Available from the ANSI
(American National Standards Institute) Electronic Standards Store.</p>
Per Brinch Hansen, <cite>Concurrent Programming Concepts</cite>, ACM Computing
Surveys, Vol. 5, No. 4, December, 1973. <a href="http://www.acm.org/pubs/articles/journals/surveys/1973-5-4/p223-hansen/p223-hansen.pdf">http://www.acm.org/pubs/articles/journals/surveys/1973-5-4/p223-hansen/</a>
<p>&quot;This paper describes the evolution of language features for
multiprogramming from event queues and semaphores to critical regions and
monitors.&quot; Includes analysis of&nbsp; why <i>events</i> are considered
error-prone. Also noteworthy because of an introductory quotation from
Christopher Alexander; Brinch Hansen was years ahead of others in recognizing
pattern concepts applied to software too.
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"McDowell-89">McDowell 89</a>]</b></td>
<td width="645"> Charles E McDowell, David P. Helmbold, <cite>Debugging Concurrent
Programs</cite>, ACM Computing Surveys, Vol. 21, No. 2, December, 1989.
<a href=
"http://www.acm.org/pubs/citations/journals/surveys/1989-21-4/p593-mcdowell/">
http://www.acm.org/pubs/citations/journals/surveys/1989-21-4/p593-mcdowell/</a>
<p>Identifies many of the unique failure modes and debugging difficulties
associated with concurrent programs.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Schmidt">Schmidt</a>]</b> </td>
<td width="102" valign="top" align="left"><b>]<a name="Butenhof-97">Butenhof
97</a>]</b></td>
<td width="645">
<p>Douglas C. Schmidt and Irfan Pyarali, <cite>Strategies for Implementing
POSIX Condition Variables on Win32</cite>, Department of Computer Science,
Washington University, St. Louis, Missouri. <a href=
"http://www.cs.wustl.edu/~schmidt/win32-cv-1.html"> http://www.cs.wustl.edu/~schmidt/win32-cv-1.html</a></p>
<p>Rationale for understanding Boost.Threads condition variables. Note that
Alexander Terekhov found some bugs in the implementation given in this
article, so pthreads-win32 and Boost.Threads are even more complicated
yet.</p>
<p> David R. Butenhof, <cite>Programming with
POSIX Threads</cite>, Addison-Wesley 1997, ISBN 0-201-63392-2&nbsp; <a href="http://cseng.aw.com/book/0,3828,0201633922,00.html">http://cseng.aw.com/book/0,3828,0201633922,00.html</a></p>
<p>This is a very readable explanation of threads and how to use them.&nbsp; Many
of the insights given apply to all multi-threaded programming, not just POSIX
Threads.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Schmidt-00">Schmidt 00</a>]</b> </td>
<td width="102" valign="top" align="left"><b>[<a name="Hoare-74">Hoare 74</a>]</b></td>
<td width="645">
<p>Douglas C. Schmidt, Michael Stal, Hans Rohnert and Frank Buschmann, <cite>Pattern-Oriented
Software Architecture Volume 2 - Patterns for Concurrent and Networked
Objects</cite>, Wiley 2000, ISBN 0-471-60695-2 <a href=
"http://www.wiley.com/Corporate/Website/Objects/Products/0,9049,104671,00.html">
http://www.wiley.com/Corporate/Website/Objects/Products/0,9049,104671,00.html</a></p>
<p>This is a very good explanation of how to apply several patterns useful
for concurrent programming. Among the patterns documented is the Monitor
Pattern mentioned frequently in the <b>Boost.Threads</b> documentation.</p>
<p>C.A.R Hoare, <cite> Monitors: An Operating System Structuring Concept</cite>,
Communications of the ACM, Vol. 17, No. 10. October
1974, pp. 549-557&nbsp; <a href="http://www.acm.org/classics/feb96/">http://www.acm.org/classics/feb96/ </a></p>
<p>Hoare and Brinch Hansen's work on Monitors is the basis for reliable
multi-threading patterns. This is one of the most often referenced papers in
all of computer science, and with good reason.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Stroustrup-00">Stroustrup 00</a>]</b></td>
<td width="645"> Bjarne Stroustrup, <cite>The C++ Programming Language</cite>,
Special Edition, Addison-Wesley 2000, ISBN 0-201-70073-5 <a href=
"http://cseng.aw.com/book/0,3828,0201700735,00.html"> http://cseng.aw.com/book/0,3828,0201700735,00.html</a>
<p>The first book a C++ programmer should own. Note that the 3rd edition
(and subsequent editions like the Special Edition) has been rewritten
to cover the ISO standard language and library.</p>
<td width="102" valign="top" align="left"><b>[<a name="ISO-98">ISO 98</a>]</b></td>
<td width="645">
<p>ISO/IEC 14882:1998(E) <cite> Programming Language C++</cite>&nbsp; <a href="http://www.ansi.org">http://www.ansi.org</a></p>
<p>This is the official C++ Standards
document. Available from the ANSI (American
National Standards Institute) Electronic Standards Store.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name="McDowell-89">McDowell
89</a>]</b></td>
<td width="645">
Charles E McDowell, David P. Helmbold, <cite>Debugging Concurrent Programs</cite>,
ACM Computing Surveys, Vol. 21, No. 2, December, 1989. <a href="http://www.acm.org/pubs/citations/journals/surveys/1989-21-4/p593-mcdowell/">http://www.acm.org/pubs/citations/journals/surveys/1989-21-4/p593-mcdowell/</a>
<p>Identifies many of the unique failure modes and debugging difficulties
associated with concurrent programs.
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"> <b>[<a name="Schmidt">Schmidt</a>]&nbsp;</b></td>
<td width="645">
<p> Douglas C. Schmidt and Irfan Pyarali, <cite>Strategies for
Implementing POSIX Condition Variables on Win32</cite>,&nbsp; Department of Computer Science, Washington University, St. Louis, Missouri.&nbsp;
<a href="http://www.cs.wustl.edu/~schmidt/win32-cv-1.html">http://www.cs.wustl.edu/~schmidt/win32-cv-1.html</a></p>
<p>Rationale for understanding Boost.Threads condition variables. Note that Alexander Terekhov found some bugs in
the implementation given in this article, so pthreads-win32 and Boost.Threads
are even more complicated yet.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"> <b>[<a name="Schmidt-00">Schmidt
00</a>]&nbsp;</b></td>
<td width="645">
<p> Douglas C. Schmidt, Michael Stal, Hans Rohnert and Frank Buschmann, <cite>Pattern-Oriented Software Architecture Volume 2 - Patterns for
Concurrent and Networked Objects</cite>,&nbsp; Wiley 2000, ISBN 0-471-60695-2&nbsp; <a href="http://www.wiley.com/Corporate/Website/Objects/Products/0,9049,104671,00.html">http://www.wiley.com/Corporate/Website/Objects/Products/0,9049,104671,00.html</a></p>
<p>This is a very good explanation of how to apply several patterns useful for concurrent programming.
Among the patterns documented is the Monitor Pattern mentioned frequently in the <b>Boost.Threads</b>
documentation.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"> <b>[<a name="Stroustrup-00">Stroustrup
00</a>]</b></td>
<td width="645">
Bjarne Stroustrup, <cite> The C++ Programming Language</cite>, Special Edition, Addison-Wesley
2000, ISBN 0-201-70073-5 <a href="http://cseng.aw.com/book/0,3828,0201700735,00.html">http://cseng.aw.com/book/0,3828,0201700735,00.html</a>
<p>The first book a C++ programmer should own.&nbsp; Note that the 3rd edition
(and subsequent editions like the Special Edition) has been rewritten to cover
the ISO standard language and library.
</td>
</tr>
</table>
<p>Note: The URL&#39;s above are provided in plain text form so that they will
be visible on printed copies of this document.</p>
<p>Note: The URL's above are provided in plain text form so that they will be visible
on printed copies of this document.</p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %b %Y" startspan -->17 Aug 2001<!--webbot bot="Timestamp" endspan i-checksum="14763" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> and
Beman Dawes 2001-2002. All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p>© Copyright Beman Dawes, 2001</p>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>{{Library}} - Overview</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Building and Testing</h2>
</td>
</tr>
</table>
<hr>
<dl class="index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#topic1">First topic</a></dt>
<dt><a href="#topic2">Second topic</a></dt>
<dt><a href="#footnotes">Footnotes</a></dt>
</dl>
<h2><a name="introduction"></a>Introduction</h2>
<p>How you build the Boost.Threads libraries, and how you build your own applications
that use those libraries, are some of the most frequently asked questions. Build
processes are difficult to deal with in a portable manner. That's one reason
why Boost.Threads makes use of <a href="../../../tools/build/index.html">Boost.Build</a>.
In general you should refer to the documentation for <a href="../../../tools/build/index.html">Boost.Build</a>.
This document will only supply you with some simple usage examples for how to
use <em>bjam</em> to build and test Boost.Threads. In addition, this document
will try and explain the build requirements so that users may create their own
build processes (for instance, create an IDE specific project), both for building
and testing Boost.Threads, as well as for building their own projects using
Boost.Threads. </p>
<h2><a name="topic1"></a>Building the Boost.Threads Libraries</h2>
<p>To build the Boost.Thread libraries using Boost.Build, simply change to the
directory <em>boost_root</em>/libs/thread/build and execute the command:</p>
<pre>bjam -sTOOLS=<em>toolset</em></pre>
<p>This will create four variants of the Boost.Threads library with the permuations
of debug/release and runtime-link-dynamic/runtime-link-static. <em><strong>Note:</strong></em>
Invoking the above command in <em>boost_root</em> will build all of the Boost
distribution, including Boost.Threads.</p>
<p>The Jamfile supplied with Boost.Threads produces a static library named <em>libboostthread</em>.
In addition, on Win32 platforms a <em>boostthreadmon.dll</em> and a coresponding
import library are created. The source files that are used to create the <em>libboostthread</em>
library are all of the *.cpp files found in <em>boost_root</em>/libs/thread/src,
except for <em>threadmon.cpp</em>. These need to be built with the compiler's
and linker's multi-threading support enabled. On Win32 platforms the <em>boostthreadmon.dll</em>
is created from <em>boost_root</em>/libs/thread/src/threadmon.cpp. This, too,
needs to be built with the compiler's and linker's multi-threading support enabled.
If you want to create your own build solution you'll have to follow these same
guidelines. One of the most frequently reported problems when trying to do this
occurs from not enabling the compiler's and linker's support for multi-threading.</p>
<h2><a name="topic2"></a>Testing the Boost.Threads Libraries</h2>
<p>To test the Boost.Threads libraries using Boost.Build, simply change to the
directory <em>boost_root</em>/libs/thread/test and execute the command:</p>
<pre><code>bjam -sTOOLS=<em>toolset</em> test</code></pre>
<p> </p>
<h2><a name="footnotes"></a>Footnotes</h2>
<dl>
<dt><a name="footnote1" class="footnote">(1)</a> {{text}}</dt>
<dt><a name="footnote2" class="footnote">(2)</a> {{text}}</dt>
</dl>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:{{address}}">{{author}}</a>
2002. All Rights Reserved.</i></p>
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<title>Boost.Threads, call_once</title>
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<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">call_once</h2>
</td>
</tr>
</table>
<hr>
<p><A href="#Introduction">Introduction</A><br>
<A href="#Header">Header</A><br>
<A href="#Synopsis">Synopsis</A><br>
<A href="#Members">Members</A><br>
<A href="#Example">Example</A></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>call_once</code> routine and <code>once_flag</code> type can be used to
run a routine exactly once. This can be used to initialize data in a
<a href="definitions.html#Thread-safe">thread-safe</a> manner.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/once.hpp">&lt;boost/thread/once.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
typedef <i>[implementation defined]</i> once_flag;
const once_flag once_init = <i>[implementation defined]</i>;
void call_once(void (*func)(), once_flag&amp; flag);
} // namespace boost
</pre>
<h2><a name="Reference">Reference</a></h2>
<hr>
<h3>once_flag</h3>
<p>This implementation defined type is used as a flag to insure a routine is called only once.
Instances of this type should be statically initialized to <code>once_init</code>.</p>
<hr>
<h3>once_init</h3>
<p>This is a constant value used to initialize <code>once_flag</code> instances
to indicate that the logically associated routine has not been run yet.</p>
<hr>
<h3>call_once</h3>
<pre>
void call_once(void (*func)(), once_flag&amp; flag);
</pre>
<p><b>Requires:</b> The function <code>func</code> shall not throw exceptions.</p>
<p><b>Effects:</b> As if (in an atomic fashion)</p>
<code>
&nbsp;&nbsp;&nbsp;if (flag == once_init)<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;func();
</code>
<p><b>Postcondition:</b> <code>flag</code> != <code>once_init</code></p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include <a href="../../../boost/thread/tss.hpp">&lt;boost/thread/once.hpp&gt;</a>
#include &lt;cassert&gt;
int value=0;
boost::once_flag once = boost::once_init;
void init()
{
++value;
}
void thread_proc()
{
boost::call_once(&amp;init, once);
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i=0; i&lt;5; ++i)
threads.create_thread(&amp;thread_proc);
threads.join_all();
assert(value == 1);
}
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
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</html>

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@@ -1,201 +1,313 @@
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<title>Boost.Threads - Header &lt;boost/thread/condition.hpp&gt;</title>
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, condition</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/condition.hpp">boost/thread/condition.hpp</a>&gt;</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-condition">Class <code>condition</code></a></dt>
<dl class="page-index">
<dt><a href="#class-condition-synopsis">Class <code>condition</code> synopsis</a></dt>
<dt><a href="#class-condition-ctors">Class <code>condition</code> constructors
and destructor</a></dt>
<dt><a href="#class-condition-modifiers">Class <code>condition</code> modifier
functions</a></dt>
</dl>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>Include the header &lt;<a href="../../../boost/thread/condition.hpp">boost/thread/condition.hpp</a>&gt;
to define the class condition.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-condition"></a>Class <code>condition</code></h3>
<p>An object of class <code>condition</code> is a synchronization primitive used
to cause a thread to wait until a particular shared-data condition (or time)
is met. A <code>condition</code> object is always used in conjunction with a
mutex object (an object whose type is a model of <a href="mutex_concept.html">Mutex</a>
or one of its refinements). The mutex object must be locked prior to waiting
on the <code>condition</code>, which is verified by passing a lock object (an
object whose type is a model of <a href="lock_concept.html">Lock</a> or one
of its refinements) to the <code>condition</code> object&#39;s <code>wait</code>
functions. Upon blocking on the condition object, the thread unlocks the mutex
object. When the thread returns from a call to one of the condition object's
wait functions the mutex object is again locked. The tricky unlock/lock sequence
is performed automatically by the <code> condition</code> object&#39;s <code>wait</code>
functions.</p>
<p>The <code>condition</code> type is often used to implement the <i> Monitor
Object</i> and other important patterns (see <a href="bibliography.html#Schmidt-00">[Schmidt
00]</a> and <a href="bibliography.html#Hoare-74">[Hoare 74]</a>). Monitors are
one of the most important patterns for creating reliable multithreaded programs.</p>
<p>See <a href="definitions.html">Formal Definitions</a> for definitions of thread
states <a href="definitions.html#state"> blocked</a> and <a href="definitions.html#state">ready</a>.
Note that &quot;waiting&quot; is a synonym for blocked.</p>
<h4><a name="class-condition-synopsis"></a>Class <code>condition</code> synopsis</h4>
<pre>
namespace boost
{
class condition : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class condition meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
{
public:
condition();
~condition();
void notify_one();
void notify_all();
template &lt;typename <a href="lock_concept.html#Lock-concept">Lock</a>&gt;
void wait(<a href="lock_concept.html#Lock-concept">Lock</a>&amp; lock);
template &lt;typename <a href="lock_concept.html#Lock-concept">Lock</a>, typename <a href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</a>&gt;
void wait(<a href="lock_concept.html#Lock-concept">Lock</a>&amp; lock, <a href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</a> pred);
template &lt;typename <a href="lock_concept.html#Lock-concept">Lock</a>&gt;
bool timed_wait(<a href="lock_concept.html#Lock-concept">Lock</a>&amp; lock, const xtime&amp; xt);
template &lt;typename <a href="lock_concept.html#Lock-concept">Lock</a>, typename <a href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</a>&gt;
bool timed_wait(<a href="lock_concept.html#Lock-concept">Lock</a>&amp; lock, const xtime&amp; XT, <a href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</a> pred);
};
};
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080" text="#000000">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">condition</h2>
</td>
</tr>
</table>
<hr>
<p><A href="#Introduction">Introduction</a><br>
<A href="#Header">Header</a><br>
<A href="#Synopsis">Synopsis</a><br>
<A href="#Members">Members</a><br>
<A href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>An object of class <code>condition</code> is a synchronization primitive used to
cause a thread to wait until a particular shared-data condition (or time) is met.
A <code>condition</code> object is always used in conjunction with a mutex
object modeling a <a href="mutex_concept.html">Mutex Concept</a>. The mutex must be locked prior to waiting on the
<code>condition</code>, which is ensured by passing a lock object modeling a <a href="lock_concept.html">Lock
Concept</a> to the <code>condition</code> object's <code>wait</code> functions. While the thread is waiting on the <code>condition</code>
object,
the mutex associated with the lock is unlocked. When the thread returns
from a call to one of the <code>condition</code> object's <code>wait</code> functions,
the mutex is again locked. The tricky lock/unlock/lock sequence is performed
automatically by the <code>condition</code> object's <code>wait</code>
functions.</p>
<p>The <code>condition</code> type is often used to implement the <i>Monitor Object</i>
and other important patterns. See <A href="bibliography.html#Schmidt-00">[Schmidt-00]</a>
and <A href="bibliography.html#Hoare-74">[Hoare 74]</a>. Monitors are one of the most
important patterns for creating reliable multithreaded programs.</p>
<p>See <A href="definitions.html">Formal Definitions</a> for definitions of thread
states <A href="definitions.html#state">blocked</a> and
<A href="definitions.html#state">ready</a>. Note that "waiting" is a synonym
for blocked.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <A href="../../../boost/thread/condition.hpp">&lt;boost/thread/condition.hpp&gt;</a>
</pre>
<h4><a name="class-condition-ctors"></a>Class <code>condition</code> constructors
and destructor</h4>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
class condition : private <A href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class condition meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
condition();
~condition();
void notify_one();
void notify_all();
template &lt;typename <a href="scoped_lock.html">ScopedLock</a>&gt;
void wait(<a href="scoped_lock.html">ScopedLock</a>&amp; lock);
template &lt;typename <a href="scoped_lock.html">ScopedLock</a>, typename <A href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</A>&gt;
void wait(<a href="scoped_lock.html">ScopedLock</a>&amp; lock, <A href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</A> pred);
template &lt;typename <a href="scoped_lock.html">ScopedLock</a>&gt;
bool timed_wait(<a href="scoped_lock.html">ScopedLock</a>&amp; lock, const xtime&amp; xt);
template &lt;typename <a href="scoped_lock.html">ScopedLock</a>, typename <A href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</A>&gt;
bool timed_wait(<a href="scoped_lock.html">ScopedLock</a>&amp; lock, const xtime&amp; xt, <A href="http://www.sgi.com/tech/stl/Predicate.html">Predicate</A> pred);
};
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
condition();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs a <code>condition</code> object.</dt>
</dl>
<p><b>Effects:</b> Constructs a <code>condition</code>.</p>
<hr>
<h3>Destructor</h3>
<pre>
~condition();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Destroys <code>*this</code>.</dt>
</dl>
<h4><a name="class-condition-modifiers"></a>Class <code>condition</code> modifier
functions</h4>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<hr>
<h3>notify_one</h3>
<pre>
void notify_one();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> If there is a thread waiting on <code>*this</code>, change
that thread&#39;s state to ready. Otherwise there is no effect.</dt>
<dt><b>Note:</b> If more than one thread is waiting on the condition, it is
unspecified which is made ready. After returning to a ready state the notified
thread must still acquire the mutex again (which occurs within the call to
one of the <code>condition</code> object's wait functions).</dt>
</dl>
<p><b>Effects:</b> If there is a thread waiting on <code>*this</code>, change
that thread's state to ready. Otherwise there is no effect.</p>
<p><b>Notes:</b> If more that one thread is waiting on the condition, it is
unspecified which is made ready.</p>
<hr>
<h3>notify_all</h3>
<pre>
void notify_all();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Change the state of all threads waiting on <code> *this</code>
to ready. If there are no waiting threads, <code> notify_all()</code> has
no effect.</dt>
</dl>
<p><b>Effects:</b> Change the state of all threads waiting on <code>*this</code>
to ready. If there are no waiting threads, <code>notify_all()</code> has no effect.</p>
<hr>
<h3>wait</h3>
<pre>
template &lt;typename ScopedLock&gt;
void wait(ScopedLock&amp; lock);
void wait(ScopedLock&amp; lock);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>ScopedLock</code> meets the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements.</dt>
<dt><b>Effects:</b> Releases the lock on the <a href="mutex_concept.html">mutex
model</a> associated with <code>lock</code>, blocks the current thread of
execution until readied by a call to <code>this-&gt;notify_one()</code> or
<code> this-&gt;notify_all()</code>, and then reacquires the lock.</dt>
<dt><b>Throws:</b> <code><a href="exceptions.html#class-lock_error">lock_error</a></code>
if <code>!lock.locked()</code></dt>
<dt><b>Danger:</b> This version should always be used within a loop checking
that the state logically associated with the <code>condition</code> has become
true. Without the loop, race conditions can ensue due to possible &quot;spurious
wake ups&quot;. The second version encapsulates this loop idiom internally
and is generally the preferred method.</dt>
</dl>
<p><b>Requires:</b> ScopedLock meets the
<A href="lock_concept.html#ScopedLock">ScopedLock</a> requirements.</p>
<p><b>Effects:</b> Releases the lock on the <A href="mutex_concept.html">mutex model</a>
associated with <code>lock</code>, blocks the current thread of execution until readied
by a call to <code>this-&gt;notify_one()</code> or <code>this-&gt;notify_all()</code>,
and then reacquires the lock. All effects occur in an atomic fashion.</p>
<p><b>Throws:</b> <code><A href="lock_error.html">lock_error</a></code>
if <code>!lock.locked()</code></p>
<p><b>Danger:</b> This version should always be used within a loop checking that the
state logically associated with the <code>condition</code> has become true. Without
the loop, race conditions can ensue due to possible "spurious wake ups". The second
version encapsulates this loop idiom internally and is generally the preferred method.</p>
<pre>
Template&lt;typename ScopedLock, typename Pr&gt;
void wait(ScopedLock&amp; lock, Pr pred);
template &lt;typename ScopedLock, typename Pr&gt;
void wait(ScopedLock&amp; lock, Pr pred);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>ScopedLock</code> meets the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements, return from <code>pred()</code> convertible to bool.</dt>
<dt><b>Effects:</b> As if: <code>while (!pred()) wait(lock)</code></dt>
<dt><b>Throws:</b> <code><a href="exceptions.html#class-lock_error">lock_error</a></code>
if <code>!lock.locked()</code></dt>
</dl>
<p><b>Requires:</b> ScopedLock meets the
<A href="lock_concept.html#ScopedLock">ScopedLock</a> requirements, return from
<code>pred()</code> convertible to bool.</p>
<p><b>Effects:</b> As if:</p>
<code>
&nbsp;&nbsp;&nbsp;while (!pred()) wait(lock)
</code>
<p><b>Throws:</b> <code><A href="lock_error.html">lock_error</a></code> if
<code>!lock.locked()</code></p>
<hr>
<h3>timed_wait</h3>
<pre>
template &lt;typename ScopedLock&gt;
bool timed_wait(ScopedLock&amp; lock, const <a href="xtime.html">xtime</a>&amp; XT);
template &lt;typename ScopedTimedLock&gt;
bool timed_wait(ScopedTimedLock&amp; lock, const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>ScopedLock</code> meets the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements.</dt>
<dt><b>Effects:</b> Releases the lock on the <a href="mutex_concept.html">mutex
model</a> associated with the <code> lock</code>, blocks the current thread
of execution until readied by a call to <code>this-&gt;notify_one()</code>
or <code> this-&gt;notify_all()</code>, or until <code>XT</code>, and then
reacquires the lock.</dt>
<dt><b>Returns:</b> <code>false</code> if <code>XT</code> is reached, otherwise
<code>true</code>.</dt>
<dt><b>Throws:</b> <code><a href="exceptions.html#class-lock_error">lock_error</a></code>
if <code>!lock.locked()</code></dt>
<dt><b>Danger:</b> This version should always be used within a loop checking
that the state logically associated with the <code>condition</code> has become
true. Without the loop, race conditions can ensue due to &quot;spurious wake
ups&quot;. The second version encapsulates this loop idiom internally and
is generally the preferred method.</dt>
</dl>
<p><b>Requires:</b> ScopedTimeLock meets the
<A href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a> requirements.</p>
<p><b>Effects:</b> Releases the lock on the <A href="mutex_concept.html">mutex model</a>
associated with the <code>lock</code>, blocks the current thread of execution until
readied by a call to <code>this-&gt;notify_one()</code> or
<code>this-&gt;notify_all()</code>, or until <code>xt</code>, and then reacquires the
lock. All effects occur in an atomic fashion.</p>
<p><b>Throws:</b> <code><A href="lock_error.html">lock_error</a></code> if
<code>!lock.locked()</code></p>
<p><b>Danger:</b> This version should always be used within a loop checking that the
state logically associated with the <code>condition</code> has become true. Without
the loop, race conditions can ensue due to "spurious wake ups". The second version
encapsulates this loop idiom internally and is generally the preferred method.</p>
<p><b>Returns:</b> <code>false</code> if <code>xt</code> is reached, otherwise
<code>true</code>.</p>
<pre>
Template&lt;typename ScopedLock, typename Pr&gt;
bool timed_wait(ScopedLock&amp; lock, const <a href="xtime.html">xtime</a>&amp; XT, Pr pred);
template &lt;typename ScopedTimedLock, typename Pr&gt;
bool timed_wait(ScopedTimedLock&amp; lock, const <a href="xtime.html">xtime</a>&amp; xt, Pr pred);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>ScopedLock</code> meets the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements, return from <code>pred()</code> convertible to bool.</dt>
<dt><b>Effects:</b> As if:<br>
<pre>
while (!pred())
<p><b>Requires: </b>ScopedTimeLock meets the
<A href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a> requirements,
return from <code>pred()</code> convertible to bool.</p>
<p><b>Effects: </b>As if:</p>
<code>
&nbsp;&nbsp;&nbsp;while (!pred())<br>
&nbsp;&nbsp;&nbsp;{<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (!timed_wait(lock, xt))<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return false;<br>
&nbsp;&nbsp;&nbsp;}
</code>
<p><b>Throws:</b> <code><A href="lock_error.html">lock_error</a></code> if
<code>!lock.locked()</code></p>
<p><b>Returns:</b> <code>false</code> if <code>xt</code> is reached, otherwise
<code>true</code>.</p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include &lt;iostream&gt;
#include &lt;vector&gt;
#include <A href="../../../boost/utility.hpp">&lt;boost/utility.hpp&gt;</a>
#include <A href="../../../boost/thread/condition.hpp">&lt;boost/thread/condition.hpp&gt;</a>
#include <A href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
class bounded_buffer : private boost::noncopyable
{
if (!timed_wait(lock, XT))
return false;
public:
typedef boost::mutex::scoped_lock lock;
bounded_buffer(int n) : begin(0), end(0), buffered(0), circular_buf(n) { }
void send (int m) {
lock lk(monitor);
while (buffered == circular_buf.size())
buffer_not_full.wait(lk);
circular_buf[end] = m;
end = (end+1) % circular_buf.size();
++buffered;
buffer_not_empty.notify_one();
}
int receive() {
lock lk(monitor);
while (buffered == 0)
buffer_not_empty.wait(lk);
int i = circular_buf[begin];
begin = (begin+1) % circular_buf.size();
--buffered;
buffer_not_full.notify_one();
return i;
}
private:
int begin, end, buffered;
std::vector&lt;int&gt; circular_buf;
boost::condition buffer_not_full, buffer_not_empty;
boost::mutex monitor;
};
bounded_buffer buf(2);
void sender() {
int n = 0;
while (n &lt; 100) {
buf.send(n);
std::cout &lt;&lt; &quot;sent: &quot; &lt;&lt; n &lt;&lt; std::endl;
++n;
}
buf.send(-1);
}
void receiver() {
int n;
do {
n = buf.receive();
std::cout &lt;&lt; &quot;received: &quot; &lt;&lt; n &lt;&lt; std::endl;
} while (n != -1); // -1 indicates end of buffer
}
int main(int, char*[])
{
boost::thread thrd1(&amp;sender);
boost::thread thrd2(&amp;receiver);
thrd1.join();
thrd2.join();
return 0;
}
return true;
</pre>
</dt>
<dt><b>Returns:</b> <code>false</code> if <code>XT</code> is reached, otherwise
<code>true</code>.</dt>
<dt><b>Throws:</b> <code><a href="exceptions.html#class-lock_error">lock_error</a></code>
if <code>!lock.locked()</code></dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<p><a href="../example/condition.cpp">libs/thread/example/condition.cpp</a></p>
<p>Typical output (dependent on scheduling policies) is:</p>
<pre>
sent: 0
sent: 1
@@ -208,18 +320,14 @@ received: 3
sent: 4
received: 4
</pre>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, Configuration Information</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Configuration Information</h2>
</td>
</tr>
</table>
<hr>
<p><b>Boost.Threads</b> uses several configuration macros in <a href="../../config/config.htm"> &lt;boost/config.hpp&gt;</a>.
These macros are documented here. Most of the macros are
of interest only to developers attempting to provide new implementations of <b>Boost.Threads</b>.
The one exception to this is BOOST_HAS_THREADS.</p>
<table cellspacing="10" width="100%">
<tr>
<td valign="top">
<b>Macro</b>
</td>
<td valign="top">
<b>Meaning</b>
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_THREADS
</td>
<td valign="top">
Indicates that threading support is available. This means both that there is a
platform specific implementation for <b>Boost.Threads</b> and that threading
support has been enabled in a platform specific manner. For instance, on the
Win32 platform there's an implementation for <b>Boost.Threads</b> but unless
the program is compiled against one of the multi-threading runtimes
(often determined by the
compiler predefining the macro _MT) the
BOOST_HAS_THREADS macro remains undefined.
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_WINTHREADS
</td>
<td valign="top">
Indicates that the platform has the Microsoft Win32 threading libraries,
and that they should be used
to implement <b>Boost.Threads</b>.
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_PTHREADS
</td>
<td valign="top">
Indicates that the platform has the POSIX pthreads libraries, and that
they should be used
to implement <b>Boost.Threads</b>.
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_FTIME
</td>
<td valign="top">
Indicates that the implementation should use GetSystemTimeAsFileTime() and
the FILETIME type to calculate the current time. This is an implementation
detail used by boost::detail::getcurtime().
</td>
</tr>
<tr>
<td valign="top">
BOOST_HAS_GETTTIMEOFDAY
</td>
<td valign="top">
Indicates that the implementation should use gettimeofday() to calculate the
current time. This is an implementation detail used by boost::detail::getcurtime().
</td>
</tr>
</table>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->18 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39344" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Configuration</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Configuration</h2>
</td>
</tr>
</table>
<hr>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#lib-defined-public">Public Library Defined Macros</a></dt>
<dt><a href="#lib-defined-impl">Library Defined Implementation Macros</a></dt>
</dl>
<h2><a name="introduction"></a>Introduction</h2>
<p><b>Boost.Threads</b> uses several configuration macros in <a href="../../config/config.htm">&lt;boost/config.hpp&gt;</a>,
as well as configuration macros meant to be supplied by the application. These
macros are documented here.</p>
<h2><a name="lib-defined-public"></a>Public Library Defined Macros</h2>
<p>These macros are defined by <b>Boost.Threads</b> but are expected to be used
by application code.</p>
<table summary="public library defined macros" cellspacing="10" width="100%">
<tr>
<td><b>Macro</b></td>
<td><b>Meaning</b></td>
</tr>
<tr>
<td>BOOST_HAS_THREADS</td>
<td>Indicates that threading support is available. This means both that there
is a platform specific implementation for <b>Boost.Threads</b> and that
threading support has been enabled in a platform specific manner. For instance,
on the Win32 platform there&#39;s an implementation for <b>Boost.Threads</b>
but unless the program is compiled against one of the multithreading runtimes
(often determined by the compiler predefining the macro _MT) the BOOST_HAS_THREADS
macro remains undefined.</td>
</tr>
</table>
<h2><a name="lib-defined-impl"></a>Library Defined Implementation Macros</h2>
<p>These macros are defined by <b>Boost.Threads</b> and are implementation details
of interest only to implementors.</p>
<table summary="library defined implementation macros" cellspacing="10" width="100%">
<tr>
<td><b>Macro</b></td>
<td><b>Meaning</b></td>
</tr>
<tr>
<td>BOOST_HAS_WINTHREADS</td>
<td>Indicates that the platform has the Microsoft Win32 threading libraries,
and that they should be used to implement <b>Boost.Threads</b>.</td>
</tr>
<tr>
<td>BOOST_HAS_PTHREADS</td>
<td>Indicates that the platform has the POSIX pthreads libraries, and that
they should be used to implement <b>Boost.Threads</b>.</td>
</tr>
<tr>
<td>BOOST_HAS_FTIME</td>
<td>Indicates that the implementation should use GetSystemTimeAsFileTime()
and the FILETIME type to calculate the current time. This is an implementation
detail used by boost::detail::getcurtime().</td>
</tr>
<tr>
<td>BOOST_HAS_GETTTIMEOFDAY</td>
<td>Indicates that the implementation should use gettimeofday() to calculate
the current time. This is an implementation detail used by boost::detail::getcurtime().</td>
</tr>
</table>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
</body>
</html>

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@@ -1,77 +1,63 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Definitions</title>
<meta http-equiv="Content-Language" content="en-us">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Boost.Threads Definitions</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<body bgcolor="#FFFFFF">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Definitions</h2>
<h2 align="center"> Definitions</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#definitions">Definitions</a></dt>
<dl class="page-index">
<dt><a href="#definition-thread">Thread</a></dt>
<dt><a href="#definition-thread-safe">Thread-safe</a></dt>
<dt><a href="#definition-thread-state">Thread State</a></dt>
<dt><a href="#definition-race-condition">Race Condition</a></dt>
<dt><a href="#definition-deadlock">Deadlock</a></dt>
<dt><a href="#definition-starvation">Starvation</a></dt>
<dt><a href="#definition-priority-failure">Priority Failure</a></dt>
<dt><a href="#definition-visibility">Memory Visibility</a></dt>
</dl>
<dt><a href="#acknowledgements">Acknowledgments</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>The definitions are given in terms of the <a href=
"bibliography.html#ISO-98">C++ Standard</a>. References to the standard
are in the form [1.2.3/4], which represents the section number, with the paragraph
number following the &quot;/&quot;.</p>
<p>Because the definitions are written in something akin to &quot;standardese&quot;,
they can be difficult to understand. The intent isn&#39;t to confuse, but rather
to clarify the additional requirements Boost.Threads places on a C++ implementation
as defined by the C++ Standard.</p>
<h2><a name="definitions"></a>Definitions</h2>
<h3><a name="definition-thread"></a>Thread</h3>
<p>Thread is short for &quot;thread of execution&quot;. A thread of execution
is an execution environment [1.9/7] within the execution environment of a C++
program [1.9]. The main() function [3.6.1] of the program is the initial function
of the initial thread. A program in a multithreading environment always has
an initial thread even if the program explicitly creates no additional threads.</p>
<p>Unless otherwise specified, each thread shares all aspects of its execution
environment with other threads in the program. Shared aspects of the execution
environment include, but are not limited to, the following:</p>
<h2>Introduction</h2>
<p>The definitions are given in terms of the <a href="bibliography.html#ISO-98"> C++ Standard</a>.&nbsp; References to the standard
are in the form [1.2.3/4], which
represents the section number, with the paragraph number following the &quot;/&quot;.</p>
<p>Because the definitions are written in something akin to
&quot;standardese&quot;, they can be difficult to understand.&nbsp; The intent
isn't to confuse, but rather to clarify the additional requirements
Boost.Threads places on a C++ implementation as defined by the C++ Standard.</p>
<h2>Definitions</h2>
<h3>Thread</h3>
<p>Thread is short for &quot;thread of execution&quot;. A thread of execution is an execution environment [1.9/7] within the execution environment
of a C++ program [1.9]. The main() function [3.6.1] of the program is the
initial function of the initial thread. A program in a multi-threading
environment always has an initial thread even if the program explicitly creates
no additional threads.</p>
<p>Unless otherwise specified, each thread shares all aspects of its execution environment with
other threads in the program. Shared aspects of the execution environment
include, but are not limited to, the following:</p>
<ul>
<li>Static storage duration (static, extern) objects [3.7.1].</li>
</ul>
<ul>
<li>Dynamic storage duration (heap) objects [3.7.3]. Thus each memory allocation
will return a unique addresses, regardless of the thread making the allocation
request.</li>
<li>Dynamic storage duration (heap) objects [3.7.3].&nbsp; Thus each memory
allocation will return a unique addresses, regardless of the thread making
the allocation request.</li>
</ul>
<ul>
<li>Automatic storage duration (stack) objects [3.7.2] accessed via pointer
or reference from another thread.</li>
<li>Automatic storage duration (stack) objects [3.7.2] accessed via pointer or
reference from another thread.</li>
</ul>
<ul>
<li>Resources provided by the operating system. For example, files.</li>
<li>Resources provided by the operating
system.&nbsp; For example, files.</li>
</ul>
<ul>
<li>The program itself. In other words, each thread is executing some function
of the same program, not a totally different program.</li>
<li>The program itself.&nbsp; In other words, each thread is executing some
function of the same program, not a totally different program.</li>
</ul>
<p>Each thread has its own:</p>
<ul>
@@ -80,16 +66,17 @@
<ul>
<li>Automatic storage duration (stack) objects [3.7.2].</li>
</ul>
<h3><a name="definition-thread-safe"></a>Thread-safe</h3>
<p>A program is thread-safe if it has no <a href="#Race condition">race conditions</a>,
does not <a href="#Deadlock">deadlock</a>, and has no <a href="#Priority failure">priority
failures</a>.</p>
<h3><a name="Thread-safe">Thread-safe</a></h3>
<p>A program is thread-safe if it has no <a href="#Race condition">race
conditions</a>, does not <a href="#Deadlock">deadlock</a>, and has no <a href="#Priority failure">priority
failures</a>.</p>
<p>Note that thread-safety does not necessarily imply efficiency, and than while
some thread-safety violations can be determined statically at compile time,
many thread-safety errors can only only be detected at runtime.</p>
<h3><a name="definition-thread-state"></a>Thread State</h3>
<p>During the lifetime of a thread, it shall be in one of the following states:</p>
<table summary="thread states" border="1" cellpadding="5">
some thread-safety violations can be determined statically at compile time, many
thread-safety errors can only only be detected at runtime.</p>
<h3>Thread <a name="State">State</a></h3>
<p>During the lifetime of a thread, it shall be in one of the following
states:</p>
<table border="1" cellpadding="5">
<tr>
<td><b>State</b></td>
<td><b>Description</b></td>
@@ -101,7 +88,7 @@
<tr>
<td>Running</td>
<td>Currently executing on a processor. Zero or more threads may be running
at any time, with a maximum equal to the number of processors.</td>
at any time, with a maximum equal to the number of processors.&nbsp;</td>
</tr>
<tr>
<td>Blocked</td>
@@ -115,7 +102,7 @@
</tr>
</table>
<p>Thread state transitions shall occur only as specified:</p>
<table summary="state transitions" border="1" cellpadding="5">
<table border="1" cellpadding="5">
<tr>
<td><b>From</b></td>
<td><b>To</b></td>
@@ -123,12 +110,11 @@
</tr>
<tr>
<td>
<p align="left">[none]</p>
</td>
<p align="left">[none]</td>
<td>Ready</td>
<td>Thread is created by a call to a library function. In the case of the
initial thread, creation is implicit and occurs during the startup of the
main() function [3.6.1].</td>
<td>Thread is created by a call to a library function.&nbsp; In the case of
the initial thread, creation is implicit and occurs during the startup of
the main() function [3.6.1].</td>
</tr>
<tr>
<td>Ready</td>
@@ -149,9 +135,9 @@
<tr>
<td>Running</td>
<td>Terminated</td>
<td>Thread returns from its initial function, calls a thread termination library
function, or is canceled by some other thread calling a thread termination
library function.</td>
<td>Thread returns from its initial function, calls a thread termination
library function, or is cancelled by some other thread calling a thread
termination library function.</td>
</tr>
<tr>
<td>Blocked</td>
@@ -162,56 +148,56 @@
<tr>
<td>Terminated</td>
<td>[none]</td>
<td>Thread is detached or joined by some other thread calling the appropriate
library function, or by program termination [3.6.3].</td>
<td>Thread is detached or joined by some other thread calling the
appropriate library function, or by program termination [3.6.3].</td>
</tr>
</table>
<p>[Note: if a suspend() function is added to the threading library, additional
transitions to the blocked state will have to be added to the above table.]</p>
<h3><a name="definition-race-condition"></a>Race Condition</h3>
<p>A race condition is what occurs when multiple threads read and write to the
same memory without proper synchronization, resulting in an incorrect value
being read or written. The result of a race condition may be a bit pattern which
isn&#39;t even a valid value for the data type. A race condition results in
undefined behavior [1.3.12].</p>
<p>Race conditions can be prevented by serializing memory access using the tools
provided by Boost.Threads.</p>
<h3><a name="definition-deadlock"></a>Deadlock</h3>
transitions to the blocked state will have to be added to the above table.]</p>
<h3><a name="Race condition">Race condition</a></h3>
<p>A race condition is what occurs when multiple threads read and
write to the same memory without proper synchronization, resulting in an
incorrect value being read or written.&nbsp; The result of a race condition may
be a bit pattern which isn't even a valid value for the data type. A race
condition results in undefined behavior [1.3.12].</p>
<p>Race conditions can be prevented by serializing memory access
using the tools provided by Boost.Threads.&nbsp;</p>
<h3><a name="Deadlock">Deadlock</a></h3>
<p>Deadlock is an execution state where for some set of threads, each thread in
the set is blocked waiting for some action by one of the other threads in the
set. Since each is waiting on the others, none will ever become ready again.</p>
<h3><a name="definition-starvation"></a>Starvation</h3>
<p>The condition in which a thread is not making sufficient progress in its work
during a given time interval.</p>
<h3><a name="definition-priority-failure"></a>Priority Failure</h3>
the set is blocked waiting for some action by one of the other threads in the
set. Since each is waiting on the others, none will ever become ready again.</p>
<h3><a name="Priority failure">Priority failure</a></h3>
<p>A priority failure (such as priority inversion or infinite overtaking) occurs
when threads executed in such a sequence that required work is not performed
in time to be useful.</p>
<h3><a name="definition-visibility"></a>Memory Visibility</h3>
<p>An address [1.7] shall always point to the same memory byte, regardless of
the thread or processor dereferencing the address.</p>
<p>An object [1.8, 1.9] is accessible from multiple threads if it is of static
storage duration (static, extern) [3.7.1], or if a pointer or reference to it
is explicitly or implicitly dereferenced in multiple threads.</p>
<p>For an object accessible from multiple threads, the value of the object accessed
from one thread may be indeterminate or different than the value accessed from
another thread, except under the conditions specified in the following table.
For the same row of the table, the value of an object accessible at the indicated
sequence point in thread A will be determinate and the same if accessed at or
after the indicated sequence point in thread B, provided the object is not otherwise
modified. In the table, the &quot;sequence point at a call&quot; is the sequence
point after the evaluation of all function arguments [1.9/17], while the &quot;sequence
point after a call&quot; is the sequence point after the copying of the returned
value...&quot; [1.9/17].</p>
<table summary="memory visibility" border="1" cellpadding="5">
when threads executed in such a sequence that required work is not performed in
time to be useful.</p>
<h2>Memory visibility between threads</h2>
<p>An address [1.7] shall always point to the same memory byte, regardless of the
thread or processor dereferencing the address.</p>
<p>An object [1.8, 1.9] is accessible from multiple threads if it is of
static storage duration (static, extern) [3.7.1], or if a pointer or reference to
it is explicitly or
implicitly dereferenced in multiple threads.</p>
<p>For an object accessible from multiple threads, the value of the object
accessed from one thread may be indeterminate or different than the value
accessed from another thread, except under the conditions specified in the following
table.&nbsp;&nbsp; For the same row of the table, the value of an object
accessible at the indicated sequence point in thread A will be determinate and the
same if accessed at or after the indicated sequence point in thread B, provided
the object is not otherwise modified. In the table, the
&quot;sequence point at a call&quot; is the sequence point after the evaluation
of all function arguments [1.9/17], while the &quot;sequence point after a
call&quot; is the sequence point after the copying of the returned
value...&quot; [1.9/17].</p>
<table border="1" cellpadding="5">
<tr>
<td align="center"><b>Thread A</b></td>
<td align="center"><b>Thread B</b></td>
</tr>
<tr>
<td>The sequence point at a call to a library thread-creation function.</td>
<td>The first sequence point of the initial function in the new thread created
by the Thread A call.</td>
<td>The sequence point at a call to a library thread-creation
function.&nbsp;</td>
<td>The first sequence point of the initial function in the new thread
created by the Thread A call.</td>
</tr>
<tr>
<td>The sequence point at a call to a library function which locks a mutex,
@@ -225,39 +211,34 @@
terminated thread.</td>
</tr>
<tr>
<td>The sequence point at a call to a library function which signals or broadcasts
a condition variable.</td>
<td>The sequence point after the call to the library function which was waiting
on that same condition variable or signal.</td>
<td>The sequence point at a call to a library function which signals or
broadcasts a condition variable.</td>
<td>The sequence point after the call to the library function which was
waiting on that same condition variable or signal.</td>
</tr>
</table>
<p>The architecture of the execution environment and the observable behavior of
the abstract machine [1.9] shall be the same on all processors.</p>
the abstract machine [1.9] shall be the same on all processors.</p>
<p>The latitude granted by the C++ standard for an implementation to alter the
definition of observable behavior of the abstract machine to include additional
library I/O functions [1.9/6] is extended to include threading library functions.</p>
definition of observable behavior of the abstract machine to include additional library I/O
functions [1.9/6] is extended to include threading library functions.</p>
<p>When an exception is thrown and there is no matching exception handler in the
same thread, behavior is undefined. The preferred behavior is the same as when
there is no matching exception handler in a program [15.3/9]. That is, terminate()
is called, and it is implementation defined whether or not the stack is unwound.</p>
<h2><a name="acknowledgements"></a>Acknowledgments</h2>
same thread, behavior is undefined.&nbsp; The preferred behavior is the same as when there is no matching exception handler
in a program [15.3/9].&nbsp; That is, terminate() is called, and it is implementation defined
whether or not the stack is unwound.</p>
<h2><a name="Acknowledgements">Acknowledgements</a></h2>
<p>This document has been much improved by the incorporation of comments from
William Kempf.</p>
<p>The visibility rules are based on <a href=
"bibliography.html#Butenhof-97">[Butenhof 97]</a>.</p>
William Kempf.</p>
<p>The visibility rules are based on <a href="bibliography.html#Butenhof-97">[Butenhof
97]</a>.&nbsp;</p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %b %Y" startspan -->07 Aug 2001<!--webbot bot="Timestamp" endspan i-checksum="14762" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p>© Copyright Beman Dawes, 2001</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/exceptions.hpp&gt;</title>
</head>
<body link="#0000ff" vlink="#800080">
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<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/exceptions.hpp">boost/thread/exceptions.hpp</a>&gt;</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-lock_error">Class <code>lock_error</code></a></dt>
<dl class="page-index">
<dt><a href="#class-lock_error-synopsis">Class <code>lock_error</code> synopsis</a></dt>
<dt><a href="#class-lock_error-ctors">Class <code>lock_error</code> constructors
and destructor</a></dt>
</dl>
<dt><a href="#class-thread_resource_error">Class <code>thread_resource_error</code></a></dt>
<dl class="page-index">
<dt><a href="#class-thread_resource_error-synopsis">Class <code>thread_resource_error</code>
synopsis</a></dt>
<dt><a href="#class-thread_resource_error-ctors">Class <code>thread_resource_error</code>
constructors and destructor</a></dt>
</dl>
</dl>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>Include the header &lt;<a href="../../../boost/thread/exceptions.hpp">boost/thread/exceptions.hpp</a>&gt;
to define the exception types that may be thrown by <b>Boost.Threads</b> classes.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-lock_error"></a>Class <code>lock_error</code></h3>
<p>The lock_error class defines an exception type thrown to indicate a locking
related error has been detected. Examples of such errors include a lock operation
which can be determined to result in a deadlock, or unlock operations attempted
by a thread that does not own the lock. </p>
<h4><a name="class-lock_error-synopsis"></a>Class <code>lock_error</code> synopsis</h4>
<pre>
namespace boost
{
class lock_error : public std::logical_error
{
public:
lock_error();
};
};
</pre>
<h4><a name="class-lock_error-ctors"></a>Class <code>lock_error</code> constructors
and destructor</h4>
<pre>
lock_error();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs a <code>lock_error</code> object.</dt>
</dl>
<h3><a name="class-thread_resource_error"></a>Class <code>thread_resource_error</code></h3>
<p>The thread_resource_error class defines an exception type that is thrown by
constructors in the Boost.Threads library when thread related resources can
not be acquired. This does not include memory allocation failures which instead
throw std::bad_alloc. </p>
<h4><a name="class-thread_resource_error-synopsis"></a>Class <code>thread_resource_error</code>
synopsis</h4>
<pre>
namespace boost
{
class thread_resource_error : public std::runtime_error
{
public:
thread_resource_error();
};
};
</pre>
<h4><a name="class-thread_resource_error-ctors"></a>Class <code>thread_resource_error</code>
constructors and destructor</h4>
<pre>
thread_resource_error();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs a <code>thread_resource_error</code> object.</dt>
</dl>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
</body>
</html>

View File

@@ -1,91 +1,83 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - FAQ</title>
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, FAQ</title>
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</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Frequently Asked Questions (FAQs)</h2>
</td>
</tr>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
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<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Frequently Asked Questions</h2>
</td>
</tr>
</table>
<hr>
<dl class="page-index">
<dt><a href="#question1">1. Are lock objects thread safe?</a></dt>
<dt><a href="#question2a">2a. Why was <b>Boost.Threads</b> modeled after (specific
library name)?</a></dt>
<dt><a href="#question2b">2b. Why wasn't <b>Boost.Threads</b> modeled after
(specific library name)?</a></dt>
<dt><a href="#question3">3. Why do mutexes have noncopyable semantics?</a></dt>
<dt><a href="#question4">4. How can you prevent deadlock from occurring when
a thread must lock multiple mutexes?</a></dt>
<dt><a href="#question5">5. Don't noncopyable mutex semantics mean that a class
with a mutex member will be noncopyable as well?</a></dt>
<dt><a href="#question6">6. How can you lock a mutex member in a const member
function (in order to implement the monitor pattern)?</a></dt>
<dt><a href="#question7">7. Why supply condition variables rather than event
variables?</a></dt>
<dt><a href="#question8">8. Why isn't thread cancellation or termination provided?</a></dt>
<dt><a href="#question9">9. Is it safe for threads to share automatic storage
duration (stack) objects via pointers or references?</a></dt>
<dt><a href="#question10">10. Why has class semaphore disappeared?</a></dt>
</dl>
<h2><a name="question1"></a>1. Are lock objects <a href="definitions.html#definition-thread-safe">
thread safe</a>?</h2>
<p><b>No!</b> Lock objects are not meant to be shared between threads. They are
meant to be short-lived objects created on automatic storage within a code block.
Any other usage is just likely to lead to errors and won&#39;t really be of
actual benefit any way. Share <a href=
"mutex_concept.html">mutexes</a>, not locks. For more information see
the <a href="rationale.html#lock_objects">rationale</a> behind the design for
lock objects.</p>
<h2><a name="question2a"></a>2a. Why was <b>Boost.Threads</b> modeled after (specific
library name)?</h2>
<p>It wasn&#39;t. Boost.Threads was designed from scratch. Extensive design discussions
involved numerous people representing a wide range of experience across many
platforms. To ensure portability, the initial implements were done in parallel
using POSIX Threads and the Win32 threading API. But the Boost.Threads design
is very much in the spirit of C++, and thus doesn&#39;t model such C based APIs.</p>
<h2><a name="question2b"></a>2b. Why wasn&#39;t Boost.Threads modeled after (specific
library name)?</h2>
<p>Existing C++ libraries either seemed dangerous (often failing to take advantage
of prior art to reduce errors) or had excessive dependencies on library components
unrelated to threading. Existing C libraries couldn&#39;t meet our C++ requirements,
and were also missing certain features. For instance, the WIN32 thread API lacks
condition variables, even though these are critical for the important Monitor
pattern <a href="bibliography.html#Schmidt-00">[Schmidt 00]</a>.</p>
<h2><a name="question3"></a>3. Why do <a href="mutex_concept.html">Mutexes</a>
have noncopyable semantics?</h2>
<p>To ensure that <a href="definitions.html#Deadlock">deadlocks</a> don&#39;t
occur. The only logical form of copy would be to use some sort of shallow copy
semantics in which multiple mutex objects could refer to the same mutex state.
This means that if ObjA has a mutex object as part of its state and ObjB is
copy constructed from it, then when ObjB::foo() locks the mutex it has effectively
locked ObjA as well. This behavior can result in deadlock. Other copy semantics
result in similar problems (if you think you can prove this to be wrong then
supply us with an alternative and we&#39;ll reconsider).</p>
<h2><a name="question4"></a>4. How can you prevent <a href="definitions.html#Deadlock">
deadlock</a> from occurring when a thread must lock multiple mutexes?</h2>
<p>Always lock them in the same order. One easy way of doing this is to use each
mutex&#39;s address to determine the order in which they are locked. A future
Boost.Threads concept may wrap this pattern up in a reusable class.</p>
<h2><a name="question5"></a>5. Don&#39;t noncopyable <a href="mutex_concept.html">mutex</a>
semantics mean that a class with a mutex member will be noncopyable as well?</h2>
<p>No, but what it does mean is that the compiler can&#39;t generate a copy constructor
and assignment operator, so they will have to be coded explicitly. This is a
<b>good thing</b>, however, since the compiler generated operations would not
be <a href=
"definitions.html#Thread-safe">thread-safe</a>. The following is a simple
example of a class with copyable semantics and internal synchronization through
a mutex member.</p>
<h2>1. Are lock objects <a href="definitions.html#Thread-safe">thread-safe</a>?</h2>
<p><b>No!</b> Lock objects are not meant to be shared between threads. They are meant to
be short lived objects created on automatic storage within a code block. Any other usage
is just likely to lead to errors and won't really be of actual benefit any way. Share
<a href="mutex_concept.html">mutexes</a>, not locks. For more information see the
<a href="rationale.html#lock_objects">rationale</a> behind the design for lock objects.</p>
<h2>2a. Why was Boost.Threads modeled after (specific library name)?</h2>
<p>It wasn't. Boost.Threads was designed from scratch. Extensive design
discussions involved numerous people representing a wide range of experience across
many platforms. To ensure portability, the initial implements were done in
parallel using POSIX Threads and theWin32 threading API. But the Boost.Threads
design is very much in the spirit of C++, and thus doesn't model such C based
APIs.</p>
<h2>2b. Why wasn't Boost.Threads modeled after (specific library name)?</h2>
<p>Existing C++ libraries either seemed dangerous (often failing to take
advantage of prior art to reduce errors) or had excessive dependencies on
library components unrelated to threading. Existing C libraries couldn't meet
our C++ requirements, and were also missing certain features. For
instance, POSIX threads doesn't support a maximum value for semaphores.
The WIN32 thread API lacks condition variables, even though these are critical
for the important Monitor pattern <a href="bibliography.html#Schmidt-00">[Schmidt
00]</a>.</p>
<h2>3. Why do <a href="mutex_concept.html"> Mutexes</a> have noncopyable semantics?</h2>
<p>To ensure that <a href="definitions.html#Deadlock"> deadlocks</a> don't occur. The only logical form of copy would be to
use some sort of shallow copy semantics in which multiple mutex objects could refer
to the same mutex state. This means that if ObjA has a mutex object as part of its state
and ObjB is copy constructed from it, then when ObjB::foo() locks the mutex it has effectively
locked ObjA as well. This behavior can result in deadlock. Other
copy semantics result in similar problems (if you think you can prove this to
be wrong then supply us with an alternative and we'll reconsider).</p>
<h2>4. How can you prevent <a href="definitions.html#Deadlock"> deadlock</a> from occurring when a thread must lock multiple
mutexes?</h2>
<p>Always lock them in the same order. One easy way of doing this is to use
each mutex's address to determine the order in which they are locked. A future
Boost.Threads concept may wrap this pattern up in a reusable class.</p>
<h2>5. Don't noncopyable <a href="mutex_concept.html"> mutex</a> semantics mean that a
class with a mutex member will be noncopyable as well?</h2>
<p>No, but what it does mean is that the compiler can't generate a copy constructor
and assignment operator, so they will have to be coded explicitly. This is a
<b>good thing</b>, however, since the compiler generated operations would not
be <a href="definitions.html#Thread-safe">thread-safe</a>. The following is a
simple example of a class with copyable semantics and internal synchronization through
a mutex member.</p>
<pre>
class counter
{
@@ -96,28 +88,28 @@ public:
: m_value(initial_value)
{
}
// We only need to synchronize other for the same reason we don't have to
// We only need to syncronize other for the same reason we don't have to
// synchronize on construction!
counter(const counter&amp; other)
{
boost::mutex::scoped_lock scoped_lock(other.m_mutex);
m_value = other.m_value;
}
// For assignment we need to synchronize both objects!
const counter&amp; operator=(const counter&amp; other)
{
if (this == &amp;other)
return *this;
boost::mutex::scoped_lock lock1(&amp;m_mutex &lt; &amp;other.m_mutex ? m_mutex : other.m_mutex);
boost::mutex::scoped_lock lock2(&amp;m_mutex &gt; &amp;other.m_mutex ? m_mutex : other.m_mutex);
m_value = other.m_value;
return *this;
}
int value() const
{
boost::mutex::scoped_lock scoped_lock(m_mutex);
@@ -128,56 +120,55 @@ public:
boost::mutex::scoped_lock scoped_lock(m_mutex);
return ++m_value;
}
private:
mutable boost::mutex m_mutex;
int m_value;
};
</pre>
<h2><a name="question6"></a>6. How can you lock a <a href="mutex_concept.html">mutex</a>
member in a const member function, in order to implement the Monitor Pattern?</h2>
<p>The Monitor Pattern mutex <a href="bibliography.html#Schmidt-00"> [Schmidt
00]</a> should simply be declared as mutable. See the example code above. The
internal state of mutex types could have been made mutable, with all lock calls
made via const functions, but this does a poor job of documenting the actual
semantics (and in fact would be incorrect since the logical state of a locked
mutex clearly differs from the logical state of an unlocked mutex). Declaring
a mutex member as mutable clearly documents the intended semantics.</p>
<h2><a name="question7"></a>7. Why supply <a href="condition.html">condition variables</a>
rather than <a href="rationale.html#Events">event variables</a>?</h2>
<p>Condition variables result in user code much less prone to <a href=
"definitions.html#Race condition">race conditions</a> than event variables.
See <a href="rationale.html#Events">Rationale</a> for analysis. Also see <a href="bibliography.html#Hoare-74">[Hoare
74]</a> and <a href="bibliography.html#Schmidt-00">[Schmidt 00]</a>.</p>
<h2><a name="question8"></a>8. Why isn&#39;t thread cancellation or termination
provided?</h2>
<p>There&#39;s a valid need for thread termination, so at some point Boost.Threads
probably will include it, but only after we can find a truly safe (and portable)
mechanism for this concept.</p>
<h2><a name="question9"></a>9. Is it safe for threads to share automatic storage
duration (stack) objects via pointers or references?</h2>
<h2>6. How can you lock a <a href="mutex_concept.html"> mutex</a> member in a const member function, in order to
implement the Monitor Pattern?</h2>
<p>The Monitor Pattern mutex <a href="bibliography.html#Schmidt-00">[Schmidt
00]</a> should simply be declared as mutable. See the example code above. The internal state of mutex
types could have been made mutable, with all lock calls made via const
functions, but
this does a poor job of documenting the actual semantics. Declaring a mutex member
as mutable clearly documentations the intended semantics.</p>
<h2>7. Why supply <a href="condition.html">condition variables</a> rather than <a href="rationale.html#Events">
event variables</a>?</h2>
<p>Condition variables result in user code much less prone to <a href="definitions.html#Race condition">race
conditions</a> than event variables. See <a href="rationale.html#Events">Rationale</a>
for analysis. Also see <a href="bibliography.html#Hoare-74">[Hoare74]</a>
and <a href="bibliography.html#Schmidt-00">[Schmidt
00]</a>.</p>
<h2>8. Why isn't thread cancellation or termination provided?</h2>
<p>There's a valid need for thread termination, so at some point Boost.Threads
probably will include it, but only after we can find a truly safe (and portable)
mechanism for this concept.</p>
<h2>9. Is it safe for threads to share automatic storage duration (stack)
objects via pointers or references?</h2>
<p>Only if you can guarantee that the lifetime of the stack object will not end
while other threads might still access the object. Thus the safest practice
is to avoid sharing stack objects, particularly in designs where threads are
created and destroyed dynamically. Restrict sharing of stack objects to simple
designs with very clear and unchanging function and thread lifetimes. (Suggested
by Darryl Green).</p>
<h2><a name="question10"></a>10. Why has class semaphore disappeared?</h2>
<p>Semaphore was removed as too error prone. The same effect can be achieved with
greater safety by the combination of a mutex and a condition variable.</p>
while other threads might still access the object. Thus the safest practice is
to avoid sharing stack objects, particularly in designs where threads are
created and destroyed dynamically. Restrict sharing of stack objects to simple
designs with very clear and unchanging function and thread lifetimes. (Suggested
by Darryl Green).</p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->04 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39335" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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@@ -1,163 +1,87 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads</title>
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<title>Boost.Threads, Index</title>
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<h1 align="center">Boost.Threads</h1>
<h2 align="center">Index</h2>
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<table border="0" cellpadding="7" cellspacing="0" width="100%">
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<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Documentation Map</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="index">
<dt><a href="overview.html">Overview</a></dt>
<dt><a href="mutex_concept.html">Mutex Concepts</a></dt>
<dl class="index">
<dt><a href="mutex_concept.html#Mutex">Mutex</a></dt>
<dt><a href="mutex_concept.html#TryMutex">TryMutex</a></dt>
<dt><a href="mutex_concept.html#TimedMutex">TimedMutex</a></dt>
</dl>
<dt><a href="lock_concept.html">Lock Concepts</a></dt>
<dl class="index">
<dt><a href="lock_concept.html#Lock">Lock</a></dt>
<dt><a href="lock_concept.html#ScopedLock">ScopedLock</a></dt>
<dt><a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a></dt>
<dt><a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a></dt>
</dl>
<dt>Reference</dt>
<dl class="index">
<dt><a href="barrier.html"><code>&lt;boost/thread/barrier.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="barrier.html#classes">Classes</a></dt>
<dl class="index">
<dt><a href="barrier.html#class-barrier"><code>barrier</code></a></dt>
</dl>
</dl>
<dt><a href="condition.html"><code>&lt;boost/thread/condition.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="condition.html#classes">Classes</a></dt>
<dl class="index">
<dt><a href="condition.html#class-condition"><code>condition</code></a></dt>
</dl>
</dl>
</dl>
<dl class="index">
<dt><a href="exceptions.html"><code>&lt;boost/thread/exceptions.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="exceptions.html#classes">Classes</a></dt>
<dl class="index">
<dt><a href="exceptions.html#class-lock_error"><code>lock_error</code></a></dt>
<dt><a href="exceptions.html#class-thread_resource_error"><code>thread_resource_error</code></a></dt>
</dl>
</dl>
</dl>
<dl class="index">
<dt><a href="mutex.html"><code>&lt;boost/thread/mutex.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="mutex.html#classes">Classes</a></dt>
<dl class="index">
<dt><a href="mutex.html#class-mutex"><code>mutex</code></a></dt>
<dt><a href="mutex.html#class-try_mutex"><code>try_mutex</code></a></dt>
<dt><a href="mutex.html#class-timed_mutex"><code>timed_mutex</code></a></dt>
</dl>
</dl>
</dl>
<dl class="index">
<dt><a href="once.html"><code>&lt;boost/thread/once.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="once.html#macros">Macros</a></dt>
<dl class="index">
<dt><a href="once.html#macro-BOOST_ONCE_INIT"><code>BOOST_ONCE_INIT</code></a></dt>
</dl>
<dt><a href="once.html#types">Types</a></dt>
<dl class="index">
<dt><a href="once.html#type-once_flag"><code>once_flag</code></a></dt>
</dl>
<dt><a href="once.html#functions">Functions</a></dt>
<dl class="index">
<dt><a href="once.html#function-call_once"><code>call_once</code></a></dt>
</dl>
</dl>
</dl>
<dl class="index">
<dt><a href="recursive_mutex.html"><code>&lt;boost/thread/recursive_mutex.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="recursive_mutex.html#classes">Classes</a></dt>
<dl class="index">
<dt><a href="recursive_mutex.html#class-recursive_mutex"><code>recursive_mutex</code></a></dt>
<dt><a href="recursive_mutex.html#class-recursive_try_mutex"><code>recursive_try_mutex</code></a></dt>
<dt><a href="recursive_mutex.html#class-recursive_timed_mutex"><code>recursive_timed_mutex</code></a></dt>
</dl>
</dl>
</dl>
<dl class="index">
<dt><a href="thread.html"><code>&lt;boost/thread/thread.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="thread.html#classes">Classes</a></dt>
<dl class="index">
<dt><a href="thread.html#class-thread"><code>thread</code></a></dt>
<dt><a href="thread.html#class-thread_group"><code>thread_group</code></a></dt>
</dl>
</dl>
</dl>
<dl class="index">
<dt><a href="tss.html"><code>&lt;boost/thread/tss.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="tss.html#classes">Classes</a></dt>
<dl class="index">
<dt><a href="tss.html#class-thread_specific_ptr"><code>thread_specific_ptr</code></a></dt>
</dl>
</dl>
</dl>
<dl class="index">
<dt><a href="xtime.html"><code>&lt;boost/thread/xtime.hpp&gt;</code></a></dt>
<dl class="index">
<dt><a href="xtime.html#values">Values</a></dt>
<dl class="page-index">
<dt><a href="xtime.html#value-spec"><code>TIME_UTC</code></a></dt>
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<dt><a href="xtime.html#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="xtime.html#class-xtime"><code>xtime</code></a></dt>
</dl>
<dt><a href="xtime.html#functions">Functions</a></dt>
<dl class="page-index">
<dt><a href="xtime.html#function-xtime_get"><code>xtime_get</code></a></dt>
</dl>
</dl>
</dl>
<dt><a href="configuration.html">Configuration Information</a></dt>
<dt><a href="build.html">Building and Testing</a></dt>
<dt><a href="introduction.html">Introduction to Design</a></dt>
<dt><a href="rationale.html">Rationale</a></dt>
<dt><a href="definitions.html">Definitions</a></dt>
<dt><a href="faq.html">Frequently Asked Questions (FAQs)</a></dt>
<dt><a href="bibliography.html">Bibliography</a></dt>
<dt><a href="acknowledgments.html">Acknowledgments</a></dt>
</dl>
<ul>
<li><a href="overview.html">Overview</a></li>
<li>Class <a href="semaphore.html">semaphore</a></li>
<li><a href="mutex_concept.html">Mutex Concepts</a></li>
<ul>
<li><a href="mutex_concept.html#Mutex">Mutex</a></li>
<li><a href="mutex_concept.html#TryMutex">TryMutex</a></li>
<li><a href="mutex_concept.html#TimedMutex">TimedMutex</a></li>
</ul>
<li>Mutex Classes</li>
<ul>
<li><a href="mutex.html">mutex / try_mutex / timed_mutex</a></li>
<li><a href="recursive_mutex.html">recursive_mutex / recursive_try_mutex / recursive_timed_mutex</a></li>
</ul>
<li><a href="lock_concept.html">Lock Concepts</a></li>
<ul>
<li><a href="lock_concept.html#Lock">Lock</a></li>
<li><a href="lock_concept.html#ScopedLock">ScopedLock</a></li>
<li><a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a></li>
<li><a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a></li>
</ul>
<li>Lock Classes</li>
<ul>
<li><a href="scoped_lock.html">scoped_lock</a></li>
<li><a href="scoped_try_lock.html">scoped_try_lock</a></li>
<li><a href="scoped_timed_lock.html">scoped_timed_lock</a></li>
</ul>
<li>Class <a href="condition.html">condition</a></li>
<li>Class <a href="thread_specific_ptr.html">thread_specific_ptr</a></li>
<li>Class <a href="thread.html">thread</a></li>
<li>Class <a href="thread_group.html">thread_group</a></li>
<li>Class <a href="xtime.html">xtime</a></li>
<li>Class <a href="lock_error.html">lock_error</a></li>
<li>Class <a href="thread_resource_error.html">thread_resource_error</a></li>
<li>Routine <a href="call_once.html">call_once</a></li>
<li><a href="config.html">Configuration Information</a></li>
<li><a href="introduction.html">Introduction to design</a></li>
<li><a href="rationale.html">Rationale for design decisions</a></li>
<li><a href="definitions.html">Definitions</a></li>
<li><a href="faq.html">Frequently Asked Questions</a></li>
<li><a href="bibliography.html">Bibliography</a></li>
<li><a href="acknowledgements.html">Acknowledgements</a></li>
</ul>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->12 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39332" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p>©<i> Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001</i></p>
<p>Permission to use, copy, modify, distribute and sell this software
and its documentation for any purpose is hereby granted without fee,
provided that the above copyright notice appear in all copies and
that both that copyright notice and this permission notice appear
in supporting documentation. William E. Kempf makes no representations
about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
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<title>Boost.Threads - Introduction to Design</title>
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<title>Boost.Threads, Introduction</title>
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<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
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<h1 align="center">Boost.Threads</h1>
<h2 align="center">Introduction to Design</h2>
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<h1 align="center">Boost.Threads</h1>
<h2 align="center">Introduction</h2>
</td>
</tr>
</table>
<hr>
<dl class="page-index">
<dt><a href="#motivation">Motivation</a></dt>
<dt><a href="#goals">Goals</a></dt>
<dt><a href="#phases">Iterative Phases</a></dt>
<dl class="page-index">
<dt><a href="#phase1">Phase 1, Synchronization Primitives</a></dt>
<dt><a href="#phase2">Phase 2, Thread Management and Thread Specific Storage</a></dt>
<dt><a href="#next-phase">The Next Phase</a></dt>
</dl>
</dl>
<h2><a name="motivation"></a>Motivation</h2>
<p>With client/server and three-tier architectures becoming common place in today&#39;s
world, it&#39;s becoming increasingly important for programs to be able to handle
parallel processing. Modern day operating systems usually provide some support
for this through native thread APIs. Unfortunately, writing portable code that
makes use of parallel processing in C++ is made very difficult by a lack of
a standard interface for these native APIs. Further, these APIs are almost universally
C APIs and fail to take advantage of C++&#39;s strengths, or to address C++&#39;s
issues.</p>
<p>The <b>Boost.Threads</b> library is an attempt to define a portable interface
for writing parallel processes in C++.</p>
<h2><a name="goals"></a>Goals</h2>
<p>The <b>Boost.Threads</b> library has several goals that should help to set
it apart from other solutions. These goals are listed in order of precedence
with full descriptions below.</p>
<h3>Motivation</h3>
<p>With client/server and three-tier architectures becoming common place in today's
world, it's becoming increasingly important for programs to be able to handle parallel
processing. Modern day operating systems usually provide some support for this
through native thread APIs. Unfortunately, writing portable code that makes use
of parallel processing in C++ is made very difficult by a lack of a standard interface
for these native APIs. Further, these APIs are almost universally C APIs and fail to
take advantage of C++'s strengths, or to address C++'s issues.</p>
<p>The <b>Boost.Threads</b> library is an attempt to define a portable interface for writing
parallel processes in C++.</p>
<h3>Goals</h3>
<p>The <b>Boost.Threads</b> library has several goals that should help to set it apart from
other solutions. These goals are listed in order of precedence with full descriptions
below.<p>
<ul>
<li> <b>Portability</b>
<p><b>Boost.Threads</b> was designed to be highly portable. The goal is for
the interface to be easily implemented on any platform that supports threads,
and possibly even on platforms without native thread support.</p>
</li>
<li> <b>Safety</b>
<p><b>Boost.Threads</b> was designed to be as safe as possible. Writing <a href="definitions.html#Thread-safe">thread-safe</a>
code is very difficult and successful libraries must strive to insulate
the programmer from dangerous constructs as much as possible. This is accomplished
in several ways:</p>
<ul>
<li>
<p align="left">C++ language features are used make correct usage easy
(if possible, the default) and error-prone impossible or at least more
difficult. For example, see the <a href="mutex_concept.html">Mutex</a>
and <a href="lock_concept.html">Lock</a> designs, and how note how they
interact.</p>
</li>
<li>
<p align="left">Certain traditional concurrent programming features are
considered so error-prone that they are not provided at all. For example,
see the <a
href="rationale.html#Events">Events Not Provided</a> rationale.</p>
</li>
<li>
<p align="left">Dangerous features, or features which may be misused,
are identified as such in the documentation to make users aware of potential
pitfalls.</p>
</li>
</ul>
</li>
<li> <b>Flexibility</b>
<p><b>Boost.Threads</b> was designed to be flexible. This goal is often at
odds with <i>safety</i>. When functionality might be compromised by the
desire to keep the interface safe, <b> Boost.Threads</b> has been designed
to provide the functionality, but to make it&#39;s use prohibitive for general
use. In other words, the interfaces have been designed such that it's usually
obvious when something is unsafe, and the documentation is written to explain
why.</p>
</li>
<li> <b>Efficiency</b>
<p><b>Boost.Threads</b> was designed to be as efficient as possible. When
building a library on top of another library there is always a danger that
the result will be so much slower than the &quot;native&quot; API that programmers
are inclined to ignore the higher level API. <b>Boost.Threads</b> was designed
to minimize the chances of this occurring. The interfaces have been crafted
to allow an implementation the greatest chance of being as efficient as
possible. This goal is often at odds with the goal for <i>safety</i>. Every
effort was made to ensure efficient implementations, but when in conflict
<i>safety</i> has always taken precedence.</p>
</li>
<li><b>Portability</b>
<p><b>Boost.Threads</b> was designed to be highly portable. The goal is for the
interface to be easily implemented on any platform that supports threads,
and possibly even on platforms without native thread support.</p>
<li><b>Safety</b>
<p><b>Boost.Threads</b> was designed to be as safe as possible. Writing
<a href="definitions.html#Thread-safe">thread-safe</a>
code is very difficult and successful libraries must strive to insulate
the programmer from dangerous constructs as much as possible. This is accomplished
in several ways:</p>
<ul>
<li><p align="left">C++ language features are used make correct usage easy (if possible,
the default) and error-prone impossible or at least more difficult.
For example, see the <a href="mutex_concept.html">Mutex</a> and <a href="lock_concept.html">Lock</a>
designs, and how note how they interact.</p></li>
<li>
<p align="left">Certain traditional concurrent programming features
are considered so error-prone that they are not provided at all. For
example, see the <a href="rationale.html#Events">Events Not Provided</a>
rationale.</p>
</li>
<li>
<p align="left">Dangerous features, or features which may be misused,
are identified as such in the documentation to make users aware of
potential pitfalls. For example, see <a href="semaphore.html#Danger">Semaphore</a>.</p>
</li>
</ul>
<li><b>Flexibility</b>
<p><b>Boost.Threads</b> was designed to be flexible. This goal is often at odds
with <i>safety</i>. When functionality might be compromised by the desire
to keep the interface safe, <b>Boost.Threads</b> has been designed to provide
the functionality, but to make it's use prohibitive for general use.</p>
<li><b>Efficiency</b>
<p><b>Boost.Threads</b> was designed to be as efficient as possible. When building
a library on top of another library there is always a danger that the result
will be so much slower than the "native" API that programmers are inclined
to ignore the higher level API. <b>Boost.Threads</b> was designed to minimize the
chances of this occurring. The interfaces have been crafted to allow an
implementation the greatest chance of being as efficient as possible. This
goal is often at odds with the goal for <i>safety</i>. Every effort was made to
ensure efficient implementations, but when in conflict <i>safety</i> has always taken
precedence.</p>
</li>
</ul>
<h2><a name="phases"></a>Iterative Phases</h2>
<p>Another goal of <b>Boost.Threads</b> was to take a dynamic, iterative approach
in its development. The computing industry is still exploring the concepts of
parallel programming. Most thread libraries supply only simple primitive concepts
for thread synchronization. These concepts are very simple, but they are very
difficult to use safely or to provide formal proofs for constructs built on
top of them. There has been a lot of research in other concepts, such as in
&quot;Communicating Sequential Processes.&quot; <b>Boost.Threads</b> was designed
in iterative steps, providing the building blocks necessary for the next step,
and giving the researcher the tools necessary to explore new concepts in a portable
manner.</p>
<p>Given the goal of following a dynamic, iterative approach <b> Boost.Threads</b>
shall go through several growth cycles. Each phase in its development shall
be roughly documented here.</p>
<h3><a name="phase1"></a>Phase 1, Synchronization Primitives</h3>
<p>Boost is all about providing high quality libraries with implementations for
many platforms. Unfortunately, there&#39;s a big problem faced by developers
wishing to supply such high quality libraries, namely thread-safety. The C++
standard doesn&#39;t address threads at all, but real world programs often make
use of native threading support. A portable library that doesn&#39;t address
the issue of thread-safety is there for not much help to a programmer who wants
to use the library in his multithreaded application. So there&#39;s a very great
need for portable primitives that will allow the library developer to create
<a href="definitions.html#Thread-safe"> thread-safe</a> implementations. This
need far out weighs the need for portable methods to create and manage threads.</p>
<p>Because of this need, the first phase of <b>Boost.Threads</b> focuses solely
on providing portable primitive concepts for thread synchronization. Types provided
in this phase include the <a href="mutex.html"> mutex/try_mutex/timed_mutex</a>,
<a href="recursive_mutex.html"> recursive_mutex/recursive_try_mutex/recursive_timed_mutex</a>
and <a href="exceptions.html#class-lock_error">lock_error</a>. These are considered
the &quot;core&quot; synchronization primitives, though there are others that
will be added in later phases.</p>
<h3><a name="phase2"></a>Phase 2, Thread Management and Thread Specific Storage</h3>
<p>This phase addresses the creation and management of threads and provides a
mechanism for thread specific storage (data associated with a thread instance).
Thread management is a tricky issue in C++, so this phase addresses only the
basic needs of multithreaded program. Later phases are likely to add additional
functionality in this area. This phase of <b>Boost.Threads</b> adds the <a href="thread.html">thread</a>
and <a href="tss.html#class-thread_specific_ptr">thread_specific_ptr</a> types.
With these additions the <b>Boost.Threads</b> library can be considered minimal
but complete.</p>
<h3><a name="next-phase"></a>The Next Phase</h3>
<p>The next phase will address more advanced synchronization concepts, such as
read/write mutexes and barriers.</p>
<h3>Iterative Phases</h3>
<p>Another goal of <b>Boost.Threads</b> was to take a dynamic, iterative
approach in its development. The computing industry is still exploring the concepts of parallel programming.
Most thread libraries supply only simple primitive concepts for thread synchronization.
These concepts are very simple, but they are very difficult to use safely or to provide
formal proofs for constructs built on top of them. Until recently, these primitives
were "state of the art" and the only concepts available to programmers. Recently
there has been a lot of research in other concepts, such as in "Communicating Sequential
Processes." <b>Boost.Threads</b> was designed in iterative steps, providing the building
blocks necessary for the next step, and giving the researcher the tools necessary to
explore new concepts in a portable manner.</p>
<p>Given the goal of following a dynamic, iterative approach <b>Boost.Threads</b> shall go through
several growth cycles. Each phase in its development shall be roughly documented here.</p>
<h4>Phase 1, Synchronization Primitives</h4>
<p>Boost is all about providing high quality libraries with implementations for many platforms.
Unfortunately, there's a big problem faced by developers wishing to supply such high quality
libraries, namely thread-safety. The C++ standard doesn't address threads at all, but real
world programs often make use of native threading support. A portable library that doesn't
address the issue of thread-safety is there for not much help to a programmer who wants to
use the library in his multi-threaded application. So there's a very great need for portable
primitives that will allow the library developer to create <a href="file:///c:/boost/site/libs/thread/doc/definitions.html#Thread-safe">thread-safe</a>
implementations. This
need far out weighs the need for portable methods to create and manage threads.</p>
<p>Because of this need, the first phase of <b>Boost.Threads</b> focuses solely on providing
portable primitive concepts for thread synchronization. Types provided in this phase include
the <A href="semaphore.html">semaphore</a>, <A href="mutex.html">mutex/try_mutex/timed_mutex</a>,
<A href="recursive_mutex.html">recursive_mutex/recursive_try_mutex/recursive_timed_mutex</a>,
<A href="scoped_lock.html">scoped_lock</a>, <A href="scoped_try_lock.html">scoped_try_lock</a>,
<A href="scoped_timed_lock.html">scoped_timed_lock</a> and <A href="lock_error.html">lock_error</a>.
These are considered the "core" synchronization primitives, though there are others that will
be added in later phases.</p>
<h4>Phase 2, Thread Management and Thread Specific Storage</h4>
<p>This phase addresses the creation and management of threads and provides a mechanism for
thread specific storage (data associated with a thread instance). Thread management is a tricky
issue in C++, so this phase addresses only the basic needs of multi-threaded program. Later
phases are likely to add additional functionality in this area. This phase of <b>Boost.Threads</b>
adds the <A href="thread.html">thread</a> and
<A href="thread_specific_ptr.html">thread_specific_ptr</a> types. With these additions
the <b>Boost.Threads</b> library can be considered minimal but complete.</p>
<h4>The Next Phase</h4>
<p>The next phase will address more advanced synchronization concepts, such as read/write mutexes
and barriers.</p>
<hr>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->03 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39333" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
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<title>Boost.Threads - ScopedLock Concept</title>
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, Lock Concept</title>
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<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">ScopedLock Concept</h2>
</td>
</tr>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
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<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Lock Concepts</h2>
</td>
</tr>
</table>
<hr>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#concept-requirements">Concept Requirements</a></dt>
<dl class="page-index">
<dt><a href="#Lock-concept">Lock Concept</a></dt>
<dt><a href="#ScopedLock-concept">ScopedLock Concept</a></dt>
<dt><a href="#ScopedTryLock-concept">ScopedTryLock Concept</a></dt>
<dt><a href="#ScopedTimedLock-concept">ScopedTimedLock Concept</a></dt>
</dl>
</dl>
<h2><a name="introduction"></a>Introduction</h2>
<p>A lock object provides a safe means for locking and unlocking a mutex object
(an object whose type is a model of <a href="mutex_concept.html">Mutex</a> or
one of its refinements). In other words they are an implementation of the <i>Scoped
Locking</i> <a href="bibliography.html#Schmidt-00">[Schmidt 00]</a> pattern.
The <a href="#ScopedLock-concept">ScopedLock</a> concept, with <a href="#ScopedTryLock-concept">ScopedTryLock</a>
and <a href="#ScopedTimedLock-concept">ScopedTimedLock</a> refinements, formalize
the requirements.</p>
<p>Lock objects are constructed with a reference to a mutex object and typically
acquire ownership of the mutex object by setting its state to locked. They also
ensure ownership is relinquished in the destructor. Lock objects also expose
functions to query the lock status and to manually lock and unlock the mutex
object.</p>
<p>Lock objects are meant to be short lived, expected to be used at block scope
only. The lock objects are not <a href="definitions.html#definition-thread-safe">thread-safe</a>.
Lock objects must maintain state to indicate whether or not they&#39;ve been
locked and this state is not protected by any synchronization concepts. For
this reason a lock object should never be shared between multiple threads.</p>
<h2><a name="concept-requirements"></a>Concept Requirements</h2>
<h3><a name="Lock-concept"></a>Lock Concept</h3>
<p>For a Lock type <code>L</code> and an object <code>lk</code> and const object
<code>clk</code> of that type, the following expressions must be well-formed
and have the indicated effects.</p>
<table summary="Lock expressions" border="1" cellpadding="5">
<p><a href="#Introduction">Introduction</a><br>
<a href="#Requirements">Concept Requirements</a><br>
<a href="#Lock">Lock Concept</a><br>
<a href="#ScopedLock">ScopedLock Concept</a><br>
<a href="#ScopedTryLock">ScopedTryLock Concept</a><br>
<a href="#ScopedTimedLock">ScopedTimedLock Concept</a><br>
<a href="#Models">Models</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The lock concepts provide exception safe means for locking and unlocking a
<a href="mutex_concept.html">mutex model</a>. In other words they are an
implementation of the <i>Scoped Locking</i>
<a href="bibliography.html#Schmidt 00">[Schmidt 00]</a> pattern. The
<a href="#ScopedLock">ScopedLock</a> concept, with
<a href="#ScopedTryLock">ScopedTryLock</a> and
<a href="#ScopedTimedLock">ScopedTimedLock</a> refinements, formalize the
requirements.</p>
<p>Lock models are constructed with a reference to a
<a href="mutex_concept.html">mutex model</a> and typically acquire ownership of the
<a href="mutex_concept.html">mutex model</a> by setting its state to locked. They also
ensure ownership is relinquished in the destructor. Lock models also expose functions
to query the lock status and to manually lock and unlock the
<a href="mutex_concept.html">mutex model</a>.</p>
<p>Instances of lock models are meant to be short lived, expected to be used at block
scope only. The lock models are not
<a href="definitions.html#Thread-safe">thread-safe</a>. Lock models must maintain state
to indicate whether or not they've been locked and this state is not protected by any
synchronization concepts. For this reason an instance of a lock model should never be
shared between multiple threads.</p>
<h2>Concept <a name="Requirements">Requirements</a></h2>
<p>[For documentation purposes, portions of the concept requirements are
repeated in the documentation for specific lock classes. Those copies need
to be kept in sync with the requirements here.]</p>
<h3><a name="Lock">Lock</a> Concept</h3>
<p>For a <a href="#ScopedLock"> ScopedLock</a>,
<a href="#ScopedTryLock">ScopedTryLock</a>, or
<a href="#ScopedTimedLock">ScopedTimedLock</a> type <code>L</code> and an object
<code>lk</code> and const object <code>clk</code> of that type, the following expressions
must be well-formed and have the indicated effects.</p>
<p>The Lock concept is used as a base for the <a href="#ScopedLock">ScopedLock</a>,
<a href="#ScopedTryLock">ScopedTryLock</a>, and
<a href="#ScopedTimedLock">ScopedTimedLock</a> refinements. The associated mutex type
is as specified for each of those refinements respectively.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
@@ -62,133 +85,158 @@
</tr>
<tr>
<td valign="top"><code>(&amp;clk)-&gt;operator const void*()</code></td>
<td>Returns type void*, non-zero if if the associated mutex object has been
locked by <code>clk</code>, otherwise 0.</td>
<td>Returns type void*, non-zero if if the associated mutex has been locked
by <code>clk</code>, otherwise 0.</td>
</tr>
<tr>
<td valign="top"><code>clk.locked()</code></td>
<td>Returns a <code>bool</code>, <code>(&amp;clk)-&gt;operator const void*()
!= 0</code></td>
<td>Returns a <code>bool</code>, <code>(&amp;clk)-&gt;operator const void*() != 0</code></td>
</tr>
<tr>
<td valign="top"><code>lk.lock()</code></td>
<td>Throws <code>lock_error</code> if <code>locked()</code>. If the associated
mutex object is already locked by some other thread, places the current
thread in the <a href="definitions.html#State">Blocked</a> state until the
associated mutex is unlocked, after which the current thread is placed in
the <a href="definitions.html#State"> Ready</a> state, eventually to be
returned to the <a href="definitions.html#State">Running</a> state. If the
associated mutex object is already locked by the same thread the behavior
is dependent on the <a href="mutex_concept.html#locking-strategies">locking
strategy</a> of the associated mutex object.<br>
Postcondition: <code>locked() == true</code></td>
<td>Throws lock_error if locked(). If the associated mutex is already locked by some other
thread, places the current thread in the
<a href="definitions.html#State">Blocked</a> state until the associated mutex is
unlocked, after which the current thread is placed in the
<a href="definitions.html#State">Ready</a> state, eventually to be returned to the
<a href="definitions.html#State">Running</a> state.<br>
Postcondition: locked()</td>
</tr>
<tr>
<td valign="top"><code>lk.unlock()</code></td>
<td>If <code>!locked()</code>, throws <code>lock_error</code>, otherwise unlocks
the associated mutex.<br>
Postcondition: <code>!locked()</code></td>
<td>If !locked(), throws lock_error, otherwise unlocks the associated mutex.<br>
Postcondition: !locked()</td>
</tr>
</table>
<h3><a name="ScopedLock-concept"></a>ScopedLock Concept</h3>
<p>A ScopedLock is a refinement of <a href="#Lock">Lock</a>. For a ScopedLock
type <code>L</code> and an object <code>lk</code> of that type, and an object
<code>m</code> of a type meeting the <a href="mutex_concept.html#Mutex-concept">Mutex</a>
requirements, and an object <code>b</code> of type <code>bool</code>, the following
expressions must be well-formed and have the indicated effects.</p>
<table summary="ScopedLock expressions" border="1" cellpadding="5">
<h3><a name="ScopedLock">ScopedLock</a> Concept</h3>
<p>A ScopedLock must meet the <a href="#Lock">Lock</a> requirements. For a ScopedLock
type <code>L</code> and an object <code>lk</code> of that type,
and an object <code>m</code> of a type meeting the
<a href="mutex_concept.html#Mutex">Mutex</a> requirements, and an object <code>b</code>
of type <code>bool</code>, the following expressions must be well-formed and have the
indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top"><code>L lk(m);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex object <code>m</code>
with it, then calls <code>lock()</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then calls <code>lock()</code></td>
</tr>
<tr>
<td valign="top"><code>L lk(m,b);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex object <code>m</code>
with it, then if <code>b</code>, calls <code>lock()</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then if <code>b</code>, calls <code>lock()</code></td>
</tr>
</table>
<h3><a name="ScopedTryLock-concept"></a>ScopedTryLock Concept</h3>
<p>A ScopedTryLock is a refinement of <a href="#Lock-concept">Lock</a>. For a
ScopedTryLock type <code>L</code> and an object <code>lk</code> of that type,
and an object <code>m</code> of a type meeting the <a href="mutex_concept.html#TryMutex-concept">TryMutex</a>
requirements, and an object <code>b</code> of type <code>bool</code>, the following
expressions must be well-formed and have the indicated effects.</p>
<table summary="ScopedTryLock expressions" border="1" cellpadding="5">
<h3><a name="ScopedTryLock">ScopedTryLock</a> Concept</h3>
<p>A ScopedTryLock must meet the <a href="#Lock">Lock</a> requirements. For a
ScopedTryLock type <code>L</code> and an object <code>lk</code> of that type,
and an object <code>m</code> of a type meeting the
<a href="mutex_concept.html#TryMutex">TryMutex</a> requirements, and an object
<code>b</code> of type <code>bool</code>, the following expressions must be well-formed
and have the indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top"><code>L lk(m);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex object <code>m</code>
with it, then calls <code>try_lock()</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then calls <code>try_lock()</code></td>
</tr>
<tr>
<td valign="top"><code>L lk(m,b);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex object <code>m</code>
with it, then if <code>b</code>, calls <code> lock()</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then if <code>b</code>, calls <code>lock()</code></td>
</tr>
<tr>
<td valign="top"><code>lk.try_lock()</code></td>
<td>If locked(), throws <code>lock_error</code>. Makes a non-blocking attempt
to lock the associated mutex object, returning <code>true</code> if the
lock attempt is successful, otherwise <code>false</code>. If the associated
mutex object is already locked by the same thread the behavior is dependent
on the <a href="mutex_concept.html#locking-strategies">locking strategy</a>
of the associated mutex object.</td>
<td>If locked(), throws <code>lock_error</code>. Makes a non-blocking attempt to
lock the associated mutex, returning <code>true</code> if the lock attempt is
successful, otherwise <code>false</code>.</td>
</tr>
</table>
<h3><a name="ScopedTimedLock-concept"></a>ScopedTimedLock Concept</h3>
<p>A ScopedTimedLock is a refinement of <a href="#Lock">Lock</a>. For a ScopedTimedLock
type <code>L</code> and an object <code>lk</code> of that type, and an object
<code>m</code> of a type meeting the <a href="mutex_concept.html#TimedMutex">TimedMutex</a>
requirements, and an object <code>b</code> of type <code>bool</code>, and an
object <code>t</code> of type <code><a href="xtime.html"> xtime</a></code>,
the following expressions must be well-formed and have the indicated effects.</p>
<table summary="ScopedTimedLock expressions" border="1" cellpadding=
"5">
<h3><a name="ScopedTimedLock">ScopedTimedLock</a> Concept</h3>
<p>A ScopedTimedLock must meet the <a href="#Lock">Lock</a> requirements. For a
ScopedTimedLock type <code>L</code> and an object <code>lk</code> of that type,
and an object <code>m</code> of a type meeting the
<a href="mutex_concept.html#TimedMutex">TimedMutex</a> requirements, and an object
<code>b</code> of type <code>bool</code>, and an object <code>t</code> of type
<code><a href="xtime.html">xtime</a></code>, the following expressions must be well-formed and have the indicated
effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top"><code>L lk(m,t);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex object <code>m</code>
with it, then calls <code> timed_lock(t)</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then calls <code>timed_lock(t)</code></td>
</tr>
<tr>
<td valign="top"><code>L lk(m,b);</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex object <code>m</code>
with it, then if <code>b</code>, calls <code> lock()</code></td>
<td>Constructs an object <code>lk</code>, and associates mutex <code>m</code> with
it, then if <code>b</code>, calls <code>lock()</code></td>
</tr>
<tr>
<td valign="top"><code>lk.timed_lock(t)</code></td>
<td>If locked(), throws lock_error. Makes a blocking attempt to lock the associated
mutex object, and returns <code>true</code> if successful within the specified
time <code>t</code>, otherwise <code>false</code>. If the associated mutex
object is already locked by the same thread the behavior is dependent on
the <a href="mutex_concept.html#locking-strategies">locking strategy</a>
of the associated mutex object.</td>
<td>If locked(), throws lock_error. Makes a blocking attempt to lock the
associated mutex, and returns <code>true</code> if successful within the specified
time <code>t</code>, otherwise <code>false</code>.</td>
</tr>
</table>
<h2><a name="Models">Models</a></h2>
<p><b>Boost.Threads</b> currently supplies three classes which model lock concepts.</p>
<p>These classes are normally accessed via typedefs of the same name supplied by
a <a href="mutex_concept.html">mutex model</a>.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Concept</b></td>
<td><b>Refines</b></td>
<td><b>Classes Modeling the Concept</b></td>
</tr>
<tr>
<td><a href="#ScopedLock">ScopedLock</a></td>
<td>&nbsp;</td>
<td><a href="scoped_lock.html">scoped_lock</a></td>
</tr>
<tr>
<td><a href="#ScopedTryLock">ScopedTryLock</a></td>
<td><a href="#ScopedLock">ScopedLock</a></td>
<td><a href="scoped_try_lock.html">scoped_try_lock</a> </td>
</tr>
<tr>
<td><a href="#ScopedTimedLock">ScopedTimedLock</a></td>
<td><a href="#ScopedLock">ScopedLock</a></td>
<td><a href="scoped_timed_lock.html">scoped_timed_lock</a></td>
</tr>
</table>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->04 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39335" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, lock_error</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">lock_error</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <tt>lock_error</tt> class defines an exception type thrown to indicate a
locking related error has been detected. Examples of such errors include a lock
operation which can be determined to result in a deadlock, or unlock operations
attempted by a thread that does not own the lock.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost
class lock_error : public std::runtime_error
{
public:
lock_error();
};
}
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
lock_error();
</pre>
<p>Constructs a <tt>lock_error</tt> object.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
int main(int, char*[])
{
boost::mutex mutex;
boost::mutex::scoped_lock scoped_lock(mutex);
try
{
boost::mutex::scoped_lock deadlock(mutex);
std::cout &lt;&lt; &quot;lock succeeded&quot; &lt;&lt; std::endl;
}
catch (boost::lock_error&amp; err)
{
std::cout &lt;&lt; err.what() &lt;&lt; &quot; - deadlock occurred.&quot; &lt;&lt; std::endl;
}
return 0;
}
</pre>
<p>The output is:</p>
<pre>
thread lock error - deadlock occurred.
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->10 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39328" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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@@ -1,243 +1,319 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/mutex.hpp&gt;</title>
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, mutex</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/mutex.hpp">boost/thread/mutex.hpp</a>&gt;</h2>
</td>
</tr>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG alt="C++ Boost" src="../../../c++boost.gif" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">mutex<br>
try_mutex<br>
timed_mutex</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-mutex">Class <code>mutex</code></a></dt>
<dl class="page-index">
<dt><a href="#class-mutex-synopsis">Class <code>mutex</code> synopsis</a></dt>
<dt><a href="#class-mutex-ctors">Class <code>mutex</code> constructors and
destructor</a></dt>
</dl>
</dl>
<dl class="page-index">
<dt><a href="#class-try_mutex">Class <code>try_mutex</code></a></dt>
<dl class="page-index">
<dt><a href="#class-try_mutex-synopsis">Class <code>try_mutex</code> synopsis</a></dt>
<dt><a href="#class-try_mutex-ctors">Class <code>try_mutex</code> constructors
and destructor</a></dt>
</dl>
</dl>
<dl class="page-index">
<dt><a href="#class-timed_mutex">Class <code>timed_mutex</code></a></dt>
<dl class="page-index">
<dt><a href="#class-timed_mutex-synopsis">Class <code>timed_mutex</code>
synopsis</a></dt>
<dt><a href="#class-timed_mutex-ctors">Class <code>timed_mutex</code> constructors
and destructor</a></dt>
</dl>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>Include the header &lt;<a href="../../../boost/thread/mutex.hpp">boost/thread/mutex.hpp</a>&gt;
to define the <code><a href="#mutex Synopsis">mutex</a></code>, <code><a href=
"#try_mutex Synopsis">try_mutex</a></code> and <code><a href=
"#timed_mutex Synopsis">timed_mutex</a></code> classes.</p>
<p>The <code><a href="#mutex Synopsis">mutex</a></code>, <code><a href=
"#try_mutex Synopsis">try_mutex</a></code> and <code><a href=
"#timed_mutex Synopsis">timed_mutex</a></code> classes are models of <a href="mutex_concept.html#Mutex-concept">Mutex</a>,
<a href="mutex_concept.html#TryMutex-concept">TryMutex</a>, and <a href="mutex_concept.html#TimedMutex-concept">TimedMutex</a>
respectively. These types should be used to non-recursively synchronize access
to shared resources. For recursive locking mechanics, see the <a href="recursive_mutex.html">recursive
mutexes</a> supplied by <b>Boost.Threads</b>.</p>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#mutex Synopsis">Class mutex Synopsis</a><br>
<a href="#mutex Members">Class mutex Members</a><br>
<a href="#try_mutex Synopsis">Class try_mutex Synopsis</a><br>
<a href="#try_mutex Members">Class try_mutex Members</a><br>
<a href="#timed_mutex Synopsis">Class timed_mutex Synopsis</a><br>
<a href="#timed_mutex Members">Class timed_mutex Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <tt><a href="#mutex Synopsis">mutex</a></tt>, <tt><a href="#try_mutex Synopsis">try_mutex</a></tt> and <tt><a href="#timed_mutex Synopsis">timed_mutex</a></tt> classes define full featured
models of the <a href="mutex_concept.html#Mutex">Mutex</a>, <a href="mutex_concept.html#TryMutex">TryMutex</a>,
and <a href="mutex_concept.html#TimedMutex">TimedMutex</a> concepts. These types should be used to
non-recursively synchronize access to
shared resources. For recursive locking mechanics, see <a href="recursive_mutex.html">recursive
mutexes</a>.</p>
<p>Each class supplies one or more typedefs for lock types which model matching
lock concepts. For the best possible performance you should use the mutex class
that supports the minimum set of lock types that you need.</p>
<table summary="lock types" border="1" cellpadding="5">
lock concepts. For the best possible performance you should use the mutex class that supports
the minimum set of lock
types that you need.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Mutex Class</b></td>
<td><b>Lock name</b></td>
<td><b>Lock Concept</b></td>
<td><b>Implementation defined Lock Type</b></td>
<td><b>&nbsp;Lock Concept</b></td>
</tr>
<tr>
<td valign="top"><a href="#mutex Synopsis"><code> mutex</code></a></td>
<td valign="top"><a href="#mutex Synopsis"><code>mutex</code></a></td>
<td valign="middle"><code>scoped_lock</code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock"> ScopedLock</a></td>
<td valign="middle"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;mutex&gt;</code></a></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a></td>
</tr>
<tr>
<td valign="top"><code><a href="#try_mutex Synopsis"> try_mutex</a></code>
</td>
<td valign="top"><tt><a href="#try_mutex Synopsis">try_mutex</a></tt> </td>
<td valign="middle"><code>scoped_lock<br>
scoped_try_lock</code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock"> ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock"> ScopedTryLock</a></td>
<td valign="middle"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;try_mutex&gt;<br>
</code></a><code><a href="scoped_try_lock.html">boost::detail::thread::scoped_try_lock&lt;try_mutex&gt;</a></code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a></td>
</tr>
<tr>
<td valign="top"><code><a href="#timed_mutex Synopsis"> timed_mutex</a></code>
</td>
<td valign="top"><code><a href="#timed_mutex Synopsis">timed_mutex</a></code> </td>
<td valign="middle"><code>scoped_lock<br>
scoped_try_lock<br>
scoped_timed_lock</code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock"> ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock"> ScopedTryLock</a><br>
<a href="lock_concept.html#ScopedTimedLock"> ScopedTimedLock</a></td>
<td valign="middle"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;timed_mutex&gt;</code></a><br>
<code><a href="scoped_try_lock.html">boost::</a></code><a href="scoped_try_lock.html"><code>detail::thread::scoped_try_lock&lt;timed_mutex&gt;</code></a><br>
<code><a href="scoped_timed_lock.html">boost::</a></code><a href="scoped_timed_lock.html"><code>detail::thread::scoped_timed_lock&lt;timed_mutex&gt;</code></a></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a><br>
<a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a></td>
</tr>
</table>
<p>The <code>mutex</code>, <code>try_mutex</code> and <code>timed_mutex</code>
classes use an <code>Unspecified</code> <a href="mutex_concept.html#LockingStrategies">locking
strategy</a>, so attempts to recursively lock them or attempts to unlock them
by threads that don&#39;t own a lock on them result in <b>undefined behavior</b>.
This strategy allows implementations to be as efficient as possible on any given
platform. It is, however, recommended that implementations include debugging
support to detect misuse when <code>NDEBUG</code> is not defined.</p>
<p>Like all the <b>Boost.Threads</b> <a href="mutex_concept.html">mutex models</a>,
the <code>mutex</code>, <code>try_mutex</code> and <code> timed_mutex</code>
leave the <a href="mutex_concept.html#SchedulingPolicies">scheduling policy</a>
as <code> Unspecified</code>. Programmers should make no assumptions about the
order in which waiting threads acquire a lock.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-mutex"></a>Class <code>mutex</code></h3>
<p>The <code>mutex</code> class is a model of <a href="mutex_concept.html#Mutex-concept">Mutex</a>
and <a href="overview.html#non-copyable">NonCopyable</a>, and provides no additional
facilities beyond the requirements of these concepts.</p>
<h4><a name="class-mutex-synopsis"></a>Class <code>mutex</code> synopsis</h4>
<p>The <tt>mutex</tt>, <tt>try_mutex</tt> and <tt>timed_mutex</tt> classes use an <tt>Unspecified</tt>
<A href="mutex_concept.html#LockingStrategies">locking strategy</a>, so attempts to recursively lock
them or attempts to unlock them by threads that don't own a lock on them result in <b>undefined behavior</b>.
This strategy allows implementations to be as efficient as possible on any given platform. It is, however,
recommended that implementations include debugging support to detect misuse when <tt>NDEBUG</tt> is
not defined.</p>
<p>Like all the <b>Boost.Threads</b> <A href="mutex_concept.html">mutex models</a>, the <tt>mutex</tt>,
<tt>try_mutex</tt> and <tt>timed_mutex</tt> leave the
<A href="mutex_concept.html#SchedulingPolicies">scheduling policy</a> as <tt>Unspecified</tt>.
Programmers should assume that threads waiting for a lock on objects of these types
acquire
the lock in a random order, even though the specific behavior for a given platform may be different.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
</pre>
<h2>Class <a name="mutex Synopsis"> mutex Synopsis</a></h2>
<pre>
namespace boost
{
class mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class mutex meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
// Class mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
mutex();
~mutex();
};
};
}
</pre>
<h4><a name="class-mutex-ctors"></a>Class <code>mutex</code> constructors and
destructor</h4>
<h2>
Class <a name="mutex Members">mutex Members</a>
</h2>
<hr>
<h3>Constructor</h3>
<pre>
mutex();
mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~mutex();
~mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in an unlocked sate.</dt>
<dt><b>Danger:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</dt>
</dl>
<h3><a name="class-try_mutex"></a>Class <code>try_mutex</code></h3>
<p>The <code>try_mutex</code> class is a model of <a href="mutex_concept.html#TryMutex-concept">TryMutex</a>
and <a href="overview.html#non-copyable">NonCopyable</a>, and provides no additional
facilities beyond the requirements of these concepts.</p>
<h4><a name="class-try_mutex-synopsis"></a>Class <code>try_mutex</code> synopsis</h4>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</p>
<hr>
<h2>
Class <a name="try_mutex Synopsis">try_mutex Synopsis</a>
</h2>
<pre>
namespace boost
{
class try_mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class try_mutex meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
class try_mutex : private boost::noncopyable // Exposition only.
// Class try_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
Public:
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_try_lock;
try_mutex();
~try_mutex();
};
};
}
</pre>
<h4><a name="class-try_mutex-ctors"></a>Class <code>try_mutex</code> constructors
and destructor</h4>
<h2>Class <a name="try_mutex Members">try_mutex Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
try_mutex();
try_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~try_mutex();
~try_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in an unlocked sate.</dt>
<dt><b>Danger:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</dt>
</dl>
<h3><a name="class-timed_mutex"></a>Class <code>timed_mutex</code></h3>
<p>The <code>timed_mutex</code> class is a model of <a href="mutex_concept.html#TimedMutex-concept">TimedMutex</a>
and <a href="overview.html#non-copyable">NonCopyable</a>, and provides no additional
facilities beyond the requirements of these concepts.</p>
<h4><a name="class-timed_mutex-synopsis"></a>Class <code>timed_mutex</code> synopsis</h4>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</p>
<hr>
<h2>
Class <a name="timed_mutex Synopsis">timed_mutex Synopsis</a>
</h2>
<pre>
namespace boost
{
class timed_mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class timed_mutex meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
class timed_mutex : private boost::noncopyable // Exposition only.
// Class timed_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
Public:
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_try_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_timed_lock;
timed_mutex();
~timed_mutex();
};
}
</pre>
<h2>Class <a name="timed_mutex Members">timed_mutex Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
timed_mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~timed_mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
boost::mutex io_mutex; // The iostreams are not guaranteed to be <a href="file:///c:/boost/site/libs/thread/doc/definitions.html#Thread-safe">thread-safe</a>!
class counter
{
public:
counter() : count(0) { }
int increment() {
boost::mutex::scoped_lock scoped_lock(mutex);
return ++count;
}
private:
boost::mutex mutex;
int count;
};
counter c;
void change_count(void*)
{
int i = c.increment();
boost::mutex::scoped_lock scoped_lock(io_mutex);
std::cout &lt;&lt; &quot;count == &quot; &lt;&lt; i &lt;&lt; std::endl;
}
int main(int, char*[])
{
const int num_threads = 4;
boost::thread_group thrds;
for (int i=0; i &lt; num_threads; ++i)
thrds.create_thread(&amp;change_count, 0);
thrds.join_all();
return 0;
}
</pre>
<h4><a name="class-timed_mutex-ctors"></a>Class <code>timed_mutex</code> constructors
and destructor</h4>
<pre>
timed_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<pre>
~timed_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in an unlocked sate.</dt>
<dt><b>Danger:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<p><a href="../example/mutex.cpp">libs/thread/example/mutex.cpp</a></p>
<p>The output is:</p>
<pre>
count == 1
count == 2
count == 3
count == 4
</pre>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

View File

@@ -1,154 +1,187 @@
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<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Mutex Concept</title>
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<title>Boost.Threads, Mutex Concept</title>
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<td valign="top" width="300"> <a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Mutex Concept</h2>
</td>
</tr>
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<table border="0" cellpadding="7" cellspacing="0" width="100%">
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<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Mutex Concepts</h2>
</td>
</tr>
</table>
<hr>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#locking-strategies">Locking Strategies</a></dt>
<dl class="page-index">
<dt><a href="#locking-strategy-recursive">Recursive</a></dt>
<dt><a href="#locking-strategy-checked">Checked</a></dt>
<dt><a href="#locking-strategy-unchecked">Unchecked</a></dt>
<dt><a href="#locking-strategy-unspecified">Unspecified</a></dt>
</dl>
<dt><a href="#scheduling-policies">Scheduling Policies</a></dt>
<dl class="page-index">
<dt><a href="#scheduling-policy-FIFO">FIFO</a></dt>
<dt><a href="#scheduling-policy-priority-driven">Priority Driven</a></dt>
<dt><a href="#scheduling-policy-unspecified">Unspecified</a></dt>
</dl>
<dt><a href="#concept-requirements">Concept Requirements</a></dt>
<dl class="page-index">
<dt><a href="#Mutex-concept">Mutex Concept</a></dt>
<dt><a href="#TryMutex-concept">TryMutex Concept</a></dt>
<dt><a href="#TimedMutex-concept">TimedMutex Concept</a></dt>
</dl>
<dt><a href="#models">Models</a></dt>
</dl>
<h2><a name="introduction"></a>Introduction</h2>
<p>A mutex (short for mutual-exclusion) object is used to serializes access to
a resource shared between multiple threads. The <a href="#Mutex">Mutex</a> concept,
with <a href="#TryMutex">TryMutex</a> and <a href="#TimedMutex">TimedMutex</a>
refinements, formalize the requirements. A model that implements Mutex and its
refinements has two states: <b>locked</b> and <b>unlocked</b>. Before using
a shared resource, a thread locks a <b>Boost.Threads</b> mutex object (an object
whose type is a model of <a href="#Mutex-concept">Mutex</a> or one of it's
refinements), insuring <a href="definitions.html#thread-safe">thread-safe</a>
access to the shared resource. When use of the shared resource is complete,
the thread unlocks the mutex object, allowing another thread to acquire the
lock and use the shared resource.</p>
<p>Traditional C thread APIs, like POSIX threads or the Windows thread APIs, expose
functions to lock and unlock a mutex object. This is dangerous since it&#39;s
easy to forget to unlock a locked mutex. When the flow of control is complex,
with multiple return points, the likelihood of forgetting to unlock a mutex
object would become even greater. When exceptions are thrown, it becomes nearly
impossible to ensure that the mutex object is unlocked properly when using these
traditional API&#39;s. The result is <a href="definitions.html#deadlock">deadlock</a>.</p>
<p>Many C++ threading libraries use a pattern known as <i>Scoped Locking</i> <a href="bibliography.html#Schmidt-00">[Schmidt
00]</a> to free the programmer from the need to explicitly lock and unlock mutex
objects. With this pattern, a <a href="lock_concept.html">Lock</a> concept is
employed where the lock object&#39;s constructor locks the associated mutex
object and the destructor automatically does the unlocking. The <b>Boost.Threads</b>
library takes this pattern to the extreme in that Lock concepts are the only
way to lock and unlock a mutex object: lock and unlock functions are not exposed
by any <b>Boost.Threads</b> mutex objects. This helps to ensure safe usage patterns,
especially when code throws exceptions.</p>
<h2><a name="locking-strategies"></a>Locking Strategies</h2>
<p>Every mutex object follows one of several locking strategies. These strategies
define the semantics for the locking operation when the calling thread already
owns a lock on the mutex object.</p>
<h3><a name="locking-strategy-recursive"></a>Recursive</h3>
<p>With a recursive locking strategy when a thread attempts to acquire a lock
on the mutex object for which it already owns a lock, the operation is successful.
Note the distinction between a thread, which may have multiple locks outstanding
on a recursive mutex object, and a lock object, which even for a recursive mutex
object cannot have any of its lock functions called multiple times without first
calling unlock.</p>
<p>Internally a lock count is maintained and the owning thread must unlock the
mutex model the same number of times that it&#39;s locked it before the mutex
object&#39;s state returns to unlocked. Since mutex objects in <b>Boost.Threads</b>
expose locking functionality only through lock concepts, a thread will always
unlock a mutex object the same number of times that it locked it. This helps
to eliminate a whole set of errors typically found in traditional C style thread
APIs.</p>
<p>Classes <a href="recursive_mutex.html#class-recursive_mutex">recursive_mutex</a>,
<a href="recursive_mutex.html#class-recursive_try_mutex">recursive_try_mutex</a>
and <a href="recursive_mutex.html#class-recursive_timed_mutex">recursive_timed_mutex</a>
use this locking strategy.</p>
<h3><a name="locking-strategy-checked"></a>Checked</h3>
<p>With a checked locking strategy when a thread attempts to acquire a lock on
the mutex object for which the thread already owns a lock, the operation will
fail with some sort of error indication. Further, attempts by a thread to unlock
a mutex object that was not locked by the thread will also return some sort
of error indication. In <b>Boost.Threads</b>, an exception of type <a href="exceptions.html#class-lock_error">
lock_error</a> would be thrown in these cases.</p>
<p><b>Boost.Threads</b> does not currently provide any mutex objects that use
this strategy.</p>
<h3><a name="locking-strategy-unchecked"></a>Unchecked</h3>
<p>With an unchecked locking strategy when a thread attempts to acquire a lock
on a mutex object for which the thread already owns a lock the operation will
<a href="definitions.html#definition-deadlock">deadlock</a>. In general this
locking strategy is less safe than a checked or recursive strategy, but it&#39;s
also a faster strategy and so is employed by many libraries.</p>
<p><b>Boost.Threads</b> does not currently provide any mutex objects that use
this strategy.</p>
<h3><a name="locking-strategy-unspecified"></a>Unspecified</h3>
<p>With an unspecified locking strategy, when a thread attempts to acquire a lock
on a mutex object for which the thread already owns a lock the operation results
in <b>undefined behavior</b>.</p>
<p>In general a mutex object with an unspecified locking strategy is unsafe, and
it requires programmer discipline to use the mutex object properly. However,
this strategy allows an implementation to be as fast as possible with no restrictions
on its implementation. This is especially true for portable implementations
that wrap the native threading support of a platform. For this reason, the classes
<a href="mutex.html#class-mutex">mutex</a>, <a href="mutex.html#class-try_mutex">try_mutex</a>
and <a href="mutex.html#class-timed_mutex">timed_mutex</a> use this locking
strategy despite the lack of safety.</p>
<h2><a name="scheduling-policies"></a>Scheduling Policies</h2>
<p>Every mutex object follows one of several scheduling policies. These policies
define the semantics when the mutex object is unlocked and there is more than
one thread waiting to acquire a lock. In other words, the policy defines which
waiting thread shall acquire the lock.</p>
<h3><a name="scheduling-policy-FIFO"></a>FIFO</h3>
<p>With a FIFO scheduling policy, threads waiting for the lock will acquire it
in a first come first serve order (or First In First Out). This can help prevent
a high priority thread from starving lower priority threads that are also waiting
on the mutex object's lock.</p>
<h3><a name="scheduling-policy-priority-driven"></a>Priority Driven</h3>
<p><a href="#Introduction">Introduction</a><br>
<a href="#LockingStrategies">Locking Strategies</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Recursive">Recursive</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#CheckedStrategy">Checked</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#UncheckedStrategy">Unchecked</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#UnspecifiedStrategy">Unspecified</a><br>
<a href="#SchedulingPolicies">Scheduling Policies</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#FIFO">FIFO</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Priority Driven">Priority Driven</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#UndefinedScheduling">Undefined</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#UnspecifiedScheduling">Unspecified</a><br>
<a href="#Requirements">Concept Requirements</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Mutex">Mutex Concept</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#TryMutex">TryMutex Concept</a><br>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="#TimedMutex">TimedMutex Concept</a><br>
<a href="#Models">Models</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>A mutex (short for mutual-exclusion) concept serializes access to
a resource shared between multiple threads. The <a href="#Mutex">Mutex</a>
concept, with <a href="#TryMutex">TryMutex</a> and <a href="#TimedMutex">TimedMutex</a>
refinements, formalize the requirements. A model that implements Mutex and its
refinements has two states: <b> locked</b> and <b>unlocked</b>. Before using a
shared resource, a thread locks a Boost.Threads mutex model object,
insuring <a href="definitions.html#Thread-safe">thread-safe</a> access to the shared
resource. When use of the shared resource is complete, the thread unlocks the mutex
model object, allowing another thread to acquire the lock and use the shared resource.</p>
<p>Traditional C thread APIs, like Pthreads or the Windows thread APIs, expose
functions to lock and unlock a mutex model. This is dangerous since it's easy to forget
to unlock a locked mutex. When the flow of control is complex, with multiple return
points, the likelihood of forgetting to unlock a mutex model would become even greater.
When exceptions are thrown, it becomes nearly impossible to ensure that the mutex is
unlocked properly when using these traditional API's. The result is
<a href="definitions.html#Deadlock">deadlock</a>.</p>
<p>Many C++ threading libraries use a pattern known as <i>Scoped Locking</i>
<a href="bibliography.html#Schmidt 00">[Schmidt 00]</a> to free the programmer from the
need to explicitly lock and unlock mutexes. With this pattern, a
<A href="lock_concept.html">lock concept</A> is employed where the lock model's
constructor locks the associated mutex model and the destructor automatically does the
unlocking. The <b>Boost.Threads</b> library takes this pattern to the extreme in that
lock concepts are the only way to lock and unlock a mutex model: lock and unlock
functions are not exposed by any <b>Boost.Threads </b>mutex models. This helps to
ensure safe usage patterns, especially when code throws exceptions.</p>
<h2><a name="LockingStrategies">Locking Strategies</a></h2>
<p>Every mutex model follows one of several locking strategies. These strategies
define the semantics for the locking operation when the calling thread already
owns a lock on the mutex model.</p>
<h3><a name="Recursive">Recursive</a></h3>
<p>With a recursive locking strategy when a thread attempts to acquire a lock on
the mutex model for which it already owns a lock, the operation is successful.
Note the distinction between a thread, which may have multiple locks outstanding
on a recursive mutex, and a lock object, which even for a recursive mutex cannot
have its lock() function called multiple times without first calling unlock().</p>
<p>Internally a lock count is maintained and the owning thread must unlock the
mutex model the same number of times that it's locked it before the mutex model's
state returns to unlocked. Since mutex models in <b>Boost.Threads</b> expose
locking functionality only through lock concepts, a thread will always unlock a mutex
model the same number of times that it locked it. This helps to eliminate a whole set
of errors typically found in traditional C style thread APIs.</p>
<p>Classes <A href="recursive_mutex.html">recursive_mutex</A>,
<A href="recursive_mutex.html">recursive_try_mutex</A> and
<A href="recursive_mutex.html">recursive_timed_mutex</A> use this locking strategy.</p>
<h3><a name="CheckedStrategy">Checked</a></h3>
<p>With a checked locking strategy when a thread attempts to acquire a lock on
the mutex model for which the thread already owns a lock, the operation will fail with
some sort of error indication. Further, attempts by a thread to unlock a mutex
that was not locked by the thread will also return some sort of error indication.
In <b>Boost.Threads</b>, an exception of type <A href="lock_error.html">lock_error</A>
would be thrown in these cases.</p>
<p><b>Boost.Threads</b> does not currently provide any mutex models that use this
strategy.</p>
<h3><a name="UncheckedStrategy">Unchecked</a></h3>
<p>With an unchecked locking strategy when a thread attempts to acquire a lock
on the mutex model for which the thread already owns a lock the operation will
<a href="definitions.html#Deadlock">deadlock</a>. In general this locking strategy is
less safe than a checked or recursive strategy, but it's also a faster strategy and so
is employed by many libraries.</p>
<p><b>Boost.Threads</b> does not currently provide any mutex models that use this
strategy.</p>
<h3><a name="UnspecifiedStrategy">Unspecified</a></h3>
<p>With an unspecified locking strategy, when a thread attempts to acquire a lock
on a mutex model for which the thread already owns a lock the operation results in
<b>undefined behavior</b>. When a mutex model has an unspecified locking strategy the
programmer must assume that the mutex model instead uses an unchecked strategy.</p>
<p>In general a mutex model with an unspecified locking strategy is unsafe, and it
requires programmer discipline to use the mutex model properly. However, this strategy
allows an implementation to be as fast as possible with no restrictions on its
implementation. This is especially true for portable implementations that wrap the
native threading support of a platform. For this reason, the classes
<A href="mutex.html">mutex</A>, <A href="mutex.html">try_mutex</A> and
<A href="mutex.html">timed_mutex</A> use this locking strategy despite the lack of
safety.</p>
<h2><a name="SchedulingPolicies">Scheduling Policies</a></h2>
<p>Every mutex model follows one of several scheduling policies. These policies
define the semantics when the mutex model is unlocked and there is more than one
thread waiting to acquire a lock. In other words, the policy defines which waiting
thread shall acquire the lock.</p>
<h3><a name="FIFO">FIFO</a></h3>
<p>With a FIFO scheduling policy, threads waiting for the lock will acquire it in
a first come first serve order (or First In First Out). This can help prevent a
high priority thread from starving lower priority threads that are also waiting
on the mutex lock.</p>
<h3><a name="Priority Driven">Priority Driven</a></h3>
<p>With a Priority Driven scheduling policy, the thread with the highest priority
acquires the lock. Note that this means that low-priority threads may never
acquire the lock if the mutex object has high contention and there is always
at least one high-priority thread waiting. This is known as thread starvation.
When multiple threads of the same priority are waiting on the mutex object's
lock one of the other scheduling priorities will determine which thread shall
acquire the lock.</p>
<h3><a name="scheduling-policy-unspecified"></a>Unspecified</h3>
<p>The mutex object does not specify a scheduling policy. In order to ensure portability,
all <b>Boost.Threads</b> mutex models use an unspecified scheduling policy.</p>
<h2><a name="concept-requirements"></a>Concept Requirements</h2>
<h3><a name="Mutex-concept"></a>Mutex Concept</h3>
<p>A Mutex object has two states: locked and unlocked. Mutex object state can
only be determined by an object meeting the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements and constructed for the Mutex object.</p>
<p>A Mutex is <a href="../../utility/utility.htm#Class noncopyable">NonCopyable</a>.</p>
<p>For a Mutex type M and an object m of that type, the following expressions
must be well-formed and have the indicated effects.</p>
<table summary="Mutex expressions" border="1" cellpadding="5">
acquires the lock. Note that this means that low-priority threads may never acquire
the lock if the mutex model has high contention and there is always at least one
high-priority thread waiting. This is known as thread starvation. When multiple threads
of the same priority are waiting on the mutex lock one of the other scheduling
priorities will determine which thread shall acquire the lock.</p>
<h3><a name="UndefinedScheduling">Undefined</a></h3>
<p>Threads acquire the lock in no particular order. Users should assume that
low-priority threads may wait indefinitely, and that threads of the same
priority acquire the lock in essentially random order.</p>
<h3><a name="UnspecifiedScheduling">Unspecified</a></h3>
<p>The mutex model does not specify which scheduling policy is used. The programmer
must assume that an undefined scheduling policy is used. In order to ensure portability,
all <b>Boost.Threads</b> mutex models use an unspecified scheduling policy.</p>
<h2>Concept <a name="Requirements">Requirements</a></h2>
<h3><a name="Mutex">Mutex</a> Concept</h3>
<p>A Mutex object has two states: locked and unlocked. Mutex object state can only be
determined by an object meeting the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements and constructed for the Mutex object.</p>
<p>A Mutex is <a href="../../utility/utility.htm#Class noncopyable">noncopyable</a>.</p>
<p>For a Mutex type M and an object m of that type, the following expressions must be
well-formed and have the indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
@@ -163,77 +196,80 @@
</tr>
<tr>
<td><code>M::scoped_lock</code></td>
<td>A model of <a href="lock_concept.html#ScopedLock">ScopedLock</a>.</td>
<td>A type meeting the <a href="lock_concept.html#ScopedLock">ScopedLock</a>
requirements.</td>
</tr>
</table>
<h3><a name="TryMutex-concept"></a>TryMutex Concept</h3>
<p>A TryMutex is a refinement of <a href="#Mutex-concept">Mutex</a>. For a TryMutex
type M and an object m of that type, the following expressions must be well-formed
and have the indicated effects.</p>
<table summary="TryMutex expressions" border="1" cellpadding="5">
<h3><a name="TryMutex">TryMutex</a> Concept</h3>
<p>A TryMutex must meet the <a href="#Mutex"> Mutex</a> requirements. In addition, for a
TryMutex type M and an object m of that type, the following expressions must be
well-formed and have the indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>M::scoped_try_lock</code></td>
<td>A model of <a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a>.</td>
<td>A type meeting the <a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a>
requirements.</td>
</tr>
</table>
<h3><a name="TimedMutex-concept"></a>TimedMutex Concept</h3>
<p>A TimedMutex is a refinement of <a href="#TryMutex-concept">TryMutex</a>. For
a TimedMutex type M and an object m of that type, the following expressions
must be well-formed and have the indicated effects.</p>
<table summary="TimedMutex expressions" border="1" cellpadding="5">
<h3><a name="TimedMutex">TimedMutex</a> Concept</h3>
<p>A TimedMutex must meet the <a href="#TryMutex"> TryMutex</a> requirements. In addition, for a
TimedMutex type M and an object m of that type, the following
expressions must be well-formed and have the indicated effects.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>M::scoped_timed_lock</code></td>
<td>A model of <a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a>.</td>
<td>A type meeting the <a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a>
requirements.</td>
</tr>
</table>
<h2><a name="models"></a>Models</h2>
<p><b>Boost.Threads</b> currently supplies six models of Mutex.</p>
<table summary="Mutex concept classes" border="1" cellpadding="5">
<h2><a name="Models">Models</a></h2>
<p> <b>Boost.Threads</b> currently supplies six classes which model mutex
concepts.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Concept</b></td>
<td><b>Refines</b></td>
<td><b>Models</b></td>
<td><b>Classes Modeling the Concept</b></td>
</tr>
<tr>
<td valign="top"><a href="#Mutex-concept">Mutex</a></td>
<td valign="top"><a href="#Mutex">Mutex</a></td>
<td valign="top">&nbsp;</td>
<td><a href="mutex.html">mutex</a><br>
<a href="recursive_mutex.html">recursive_mutex</a></td>
<td><A href="mutex.html">mutex</A><br>
<A href="recursive_mutex.html">recursive_mutex</A></td>
</tr>
<tr>
<td valign="top"><a href="#TryMutex-concept">TryMutex</a></td>
<td valign="top"><a href="#Mutex-concept">Mutex</a></td>
<td><a href="mutex.html">try_mutex<br>
</a> <a href="recursive_mutex.html">recursive_try_mutex</a> </td>
<td valign="top"><a href="#TryMutex">TryMutex</a></td>
<td valign="top"><a href="#Mutex">Mutex</a></td>
<td><A href="mutex.html">try_mutex<br>
</A><A href="recursive_mutex.html">recursive_try_mutex</A> </td>
</tr>
<tr>
<td valign="top"><a href="#TimedMutex-concept">TimedMutex</a></td>
<td valign="top"><a href="#TryMutex-concept">TryMutex</a></td>
<td><a href="mutex.html">timed_mutex<br>
</a> <a href="recursive_mutex.html"> recursive_timed_mutex</a></td>
<td valign="top"><a href="#TimedMutex">TimedMutex</a></td>
<td valign="top"><a href="#TryMutex">TryMutex</a></td>
<td><A href="mutex.html">timed_mutex<br>
</A><A href="recursive_mutex.html">recursive_timed_mutex</A></td>
</tr>
</table>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->03 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39333" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</A>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/once.hpp&gt;</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/once.hpp">boost/thread/once.hpp</a>&gt;</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#macros">Macros</a></dt>
<dl class="page-index">
<dt><a href="#macro-BOOST_ONCE_INIT">BOOST_ONCE_INIT</a></dt>
</dl>
<dt><a href="#types">Types</a></dt>
<dl class="page-index">
<dt><a href="#type-once_flag">once_flag</a></dt>
</dl>
<dt><a href="#functions">Functions</a></dt>
<dl class="page-index">
<dt><a href="#function-call_once">call_once</a></dt>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>Include the header &lt;<a href="../../../boost/thread/once.hpp">boost/thread/once.hpp</a>&gt;
to define the <code>call_once</code> function, <code>once_flag</code> type and
<code>BOOST_ONCE_INIT</code> constant.</p>
<p>The <code>call_once</code> function and <code>once_flag</code> type (statically
initialized to <code>BOOST_ONCE_INIT</code>) can be used to run a routine exactly
once. This can be used to initialize data in a <a href="definitions.html#Thread-safe">
thread-safe</a> manner.</p>
<h2><a name="macros"></a>Macros</h2>
<pre>
<a name="macro-BOOST_ONCE_INIT"></a>#define BOOST_ONCE_INIT <i>implementation defined</i>
</pre>
<p>This is a constant value used to initialize <code>once_flag</code> instances
to indicate that the logically associated routine has not been run yet.</p>
<h2><a name="types"></a>Types</h2>
<pre>
<a name="type-once_flag"></a>typedef <i>implementation defined</i> once_flag;
</pre>
<p>This implementation defined type is used as a flag to insure a routine is called
only once. Instances of this type should be statically initialized to <code>BOOST_ONCE_INIT</code>.</p>
<h2><a name="functions"></a>Functions</h2>
<pre>
<a name="function-call_once"></a>void call_once(void (*func)(), once_flag& flag);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> The function <code>func</code> shall not throw exceptions.</dt>
<dt><b>Effects:</b> As if (in an atomic fashion):
<pre>
if (flag == BOOST_ONCE_INIT)
func();
</pre>
</dt>
<dt><b>Postconditions:</b> <code>flag != BOOST_ONCE_INIT</code></dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<p><a href="../example/once.cpp">libs/thread/example/once.cpp</a></p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
</body>
</html>

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@@ -1,173 +1,156 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Overview</title>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Boost.Threads Overview</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Overview</h2>
</td>
</tr>
<body>
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Overview</h2>
</td>
</tr>
</table>
<hr>
<dl class="index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#dangers">Dangers</a></dt>
<dl class="index">
<dt><a href="#testing-debugging">Testing and debugging considerations</a></dt>
<dt><a href="#head-start">Getting a head start</a></dt>
</dl>
<dt><a href="#library">C++ Standard Library usage in multithreaded programs</a></dt>
<dl class="index">
<dt><a href="#runtime-libraries">Runtime libraries</a></dt>
<dt><a href="#non-thread-safe-functions">Potentially non-thread-safe functions</a></dt>
</dl>
<dt><a href="#common-requirements">Common requirements for all Boost.Threads
components</a></dt>
<dl class="index">
<dt><a href="#exceptions">Exceptions</a></dt>
<dt><a href="#non-copyable">NonCopyable requirement</a></dt>
</dl>
</dl>
<h2><a name="introduction"></a>Introduction</h2>
<p>Boost.Threads allows C++ programs to execute as multiple, asynchronous, independent,
threads-of-execution. Each thread has its own machine state including program
instruction counter and registers. Programs which execute as multiple threads
are called multithreaded programs to distinguish them from traditional single-threaded
programs. <a href="definitions.html">Definitions</a> gives a more complete description
of the multithreading execution environment.</p>
<p>Multithreading provides several advantages:</p>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Dangers">Dangers</a><br>
<a href="#Library">C++ Standard Library usage</a><br>
<a href="#Common">Common requirements</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>Boost.Threads allows C++ programs to execute as multiple, asynchronous,
independent, threads-of-execution. Each thread has its own machine state
including program instruction counter and registers. Programs which execute as
multiple threads are call multi-threaded programs to distinguish them from
traditional single-threaded programs. <a href="definitions.html">Definitions</a>
gives a more complete description of the multi-threading execution environment.</p>
<p>Multi-threading provides several advantages:</p>
<ul>
<li>Programs which would otherwise block waiting for some external event can
continue to respond if the blocking operation is placed in a separate thread.
Multithreading is usually an absolute requirement for these programs.</li>
continue to respond if the blocking operation is placed in a separate
thread.&nbsp; Multi-threading is usually an absolute requirement for these
programs.</li>
</ul>
<ul>
<li>Well-designed multithreaded programs may execute faster than single-threaded
programs, particularly on multiprocessor hardware. Note, however, that poorly-designed
multithreaded programs are often slower that single-threaded programs.</li>
<li>Well-designed multi-threaded programs may execute faster than single-threaded
programs, particularly on multi-processor hardware.&nbsp;
Note, however, that poorly-designed multi-threaded programs are often slower
that single-threaded programs.</li>
</ul>
<ul>
<li>Some program designs may be easier to formulate using a multithreaded approach.
After all, the real world is asynchronous!</li>
<li>Some program designs may be easier to formulate using a multi-threaded
approach.
After all, the real world is asynchronous!&nbsp;</li>
</ul>
<h2><a name="dangers"></a>Dangers</h2>
<p>Beyond the errors which can occur in single-threaded programs, multithreaded
programs are subject to additional errors:</p>
<h2><a name="Dangers">Dangers</a></h2>
<p>Beyond the errors which can occur in single-threaded programs, multi-threaded
programs are subject to additional errors:</p>
<ul>
<li><a href="definitions.html#definition-race-condition">Race conditions</a>.</li>
<li><a href="definitions.html#definition-deadlock">Deadlock</a> (sometimes called
&quot;deadly embrace&quot;)</li>
<li><a href="definitions.html#definition-priority-failure">Priority failures</a>
<li><a href="definitions.html#Race condition">Race conditions</a>.
<li><a href="definitions.html#Deadlock">Deadlock</a> (sometimes called
&quot;deadly embrace&quot;)
<li><a href="definitions.html#Priority failure">Priority failures</a>
(priority inversion, infinite overtaking, starvation, etc.)</li>
</ul>
<p>Every multithreaded program must be designed carefully to avoid race conditions,
priority failures and deadlock. These aren&#39;t rare or exotic failures - they
are virtually guaranteed to occur unless multithreaded code is designed to avoid
them. Priority failures are somewhat less common, but are nonetheless serious.</p>
<p>Every multi-threaded program must be designed carefully to avoid race
conditions and deadlock.&nbsp; These aren't rare or exotic failures - they are
virtually guaranteed to occur unless multi-threaded code is designed to avoid
them.&nbsp; Priority failures are somewhat less common, but are none-the-less
serious.</p>
<p>The <a href="introduction.html">Boost.Threads design</a> attempts to minimize
these errors, but they will still occur unless the programmer proactively designs
to avoid them.</p>
<h3><a name="testing-debugging"></a>Testing and debugging considerations</h3>
<p>Multithreaded programs are non-deterministic. In other words, the same program
with the same input data may follow different execution paths each time it is
invoked. That can make testing and debugging a nightmare:</p>
these errors, but they will still occur unless the programmer proactively
designs to avoid them.</p>
<h3>Testing and debugging considerations</h3>
<p>Multi-threaded programs are non-deterministic. In other words, the same
program with the same input data may follow different execution paths each time
it is invoked.&nbsp; That can make testing and debugging a nightmare:</p>
<ul>
<li>Failures are often not repeatable.</li>
<li>Probe effect causes debuggers to produce very different results from non-debug
uses.</li>
<li>Debuggers require special support to show thread state.</li>
<li>Tests on a single processor system may give no indication of serious errors
which would appear on multiprocessor systems, and visa versa. Thus test cases
should include a varying number of processors.</li>
<li>For programs which create a varying number of threads according to workload,
tests which don&#39;t span the full range of possibilities may miss serious
errors.</li>
<li>Failures are often not repeatable.
<li>Probe effect causes debuggers to produce very different results from
non-debug uses.
<li>Debuggers require special support to show thread state.
<li>Tests on a single processor system may give no indication of serious
errors which would appear on multiprocessor systems, and visa versa. Thus test
cases should include a varying number of processors.&nbsp;</li>
<li>For programs which create a varying number of threads according to
workload, tests which don't span the full range of possibilities may miss
serious errors.</li>
</ul>
<h3><a name="head-start"></a>Getting a head start</h3>
<p>Although it might appear that multithreaded programs are inherently unreliable,
many reliable multithreaded programs do exist. Multithreading techniques are
known which lead to reliable programs.</p>
<p>Design patterns for reliable multithreaded programs, including the important
<i>monitor</i> pattern, are presented in <cite> Pattern-Oriented Software Architecture
Volume 2 - Patterns for Concurrent and Networked Objects</cite> [<a href=
"bibliography.html#Schmidt-00">Schmidt 00</a>]. Many important multithreading
programming considerations (independent of threading library) are discussed
in <cite>Programming with POSIX Threads</cite> [<a href="bibliography.html#Butenhof-97">Butenhof
97</a>].</p>
<p>Doing some reading before attempting multithreaded designs will give you a
head start toward reliable multithreaded programs.</p>
<h2><a name="library"></a>C++ Standard Library usage in multithreaded programs</h2>
<h3><a name="runtime-libraries"></a>Runtime libraries</h3>
<p><b>Warning:</b> Multithreaded programs such as those using <b> Boost.Threads</b>
must link to <a href="definitions.html#Thread-safe"> thread-safe</a> versions
of all runtime libraries used by the program, including the runtime library
for the C++ Standard Library. Otherwise <a href="definitions.html#Race condition">race
conditions</a> will occur when multiple threads simultaneously execute runtime
library functions for <i>new</i>, <i>delete</i>, or other language features
which imply shared state.</p>
<h3><a name="non-thread-safe-functions"></a>Potentially non-thread-safe functions</h3>
<p>Certain C++ Standard Library functions inherited from C are particular problems
because they hold internal state between calls:</p>
<h3>Getting a head start</h3>
<p>Although it might appear that multi-threaded programs are inherently
unreliable, many reliable multi-threaded programs do exist. Multi-threading
techniques are known which lead to reliable programs.</p>
<p>Design patterns for reliable multi-threaded programs, including the important
<i>monitor</i> pattern, are presented in <cite>Pattern-Oriented Software Architecture Volume 2 - Patterns for
Concurrent and Networked Objects</cite> [<a href="bibliography.html#Schmidt-00">Schmidt
00</a>].&nbsp; Many important multi-threading programming considerations
(independent of threading library) are discussed in <cite>Programming with
POSIX Threads</cite> [<a href="bibliography.html#Butenhof-97">Butenhof 97</a>].</p>
<p>Reading and study first yields a head start toward designing reliable
multi-threaded programs.</p>
<h2><a name="Library">C++ Standard Library usage in multi-threaded programs</a></h2>
<h3>Runtime libraries</h3>
<p><b>Warning:</b> Multi-threaded programs such as those using <b>Boost.Threads</b> must link to
<a href="definitions.html#Thread-safe">thread-safe</a> versions of all runtime
libraries used by the program, including the runtime library for the C++
Standard Library. Otherwise <a href="definitions.html#Race condition">race
conditions</a> will occur when multiple threads simultaneously execute runtime
library functions for <i>new</i>, <i>delete</i>, or other language features
which imply shared state.&nbsp;&nbsp;</p>
<h3>Potentially non-thread-safe functions</h3>
<p>Certain C++ Standard Library functions inherited from C are particular
problems because they hold internal state between calls:</p>
<ul>
<li>rand</li>
<li>strtok</li>
<li>asctime</li>
<li>ctime</li>
<li>ctime&nbsp;</li>
<li>gmtime</li>
<li>localtime</li>
</ul>
<p>It is possible to write thread-safe implementations of these by using <a href="tss.html#class-thread_specific_ptr">thread-specific
storage</a>, and several C++ compiler vendors do just that. The technique is
well-know and is explained in [<a href=
"bibliography.html#Butenhof-97">Buttenhof 97</a>].</p>
<p>It is possible to write thread-safe implementations of these by using <a href="thread_specific_ptr.html">thread-specific
storage</a>, and several C++ compiler vendors do just that.&nbsp; The technique
is well-know and is explained in [<a href="bibliography.html#Butenhof-97">Buttenhof-97</a>].</p>
<p>But at least one vendor (HP-UX) does not provide thread-safe implementations
of the above functions in their otherwise thread-safe runtime library. Instead
they provide replacement functions with different names and arguments.</p>
of the above functions in their otherwise thread-safe runtime library.&nbsp;
Instead they provide replacement functions with different names and arguments.</p>
<p><b>Recommendation:</b> For the most portable, yet thread-safe code, use Boost
replacements for the problem functions. See the <a href=
"../../random/index.html">Boost Random Number Library</a> and <a href=
"../../tokenizer/index.htm">Boost Tokenizer Library</a>.</p>
<h2><a name="common-gaurantees"></a>Common guarantees for all Boost.Threads components</h2>
<h3><a name="exceptions"></a>Exceptions</h3>
<p><b>Boost.Threads</b> destructors never throw exceptions. Unless otherwise specified,
other <b>Boost.Threads</b> functions that do not have an exception-specification
may throw implementation-defined exceptions.</p>
<p>In particular, <b>Boost.Threads</b> reports failure to allocate storage by
throwing an exception of type std::bad_alloc, or a class derived from std::bad_alloc,
failure to obtain thread resources other than memory by throwing an exception
of type <a href="exceptions.html#class-thread_resource_error">boost::thread_resource_error</a>,
and certain lock related failures by throwing an exception of type <a href="exceptions.html#class-lock_error">boost::lock_error</a></p>
<p><b>Rationale:</b> Follows the C++ Standard Library practice of allowing all
functions except destructors or other specified functions to throw exceptions
on errors.</p>
<h3><a name="non-copyable"></a>NonCopyable requirement</h3>
<p><b>Boost.Threads</b> classes documented as meeting the NonCopyable requirement
disallow copy construction and copy assignment. For the sake of exposition,
the synopsis of such classes show private derivation from <a href="../../utility/utility.htm">
boost::noncopyable</a>. Users should not depend on this derivation, however,
as implementations are free to meet the NonCopyable requirement in other ways.</p>
replacements for the problem functions.&nbsp; See the <a href="../../random/index.html">Boost
Random Number Library</a> and <a href="../../tokenizer/index.htm">Boost
Tokenizer Library</a>.</p>
<h2><a name="Common">Common</a> requirements for all Boost.Threads components</h2>
<h3>Exceptions</h3>
<p> <b>Boost.Threads</b> destructors never throw exceptions. Unless otherwise
specified, other <b>Boost.Threads</b>
functions that do not have an exception-specification may throw implementation-defined exceptions.</p>
<p>In particular, <b>Boost.Threads</b> reports failure to allocate storage by throwing an exception of type
std::bad_alloc, or a class derived from std::bad_alloc, failure to obtain
thread resources other than memory by throwing an exception of type <a href="thread_resource_error.html">boost::thread_resource_error</a>,
and certain lock related failures by throwing an exception of type <a href="lock_error.html">boost::lock_error</a></p>
<p><b>Rationale: </b>Follows the C++ Standard Library practice of allowing all
functions except destructors or other specified functions to throw exceptions on
errors.</p>
<h3><a name="NonCopyable">NonCopyable</a> requirement</h3>
<p><b>Boost.Threads</b> classes documented as meeting the NonCopyable requirement disallow copy
construction and copy assignment. For the sake of exposition, the synopsis of
such classes show private derivation from <a href="../../utility/utility.htm">boost::noncopyable</a>.
Users should not depend on this derivation, however, as implementations are free
to meet the NonCopyable requirement in other ways.</p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->12 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39332" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p>© Copyright 2001 Beman Dawes</p>
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<dl class="index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#library">Rationale for the Creation of <b>Boost.Threads</b></a></dt>
<dt><a href="#primitives">Rationale for the Low Level Primitives Supported in
<b>Boost.Threads</b></a></dt>
<dt><a href="#lock_objects">Rationale for the Lock Design</a></dt>
<dt><a href="#non-copyable">Rationale for NonCopyable Thread Type</a></dt>
<dt><a href="#events">Rationale for not providing <i>Event Variables</i></a></dt>
</dl>
<h2><a name="introduction"></a>Introduction</h2>
<p>This page explains the rationale behind various design decisions in the <b>Boost.Threads</b>
library. Having the rationale documented here should explain how we arrived
at the current design as well as prevent future rehashing of discussions and
thought processes that have already occurred. It can also give users a lot of
insight into the design process required for this library.</p>
<h2><a name="library"></a>Rationale for the Creation of <b>Boost.Threads</b></h2>
<p>Processes often have a degree of &quot;potential parallelism&quot; and it can
often be more intuitive to design systems with this in mind. Further, these
parallel processes can result in more responsive programs. The benefits for
multithreaded programming are quite well known to most modern programmers, yet
the C++ language doesn&#39;t directly support this concept.</p>
<p>Many platforms support multithreaded programming despite the fact that the
language doesn&#39;t support it. They do this through external libraries, which
are, unfortunately, platform specific. POSIX has tried to address this problem
through the standardization of a &quot;pthread&quot; library. However, this
is a standard only on POSIX platforms, so its portability is limited.</p>
<p>Another problem with POSIX and other platform specific thread libraries is
that they are almost universally C based libraries. This leaves several C++
specific issues unresolved, such as what happens when an exception is thrown
in a thread. Further, there are some C++ concepts, such as destructors, that
can make usage much easier than what&#39;s available in a C library.</p>
<p>What&#39;s truly needed is C++ language support for threads. However, the C++
standards committee needs existing practice or a good proposal as a starting
point for adding this to the standard.</p>
<p>The <b>Boost.Threads</b> library was developed to provide a C++ developer with
a portable interface for writing multithreaded programs on numerous platforms.
There&#39;s a hope that the library can be the basis for a more detailed proposal
for the C++ standards committee to consider for inclusion in the next C++ standard.</p>
<h2><a name="primitives"></a>Rationale for the Low Level Primitives Supported
in <b>Boost.Threads</b></h2>
<p>The <b>Boost.Threads</b> library supplies a set of low level primitives for
writing multithreaded programs, such as mutexes and condition variables. In
fact, the first release of <b>Boost.Threads</b> supports only these low level
primitives. However, computer science research has shown that use of these primitives
is difficult since it's difficult to mathematically prove that a usage pattern
is correct, meaning it doesn&#39;t result in race conditions or deadlocks. There
are several algebras (such as CSP, CCS and Join calculus) that have been developed
to help write provably correct parallel processes. In order to prove the correctness
these processes must be coded using higher level abstractions. So why does <b>Boost.Threads</b>
support the lower level concepts?</p>
<p>The reason is simple: the higher level concepts need to be implemented using
at least some of the lower level concepts. So having portable lower level concepts
makes it easier to develop the higher level concepts and will allow researchers
to experiment with various techniques.</p>
<p>Beyond this theoretical application of higher level concepts, however, the
fact remains that many multithreaded programs are written using only the lower
level concepts, so they are useful in and of themselves, even if it&#39;s hard
to prove that their usage is correct. Since many users will be familiar with
these lower level concepts but be unfamiliar with any of the higher level concepts
there&#39;s also an argument for accessibility.</p>
<h2><a name="lock_objects"></a>Rationale for the Lock Design</h2>
<p>Programmers who are used to multithreaded programming issues will quickly note
that the Boost.Thread&#39;s design for mutex lock concepts is not <a href="definitions.html#Thread-safe">thread-safe</a>
(this is clearly documented as well). At first this may seem like a serious
design flaw. Why have a multithreading primitive that&#39;s not thread-safe
itself?</p>
<p>A lock object is not a synchronization primitive. A lock object&#39;s sole
responsibility is to ensure that a mutex is both locked and unlocked in a manner
that won&#39;t result in the common error of locking a mutex and then forgetting
to unlock it. This means that instances of a lock object are only going to be
created, at least in theory, within block scope and won&#39;t be shared between
threads. Only the mutex objects will be created outside of block scope and/or
shared between threads. Though it&#39;s possible to create a lock object outside
of block scope and to share it between threads to do so would not be a typical
usage (in fact, to do so would likely be an error). Nor are there any cases
when such usage would be required.</p>
<p>Lock objects must maintain some state information. In order to allow a program
to determine if a try_lock or timed_lock was successful the lock object must
retain state indicating the success or failure of the call made in its constructor.
If a lock object were to have such state and remain thread-safe it would need
to synchronize access to the state information which would result in roughly
doubling the time of most operations. Worse, since checking the state can occur
only by a call after construction we&#39;d have a race condition if the lock
object were shared between threads.</p>
<p>So, to avoid the overhead of synchronizing access to the state information
and to avoid the race condition the <b>Boost.Threads</b> library simply does
nothing to make lock objects thread-safe. Instead, sharing a lock object between
threads results in undefined behavior. Since the only proper usage of lock objects
is within block scope this isn&#39;t a problem, and so long as the lock object
is properly used there&#39;s no danger of any multithreading issues.</p>
<h2><a name="non-copyable"></a>Rationale for NonCopyable Thread Type</h2>
<p>Programmers who are used to C libraries for multithreaded programming are likely
to wonder why <b>Boost.Threads</b> uses a noncopyable design for <a href="thread.html">boost::thread</a>.
After all, the C thread types are copyable, and you often have a need for copying
them within user code. However, careful comparison of C designs to C++ designs
shows a flaw in this logic.</p>
<p>All C types are copyable. It is, in fact, not possible to make a noncopyable
type in C. For this reason types that represent system resources in C are often
designed to behave very similarly to a pointer to dynamic memory. There&#39;s
an API for acquiring the resource and an API for releasing the resources. For
memory we have pointers as the type and alloc/free for the acquisition and release
APIs. For files we have FILE* as the type and fopen/fclose for the acquisition
and release APIs. You can freely copy instances of the types but must manually
manage the lifetime of the actual resource through the acquisition and release
APIs.</p>
<p>C++ designs recognize that the acquisition and release APIs are error prone
and try to eliminate possible errors by acquiring the resource in the constructor
and releasing it in the destructor. The best example of such a design is the
std::iostream set of classes which can represent the same resource as the FILE*
type in C. A file is opened in the std::fstream&#39;s constructor and closed
in its destructor. However, if an iostream were copyable it could lead to a
file being closed twice, an obvious error, so the std::iostream types are noncopyable
by design. This is the same design used by boost::thread, which is a simple
and easy to understand design that&#39;s consistent with other C++ standard
types.</p>
<p>During the design of boost::thread it was pointed out that it would be possible
to allow it to be a copyable type if some form of &quot;reference management&quot;
were used, such as ref-counting or ref-lists, and many argued for a boost::thread_ref
design instead. The reasoning was that copying &quot;thread&quot; objects was
a typical need in the C libraries, and so presumably would be in the C++ libraries
as well. It was also thought that implementations could provide more efficient
reference management than wrappers (such as boost::shared_ptr) around a noncopyable
thread concept. Analysis of whether or not these arguments would hold true doesn&#39;t
appear to bear them out. To illustrate the analysis we&#39;ll first provide
pseudo-code illustrating the six typical usage patterns of a thread object.</p>
<p>This page explains the rationale behind various design decisions in the <b> Boost.Threads</b>
library. Having the rationale documented here should explain how we arrived at the current
design as well as prevent future rehashing of discussions and thought processes that have
already occurred. It can also give users a lot of insight into the design process required
for this library.</p>
<h2><a name="library">Rationale for the Creation of Boost.Threads</a></h2>
<p>Processes often have a degree of "potential parallelism" and it can often be more intuitive
to design systems with this in mind. Further, these parallel processes can result in more responsive
programs. The benefits for multi-threaded programming are quite well known to most modern programmers,
yet the C++ language doesn't directly support this concept.</p>
<p>Many platforms support multi-threaded programming despite the fact that the language doesn't support
it. They do this through external libraries, which are, unfortunately, platform specific. POSIX has
tried to address this problem through the standardization of a "pthread" library. However, this
is a standard only on POSIX platforms, so its portability is limited.</p>
<p>Another problem with POSIX and other platform specific thread libraries is that they are
almost universally C based libraries. This leaves several C++ specific issues unresolved, such
as what happens when an exception is thrown in a thread. Further, there are some C++ concepts,
such as destructors, that can make usage much easier than what's available in a C library.</p>
<p>What's truly needed is C++ language support for threads. However, the C++ standards committee needs
existing practice or a good proposal as a starting point for adding this to the standard.</p>
<p>The Boost.Threads library was developed to provide a C++ developer with a portable interface
for writing multi-threaded programs on numerous platforms. There's a hope that the library can
be the basis for a more detailed proposal for the C++ standards committee to consider for inclusion
in the next C++ standard.</p>
<h2><a name="primitives">Rationale for the Low Level Primitives Supported in Boost.Threads</a></h2>
<p>The Boost.Threads library supplies a set of low level primitives for writing multi-threaded
programs, such as semaphores, mutexes and condition variables. In fact, the first release of
Boost.Threads supports only these low level primitives. However, computer
science research has shown
that use of these primitives is difficult since there's no way to mathematically prove that a
usage pattern is correct, meaning it doesn't result in race conditions or deadlocks. There
are several algebras (such as CSP, CCS and Join calculus) that have been developed to help write
provably correct parallel processes. In order to prove the correctness these processes must
be coded using higher level abstractions. So why does Boost.Threads support the lower level
concepts?</p>
<p>The reason is simple: the higher level concepts need to be implemented using at least some
of the lower level concepts. So having portable lower level concepts makes it easier to develop
the higher level concepts and will allow researchers to experiment with various techniques.</p>
<p>Beyond this theoretical application of higher level concepts, however, the fact remains that
many multi-threaded programs are written using only the lower level concepts, so they are
useful in and of themselves, even if it's hard to prove that their usage is correct. Since
many users will be familiar with these lower level concepts but be unfamiliar with any of the
higher level concepts there's also an argument for accessibility.</p>
<h2><a name="lock_objects">Rationale for the Lock Design</a></h2>
<p>Programmers who are used to multi-threaded programming issues will quickly note that the
Boost.Thread's design for mutex lock concepts is not <a href="file:///c:/boost/site/libs/thread/doc/definitions.html#Thread-safe">thread-safe</a>
(this is clearly documented
as well). At first this may seem like a serious design flaw. Why have a multi-threading primitive
that's not thread-safe itself?</p>
<p>A lock object is not a synchronization primitive. A lock object's sole responsibility is
to ensure that a mutex is both locked and unlocked in a manner that won't result in the common
error of locking a mutex and then forgetting to unlock it. This means that instances of a
lock object are only going to be created, at least in theory, within block scope and won't
be shared between threads. Only the mutex objects will be created outside of block scope and/or
shared between threads. Though it's possible to create a lock object outside of block scope and
to share it between threads to do so would not be a typical usage. Nor are there any cases when
such usage would be required.</p>
<p>Lock objects must maintain some state information. In order to allow a program to determine
if a try_lock or timed_lock was successful the lock object must retain state indicating
the success or failure of the call made in its constructor. If a lock object were to have
such state and remain thread-safe it would need to synchronize access to the state information
which would result in roughly doubling the time of most operations. Worse, since checking
the state can occur only by a call after construction we'd have a race condition if the lock
object were shared between threads.</p>
<p>So, to avoid the overhead of synchronizing access to the state information and to avoid
the race condition the Boost.Threads library simply does nothing to make lock objects thread-safe. Instead, sharing a lock object between threads results in undefined behavior. Since the
only proper usage of lock objects is within block scope this isn't a problem, and so long
as the lock object is properly used there's no danger of any multi-threading issues.</p>
<h2><a name="thread">Rationale for Non-copyable Thread Type</a></h2>
<p>Programmers who are used to C libraries for multi-threaded programming are likely to
wonder why Boost.Threads uses a non-copyable design for <a href="thread.html">boost::thread</a>. After all, the C
thread types are copyable, and you often have a need for copying them within user code.
However, careful comparison of C designs to C++ designs shows a flaw in this logic.</p>
<p>All C types are copyable. It is, in fact, not possible to make a non-copyable type in
C. For this reason types that represent system resources in C are often designed to behave
very similarly to a pointer to dynamic memory. There's an API for acquiring the resource
and an API for releasing the resources. For memory we have pointers as the type and
alloc/free for the acquisition and release APIs. For files we have FILE* as the type
and fopen/fclose for the acquisition and release APIs. You can freely copy instances of the
types but must manually manage the lifetime of the actual resource through the acquisition
and release APIs.</p>
<p>C++ designs recognize that the acquisition and release APIs are error prone and try
to eliminate possible errors by acquiring the resource in the constructor and releasing it
in the destructor. The best example of such a design is the std::iostream set of classes
which can represent the same resource as the FILE* type in C. A file is opened in the
std::fstream's constructor and closed in its destructor. However, if an iostream were
copyable it could lead to a file being closed twice, an obvious error, so the std::iostream
types are noncopyable by design. This is the same design used by boost::thread, which
is a simple and easy to understand design that's consistent with other C++ standard types.</p>
<p>During the design of boost::thread it was pointed out that it would be possible to allow
it to be a copyable type if some form of "reference management" were used, such as ref-counting
or ref-lists, and many argued for a boost::thread_ref design instead. The reasoning was
that copying "thread" objects was a typical need in the C libraries, and so presumably would
be in the C++ libraries as well. It was also thought that implementations could provide
more efficient reference management then wrappers (such as boost::shared_ptr) around a noncopyable
thread concept. Analysis of whether or not these arguments would hold true don't appear to
bear them out. To illustrate the analysis we'll first provide pseudo-code illustrating the six
typical usage patterns of a thread object.</p>
<h3>1. Simple creation of a thread.</h3>
<pre>
void foo()
{
create_thread(&amp;bar);
}
</pre>
<h3>2. Creation of a thread that's later joined.</h3>
<pre>
Void foo()
void foo()
{
thread = create_thread(&amp;bar);
join(thread);
}
</pre>
<h3>3. Simple creation of several threads in a loop.</h3>
<h3>3. Simple creation of several threads in a loop.</h3>
<pre>
Void foo()
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
create_thread(&amp;bar);
}
</pre>
<h3>4. Creation of several threads in a loop which are later joined.</h3>
<pre>
Void foo()
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = create_thread(&amp;bar);
@@ -176,41 +181,51 @@ Void foo()
threads[i].join();
}
</pre>
<h3>5. Creation of a thread whose ownership is passed to another object/method.</h3>
<h3>5. Creation of a thread whose ownership is passed to another object/method.</h3>
<pre>
Void foo()
void foo()
{
thread = create_thread(&amp;bar);
manager.owns(thread);
}
</pre>
<h3>6. Creation of a thread whose ownership is shared between multiple objects.</h3>
<h3>6. Creation of a thread whose ownership is shared between multiple objects.</h3>
<pre>
Void foo()
void foo()
{
thread = create_thread(&amp;bar);
manager1.add(thread);
manager2.add(thread);
}
</pre>
<p>Of these usage patterns there&#39;s only one that requires reference management
(number 6). Hopefully it&#39;s fairly obvious that this usage pattern simply
won&#39;t occur as often as the other usage patterns. So there really isn&#39;t
a &quot;typical need&quot; for a thread concept, though there is some need.</p>
<p>Since the need isn&#39;t typical we must use different criteria for deciding
on either a thread_ref or thread design. Possible criteria include ease of use
and performance. So let&#39;s analyze both of these carefully.</p>
<p>With ease of use we can look at existing experience. The standard C++ objects
that represent a system resource, such as std::iostream, are noncopyable, so
we know that C++ programmers must at least be experienced with this design.
Most C++ developers are also used to smart pointers such as boost::shared_ptr,
so we know they can at least adapt to a thread_ref concept with little effort.
So existing experience isn&#39;t going to lead us to a choice.</p>
<p>The other thing we can look at is how difficult it is to use both types for
the six usage patterns above. If we find it overly difficult to use a concept
for any of the usage patterns there would be a good argument for choosing the
other design. So we&#39;ll code all six usage patterns using both designs.</p>
<p>Of these usage patterns there's only one that requires reference management (number 6).
Hopefully it's fairly obvious that this usage pattern simply won't occur as often as the
other usage patterns. So there really isn't a "typical need" for a thread concept, though
there is some need.</p>
<p>Since the need isn't typical we must use different criteria for deciding on either a
thread_ref or thread design. Possible criteria include ease of use and performance. So let's
analyze both of these carefully.</p>
<p>With ease of use we can look at existing experience. The standard C++ objects that
represent a system resource, such as std::iostream, are noncopyable, so we know that C++
programmers must at least be experienced with this design. Most C++ developers are also
used to smart pointers such as boost::shared_ptr, so we know they can at least adapt to
a thread_ref concept with little effort. So existing experience isn't going to lead us
to a choice.</p>
<p>The other thing we can look at is how difficult it is to use both types for the six usage
patterns above. If we find it overly difficult to use a concept for any of the usage patterns
there would be a good argument for choosing the other design. So we'll code all six usage
patterns using both designs.</p>
<h3>1.</h3>
<pre>
void foo()
{
@@ -222,7 +237,9 @@ void foo()
thread_ref thrd = create_thread(&amp;bar);
}
</pre>
<h3>2.</h3>
<pre>
void foo()
{
@@ -232,11 +249,13 @@ void foo()
void foo()
{
thread_ref thrd =
thread_ref thrd =
create_thread(&amp;bar);thrd-&gt;join();
}
</pre>
<h3>3.</h3>
<pre>
void foo()
{
@@ -250,7 +269,9 @@ void foo()
thread_ref thrd = create_thread(&amp;bar);
}
</pre>
<h3>4.</h3>
<pre>
void foo()
{
@@ -267,10 +288,12 @@ void foo()
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = create_thread(&amp;bar);
for (int i= 0; i&lt;NUM_THREADS;
++i)threads[i]-&gt;join();
++i)threads[i]-&gt;join();
}
</pre>
<h3>5.</h3>
<pre>
void foo()
{
@@ -284,7 +307,9 @@ void foo()
manager.owns(thrd);
}
</pre>
<h3>6.</h3>
<pre>
void foo()
{
@@ -300,14 +325,15 @@ void foo()
manager2.add(thrd);
}
</pre>
<p>This shows the usage patterns being nearly identical in complexity for both
designs. The only actual added complexity occurs because of the use of operator
new in (4), (5) and (6) and the use of std::auto_ptr and boost::shared_ptr in
(4) and (6) respectively. However, that&#39;s not really much added complexity,
and C++ programmers are used to using these idioms any way. Some may dislike
the presence of operator new in user code, but this can be eliminated by proper
design of higher level concepts, such as the boost::thread_group class that
simplifies example (4) down to:</p>
<p>This shows the usage patterns being nearly identical in complexity for both designs.
The only actual added complexity occurs because of the use of operator new in (4), (5)
and (6) and the use of std::auto_ptr and boost::shared_ptr in (4) and (6) respectively.
However, that's not really much added complexity, and C++ programmers are used to using
these idioms any way. Some may dislike the presence of operator new in user code,
but this can be eliminated by proper design of higher level concepts, such as the
boost::thread_group class that simplifies example (4) down to:</p>
<pre>
void foo()
{
@@ -317,83 +343,89 @@ void foo()
threads.join_all();
}
</pre>
<p>So ease of use is really a wash and not much help in picking a design.</p>
<p>So what about performance? If you look at the above code examples we can analyze
the theoretical impact to performance that both designs have. For (1) we can
see that platforms that don&#39;t have a ref-counted native thread type (POSIX,
for instance) will be impacted by a thread_ref design. Even if the native thread
type is ref-counted there may be an impact if more state information has to
be maintained for concepts foreign to the native API, such as clean up stacks
for Win32 implementations. For (2) the performance impact will be identical
to (1). The same for (3). For (4) things get a little more interesting and we
find that theoretically at least the thread_ref may perform faster since the
thread design requires dynamic memory allocation/deallocation. However, in practice
there may be dynamic allocation for the thread_ref design as well, it will just
be hidden from the user. As long as the implementation has to do dynamic allocations
the thread_ref loses again because of the reference management. For (5) we see
the same impact as we do for (4). For (6) we still have a possible impact to
the thread design because of dynamic allocation but thread_ref no longer suffers
because of its reference management, and in fact, theoretically at least, the
thread_ref may do a better job of managing the references. All of this indicates
that thread wins for (1), (2) and (3), with (4) and (5) the winner depends on
the implementation and the platform but the thread design probably has a better
chance, and with (6) it will again depend on the implementation and platform
but this time we favor thread_ref slightly. Given all of this it&#39;s a narrow
margin, but the thread design prevails.</p>
<p>Given this analysis, and the fact that noncopyable objects for system resources
are the normal designs that C++ programmers are used to dealing with, the <b>Boost.Threads</b>
library has gone with a noncopyable design.</p>
<h2><a name="events"></a>Rationale for not providing <i>Event Variables</i></h2>
<p><i>Event variables</i> are simply far too error-prone. <a href=
"condition.html">Condition variables</a> are a much safer alternative.</p>
<p>So what about performance? If you look at the above code examples we can analyze
the theoretical impact to performance that both designs have. For (1) we can see that
platforms that don't have a ref-counted native thread type (POSIX, for instance) will
be impacted by a thread_ref design. Even if the native thread type is ref-counted there
may be an impact if more state information has to be maintained for concepts foreign
to the native API, such as clean up stacks for Win32 implementations. For (2) the
performance impact will be identical to (1). The same for (3). For (4) things get a
little more interesting and we find that theoretically at least the thread_ref may
perform faster since the thread design requires dynamic memory allocation/deallocation.
However, in practice there may be dynamic allocation for the thread_ref design as well,
it will just be hidden from the user. As long as the implementation has to do dynamic
allocations the thread_ref loses again because of the reference management. For (5)
we see the same impact as we do for (4). For (6) we still have a possible impact
to the thread design because of dynamic allocation but thread_ref no longer suffers
because of it's reference management, and in fact, theoretically at least, the thread_ref
may do a better job of managing the references. All of this indicates that thread wins
for (1), (2) and (3), with (4) and (5) the winner depends on the implementation and the platform
but the thread design probably has a better chance, and with (6) it will again
depend on the implementation and platform but this time we favor thread_ref slightly.
Given all of this it's a narrow margin, but the thread design prevails.</p>
<p>Given this analysis, and the fact that noncopyable objects for system resources are
the normal designs that C++ programmers are used to dealing with, the Boost.Threads
library has gone with a noncopyable design.</p>
<h2>Rationale for not providing <i><a name="Events">Event</a> Variables</i></h2>
<p><i>Event variables </i>are simply far too error-prone.&nbsp; <a href="condition.html">Condition
variables</a> are a much safer alternative.</p>
<p>[Note that Graphical User Interface <i>events</i> are a different concept,
and are not what is being discussed here.]</p>
and are not what is being discussed here.]</p>
<p>Event variables were one of the first synchronization primitives. They are
still used today, for example, in the native Windows multithreading API.</p>
<p>Yet both respected computer science researchers and experienced multithreading
practitioners believe event variables are so inherently error-prone that they
should never be used, and thus should not be part of a multithreading library.</p>
<p>Per Brinch Hansen <a href="bibliography.html#Brinch-Hansen-73"> [Brinch Hansen
73]</a> analyzed event variables in some detail, pointing out [emphasis his]
that &quot;<i>event operations force the programmer to be aware of the relative
speeds of the sending and receiving processes</i>&quot;. His summary:</p>
still used today, for example, in the native Windows multithreading API.</p>
<p>Yet both respected computer science researchers and experienced
multithreading practitioners believe event variables are so inherently
error-prone that they should never be used, and thus should not be part of a
multithreading library.</p>
<p>Per Brinch Hansen <a href="bibliography.html#Brinch-Hansen-73">[Brinch Hansen
73]</a> analyzed event variables in some detail, pointing out [emphasis his]
that &quot;<i>event operations force the programmer to be aware of the relative
speeds of the sending and receiving processes</i>&quot;. His summary:</p>
<blockquote>
<p>We must therefore conclude that event variables of the previous type are
impractical for system design. <i>The effect of an interaction between two
processes must be independent of the speed at which it is carried out.</i></p>
impractical for system design. <i>The effect of an interaction between two
processes must be independent of the speed at which it is carried out.</i></p>
</blockquote>
<p>Experienced programmers using the Windows platform today report that event
variables are a continuing source of errors, even after previous bad experiences
caused them to be very careful in their use of event variables. Overt problems
can be avoided, for example, by teaming the event variable with a mutex, but
that may just convert a <a href=
"definitions.html#Race condition">race condition</a> into another problem,
such as excessive resource use. One of the most distressing aspects of the experience
reports is the claim that many defects are latent. That is, the programs appear
to work correctly, but contain hidden timing dependencies which will cause them
to fail when environmental factors or usage patterns change, altering relative
thread timings.</p>
<p>The decision to exclude event variables from <b>Boost.Threads</b> has been
surprising to some Windows programmers. They have written programs which work
using event variables, and wonder what the problem is. It seems similar to the
&quot;goto considered harmful&quot; controversy of 30 years ago. It isn&#39;t
that events, like gotos, can&#39;t be made to work, but rather that virtually
all programs using alternatives will be easier to write, debug, read, maintain,
and be less likely to contain latent defects.</p>
<p>Experienced programmers using the Windows platform today
report that event variables are a continuing source of errors, even after previous
bad experiences caused them to be very careful in their use of event
variables.&nbsp; Overt problems can be avoided, for example, by teaming the
event variable with a mutex, but that may just convert a <a href="definitions.html#Race condition">race
condition</a> into another problem, such as excessive resource use. One of the most
distressing aspects of the experience reports is the claim that many defects are
latent.&nbsp; That is, the programs appear to work correctly, but contain
hidden timing dependencies which will cause them to fail when environmental
factors or usage patterns change, altering relative thread timings.</p>
<p>The decision to exclude event variables from Boost.Threads has been
surprising to some Windows programmers.&nbsp; They have written programs which
work using event variables, and wonder what the problem is.&nbsp; It seems
similar to the &quot;goto considered harmful&quot; controversy of 30 years ago.
It isn't that events, like gotos, can't be made to work, but rather that
virtually all programs using alternatives will be easier to write, debug,
read, maintain, and be less likely to contain latent defects.</p>
<p>[Rationale provided by Beman Dawes]</p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->17 August, 2001<!--webbot bot="Timestamp" endspan i-checksum="34355" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</A>
2001 all rights reserved.</i></p>
</body>
</html>

View File

@@ -1,244 +1,327 @@
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<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/recursive_mutex.hpp&gt;</title>
<meta name="keywords" content="threads, BTL, thread library, C++">
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<title>Boost.Threads, recursive_mutex</title>
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<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/recursive_mutex.hpp">boost/thread/recursive_mutex.hpp</a>&gt;</h2> </td>
</tr>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">recursive_mutex<br>
recursive_try_mutex<br>
recursive_timed_mutex</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-recursive_mutex">Class <code>recursive_mutex</code></a></dt>
<dl class="page-index">
<dt><a href="#class-recursive_mutex-synopsis">Class <code>recursive_mutex</code>
synopsis</a></dt>
<dt><a href="#class-recursive_mutex-ctors">Class <code>recursive_mutex</code>
constructors and destructor</a></dt>
</dl>
<dt><a href="#class-recursive_try_mutex">Class <code>recursive_try_mutex</code></a></dt>
<dl class="page-index">
<dt><a href="#class-recursive_try_mutex-synopsis">Class <code>recursive_try_mutex</code>
synopsis</a></dt>
<dt><a href="#class-recursive_try_mutex-ctors">Class <code>recursive_try_mutex</code>
constructors and destructor</a></dt>
</dl>
<dt><a href="#class-recursive_timed_mutex">Class <code>recursive_timed_mutex</code></a></dt>
<dl class="page-index">
<dt><a href="#class-recursive_timed_mutex-synopsis">Class <code>recursive_timed_mutex</code>
synopsis</a></dt>
<dt><a href="#class-recursive_timed_mutex-ctors">Class <code>recursive_timed_mutex</code>
constructors and destructor</a></dt>
</dl>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>Include the header &lt;<a href="../../../boost/thread/recursive_mutex.hpp">boost/thread/recursive_mutex.hpp</a>&gt;
to define the <a href="#class-recursive_mutex">recursive_mutex</a>, <a href="#class-recursive_try_mutex">recursive_try_mutex</a>
and <a href="#class-recursive_timed_mutex">recursive_timed_mutex</a> classes.</p>
<p>The <a href="#class-recursive_mutex">recursive_mutex</a>, <a href="#class-recursive_try_mutex">recursive_try_mutex</a>
and <a href="#class-recursive_timed_mutex">recursive_timed_mutex</a> classes
are models of <a href="mutex_concept.html#Mutex-concept">Mutex</a>, <a href="mutex_concept.html#TryMutex-concept">TryMutex</a>,
and <a href="mutex_concept.html#TimedMutex-concept">TimedMutex</a> respectively.
These types should be used to synchronize access to shared resources when recursive
locking by a single thread is likely to occur. A good example for this is when
a class supplies &quot;internal synchronization&quot; to ensure <a href="definitions.html#Thread-safe">
thread-safety</a> and a function of the class may have to call other functions
of the class which also attempt to lock the mutex. For recursive locking mechanics,
see <a href="mutex.html">mutexes</a>.</p>
<p>Each class supplies one or more typedefs for lock types which model matching
lock concepts. For the best possible performance you should use the mutex class
that supports the minimum set of lock types that you need.</p>
<table summary="lock types" border="1" cellpadding="5">
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#recursive_mutex Synopsis">Class recursive_mutex Synopsis</a><br>
<a href="#recursive_mutex Members">Class recursive_mutex Members</a><br>
<a href="#recursive_try_mutex Synopsis">Class recursive_try_mutex Synopsis</a><br>
<a href="#recursive_try_mutex Members">Class recursive_try_mutex Members</a><br>
<a href="#recursive_timed_mutex Synopsis">Class recursive_timed_mutex Synopsis</a><br>
<a href="#recursive_timed_mutex Members">Class recursive_timed_mutex Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>recursive_mutex</code>, <code>recursive_try_mutex</code> and
<code>recursive_timed_mutex</code> classes define full featured models of the
<a href="mutex_concept.html#Mutex">Mutex</a>,
<a href="mutex_concept.html#TryMutex">TryMutex</a> and
<a href="mutex_concept.html#TimedMutex">TimedMutex</a> concepts with recursive locking
semantics. These types should be used to synchronize access to shared resources
when recursive locking by a single thread is likely to occur. A good example for this
is when a class supplies "internal synchronization" to ensure
<a href="definitions.html#Thread-safe">thread-safety</a> and a function of the class
may have to call other functions of the class which also attempt to lock the mutex.
For recursive locking mechanics, see <a href="mutex.html">mutexes</a>.
<p>Each class supplies one or more typedefs for lock types which model matching
lock concepts. For the best possible performance you should use the mutex class that
supports the minimum set of lock types that you need.</p>
<table border="1" cellpadding="5">
<tr>
<td><b>Mutex Class</b></td>
<td><b>Lock name</b></td>
<td><b>Implementation defined Lock Type</b></td>
<td><b>Lock Concept</b></td>
</tr>
<tr>
<td valign="top"><a href="#recursive_mutex Synopsis"><code> recursive_mutex</code></a></td>
<td valign="top"><a href="#recursive_mutex Synopsis"><code>recursive_mutex</code></a></td>
<td valign="middle"><code>scoped_lock</code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock"> ScopedLock</a></td>
<td valign="middle"><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;recursive_mutex&gt;</code></a></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a></td>
</tr>
<tr>
<td valign="top"><code><a href="#recursive_try_mutex Synopsis"> recursive_try_mutex</a></code></td>
<td valign="top"><code><a href="#recursive_try_mutex Synopsis">recursive_try_mutex</a></code></td>
<td valign="middle"><code>scoped_lock<br>
scoped_try_lock</code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock"> ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock"> ScopedTryLock</a></td>
<td valign="middle"><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;recursive_try_mutex&gt;<br>
</code></a><code><a href="scoped_try_lock.html">detail::thread::scoped_try_lock&lt;recursive_try_mutex&gt;</a></code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a></td>
</tr>
<tr>
<td valign="top"><code><a href=
"#recursive_timed_mutex Synopsis"> recursive_timed_mutex</a></code>
</td>
<td valign="top"><code><a href="#recursive_timed_mutex Synopsis">recursive_timed_mutex</a></code> </td>
<td valign="middle"><code>scoped_lock<br>
scoped_try_lock<br>
scoped_timed_lock</code></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock"> ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock"> ScopedTryLock</a><br>
<a href="lock_concept.html#ScopedTimedLock"> ScopedTimedLock</a></td>
<td valign="middle"><a href="scoped_lock.html"><code>detail::thread::scoped_lock&lt;recursive_timed_mutex&gt;</code></a><br>
<a href="scoped_try_lock.html"><code>detail::thread::scoped_try_lock&lt;recursive_timed_mutex&gt;</code></a><br>
<a href="scoped_timed_lock.html"><code>detail::thread::scoped_timed_lock&lt;recursive_timed_mutex&gt;</code></a></td>
<td valign="middle"><a href="lock_concept.html#ScopedLock">ScopedLock</a><br>
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a><br>
<a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a></td>
</tr>
</table>
<p>The <code>recursive_mutex</code>, <code>recursive_try_mutex</code> and <code>recursive_timed_mutex</code>
employ a <code>Recursive</code> <a href="mutex_concept.html#LockingStrategies">locking
strategy</a>, so attempts to recursively lock them succeed and an internal &quot;lock
count&quot; is maintained. Attempts to unlock them by a thread that does not
own a lock on them will result in <b>undefined behavior</b>.</p>
<p>The <code>recursive_mutex</code>, <code>recursive_try_mutex</code> and <code>recursive_timed_mutex</code>
leave the <a href=
"mutex_concept.html#SchedulingPolicies">scheduling policy</a> as <code>
Unspecified</code>. Programmers should assume that threads waiting for a lock
on objects of these types acquire the lock in a random order, even though the
specific behavior for a given platform may be different.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-recursive_mutex"></a>Class <code>recursive_mutex</code></h3>
<p>The <code>recursive_mutex</code> class is a model of <a href="mutex_concept.html#Mutex-concept">Mutex</a>
and <a href="overview.html#non-copyable">NonCopyable</a>, and provides no additional
facilities beyond the requirements of these concepts.</p>
<h4><a name="class-recursive_mutex-synopsis"></a>Class <code>recursive_mutex</code>
synopsis</h4>
<p>The <code>recursive_mutex</code>, <code>recursive_try_mutex</code> and
<code>recursive_timed_mutex</code> employ a <code>Recursive</code>
<a href="mutex_concept.html#LockingStrategies">locking strategy</a>, so attempts to
recursively lock them succeed and an internal "lock count" is maintained. Attempts
to unlock them by a thread that does not own a lock on them will result in a
<a href="lock_error.html">lock_error</a> exception being thrown.</p>
<p>The <code>recursive_mutex</code>, <code>recursive_try_mutex</code> and
<code>recursive_timed_mutex</code> leave the
<a href="mutex_concept.html#SchedulingPolicies">scheduling policy</a> as
<code>Unspecified</code>. Programmers should assume that threads waiting for a lock on
objects of these types acquire the lock in a random order, even though the specific
behavior for a given platform may be different.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a>
</pre>
<h2>Class <a name="recursive_mutex Synopsis"> recursive_mutex Synopsis</a></h2>
<hr>
<pre>
namespace boost
{
class recursive_mutex : private boost::noncopyable // Exposition only.
// Class recursive_mutex meets the NonCopyable requirement.
class recursive_mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class recursive_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
recursive_mutex();
~recursive_mutex();
};
}
</pre>
<h2>Class <a name="recursive_mutex Members">recursive_mutex Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
recursive_mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~recursive_mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash..</p>
<hr>
<h2>
Class <a name="recursive_try_mutex Synopsis">recursive_try_mutex Synopsis</a>
</h2>
<pre>
namespace boost
{
class recursive_try_mutex : private boost::noncopyable // Exposition only.
// Class recursive_try_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef [implementation defined; see Introduction] scoped_lock;
recursive_mutex();
~recursive_mutex();
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_try_lock;
recursive_try_mutex();
~recursive_try_mutex();
};
};
}
</pre>
<h4><a name="class-recursive_mutex-ctors"></a>Class <code>recursive_mutex</code>
constructors and destructor</h4>
<pre>
recursive_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<pre>
~recursive_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in an unlocked sate.</dt>
<dt><b>Danger:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</dt>
</dl>
<h3><a name="class-recursive_try_mutex"></a>Class <code>recursive_try_mutex</code></h3>
<p>The <code>recursive_try_mutex</code> class is a model of <a href="mutex_concept.html#TryMutex-concept">TryMutex</a>
and <a href="overview.html#non-copyable">NonCopyable</a>, and provides no additional
facilities beyond the requirements of these concepts.</p>
<h4><a name="class-recursive_try_mutex-synopsis"></a>Class <code>recursive_try_mutex</code>
synopsis</h4>
<pre>
namespace boost
{
class recursive_mutex : private boost::noncopyable // Exposition only.
// Class recursive_mutex meets the NonCopyable requirement.
{
Public:
typedef [implementation defined; see Introduction] scoped_lock;
typedef [implementation defined; see Introduction] scoped_try_lock;
recursive_try_mutex();
~recursive_try_mutex();
};
};
</pre>
<h4><a name="class-recursive_try_mutex-ctors"></a>Class <code>recursive_try_mutex</code>
constructors and destructor</h4>
<h2>Class <a name="recursive_try_mutex Members">recursive_try_mutex Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
recursive_try_mutex();
recursive_try_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~recursive_try_mutex();
~recursive_try_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in an unlocked sate.</dt>
<dt><b>Danger:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</dt>
</dl>
<h3><a name="class-recursive_timed_mutex"></a>Class <code>recursive_timed_mutex</code></h3>
<p>The <code>recursive_timed_mutex</code> class is a model of <a href="mutex_concept.html#TimedMutex-concept">TimedMutex</a>
and <a href="overview.html#non-copyable">NonCopyable</a>, and provides no additional
facilities beyond the requirements of these concepts.</p>
<h4><a name="class-recursive_timed_mutex-synopsis"></a>Class <code>recursive_timed_mutex</code>
synopsis</h4>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash..</p>
<hr>
<h2>
Class <a name="recursive_timed_mutex Synopsis">recursive_timed_mutex Synopsis</a>
</h2>
<pre>
namespace boost
{
class recursive_timed_mutex : private boost::noncopyable // Exposition only.
// Class recursive_mutex meets the NonCopyable requirement.
// Class recursive_timed_mutex meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
Public:
typedef [implementation defined; see Introduction] scoped_lock;
typedef [implementation defined; see Introduction] scoped_try_lock;
typedef [implementation defined; see Introduction] scoped_timed_lock;
recursive_timed_mutex();
~recursive_timed_mutex();
public:
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_try_lock;
typedef <i>[implementation defined; see <a href="#Introduction">Introduction</a>]</i> scoped_timed_lock;
recursive_timed_mutex();
~recursive_timed_mutex();
};
}
</pre>
<h2>
Class <a name="recursive_timed_mutex Members">recursive_timed_mutex Members</a>
</h2>
<hr>
<h3>Constructor</h3>
<pre>
recursive_timed_mutex();
</pre>
<p><b>Postconditions: </b><code>*this</code> is in the unlocked state.</p>
<hr>
<h3>Destructor</h3>
<pre>
~recursive_timed_mutex();
</pre>
<p><b>Requires:</b> <code>*this</code> is in the unlocked state.</p>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<p><b>Dangers:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash..</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
class counter
{
public:
counter() : count(0) { }
int add(int val) {
boost::recursive_mutex::scoped_lock scoped_lock(mutex);
count += val;
return count;
}
int increment() {
boost::recursive_mutex::scoped_lock scoped_lock(mutex);
return add(1);
}
private:
boost::recursive_mutex mutex;
int count;
};
counter c;
void change_count(void*)
{
std::cout &lt;&lt; &quot;count == &quot; &lt;&lt; c.increment() &lt;&lt; std::endl;
}
int main(int, char*[])
{
const int num_threads=4;
boost::thread_group threads;
for (int i=0; i &lt; num_threads; ++i)
threads.create_thread(&amp;change_count, 0);
threads.join_all();
return 0;
}
</pre>
<h4><a name="class-recursive_timed_mutex-ctors"></a>Class <code>recursive_timed_mutex</code>
constructors and destructor</h4>
<pre>
recursive_timed_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<pre>
~recursive_timed_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in an unlocked sate.</dt>
<dt><b>Danger:</b> Destruction of a locked mutex is a serious programming error
resulting in undefined behavior such as a program crash.</dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<p><a href="../example/recursive_mutex.cpp">libs/thread/example/recursive_mutex.cpp</a></p>
<p>The output is:</p>
<pre>
count == 1
count == 2
count == 3
count == 4
</pre>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<title>Boost.Threads, atomic_t</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">atomic_t</h2>
</td>
</tr>
</table>
<hr>
<h2>Header</h2>
<p>The <tt>atomic_t</tt> class defines an "atomic integer" type. This class should be used
to perform thread safe operations on an integral type with out the overhead of locks. Only
a limited set of integer operations are available with an <tt>atomic_t</tt> instance.</p>
<pre>
#include &lt;boost/thread/atomic.hpp&gt;
</pre>
<h2>Public Interface</h2>
<pre>
class atomic_t
{
public:
typedef <b>implementation defined</b> value_type;
explicit atomic_t(value_type val=0);
};
atomic_t::value_type read(const atomic_t&amp; x);
atomic_t::value_type increment(atomic_t&amp; x);
atomic_t::value_type decrement(atomic_t&amp; x);
atomic_t::value_type swap(atomic_t&amp; x, atomic_t::value_type y);
atomic_t::value_type compare_swap(atomic_t&amp; x, atomic_t::value_type y, atomic_t::value_type z);
</pre>
<h3>Constructor</h3>
<pre>
atomic_t(atomic_t::value_type val=0);
</pre>
<p>Constructs an <tt>atomic_t</tt> and sets its value to <tt>val</tt>.</p>
<h3>read</h3>
<pre>
atomic_t::value_type read(const atomic_t&amp; x);
</pre>
<p>Gets the current value of <tt>x</tt>.</p>
<h3>increment</h3>
<pre>
atomic_t::value_type increment(atomic_t&amp; x);
</pre>
<p>Increments <tt>x</tt> and returns a value <tt>&lt; 0</tt> if the result is less than 0,
<tt>&gt; 0</tt> if the result is greater than 0 and <tt>== 0</tt> if the result is equal to
0.</p>
<h3>decrement</h3>
<pre>
atomic_t::value_type decrement(atomic_t&amp; x);
</pre>
<p>Decrements <tt>x</tt> and returns a value <tt>&lt; 0</tt> if the result is less than 0,
<tt>&gt; 0</tt> if the result is greater than 0 and <tt>== 0</tt> if the result is equal to
0.</p>
<h3>swap</h3>
<pre>
atomic_t::value_type swap(atomic_t&amp; x, atomic_t::value_type y);
</pre>
<p>Assigns the value of <tt>y</tt> to <tt>x</tt> and returns the value of <tt>x</tt> prior
to the swap.</p>
<h3>compare_swap</h3>
<pre>
atomic_t::value_type compare_swap(atomic_t&amp; x, atomic_t::value_type y, atomic_t::value_type z);
</pre>
<p>Compares the value of <tt>z</tt> to the value of <tt>x</tt> and if equal sets the value of
<tt>x</tt> to the value of <tt>y</tt> and returns the value of <tt>x</tt> prior to the swap.</p>
<h2>Example Usage</h2>
<pre>
#include &lt;boost/thread/atomic.hpp&gt;
#include &lt;boost/test/test_tools.hpp&gt;
int test_main(int, char*[])
{
boost::atomic_t a;
BOOST_TEST_VERIFY(boost::read(a) == 0);
BOOST_TEST_VERIFY(boost::increment(a) &gt; 0);
BOOST_TEST_VERIFY(boost::decrement(a) == 0);
BOOST_TEST_VERIFY(boost::swap(a, 1) == 0);
BOOST_TEST_VERIFY(boost::swap(a, 2, 0) == 1);
BOOST_TEST_VERIFY(boost::read(a) == 1);
}
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->06 August, 2001<!--webbot bot="Timestamp" endspan i-checksum="34352" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - RWLock Concepts</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">RWLock Concepts</h2>
</td>
</tr>
</table>
<hr>
<dl class="index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#requirements">Concept Requirements</a></dt>
<dl class="index">
<dt><a href="#lock-state-enumeration">Lock State Enumeration</a></dt>
<dt><a href="#RWLock-concept">RWLock Concept</a></dt>
<dt><a href="#ScopedRWLock-concept">ScopedRWLock Concept</a></dt>
<dt><a href="#ScopedTryRWLock-concept">ScopedTryRWLock Concept</a></dt>
<dt><a href="#ScopedTimedRWLock-concept">ScopedTimedRWLock Concept</a></dt>
</dl>
<dt><a href="#models">Models</a></h2>
<dt><a href="#footnotes">Footnotes</a></dt>
</dl>
<h2><a name="introduction"></a>Introduction</h2>
<p>The lock concepts provide exception safe means for locking and unlocking a
<a href="rw_mutex_concept.html"> rw_mutex model</a>. In other words they are
an implementation of the <i>Scoped Locking</i> <a href="bibliography.html#Schmidt 00">[Schmidt
00]</a> pattern. The <a href="#ScopedRWLock">ScopedRWLock</a> concept, with
<a href="#ScopedTryRWLock"> ScopedTryRWLock</a> and <a href="#ScopedTimedRWLock">ScopedTimedRWLock</a>
refinements, formalize the requirements.</p>
<p>Lock models are constructed with a reference to a <a href="mutex_concept.html">mutex
model</a> and typically acquire ownership of the <a href="mutex_concept.html">mutex
model</a> by setting its state to locked. They also ensure ownership is relinquished
in the destructor. Lock models also expose functions to query the lock status
and to manually lock and unlock the <a href="mutex_concept.html">mutex model</a>.</p>
<p>Instances of lock models are meant to be short lived, expected to be used at
block scope only. The lock models are not <a href="definitions.html#Thread-safe">thread-safe</a>.
Lock models must maintain state to indicate whether or not they've been locked
and this state is not protected by any synchronization concepts. For this reason
an instance of a lock model should never be shared between multiple threads.</p>
<h2><a name="requirements"></a>Concept Requirements</h2>
<p>[For documentation purposes, portions of the concept requirements are repeated
in the documentation for specific lock classes. Those copies need to be kept
in sync with the requirements here.]</p>
<h3><a name="lock-state-enumeration"></a>Lock State Enumeration</h3>
<p>An enumerated value that can be one of three possible values - {NO_LOCK, SHARED_LOCK,
or EXCL_LOCK).&nbsp; Each class modeling the Lock Concept will maintain this
state as its view of the lock-state of the controlled rw_mutex.</p>
<h3><a name="RWLock-concept"></a>RWLock Concept</h3>
<p>For a <a href="#ScopedRWLock">ScopedRWLock</a>, <a href="#ScopedTryRWLock">ScopedTryRWLock</a>,
or <a href="#ScopedTimedRWLock">ScopedTimedRWLock</a> type <code>L</code> and
an object <code>lk</code> and const object <code>clk</code> of that type, the
following expressions must be well-formed and have the indicated effects.</p>
<p>The Lock concept is used as a base for the <a href="#ScopedRWLock">ScopedRWLock</a>,
<a href="#ScopedTryRWLock">ScopedTryRWLock</a>, and <a href="#ScopedTimedRWLock">ScopedTimedRWLock</a>
refinements. The associated rw_mutex type is as specified for each of those
refinements respectively.</p>
<table summary="Lock expressions" border="1" cellpadding="5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top"><code>(&amp;lk)-&gt;~L();</code></td>
<td><code>if (locked()) unlock();</code></td>
</tr>
<tr>
<td valign="top"><code>(&amp;clk)-&gt;operator const void*()</code></td>
<td>Returns type void*, non-zero if if the associated rw_mutex has been locked
by <code> clk</code>, otherwise 0.</td>
</tr>
<tr>
<td valign="top"><code>clk.locked()</code></td>
<td>Returns a <code>bool</code>, <code>(&amp;clk)-&gt;operator const void*()
!= 0</code></td>
</tr>
<tr>
<td valign="top"><code>clk.lockstate()</code></td>
<td><code>Returns an enumeration of the lock state,&nbsp;NO_LOCK, EXCL_LOCK
or SHARED_LOCK</code></td>
</tr>
<tr>
<td valign="top"><code>lk.wrlock()</code></td>
<td>Throws lock_error if locked(). If the associated rw_mutex is already locked
by some other thread, places the current thread in the <a href="definitions.html#State">
Blocked</a> state until the associated rw_mutex is unlocked, after which
the current thread is placed in the <a href="definitions.html#State">Ready</a>
state, eventually to be returned to the <a href="definitions.html#State">Running</a>
state.<br>
Postcondition: locked() and lockstate() == EXCL_LOCK</td>
</tr>
<tr>
<td valign="top"><code>lk.rdlock()</code></td>
<td>Throws lock_error if locked().&nbsp; If the associated rw_mutex cannot
immediately grant the shared lock, places the current thread in the <a href="definitions.html#State">
Blocked</a> state until the associated rw_ mutex can grant a shared lock,
after which the current thread is placed in the <a href="definitions.html#State">Ready</a>
state, eventually to be returned to the <a href="definitions.html#State">Running</a>
state.&nbsp;<br>
Postcondition: locked() and lockstate() == SHARED_LOCK</td>
</tr>
<tr>
<td valign="top"><code>lk.unlock()</code></td>
<td>If !locked(), throws lock_error, otherwise unlocks the associated rw_mutex.<br>
Postcondition: !locked()</td>
</tr>
</table>
<h3><a name="ScopedRWLock-concept"></a>ScopedRWLock Concept</h3>
<p>A ScopedRWLock must meet the <a href="#Lock">RWLock</a> requirements. For a
ScopedRWLock type <code>L</code> and an object <code>lk</code> of that type,
and an object <code>m</code> of a type meeting the <a href="mutex_concept.html#Mutex">
RWMutex</a> requirements, and an object <code>s</code> of type <code>lock_state</code>,
the following expressions must be well-formed and have the indicated effects.</p>
<table summary="ScopedRWLock expressions" border="1" cellpadding="5" width="732">
<tr>
<td width="91"><b>Expression</b></td>
<td width="609"><b>Effects</b></td>
</tr>
<tr>
<td valign="top" width="91"><code>L lk(m);</code></td>
<td width="609">Constructs an object <code>lk</code>, and associates rw_mutex
<code>m</code> with it, then calls <code>lock()</code></td>
</tr>
<tr>
<td valign="top" width="91"><code>L lk(m,s);</code></td>
<td width="609">Constructs an object <code>lk</code>, and associates rw_mutex
<code>m</code> with it, then if <code>s==SHARED_LOCK</code>, calls <code>sharedlock()
or if s==EXCL_LOCK then calls lock()</code></td>
</tr>
</table>
<h3><a name="ScopedTryRWLock-concept"></a>ScopedTryRWLock Concept</h3>
<p>A ScopedTryRWLock must meet the <a href="#Lock">RWLock</a> requirements. For
a ScopedTryRWLock type <code>L</code> and an object <code>lk</code> of that
type, and an object <code>m</code> of a type meeting the <a href="mutex_concept.html#TryMutex">
TryRWMutex</a> requirements, and an object <code>s</code> of type <code>lock_state</code>,
the following expressions must be well-formed and have the indicated effects.</p>
<table summary="ScopedTryRWLock expressions" border="1" cellpadding="5">
<tr>
<td width="157"><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top" width="157"><code>L lk(m);</code></td>
<td>Constructs an object <code>lk</code>, and associates rw_mutex <code>m</code>
with it, then calls <code>try_lock()</code></td>
</tr>
<tr>
<td valign="top" width="157"><code>L lk(m,s);</code></td>
<td>Constructs an object <code>lk</code>, and associates rw_mutex <code>m</code>
with it, then if <code>s==SHARED_LOCK</code>, calls <code>sharedlock() or
if s==EXCL_LOCK then calls lock()</code></td>
</tr>
<tr>
<td valign="top" width="157"><code>lk.try_wrlock()</code></td>
<td>If locked(), throws <code>lock_error</code>. Makes a non-blocking attempt
to exclusive-lock the associated rw_mutex, returning <code>true</code> if
the lock attempt is successful, otherwise <code>false</code>.</td>
</tr>
<tr>
<td valign="top" width="157"><code>lk.try_rdlock()</code></td>
<td>If locked(), throws <code>lock_error</code>. Makes a non-blocking attempt
to shared-lock the associated rw_mutex, returning <code>true</code> if the
lock attempt is successful, otherwise <code>false</code>.</td>
</tr>
</table>
<h3><a name="ScopedTimedRWLock-concept"></a>ScopedTimedRWLock Concept</h3>
<p>A ScopedTimedRWLock must meet the <a href="#Lock">RWLock</a> requirements.
For a ScopedTimedRWLock type <code>L</code> and an object <code>lk</code> of
that type, and an object <code>m</code> of a type meeting the <a href="mutex_concept.html#TimedMutex">
TimedRWMutex</a> requirements, and an object <code>s</code> of type <code>lock_state</code>,
and an object <code>t</code> of type <code><a href="xtime.html">xtime</a></code>,
the following expressions must be well-formed and have the indicated effects.</p>
<table summary="ScopedTimedRWLock expressions" border="1" cellpadding="5">
<tr>
<td width="164"><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td valign="top" width="164"><code>L lk(m,t);</code></td>
<td>Constructs an object <code>lk</code>, and associates rw_mutex <code>m</code>
with it, then calls <code>timed_lock(t)</code></td>
</tr>
<tr>
<td valign="top" width="164"><code>L lk(m,s);</code></td>
<td>Constructs an object <code>lk</code>, and associates rw_ mutex <code>m</code>
with it, then if <code>s==SHARED_LOCK</code>, calls <code>sharedlock() or
if s==EXCL_LOCK then calls lock()</code></td>
</tr>
<tr>
<td valign="top" width="164"><code>lk.timed_wrlock(t)</code></td>
<td>If locked(), throws lock_error. Makes a blocking attempt to exclusive-lock
the associated rw_mutex, and returns <code>true</code> if successful within
the specified time <code>t</code>, otherwise <code>false</code>.</td>
</tr>
<tr>
<td valign="top" width="164"><code>lk.timed_rdlock(t)</code></td>
<td>If locked(), throws lock_error. Makes a blocking attempt to shared-lock
the associated rw_mutex, and returns <code>true</code> if successful within
the specified time <code>t</code>, otherwise <code>false</code>.</td>
</tr>
</table>
<h2><a name="models"></a>Models</h2>
<p><b>Boost.Threads</b> currently supplies three classes which model lock concepts.</p>
<p>These classes are normally accessed via typedefs of the same name supplied
by a <a href="mutex_concept.html"> mutex model</a>.</p>
<table summary="Lock concept classes" border="1" cellpadding="5">
<tr>
<td><b>Concept</b></td>
<td><b>Refines</b></td>
<td><b>Classes Modeling the Concept</b></td>
</tr>
<tr>
<td><a href="#ScopedRWLock">ScopedRWLock</a></td>
<td>&nbsp;</td>
<td><a href="scoped_rw_lock.html">scoped_rw_lock</a></td>
</tr>
<tr>
<td><a href="#ScopedTryRWLock">ScopedTryRWLock</a></td>
<td><a href="#ScopedRWLock">ScopedRWLock</a></td>
<td><a href="scoped_try_rw_lock.html">scoped_try_rw_lock</a> </td>
</tr>
<tr>
<td><a href="#ScopedTimedRWLock">ScopedTimedRWLock</a></td>
<td><a href="#ScopedRWLock">ScopedRWLock</a></td>
<td><a href="scoped_timed_rw_lock.html">scoped_timed_rw_lock</a></td>
</tr>
</table>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:{{address}}">{{author}}</a> 2002. All Rights
Reserved.</i></p>
</body>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/rw_mutex.hpp&gt;</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/rw_mutex.hpp">boost/thread/rw_mutex.hpp</a>&gt;</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#macros">Macros</a></dt>
<dl class="page-index">
<dt><a href="#macro-spec">{{macro name}}</a></dt>
</dl>
<dt><a href="#values">Values</a></dt>
<dl class="page-index">
<dt><a href="#value-spec">{{value name}}</a></dt>
</dl>
<dt><a href="#types">Types</a></dt>
<dl class="page-index">
<dt><a href="#type-spec">{{type name}}</a></dt>
</dl>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-spec">Class <code>{{class name}}</code></a></dt>
<dl class="page-index">
<dt><a href="#class-spec-synopsis">Class <code>{{class name}}</code> synopsis</a></dt>
<dt><a href="#class-spec-ctors">Class <code>{{class name}}</code> constructors
and destructor</a></dt>
<dt><a href="#class-spec-comparisons">Class <code>{{class name}}</code>
comparison functions</a></dt>
<dt><a href="#class-spec-modifiers">Class <code>{{class name}}</code> modifier
functions</a></dt>
<dt><a href="#class-spec-observers">Class <code>{{class name}}</code> observer
functions</a></dt>
<dt><a href="#class-spec-statics">Class <code>{{class name}}</code> static
functions</a></dt>
</dl>
</dl>
<dt><a href="#functions">Functions</a></dt>
<dl class="page-index">
<dt><a href="#function-spec">{{function name}}</a></dt>
</dl>
<dt><a href="#objects">Objects</a></dt>
<dl class="page-index">
<dt><a href="#object-spec">{{object name}}</a></dt>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>The <tt><a href="#rw_mutex Synopsis">rw_mutex</a></tt>, <tt><a href="#try_rw_mutex Synopsis">
try_rw_mutex</a></tt> and <tt><a href="#timed_rw_mutex Synopsis">timed_rw_mutex</a></tt>
classes define full featured models of the <a href="rw_mutex_concept.html#rw_mutex">
RWMutex</a>, <a href="rw_mutex_concept.html#TryMutex">TryRWMutex</a>, and <a href="rw_mutex_concept.html#TimedMutex">
TimedRWMutex</a> concepts. These types should be used to synchronize access
to shared resources.&nbsp; Recursive or non-recursive locking mechanics are
acheived by supplying the appropriate Mutex type as a parameter.</p>
<p>Each class supplies one or more typedefs for lock types which model matching
lock concepts. For the best possible performance you should use the rw_mutex
class that supports the minimum set of lock types that you need.</p>
<table summary="lock types" border="1" cellpadding="5">
<tr>
<td><b>rw_mutex Class</b></td>
<td><b>Lock name</b></td>
<td><b>Implementation defined Lock Type</b></td>
<td><b>Lock Concept</b></td>
</tr>
<tr>
<td valign="top"><a href="#rw_mutex Synopsis"><code> rw_mutex</code></a></td>
<td valign="center"><code> scoped_rw_lock</code></td>
<td valign="center"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_rw_lock&lt;rw_mutex&gt;</code></a></td>
<td valign="center">ScopedRWLock</td>
</tr>
<tr>
<td valign="top"><tt><a href="#try_rw_mutex Synopsis"> try_rw_mutex</a></tt>
</td>
<td valign="center"><code> scoped_rw_lock<br>
scoped_try_rw_lock</code></td>
<td valign="center"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_rw_lock&lt;try_rw_mutex&gt;</code></a>
<code><a href="scoped_try_lock.html"> <br>
</a><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_try_rw_lock&lt;try_rw_mutex&gt;</code></a></td>
<td valign="center">ScopedRWLock<br>
ScopedRWTryLock</td>
</tr>
<tr>
<td valign="top"><code><a href="#timed_rw_mutex Synopsis"> timed_rw_mutex</a></code>
</td>
<td valign="center"><code> scoped_rw_lock<br>
scoped_try_rw_lock<br>
scoped_timed_rw_lock</code></td>
<td valign="center"><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_rw_lock&lt;timed_rw_mutex&gt;</code></a>
<code><a href="scoped_try_lock.html"> <br>
</a><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_try_rw_lock&lt;timed_rw_mutex&gt;</code></a><a href="scoped_timed_lock.html"><code><br>
</code></a><code><a href="scoped_lock.html">boost::</a></code><a href="scoped_lock.html"><code>detail::thread::scoped_timed_rw_lock&lt;timed_rw_mutex&gt;</code></a></td>
<td valign="center">ScopedRWLock<br>
ScopedRWTryLock<br>
ScopedRWTimedLock</td>
</tr>
</table>
<p>The <tt>rw_mutex</tt>, <tt>try_rw_mutex</tt> and <tt>timed_rw_mutex</tt> classes
leave the locking strategy as Unspecified.&nbsp; Programmers should assume that
threads that lock a rw_mutex, try_rw_mutex, or timed_rw_mutex multiple times
will deadlock, unless all of the lock requests are for read-locks.&nbsp;&nbsp;</p>
<p>The <tt>rw_mutex</tt>, <tt>try_rw_mutex</tt> and <tt>timed_rw_mutex</tt> allow
the programmer to explicitly choose&nbsp;the <a href="rw_mutex_concept.html#SchedulingPolicies">
scheduling policy</a> for the lock.&nbsp; This scheduling policy will dictate
how competing readers and writers will acquire the lock.&nbsp; It does not,
however, dictate the order that individual read or write requests will be granted,
in comparison to other requests of the same type.&nbsp;&nbsp;Programmers should
assume that threads waiting for a lock on objects of these types acquire the
lock in a random order, even though the specific behavior for a given platform
may be different.</p>
<H2>Release Notes/Caveats</H2>
<UL>
<LI> Self-deadlock is virtually guaranteed if a thread tries to lock the same
rw_mutex multiple times, unless all locks are read-locks (but see below)</LI>
<LI> This implementation does not protect against reader overflow.&nbsp; If
more than INT_MAX readers obtain or try to obtain a lock simultaneously, the
behavior is undefined.&nbsp; This will be addressed in a future release, but
it seems that detecting this condition &amp; reporting an error or throwing
an exception should suffice for realistic uses.&nbsp; Having readers beyond
INT_MAX wait for the count to decrease only pushes the overflow problem onto
another variable...&nbsp; Suggestions?</LI>
<LI> See the comments at the head of rw_mutex.cpp for a description of the implementation
itself.</LI>
</UL>
<h2><a name="macros"></a>Macros</h2>
<p><a name="macro-spec"></a>{{Macro specifications}}</p>
<h2><a name="values"></a>Values</h2>
<pre>
namespace boost {
typedef enum
{
sp_writer_priority,
sp_reader_priority,
sp_alternating_many_reads,
sp_alternating_single_reads
} rw_scheduling_policy;
typedef enum
{
NO_LOCK,
SHARED_LOCK,
EXCL_LOCK
} lockstate;
}
</pre>
<h2><a name="types"></a>Types</h2>
<p><a name="type-spec"></a>{{Type specifications}}</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-rw_mutex"></a>Class <code>rw_mutex</code></h3>
<p>{{text}}</p>
<h4><a name="class-rw_mutex-synopsis"></a>Class <code>rw_mutex</code> synopsis</h4>
<pre>
namespace boost
{
class rw_mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class mutex meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#introduction">Introduction</a>]</i> scoped_rw_lock;
rw_mutex(rw_scheduling_policy sp=sp_writer_priority);
~rw_mutex();
};
};
</pre>
<h4><a name="class-rw_mutex-ctors"></a>Class <code>rw_mutex</code> constructors
and destructor</h4>
<pre>
rw_mutex(rw_scheduling_policy sp=sp_writer_priority);
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in the NO_LOCK state.</dt>
</dl>
<pre>
~rw_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in the NO_LOCK state.</dt>
<dt><b>Effects:</b> Destroys <code>*this</code>.</dt>
<dt><b>Danger:</b> Destruction of a locked rw_mutex is a serious programming
error resulting in undefined behavior such as a program crash.</dt>
</dl>
<h3><a name="class-rw_try_mutex"></a>Class <code>rw_try_mutex</code></h3>
<p>{{text}}</p>
<h4><a name="class-rw_try_mutex-synopsis"></a>Class <code>rw_try_mutex</code>
synopsis</h4>
<pre>
namespace boost
{
class rw_mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class mutex meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#introduction">Introduction</a>]</i> scoped_rw_lock;
typedef <i>[implementation defined; see <a href="#introduction">Introduction</a>]</i> scoped_rw_try_lock;
rw_try_mutex(rw_scheduling_policy sp=sp_writer_priority);
~rw_try_mutex();
};
};
</pre>
<h4><a name="class-rw_try_mutex-ctors"></a>Class <code>rw_try_mutex</code> constructors
and destructor</h4>
<pre>
rw_try_mutex(rw_scheduling_policy sp=sp_writer_priority);
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in the NO_LOCK state.</dt>
</dl>
<pre>
~rw_try_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in the NO_LOCK state.</dt>
<dt><b>Effects:</b> Destroys <code>*this</code>.</dt>
<dt><b>Danger:</b> Destruction of a locked rw_mutex is a serious programming
error resulting in undefined behavior such as a program crash.</dt>
</dl>
<h3><a name="class-rw_timed_mutex"></a>Class <code>rw_timed_mutex</code></h3>
<p>{{text}}</p>
<h4><a name="class-rw_timed_mutex-synopsis"></a>Class <code>rw_timed_mutex</code>
synopsis</h4>
<pre>
namespace boost
{
class rw_timed_mutex : private <a href="../../utility/utility.htm">boost::noncopyable</a> // Exposition only.
// Class mutex meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
{
public:
typedef <i>[implementation defined; see <a href="#introduction">Introduction</a>]</i> scoped_rw_lock;
typedef <i>[implementation defined; see <a href="#introduction">Introduction</a>]</i> scoped_rw_try_lock;
typedef <i>[implementation defined; see <a href="#introduction">Introduction</a>]</i> scoped_rw_timed_lock;
rw_timed_mutex(rw_scheduling_policy sp=sp_writer_priority);
~rw_timed_mutex();
};
};
</pre>
<h4><a name="class-rw_timed_mutex-ctors"></a>Class <code>rw_timed_mutex</code>
constructors and destructor</h4>
<pre>
rw_timed_mutex(rw_scheduling_policy sp=sp_writer_priority);
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in the NO_LOCK state.</dt>
</dl>
<pre>
~rw_timed_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is in the NO_LOCK state.</dt>
<dt><b>Effects:</b> Destroys <code>*this</code>.</dt>
<dt><b>Danger:</b> Destruction of a locked rw_mutex is a serious programming
error resulting in undefined behavior such as a program crash.</dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<pre>
#include <a href="../../../boost/thread/rw_mutex.hpp">&lt;boost/thread/rw_mutex.hpp&gt;</a>
#include &lt;boost/thread/mutex.hpp&gt;
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
boost::mutex io_mutex; // The iostreams are not guaranteed to be <a href="definitions.html#Thread-safe">thread-safe</a>!
class counter
{
public:
counter() : count(0) { }
int increment() {
boost::rw_mutex::scoped_lock scoped_rw_lock(rw_mutex);
return ++count;
}
int get() {
boost::rw_mutex::scoped_lock scoped_rw_lock(rw_mutex,SHARED_LOCK);
return count;
}
private:
boost::rw_mutex rwm(boost::sp_writer_priority);
int count;
};
counter c;
void change_count(void*)
{
int i = c.increment();
boost::rw_mutex::scoped_lock scoped_lock(io_mutex);
std::cout &lt;&lt; "count == " &lt;&lt; i &lt;&lt; std::endl;
}
void get_count(void*)
{
int i = c.get();
boost::rw_mutex::scoped_lock scoped_lock(io_mutex);
std::cout &lt;&lt; "get_count == " &lt;&lt; i &lt;&lt; std::endl;
}
int main(int, char*[])
{
const int num_threads = 4;
boost::thread_group thrds;
for (int i=0; i &lt; num_threads; ++i)
{
thrds.create_thread(&amp;change_count, 0);
thrds.create_thread(&amp;get_count,0);
}
thrds.join_all();
return 0;
}
</pre>
<p>Typicial output might be:</p>
<pre>
count == 1
get_count == 1
get_count == 1
count == 2
count == 3
get_count == 3
count == 4
get_count == 4
</pre>
<p>Of course, exact output is platform dependent since the locking behavior with
competing readers and writers is undefined.</p>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:{{address}}">{{author}}</a> 2002. All Rights
Reserved.</i></p>
</body>
</html>

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@@ -1,611 +0,0 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - RWMutex Concept</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">RWMutex Concept</h2>
</td>
</tr>
</table>
<hr>
<dl class="index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#locking-strategies">Locking Strategies</a></dt>
<dl class="page-index">
<dt><a href="#locking-strategy-recursive">Recursive</a></dt>
<dt><a href="#locking-strategy-checked">Checked</a></dt>
<dt><a href="#locking-strategy-unchecked">Unchecked</a></dt>
<dt><a href="#locking-strategy-unspecified">Unspecified</a></dt>
</dl>
<dt><a href="#scheduling-policies">Scheduling Policies</a></dt>
<dt><a href="#requirements">Concept Requirements</a></dt>
<dt><a href="#models">Models</a></dt>
</dl>
<h2><a name="introduction"></a>Introduction</h2>
<p>A rw_mutex (short for reader-writer mutual-exclusion) concept serializes access
to a resource shared between multiple threads, where multiple readers can share
simultaneous access, but writers require exclusive access.&nbsp; The <a href="#Mutex">
RWMutex</a> concept, with <a href="#TryMutex">TryRWMutex</a> and <a href="#TimedMutex">
TimedRWMutex</a> refinements, formalize the requirements. A model that implements
RWMutex and its refinements has three states: <b>shared-locked</b> ,<b>exclusive-locked</b>
and <b>unlocked</b>. Before reading from a&nbsp; shared resource, a thread <b>shared-locks</b>
a Boost.Threads rw_mutex model object, insuring <a href="definitions.html#Thread-safe">
thread-safe</a> access for reading from the shared resource. Before writing
to a shared resource, a thread <b>exclusive-locks</b> a Boost.Threads rw_mutex
model object, insuring <a href="definitions.html#Thread-safe">thread-safe</a>
access for altering the shared resource.&nbsp; When use of the shared resource
is complete, the thread unlocks the mutex model object, allowing another thread
to acquire the lock and use the shared resource.</p>
<p> Some traditional C thread APIs like Pthreads provide implementations for rw_mutex
(also known as reader-writer locks).&nbsp; Others like Windows thread APIs do
not provide a rw_mutex primitive.&nbsp; Some of those APIs expose functions
to lock and unlock a rw_mutex model. This is dangerous since it's easy to forget
to unlock a locked rw_mutex. When the flow of control is complex, with multiple
return points, the likelihood of forgetting to unlock a rw_mutex model would
become even greater. When exceptions are thrown, it becomes nearly impossible
to ensure that the rw_mutex is unlocked properly when using these traditional
API's. The result is <a href="definitions.html#Deadlock">deadlock</a>.</p>
<p>Many C++ threading libraries use a pattern known as <i>Scoped Locking</i> <a href="bibliography.html#Schmidt 00">
[Schmidt 00]</a> to free the programmer from the need to explicitly lock and
unlock rw_mutexes. With this pattern, a <a href="lock_concept.html">lock concept</a>
is employed where the lock model's constructor locks the associated rw_mutex
model and the destructor automatically does the unlocking. The <b>Boost.Threads</b>
library takes this pattern to the extreme in that lock concepts are the only
way to lock and unlock a rw_mutex model: lock and unlock functions are not exposed
by any <b>Boost.Threads</b> rw_mutex models. This helps to ensure safe usage
patterns, especially when code throws exceptions.</p>
<h2><a name="locking-strategies"></a>Locking Strategies</h2>
<P>Every rw_mutex model follows one of several locking strategies. These strategies
define the semantics for the locking operation when the calling thread already
owns a lock on the rw_mutex model.</P>
<h3><a name="locking-strategy-recursive"></a>Recursive</h3>
<P>With a recursive locking strategy when a thread attempts to acquire an additional&nbsp;lock
on the rw_mutex model for which it already owns a lock, the operation is successful,
except&nbsp;possibly in the case where a shared-lock holding thread attempts
to&nbsp;obtain an exclusive lock.&nbsp; </P>
<P>
<TABLE id="Table9" width="100%" border="1">
<TR>
<TD width="22%">Lock Type Held</TD>
<TD width="18%">Lock Request Type</TD>
<TD width="60%">Action</TD>
</TR>
<TR>
<TD width="22%">shared-lock</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Grant the shared lock immediately</TD>
</TR>
<TR>
<TD width="22%">shared-lock</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%">
<P>If this thread is the only holder of the shared-lock, grants the exclusive
lock immediately.&nbsp; Otherwise throws lock_error() exception.</P>
</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Grants the (additional) shared lock immediately.</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%"> Grant the exclusive lock immediately</TD>
</TR>
</TABLE>
<P>Internally a lock count is maintained and the owning thread must unlock the
mutex model the same number of times that it's locked it before the mutex model's
state returns to unlocked. Since mutex models in <B>Boost.Threads</B> expose
locking functionality only through lock concepts, a thread will always unlock
a mutex model the same number of times that it locked it. This helps to eliminate
a whole set of errors typically found in traditional C style thread APIs.</P>
<P>Classes <A href="recursive_mutex.html">recursive_rw_mutex</A>, <A href="recursive_mutex.html">
recursive_try_rw_mutex</A> and <A href="recursive_mutex.html">recursive_timed_rw_mutex</A>
will use this locking strategy.&nbsp; Successful implementation of this locking
strategy may require thread identification (see below).</P>
<h3><a name="locking-strategy-checked"></a>Checked</h3>
<P>With a checked locking strategy when a thread attempts to acquire a lock on
the mutex model for which the thread already owns a lock, the operation will
fail with some sort of error indication, except in the case of multiple&nbsp;shared-lock
acquisition which is&nbsp;a normal operation for ANY RWMutex. &nbsp;Further,
attempts by a thread to unlock a mutex that was not locked by the thread will
also return some sort of error indication. In <B>Boost.Threads</B>, an exception
of type <A href="lock_error.html">lock_error</A> would be thrown in these cases.</P>
<B>
<P>
<TABLE id="Table10" width="100%" border="1">
<TR>
<TD width="22%">Lock Type Held</TD>
<TD width="18%">Lock Request Type</TD>
<TD width="60%">Action</TD>
</TR>
<TR>
<TD width="22%">shared-lock</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Grant the shared lock immediately</TD>
</TR>
<TR>
<TD width="22%">shared-lock</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%">
<P>Throw lock_error()</P>
</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Throw lock_error()</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%"> Throw lock_error()</TD>
</TR>
</TABLE>
<p></P>
</B>
<P><B> Boost.Threads</b> does not currently provide any rw_mutex models that use
this strategy.&nbsp; A successful implementation of this locking strategy would
likely require thread identification.</P>
<h3><a name="locking-strategy-unchecked"></a>Unchecked</h3>
<P>With an unchecked locking strategy when a thread attempts to acquire a lock
on the rw_mutex model for which the thread already owns a lock the operation
will <A href="definitions.html#Deadlock"> deadlock</A>. In general this locking
strategy is less safe than a checked or recursive strategy, but it can be&nbsp;a
faster strategy and so is employed by many libraries.</P>
<P>
<TABLE id="Table11" width="100%" border="1">
<TR>
<TD width="22%">Lock Type Held</TD>
<TD width="18%">Lock Request Type</TD>
<TD width="60%">Action</TD>
</TR>
<TR>
<TD width="22%">shared-lock</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Grant the shared lock immediately</TD>
</TR>
<TR>
<TD width="22%">shared-lock</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%">
<P>Deadlock</P>
</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Deadlock</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%"> Deadlock</TD>
</TR>
</TABLE>
<p></P>
<P><B>Boost.Threads</B> does not currently provide any mutex models that use this
strategy.&nbsp; For RWMutexes on platforms that contain natively recursive synchronization
primitives, implementing a guaranteed-deadlock can actually involve extra work,
and would likely require thread identification.</P>
<h3><a name="locking-strategy-unspecified"></a>Unspecified</h3>
<P>With an unspecified locking strategy, when a thread attempts to acquire a lock
on a rw_mutex model for which the thread already owns a lock the operation results
in <B>undefined behavior</B>. When a rw_mutex model has an unspecified locking
strategy the programmer must assume that the rw_mutex model instead uses an
unchecked strategy as the worse case, although some platforms may exhibit a
mix of unchecked and recursive behavior.</P>
<P>
<TABLE id="Table12" width="100%" border="1">
<TR>
<TD width="22%">Lock Type Held</TD>
<TD width="18%">Lock Request Type</TD>
<TD width="60%">Action</TD>
</TR>
<TR>
<TD width="22%">shared-lock</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Grant the shared lock immediately</TD>
</TR>
<TR>
<TD width="22%">shared-lock</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%">
<P>Undefined, but generally deadlock</P>
</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Undefined, but generally deadlock</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%"> Undefined, but generally deadlock</TD>
</TR>
</TABLE>
<p></P>
<P>In general a rw_mutex model with an unspecified locking strategy is unsafe,
and it requires programmer discipline to use the rw_mutex model properly. However,
this strategy allows an implementation to be as fast as possible with no restrictions
on its implementation. This is especially true for portable implementations
that wrap the native threading support of a platform. For this reason, the classes
<A href="rw_mutex.html">rw_mutex</A>, <A href="rw_mutex.html">try_rw_mutex</A>
and <A href="rw_mutex.html">timed_rw_mutex</A> use this locking strategy despite
the lack of safety.</P>
<h3>An Aside - Thread Identification</h3>
<P>RWMutexes can support specific Locking Strategies (recursive and checked) which
help to detect and protect against self-deadlock.&nbsp; Self-deadlock can occur
when a holder of a locked RWMutex attempts to obtain another lock.&nbsp; Given
an implemention "I" which is susceptible to self-deadlock but otherwise correct
and efficient, a recursive or checked implementation "Ir" or "Ic" can use the
same basic implementation, but make special checks against self-deadlock by
tracking the identities of thread(s) currently holding locks.&nbsp; This approach
makes deadlock detection othrogonal to the basic RWMutex implementaion.&nbsp;
</P>
<P> Alternatively, a different basic implementation for RWMutex concepts&nbsp;,
I' (I-Prime) may exist which uses recursive or checked versions of synchronization
primitives to produce a recursive or checked RWMutex while still providing flexibility
in terms of Scheduling Policies.
<P>Please refer to the <b>Boost.Threads</b> <a href="mutex_concept.html#LockingStrategies">
mutex concept</a> documentation for a discussion of locking strategies.&nbsp;
The rw_mutex supports both the <a href="mutex_concept.html#Recursive"> recursive</a>
and <a href="mutex_concept.html#Unspecified">unspecified</a> locking strategies.&nbsp;
RWMutexes are parameterized on a Mutex type which they use to control exclusive-locking
and access to internal state.
<H3>Another Aside - <A name="LockingPromotion">Lock Promotion</A></H3>
<P>RWMutexes can support lock promotion, where a mutex which is in the shared-locked
state transitions to an exclusive-locked state without releasing the lock.&nbsp;
If this functionality is supported at all by Boost.Threads, it will only be
through an explicit promote() operations.&nbsp; Extra care must be taken to
ensure that only one thread holding a shared lock can block awaiting promotion
at any given time.&nbsp;&nbsp;If more than one shared-lock holder is allowed
to enter a blocked state while waiting to be promoted, deadlock will result
since both threads will be waiting for the other to release their shared lock.
<h2><a name="scheduling-policies"></a>Scheduling Policies</h2>
<p>Every rw_mutex model follows one of several scheduling policies. These policies
define the semantics when the mutex model is unlocked and there is more than
one thread waiting to acquire a lock. In other words, the policy defines which
waiting thread shall acquire the lock.&nbsp; For rw_mutex, it is particularly
important to define the behavior when threads are requesting both shared and
exclusive access simultaneously.&nbsp; This will be referred to as "inter-class
scheduling".&nbsp;&nbsp;</p>
<p>For some types of inter-class scheduling, an intra-class scheduling policy
can also be defined that will describe the order in which waiting threads of
the same class will acquire the thread.</p>
<h3><a name="ReaderPriority">ReaderPriority</a></h3>
<p>With ReaderPriority, any pending request for a shared lock will have priority
over a pending request for an exclusive lock, irrespective of the current lock
state of the rw_mutex, and irrespective of the relative order that the pending
requests arrive.</p>
<table border="1" width="100%" id="Table1">
<tr>
<td width="22%">Current rw_mutex state</td>
<td width="18%">Request Type</td>
<td width="60%">Action</td>
</tr>
<tr>
<td width="22%">unlocked</td>
<td width="18%">shared-lock</td>
<td width="60%">Grant the shared lock immediately</td>
</tr>
<tr>
<td width="22%">shared-locked</td>
<td width="18%">shared-lock</td>
<td width="60%">Grant the additional shared lock immediately.</td>
</tr>
<tr>
<td width="22%">exclusive-locked</td>
<td width="18%">shared-lock</td>
<td width="60%">Wait to acquire the lock until the thread holding the exclusive-lock
releases its lock.&nbsp; A shared lock will be granted to all pending readers
before&nbsp;any other thread can acquire an exclusive lock.</td>
</tr>
<tr>
<td width="22%">unlocked</td>
<td width="18%">exclusive-lock</td>
<td width="60%">Grant the exclusive lock immediately, if and only if there
are no pending shared-lock requests.</td>
</tr>
<tr>
<td width="22%">shared-locked</td>
<td width="18%">exclusive-lock</td>
<td width="60%"> Wait to acquire the lock until all threads holding shared
locks release their locks -AND- no requests for shared locks exist.&nbsp;
If other exclusive-lock requests exist, the lock is granted in accordance
with the intra-request scheduling policy.</td>
</tr>
<tr>
<td width="22%">exclusive-locked</td>
<td width="18%">exclusive-lock</td>
<td width="60%">Wait to acquire the lock until the thread holding the exclusive
lock releases its lock -AND- no requests for shared locks exist.&nbsp; If
other exclusive-lock requests exist, the lock is granted in accordance with
the intra-request scheduling policy.</td>
</tr>
</table>
<h3><a name="WriterPriority">WriterPriority</a></h3>
<p>With WriterPriority, any pending request for an exclusive lock will have priority
over a pending request for a shared lock, irrespective of the current lock state
of the rw_mutex, and irrespective of the relative order that the pending requests
arrive.</p>
<table border="1" width="100%" id="Table2">
<tr>
<td width="22%">Current rw_mutex state</td>
<td width="18%">Request Type</td>
<td width="60%">Action</td>
</tr>
<tr>
<td width="22%">unlocked</td>
<td width="18%">shared-lock</td>
<td width="60%">Grant the shared lock immediately.</td>
</tr>
<tr>
<td width="22%">shared-locked</td>
<td width="18%">shared-lock</td>
<td width="60%">Grant the additional shared lock immediately, -IF- no outstanding
requests for an exclusive lock exist.</td>
</tr>
<tr>
<td width="22%">exclusive-locked</td>
<td width="18%">shared-lock</td>
<td width="60%"> Wait to acquire the lock until the thread holding the exclusive-lock
releases its lock.&nbsp; The shared lock will be granted once&nbsp;no other
outstanding exclusive-lock requests exist.</td>
</tr>
<tr>
<td width="22%">unlocked</td>
<td width="18%">exclusive-lock</td>
<td width="60%">Grant the exclusive lock immediately.</td>
</tr>
<tr>
<td width="22%">shared-locked</td>
<td width="18%">exclusive-lock</td>
<td width="60%">Wait to acquire the lock until all threads holding shared
locks release their locks.&nbsp; If other exclusive-lock requests exist,
the lock is granted in accordance with the intra-request scheduling policy.&nbsp;
This request will be granted before any new shared-lock requests are granted.</td>
</tr>
<tr>
<td width="22%">exclusive-locked</td>
<td width="18%">exclusive-lock</td>
<td width="60%">Wait to acquire the lock until the thread holding the exclusive
lock releases its lock.&nbsp; If other exclusive-lock requests exist, the
lock is granted in accordance with the intra-request scheduling policy.&nbsp;
This request will be granted before any new shared-lock requests are granted.</td>
</tr>
</table>
<h3><a name="AlteratingManyPriority">AlternatingPriority</a>/ManyReads</h3>
<p>With AlternatingPriority/ManyReads, reader or writer starvation is avoided
by alternatively granting shared or exclusive access when pending requests exist
for both types of locks.&nbsp; Outstanding shared-lock requests are treated
as a group when it is the "reader's turn"</p>
<table border="1" width="100%" id="Table3">
<tr>
<td width="22%">Current rw_mutex state</td>
<td width="18%">Request Type</td>
<td width="60%">Action</td>
</tr>
<tr>
<td width="22%">unlocked</td>
<td width="18%">shared-lock</td>
<td width="60%">Grant the shared lock immediately.</td>
</tr>
<tr>
<td width="22%">shared-locked</td>
<td width="18%">shared-lock</td>
<td width="60%">Grant the additional shared lock immediately, -IF- no outstanding
requests for an exclusive lock exist.&nbsp; If outstanding exclusive-lock
requests exist, this lock will not be granted until at least one of the
exclusive locks is granted and released. If other shared-lock requests exist,
all shared-locks will be granted as a group.</td>
</tr>
<tr>
<td width="22%">exclusive-locked</td>
<td width="18%">shared-lock</td>
<td width="60%"> Wait to acquire the lock until the thread holding the exclusive-lock
releases its lock.&nbsp; If other outstanding exclusive-lock requests exist,
they will have to wait until all current shared-lock requests are serviced.</td>
</tr>
<tr>
<td width="22%">unlocked</td>
<td width="18%">exclusive-lock</td>
<td width="60%">Grant the exclusive lock immediately.</td>
</tr>
<tr>
<td width="22%">shared-locked</td>
<td width="18%">exclusive-lock</td>
<td width="60%">
<P>Wait to acquire the lock until all threads holding shared locks release
their locks.&nbsp; </P>
<P>If other&nbsp;exclusive-lock requests exist, this lock will be granted
to one of them in accordance with the intra-request scheduling policy.</P>
</td>
</tr>
<tr>
<td width="22%">exclusive-locked</td>
<td width="18%">exclusive-lock</td>
<td width="60%">Wait to acquire the lock until the thread holding the exclusive
lock releases its lock.&nbsp;&nbsp; If other outstanding shared-lock requests
exist, this lock will not be granted until all of the currently waiting
shared locks&nbsp;are granted and released.&nbsp; If other exclusive-lock
requests exist, this lock will be granted in accordance with the intra-request
scheduling policy.</td>
</tr>
</table>
<H3>
<H3><A name="AlteratingSinglePriority">AlternatingPriority</A>/SingleReads</H3>
</H3>
<P>With AlternatingPriority/ManyReads, reader or writer starvation is avoided
by alternatively granting shared or exclusive access when pending requests exist
for both types of locks.&nbsp; Outstanding shared-lock requests are services
one at a time&nbsp;when it is the "reader's turn"</P>
<H3>
<TABLE id="Table13" width="100%" border="1">
<TR>
<TD width="22%">Current rw_mutex state</TD>
<TD width="18%">Request Type</TD>
<TD width="60%">Action</TD>
</TR>
<TR>
<TD width="22%">unlocked</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Grant the shared lock immediately.</TD>
</TR>
<TR>
<TD width="22%">shared-locked</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">Grant the additional shared lock immediately, -IF- no outstanding
requests for an exclusive lock exist.&nbsp; If outstanding exclusive-lock
requests exist, this lock will not be granted until at least one of the
exclusive locks is granted and released. </TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">shared-lock</TD>
<TD width="60%">
<P>Wait to acquire the lock until the thread holding the exclusive-lock
releases its lock.</P>
<P>If other outstanding exclusive-lock requests exist, exactly one shared-lock
request will be granted before the next exclusive lock is granted.</P>
</TD>
</TR>
<TR>
<TD width="22%">unlocked</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%">Grant the exclusive lock immediately.</TD>
</TR>
<TR>
<TD width="22%">shared-locked</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%">
<P>Wait to acquire the lock until all threads holding shared locks release
their locks.&nbsp; </P>
<P>If other&nbsp;exclusive-lock requests exist, this lock will be granted
to one of them in accordance with the intra-request scheduling policy.</P>
</TD>
</TR>
<TR>
<TD width="22%">exclusive-locked</TD>
<TD width="18%">exclusive-lock</TD>
<TD width="60%">Wait to acquire the lock until the thread holding the exclusive
lock releases its lock.&nbsp;&nbsp; If other outstanding shared-lock requests
exist, this lock can not be granted until exactly one shared-lock request
is granted and released.&nbsp; If other exclusive-lock requests exist,
this lock will be granted in accordance with the intra-request scheduling
policy.</TD>
</TR>
</TABLE>
</H3>
<h3>Intra-Request Scheduling Policy</h3>
<p>Please refer to the <b>Boost.Threads</b> <a href="mutex_concept.html#SchedulingPolicies">
mutex concept</a> documentation for a discussion of mutex scheduling policies,
which are identical to RWMutex Intra-Request scheduling policies.&nbsp; The
rw_mutex supports only the <a href="mutex_concept.html#UnspecifiedScheduling">
Unspecified</a> intra-request scheduling policy.&nbsp; That is, given a set
of threads waiting for exclusive locks, the order (amongst themselves) in which
they receive the lock is unspecified.</p>
<h2><a name="requirements"></a>Concept Requirements</h2>
<h3>RW<a name="Mutex">Mutex</a> Concept</h3>
<p>A RWMutex object has three states: shared-locked, exclusive-locked, and unlocked.
RWMutex object state can only be determined by an object meeting the <a href="rw_lock_concept.html#ScopedLock">
ScopedRWLock</a> requirements and constructed for the RWMutex object.</p>
<p>A RWMutex is <a href="../../utility/utility.htm#Class noncopyable">noncopyable</a>.</p>
<p> For a RWMutex type RWM,&nbsp;and an object m of that type, the following expressions
must be well-formed and have the indicated effects.</p>
<table summary="Mutex expressions" border="1" cellpadding="5" id="Table5">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>RWM m;</code></td>
<td>Constructs a rw_mutex object m. Post-condition: m is unlocked.</td>
</tr>
<tr>
<td><code>(&amp;m)-&gt;~RWM();</code></td>
<td>Precondition: m is unlocked. Destroys a rw_mutex object m.</td>
</tr>
<tr>
<td><code>RWM::scoped_rw_lock</code></td>
<td>A type meeting the <a href="rw_lock_concept.html#ScopedRWLock">ScopedRWLock</a>
requirements.&nbsp;&nbsp;</td>
</tr>
</table>
<h3><a name="TryMutex">TryRWMutex</a> Concept</h3>
<p>A TryRWMutex must meet the <a href="#RWMutex">RWMutex</a> requirements. In
addition, for a TryRWMutex type RWM and an object m of that type, the following
expressions must be well-formed and have the indicated effects.</p>
<table summary="TryMutex expressions" border="1" cellpadding="5" id="Table6">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>RWM::scoped_try_rw_lock</code></td>
<td>A type meeting the <a href="rw_lock_concept.html#ScopedTryRWLock">ScopedTryRWLock</a>
requirements.</td>
</tr>
</table>
<h3><a name="TimedMutex">TimedRWMutex</a> Concept</h3>
<p>A TimedRWMutex must meet the <a href="#TryMutex">TryRWMutex</a> requirements.
In addition, for a TimedRWMutex type RWM and an object m of that type, the following
expressions must be well-formed and have the indicated effects.</p>
<table summary="TimedMutex expressions" border="1" cellpadding="5" id="Table7">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>RWM::scoped_timed_rw_lock</code></td>
<td>A type meeting the <a href="rw_lock_concept.html#ScopedTimedRWLock">ScopedTimedRWLock</a>
requirements.</td>
</tr>
</table>
<h2><a name="models"></a>Models</h2>
<p><b>Boost.Threads</b> currently supplies three classes which model rw_mutex
concepts.</p>
<table summary="Mutex concept classes" border="1" cellpadding="5" id="Table8">
<tr>
<td><b>Concept</b></td>
<td><b>Refines</b></td>
<td><b>Classes Modeling the Concept</b></td>
</tr>
<tr>
<td valign="top"><a href="#Mutex">RWMutex</a></td>
<td valign="top">&nbsp;</td>
<td><a href="rw_mutex.html">rw_mutex&lt;Mutex&gt;</a></td>
</tr>
<tr>
<td valign="top"><a href="#TryMutex">TryRWMutex</a></td>
<td valign="top"><a href="#Mutex">RWMutex</a></td>
<td><a href="rw_mutex.html">try_rw_mutex&lt;TryMutex&gt; </a> </td>
</tr>
<tr>
<td valign="top"><a href="#TimedMutex">TimedRWMutex</a></td>
<td valign="top"><a href="#TryMutex">TryRWMutex</a></td>
<td><a href="rw_mutex.html">timed_rw_mutex&lt;TimedMutex&gt; </a> </td>
</tr>
</table>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:{{address}}">{{author}}</a> 2002. All Rights
Reserved.</i></p>
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<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, scoped_lock</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">scoped_lock</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>This class template defines a generic lock type which meets the
<a href="lock_concept.html#ScopedLock">ScopedLock</a> requirements. The
<a href="mutex.html">mutex</a>, <a href="mutex.html">try_mutex</a>,
<a href="mutex.html">timed_mutex</a>, <a href="recursive_mutex.html">recursive_mutex</a>,
<a href="recursive_mutex.html">recursive_try_mutex</a> and
<a href="recursive_mutex.html">recursive_timed_mutex</a> classes all use this template
to define their <code>scoped_lock</code> types.</p>
<p>Like all the <b>Boost.Threads</b> <a href="lock_concept.html">lock models</a>,
<code>scoped_lock</code> objects are meant to be short-lived. Objects of the class
are not <a href="definitions.html#thread-safe">thread-safe</a>, and so should not be
shared between threads.</p>
<p>Class <code> scoped_lock</code> follows the &quot;resource acquisition is
initialization&quot; idiom <a href="bibliography.html#Stroustrup-00">[Stroustrup
00 14.4.1]</a> and is a realization of the &quot;Scoped Locking Pattern&quot;
<a href="bibliography.html#Schmidt-00">[Schmidt-00]</a>. Thus the usage is to let the
constructor do the locking, and then let the destructor do the unlocking automatically at
the end of the enclosing scope. The lock() and unlock() members are usually not
explicitly called, but are provided to allow for complex overlapping locks of multiple
mutexes.</p>
<p>The type used to instantiate the class must meet the
<a href="mutex_concept.html#Mutex">Mutex</a> requirements.</p>
<p>Although this class is an implementation detail, it is publicly documented here because
of its importance.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/detail/lock.hpp">&lt;boost/thread/detail/lock.hpp&gt;</a>
<i>This header is usually not included directly by programmers
because it is supplied by <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a> or
<a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a></i>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost { namespace detail { namespace thread {
template &lt;typename Mutex&gt;
class scoped_lock : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class scoped_lock meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef Mutex mutex_type;
explicit scoped_lock(Mutex&amp; mx, bool initially_locked=true);
~scoped_lock();
void lock();
void unlock();
operator const void*() const;
bool locked() const;
};
} // namespace thread
} // namespace detail
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
explicit scoped_lock(Mutex&amp; mx, bool initially_locked=true);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
If <code>initially_locked</code> is <code>true,</code> calls <code>lock()</code>.</p>
<hr>
<h3>Destructor</h3>
<pre>
~scoped_lock();
</pre>
<p><b>Effects:</b> If <code> locked()</code>, calls <code>unlock()</code>. Destroys
<code>*this</code>.</p>
<hr>
<h3>lock</h3>
<pre>
void lock();
</pre>
<p><b>Effects:</b> If the associated mutex is already locked by another lock in the
current thread, the effects depend on the locking strategy of the associated mutex, as
shown in the following table:</p>
<table border="1" cellpadding="5">
<tr>
<td><i><a href="mutex_concept.html#LockingStrategies">Locking Strategy</a><br>
of associated mutex</i></td>
<td><i>Effect if associated mutex is already locked by the current thread</i></td>
</tr>
<tr>
<td>Recursive</td>
<td>As if an additional lock were added to the mutex.</td>
</tr>
<tr>
<td>Checked</td>
<td>Throws <a href="lock_error.html">lock_error</a>.</td>
</tr>
<tr>
<td>Unchecked</td>
<td>Undefined behavior [<a href="bibliography.html#ISO">ISO</a> 1.3.12] (but
typically, <a href="definitions.html#Deadlock">deadlock</a>.)</td>
</tr>
</table>
<p>If the associated mutex is already locked by some other thread, places the
current thread in the <a href="definitions.html#State">Blocked</a> state until
the associated mutex is unlocked, after which the current thread is placed in
the <a href="definitions.html#State">Ready</a> state, eventually to be returned
to the <a href="definitions.html#State">Running</a> state.
<p><b>Postcondition:</b> locked()
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>unlock</h3>
<pre>
void unlock();
</pre>
<p><b>Effects: </b>Unlocks the associated mutex.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>!locked()</code>.</p>
<hr>
<h3>const void* Conversion</h3>
<pre>
operator const void*() const;
</pre>
<p><b>Returns:</b> If the associated mutex is currently locked, a value convertible to
<code>true</code>, else a value convertible to <code>false</code>.</p>
<p><b>Rationale:</b> A <code>const void*</code> conversion is considered safer than a
conversion to <code>bool</code>.</p>
<hr>
<h3>locked</h3>
<pre>
bool locked() const;
</pre>
<p><b>Returns:</b> <code>this-&gt;operator const void*() != 0</code>.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<p>See the example given in the documentation for the <a href="mutex.html">mutex</a>
class.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
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<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">scoped_timed_lock</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>This class template defines a generic lock type which meets the
<a href="lock_concept.html#ScopedTimedLock">ScopedTimedLock</a> requirements. The
<a href="mutex.html">timed_mutex</a> and
<a href="recursive_mutex.html">recursive_timed_mutex</a> classes use this template to
define their <code>scoped_timed_lock</code> types.</p>
<p>Like all the <b>Boost.Threads</b> <a href="lock_concept.html">lock models</a>,
<code>scoped_timed_lock</code> objects are meant to be short-lived. Objects of the
class are not <a href="definitions.html#thread-safe">thread-safe</a>, and so should
not be shared between threads.</p>
<p>Class <code>scoped_timed_lock</code> follows the &quot;resource acquisition is
initialization&quot; idiom <a href="bibliography.html#Stroustrup-00">[Stroustrup
00 14.4.1]</a> and is a realization of the &quot;Scoped Locking Pattern&quot;
<a href="bibliography.html#Schmidt-00">[Schmidt-00]</a>. Thus the usage is to let the
constructor do the locking, and then let the destructor do the unlocking automatically
at the end of the enclosing scope. The lock() and unlock() members are usually not
explicitly called, but are provided to allow for complex overlapping locks of multiple
mutexes.</p>
<p>The type used to instantiate the class must meet the
<a href="mutex_concept.html#TimedMutex">TimedMutex</a> requirements.</p>
<p>Although this class is an implementation detail, it is publicly documented here because
of its importance.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/detail/lock.hpp">&lt;boost/thread/detail/lock.hpp&gt;</a>
<i>This header is usually not included directly by programmers
because it is supplied by <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a> or
<a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a></i>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost { namespace detail { namespace thread {
template &lt;typename TimedMutex&gt;
class scoped_timed_lock : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class scoped_timed_lock meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef TimedMutex mutex_type;
scoped_timed_lock(TimedMutex&amp; mx, const boost::xtime&amp; xt);
scoped_timed_lock(TimedMutex&amp; mx, bool initially_locked);
~scoped_timed_lock();
void lock();
bool timed_lock(const xtime&amp; xt);
void unlock();
operator const void*() const;
};
} // namespace thread
} // namesapce detail
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
scoped_timed_lock(TimedMutex&amp; mx, const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
Calls <code>timed_lock</code>( <code>xt</code>)</p>
<hr>
<pre>
scoped_timed_lock(TimedMutex&amp; mx, bool initially_locked);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
If <code>initially_locked</code> is <code>true</code>, calls <code>lock()</code>.</p>
<hr>
<h3>Destructor</h3>
<pre>
~scoped_timed_lock();
</pre>
<p><b>Effects:</b> If <code> locked()</code>, calls <code>unlock()</code>. Destroys
<code>*this</code>.</p>
<hr>
<h3>lock</h3>
<pre>
void lock();
</pre>
<p><b>Effects:</b> If the associated mutex is already locked by another lock in the
current thread, the effects depend on the locking strategy of the associated mutex, as
shown in the following table:</p>
<table border="1" cellpadding="5">
<tr>
<td><i><a href="mutex_concept.html#LockingStrategies">Locking Strategy</a><br>
of associated mutex</i></td>
<td><i>Effect if associated mutex is already locked by the current thread</i></td>
</tr>
<tr>
<td>Recursive</td>
<td>As if an additional lock were added to the mutex.</td>
</tr>
<tr>
<td>Checked</td>
<td>Throws <a href="lock_error.html">lock_error</a>.</td>
</tr>
<tr>
<td>Unchecked</td>
<td>Undefined behavior [<a href="bibliography.html#ISO">ISO</a> 1.3.12] (but
typically, <a href="definitions.html#Deadlock">deadlock</a>.)</td>
</tr>
</table>
<p>If the associated mutex is already locked by some other thread, places the
current thread in the <a href="definitions.html#State">Blocked</a> state until
the associated mutex is unlocked, after which the current thread is placed in
the <a href="definitions.html#State">Ready</a> state, eventually to be returned
to the <a href="definitions.html#State">Running</a> state. Places the associated
mutex in the locked state.
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>timed_lock</h3>
<pre>
bool timed_lock(const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<p><b>Effects:</b> Same as <code>lock()</code>, except that if xt is reached,
places the current thread in the <a href="definitions.html#State">Ready</a>
state without further ado.</p>
<p><b>Returns:</b> <code>locked()</code>.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>unlock</h3>
<pre>
void unlock();
</pre>
<p><b>Effects: </b>Unlocks the associated mutex.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>!locked()</code>.</p>
<hr>
<h3>const void* Conversion</h3>
<pre>
operator const void*() const;
</pre>
<p><b>Returns:</b> If the associated mutex is currently locked, a value convertible to
<code>true</code>, else a value convertible to <code>false</code>.</p>
<p><b>Rationale:</b> A <code>const void*</code> conversion is considered safer than a
conversion to <code>bool</code>.</p>
<hr>
<h3>locked</h3>
<pre>
bool locked() const;
</pre>
<p><b>Returns:</b> <code>this-&gt;operator const void*() != 0</code>.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include &lt;boost/thread/mutex.hpp&gt;
#include &lt;iostream&gt;
int main(int, char*[])
{
boost::timed_mutex mutex;
boost::xtime xt;
boost::get_xtime(&amp;xt, boost::TIME_UTC);
xt.sec += 1;
boost::mutex::scoped_timed_lock scope_timed_lock(mutex, xt);
if (scope_timed_lock.locked())
std::cout &lt;&lt; &quot;locked&quot; &lt;&lt; std::endl;
else
std::cout &lt;&lt; &quot;unlocked&quot; &lt;&lt; std::endl;
return 0;
}
</pre>
<p>The output is:</p>
<pre>
locked
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%B %d, %Y" startspan -->September 13, 2001<!--webbot bot="Timestamp" endspan i-checksum="37965" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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@@ -0,0 +1,282 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, scoped_try_lock</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">scoped_try_lock</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>This class template defines a generic lock type which meets the
<a href="lock_concept.html#ScopedTryLock">ScopedTryLock</a> requirements. The
<a href="mutex.html">try_mutex</a>, <a href="mutex.html">timed_mutex</a>,
<a href="recursive_mutex.html">recursive_try_mutex</a> and
<a href="recursive_mutex.html">recursive_timed_mutex</a> classes use this template
to define their <code>scoped_try_lock</code> types.</p>
<p>Like all the <b>Boost.Threads</b> <a href="lock_concept.html">lock models</a>,
<code>scoped_try_lock</code> objects are meant to be short-lived. Objects of the
class are not <a href="definitions.html#thread-safe">thread-safe</a>, and
so should not be shared between threads.</p>
<p>Class <code> scoped_try_lock</code> follows the &quot;resource acquisition is
initialization&quot; idiom <a href="bibliography.html#Stroustrup-00">[Stroustrup
00 14.4.1]</a> and is a realization of the &quot;Scoped Locking Pattern&quot;
<a href="bibliography.html#Schmidt-00">[Schmidt-00]</a>. Thus the usage is to let the
constructor do the locking, and then let the destructor do the unlocking automatically at
the end of the enclosing scope. The lock() and unlock() members are usually not
explicitly called, but are provided to allow for complex overlapping locks of multiple
mutexes.</p>
<p>Although this class is an implementation detail, it is publicly documented here because
of its importance.</p>
<p>The type used to instantiate the class must meet the <a href="mutex_concept.html#TryMutex">TryMutex</a> requirements.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/detail/lock.hpp">&lt;boost/thread/detail/lock.hpp&gt;</a>
<i>This header is usually not included directly by programmers
because it is supplied by <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a> or
<a href="../../../boost/thread/recursive_mutex.hpp">&lt;boost/thread/recursive_mutex.hpp&gt;</a></i>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost { namespace detail { namespace thread {
template &lt;typename TryMutex&gt;
class scoped_try_lock : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class scoped_try_lock meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
typedef TryMutex mutex_type;
explicit scoped_try_lock(TryMutex&amp; mx);
scoped_try_lock(TryMutex&amp; mx, bool initially_locked);
~scoped_try_lock();
void lock();
bool try_lock();
void unlock();
operator const void*() const;
};
} // namespace thread
} // namespace detail
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructors</h3>
<pre>
explicit scoped_try_lock(TryMutex&amp; mx);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
Calls <code>try_lock()</code>.</p>
<hr>
<pre>
scoped_try_lock(TryMutex&amp; mx, bool initially_locked);
</pre>
<p><b>Effects:</b> Associates mutex <code>mx</code> with <code>*this</code>.
If <code>initially_locked</code> is <code>true,</code> calls <code>lock()</code>.</p>
<hr>
<h3>Destructor</h3>
<pre>
~scoped_try_lock();
</pre>
<p><b>Effects:</b> If <code>locked()</code>, calls <code>unlock()</code>. Destroys
<code>*this</code>.</p>
<hr>
<h3>lock</h3>
<pre>
void lock();
</pre>
<p><b>Effects:</b> If the associated mutex is already locked by another lock in the
current thread, the effects depend on the locking strategy of the associated mutex, as
shown in the following table:</p>
<table border="1" cellpadding="5" height="147">
<tr>
<td height="34"><i><a href="mutex_concept.html#LockingStrategies">Locking Strategy</a><br>
of associated mutex</i></td>
<td height="34"><i>Effect if associated mutex is already locked by the
current thread</i></td>
</tr>
<tr>
<td height="19">Recursive</td>
<td height="19">As if an additional lock were added to the mutex.</td>
</tr>
<tr>
<td height="19">Checked</td>
<td height="19">Throws <a href="lock_error.html">lock_error</a>.</td>
</tr>
<tr>
<td height="19">Unchecked</td>
<td height="19">Undefined behavior [<a href="bibliography.html#ISO">ISO</a> 1.3.12] (but
typically, <a href="definitions.html#Deadlock">deadlock</a>.)</td>
</tr>
</table>
<p>If the associated mutex is already locked by some other thread, places the
current thread in the <a href="definitions.html#State">Blocked</a> state until
the associated mutex is unlocked, after which the current thread is placed in
the <a href="definitions.html#State">Ready</a> state, eventually to be returned
to the <a href="definitions.html#State">Running</a> state. Places the associated
mutex in the locked state.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>try_lock</h3>
<pre>
bool try_lock();
</pre>
<p><b>Effects:</b> If the associated mutex is already locked by another lock in the
current thread, the effects depend on the locking strategy of the associated mutex, as
shown in the following table:</p>
<table border="1" cellpadding="5" height="147">
<tr>
<td height="34"><i><a href="mutex_concept.html#LockingStrategies">Locking Strategy</a><br>
of associated mutex</i></td>
<td height="34"><i>Effect if associated mutex is already locked by the
current thread</i></td>
</tr>
<tr>
<td height="19">Recursive</td>
<td height="19">As if an additional lock were added to the mutex.</td>
</tr>
<tr>
<td height="19">Checked</td>
<td height="19">Throws <a href="lock_error.html">lock_error</a>.</td>
</tr>
<tr>
<td height="19">Unspecified</td>
<td height="19">Undefined behavior [<a href="bibliography.html#ISO">ISO</a> 1.3.12] (but
typically, <a href="definitions.html#Deadlock">deadlock</a>.)</td>
</tr>
</table>
<p>If the associated mutex is not already locked by some other thread, locks the
associated mutex and returns true, else returns false.</p>
<p><b>Returns:</b> See effects.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>locked()</code> or
as indicated in <b>Effects</b>.</p>
<hr>
<h3>unlock</h3>
<pre>
void unlock();
</pre>
<p><b>Effects: </b>Unlocks the associated mutex.</p>
<p><b>Throws:</b> <a href="lock_error.html">lock_error</a> if <code>!locked()</code>.</p>
<hr>
<h3>const void* Conversion</h3>
<pre>
operator const void*() const;
</pre>
<p><b>Returns:</b> If the associated mutex is currently locked, a value convertible to
<code>true</code>, else a value convertible to <code>false</code>.</p>
<p><b>Rationale:</b> A <code>const void*</code> conversion is considered safer
than a conversion to <code>bool</code>.</p>
<hr>
<h3>locked</h3>
<pre>
bool locked() const;
</pre>
<p><b>Returns:</b> <code>this-&gt;operator const void*() != 0</code>.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/mutex.hpp">&lt;boost/thread/mutex.hpp&gt;</a>
#include &lt;iostream&gt;
int main(int, char*[])
{
boost::mutex mutex;
boost::mutex::try_lock lock(mutex);
if (lock)
std::cout &lt;&lt; &quot;locked&quot; &lt;&lt; std::endl;
else
std::cout &lt;&lt; &quot;unlocked&quot; &lt;&lt; std::endl;
return 0;
}
</pre>
<p>The output is:</p>
<pre>
locked
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, semaphore</title>
</head>
<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><IMG height=86 alt="C++ Boost" src="../../../c++boost.gif" width=277></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">semaphore</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <tt>semaphore</tt> class defines a classic synchronization primitive invented by the
Dutch computer scientist Edsger W. Dijkstra. A semaphore manages an internal counter. This
counter never goes below zero, or above a specified maximum value. When calling
<tt>semaphore::down</tt> the calling thread will block until the value is non-zero and then
decrement the value in a single atomic operation. When calling <tt>semaphore::up</tt> the
calling thread will increment the value in a single atomic operation, failing if the value has
already reached the specified maximum.</p>
<p><b>Rationale:</b> The semaphore is the simplest synchronization primitive available and is generally the
primitive used to build other synchronization concepts at some level of implementation. For this
reason <b>Boost.Threads</b> defines the <tt>semaphore</tt> type in the classic form. This simplifies
usage and implementation, but it means that the interface is not as safe as other <b>Boost.Threads</b>
interfaces.</p>
<p><b><a name="Danger">Danger</a>:</b> Unlike the <A href="mutex_concept.html">mutex models</a> supplied by <b>Boost.Threads,</b>
there is no <A href="lock_concept.html">lock_concept</a> for the semaphore to help ensure proper
usage. Great care must be taken when using a <tt>semaphore</tt> object to ensure
<a href="definitions.html#Deadlock"> deadlock</a> or <a href="definitions.html#Race condition">race conditions</a> do not occur.&nbsp;</p>
<p>The dangers are spelled out by <a href="bibliography.html#Andrews-83">[Andrews-83]</a>
(function names updated, see historical note below):&nbsp;</p>
<blockquote>
<p>Although semaphores can be used to program almost any kind of synchronization,
<b>down()</b> and <b>up()</b> are rather unstructured primitives, and so it is easy to err when using them. Execution of each critical section must begin with a
<b>down()</b> and end with a <b>up()</b> (on the same semaphore). Omitting a <b>down()</b>
or <b>up()</b>, or accidentally coding a <b>down()</b> on one semaphore and a <b>up()</b>
on another can have disastrous effects, since mutually exclusive execution would no longer be ensured. Also, when using semaphores, a programmer can forget to include in critical sections all statements that reference shared objects. This, too, could destroy the mutual exclusion required within critical sections. A second difficulty with using semaphores is that both condition synchronization and mutual exclusion are programmed using the same pair of primitives. This makes it difficult to identify the purpose of a given
<b>down()</b> or <b>up()</b> operation without looking at the other operations on the corresponding semaphore. Since mutual exclusion and condition synchronization are distinct concepts, they should have distinct notations.</p>
</blockquote>
<p><b>Historical note: </b>Dijkstra's original name for <b>down()</b> was <b>P</b>
(short for the Dutch &quot;passeren&quot;, &quot;to pass&quot;), and for <b>up()</b>
was <b>V</b> (short for the Dutch &quot;vrygeven&quot;, &quot;to release&quot;).</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/semaphore.hpp">&lt;boost/thread/semaphore.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost
{
class semaphore : private <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class semaphore meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
explicit semaphore(unsigned count=0, unsigned max=0);
~semaphore();
bool up(unsigned count=1, unsigned* prev=0);
void down();
bool down(const xtime&amp; xt);
private:
unsigned m_count; <i>exposition only [ISO 17.3.2.3/2]
</i> unsigned m_max; <i>exposition only [ISO 17.3.2.3/2]</i>
};
}
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
explicit semaphore(unsigned count=0, unsigned max=0);
</pre>
<p><b>Effects:</b> As if:</p>
<p><code>&nbsp;&nbsp;&nbsp;&nbsp; m_count = count;<br>
&nbsp;&nbsp;&nbsp;&nbsp; m_max = (max == 0 ? std::numeric_limits&lt;unsigned&gt;::max()
? max );</code></p>
<hr>
<h3>Destructor</h3>
<pre>
~semaphore();
</pre>
<p><b>Effects:</b> Destroys <code>*this</code>.</p>
<hr>
<h3>up</h3>
<pre>
bool up(unsigned count=1, unsigned* prev=0);
</pre>
<p><b>Effects:</b> As if:</p>
<p><code>&nbsp;&nbsp;&nbsp; unsigned ct;<br>
&nbsp;&nbsp;&nbsp; bool ret;<br>
&nbsp;&nbsp;&nbsp; { // as a single atomic operation:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ct = m_count;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (m_count == m_max) ret =
false;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; else<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; {<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ret =
true;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ++m_count;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br>
&nbsp;&nbsp;&nbsp; }<br>
&nbsp;&nbsp;&nbsp; if (prev) *prev = m_count;<br>
&nbsp;&nbsp;&nbsp; return ret;</code></p>
<hr>
<h3>down</h3>
<pre>
void down();
</pre>
<p><b>Effects:</b> If <code>m_count == 0</code>, places the current thread in
the <a href="definitions.html#State">blocked</a> state until <code>m_count != 0</code>.
Finally, <code>--m_count</code>.<code>&nbsp;</code></p>
<hr>
<pre>
bool down(const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<p><b>Effects:</b> If <code>m_count == 0</code>, places the current thread in
the <a href="definitions.html#State">blocked</a> state until <code>m_count != 0</code>
or <code>xt</code> is reached. Finally, <code>--m_count</code>.<code>&nbsp;</code></p>
<p><b>Returns:</b> If xt was reached, true, else false.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include <a href="../../../boost/thread/semaphore.hpp">&lt;boost/thread/semaphore.hpp&gt;</a>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include &lt;iostream&gt;
int global_data = 0;
boost::semaphore global_semaphore(1);
void change_global_data(void*)
{
global_semaphore.down();
++global_data;
std::cout &lt;&lt; &quot;global_data == &quot; &lt;&lt; global_data &lt;&lt; std::endl;
global_semaphore.up();
}
int main(int, char*[])
{
const int num_threads = 4;
boost::thread_group thrds;
for (int i=0; i &lt; num_threads; ++i)
thrds.create_thread(&amp;change_global_data, 0);
thrds.join_all();
return 0;
}
</pre>
<p>The output is:</p>
<pre>
global_data == 1
global_data == 2
global_data == 3
global_data == 4
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<title>Boost.Threads - &lt;boost/thread.hpp&gt;</title>
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<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/thread.hpp">boost/thread.hpp</a>&gt;</h2>
</td>
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<body bgcolor="#ffffff" link="#0000ff" vlink="#800080">
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<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Class thread</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-thread">Class <code>thread</code></a></dt>
<dl class="page-index">
<dt><a href="#class-thread-synopsis">Class <code>thread</code> synopsis</a></dt>
<dt><a href="#class-thread-ctors">Class <code>thread</code> constructors
and destructor</a></dt>
<dt><a href="#class-thread-comparisons">Class <code>thread</code> comparison
functions</a></dt>
<dt><a href="#class-thread-modifiers">Class <code>thread</code> modifier
functions</a></dt>
<dt><a href="#class-thread-statics">Class <code>thread</code> static functions</a></dt>
</dl>
<dt><a href="#class-thread_group">Class <code>thread_group</code></a></dt>
<dl class="page-index">
<dt><a href="#class-thread_group-synopsis">Class <code>thread_group</code>
synopsis</a></dt>
<dt><a href="#class-thread_group-ctors">Class <code>thread_group</code>
constructors and destructor</a></dt>
<dt><a href="#class-thread_group-modifiers">Class <code>thread_group</code>
modifier functions</a></dt>
</dl>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
<dl class="page-index">
<dt><a href="#example-thread">Simple usage of <code>boost::thread</code></a></dt>
<dt><a href="#example-thread_group">Simple usage of <code>boost::thread_group</code></a></dt>
</dl>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>The header &lt;<a href="../../../boost/thread/thread.hpp">boost/thread.hpp</a>&gt;
defines the classes <a href="#class-thread">thread</a> and <a href="#class-thread_group">thread_group</a>
which are used to create, observe and manage threads and groups of threads.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-thread"></a>Class <code>thread</code></h3>
<p><A href="#Introduction">Introduction</A><br>
<A href="#Header">Header</A><br>
<A href="#Synopsis">Synopsis</A><br>
<A href="#Members">Members</A><br>
<A href="#Example">Example</A></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>thread</code> class represents threads of execution, and provides
the functionality to create and manage threads within the <b> Boost.Threads</b>
library. See <a href="definitions.html"> Definitions</a> for a precise description
of &quot;thread of execution&quot;, and for definitions of threading related
terms and of thread states such as &quot;blocked&quot;.</p>
<p>A thread of execution has an initial function. For the program&#39;s initial
thread, the initial function is <code>main()</code>. For other threads, the
initial function is <code>operator()</code> of the function object passed to
the class <code>thread</code> constructor.</p>
<p>A thread of execution is said to be &quot;finished&quot; or &quot;finished
execution&quot; when its initial function returns or is terminated. This includes
completion of all thread cleanup handlers, and completion of the normal C++
function return behaviors, such as destruction of automatic storage (stack)
objects and releasing any associated implementation resources.</p>
<p>A thread object has an associated state which is either &quot;joinable&quot;
or &quot;non-joinable&quot;.</p>
<p>Except as described below, the policy used by an implementation of <b>Boost.Threads</b>
to schedule transitions between thread states is unspecified.</p>
<p><b>Note:</b> Just as the lifetime of a file may be different from the lifetime
of an iostream object which represents the file, the lifetime of a thread of
execution may be different from the <code> thread</code> object which represents
the thread of execution. In particular, after a call to <code>join()</code>,
the thread of execution will no longer exist even though the <code>thread</code>
object continues to exist until the end of its normal lifetime. The converse
is also possible; if a <code>thread</code> object is destroyed without <code>join()</code>
having first been called, the thread of execution continues until its initial
function completes.</p>
<h4><a name="class-thread-synopsis"></a>Class <code>thread</code> synopsis</h4>
the functionality to create and manage threads within the <b>Boost.Threads</b>
library. See <A href="definitions.html">Definitions</A> for a precise description of
"thread of execution", and for definitions of threading related terms and of thread
states such as "blocked".</p>
<p>A thread of execution has an initial function. For the program's
initial thread, the initial function is <code>main()</code>. For other
threads, the initial function is <code>operator()</code> of the function object
passed to the class <code>thread</code> constructor.</p>
<p>A thread of execution is said to be "finished" or "finished execution" when its
initial function returns or is terminated. This includes completion of all thread
cleanup handlers, and completion of the normal C++ function return behaviors, such
as destruction of automatic storage (stack) objects and releasing any associated
implementation resources.</p>
<p>A thread object has an associated state which is either "joinable" or
"non-joinable".</p>
<p>Except as described below, the policy used by an implementation of
<b>Boost.Threads</b> to schedule transitions between thread states is unspecified.</p>
<p><b>Note: </b>Just as the lifetime of a file may be different from the
lifetime of an iostream object which represents the file, the lifetime of a
thread of execution may be different from the <code>thread</code> object which
represents the thread of execution. In particular, after a call to <code>join()</code>,
the thread of execution will no longer exist even though the <code>thread</code>
object continues to exist until the end of its normal lifetime. The
converse is also possible; if a <code>thread</code> object is destroyed without
<code>join()</code> having first been called, the thread of execution continues until
its initial function completes.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <A href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</A>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
class thread : <a href=
"../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class thread meets the <a href=
"overview.html#non-copyable">NonCopyable</a> requirement.
class thread : <a href="../../utility/utility.htm#noncopyable">boost::noncopyable</a> // Exposition only.
// Class thread meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
thread();
@@ -105,219 +91,164 @@ public:
static void sleep(const xtime&amp; xt);
static void yield();
};
} // namespace boost
</pre>
<h4><a name="class-thread-ctors"></a>Class <code>thread</code> constructors and
destructor</h4>
<pre>
thread();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs a <code>thread</code> object representing the
current thread of execution.</dt>
<dt><b>Postconditions:</b> <code>*this</code> is non-joinable.</dt>
<dt><b>Danger:</b> <code>*this</code> is valid only within the current thread.</dt>
</dl>
<pre>
thread(const <a href="../../function/index.html">boost::function0</a>&lt;void&gt;&amp; threadfunc);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Starts a new thread of execution and constructs a <code>thread</code>
object representing it. Copies <code> threadfunc</code> (which in turn copies
the function object wrapped by <code>threadfunc</code>) to an internal location
which persists for the lifetime of the new thread of execution. Calls <code>operator()</code>
on the copy of the <code>threadfunc</code> function object in the new thread
of execution.</dt>
<dt><b>Postconditions:</b> <code>*this</code> is joinable.</dt>
<dt><b>Throws:</b> <code>boost::thread_resource_error</code> if a new thread
of execution cannot be started.</dt>
</dl>
<pre>
~Thread();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Destroys <code>*this</code>. The actual thread of execution
may continue to execute after the <code>thread</code> object has been destroyed.</dt>
<dt><b>Note:</b> If <code>*this</code> is joinable the actual thread of execution
becomes &quot;detached&quot;. Any resources used by the thread will be reclaimed
when the thread of execution completes. To ensure such a thread of execution
runs to completion before the <code> thread</code> object is destroyed, call
<code>join()</code>.</dt>
</dl>
<h4><a name="class-thread-comparisons"></a>Class <code>thread</code> comparison
functions</h4>
<pre>
bool operator==(const thread&amp; rhs) const;
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> The thread is non-terminated or <code>*this</code> is joinable.</dt>
<dt><b>Returns:</b> <code>true</code> if <code>*this</code> and <code> rhs</code>
represent the same thread of execution.</dt>
</dl>
<pre>
bool operator!=(const thread&amp; rhs) const;
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> The thread is non-terminated or <code>*this</code> is joinable.</dt>
<dt><b>Returns:</b> <code>!(*this==rhs)</code>.</dt>
</dl>
<h4><a name="class-thread-modifiers"></a>Class <code>thread</code> modifier functions</h4>
<pre>
void join();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>*this</code> is joinable.</dt>
<dt><b>Effects:</b> The current thread of execution blocks until the initial
function of the thread of execution represented by <code> *this</code> finishes
and all resources are reclaimed.</dt>
<dt><b>Postconditions:</b> <code>*this</code> is non-joinable.</dt>
<dt><b>Notes:</b> If <code>*this == thread()</code> the result is implementation
defined. If the implementation doesn&#39;t detect this the result will be
<a href="definitions.html#Deadlock"> deadlock</a>.</dt>
</dl>
<h4><a name="class-thread-statics"></a>Class <code>thread</code> static functions</h4>
<pre>
static void sleep(const <a href="xtime.html">xtime</a>&amp; XT);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> The current thread of execution blocks until <code> XT</code>
is reached.</dt>
</dl>
<pre>
static void yield();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> The current thread of execution is placed in the &quot;ready&quot;
state.</dt>
<dt><b>Notes:</b> Allow the current thread to give up the rest of its time slice
(or other scheduling quota) to another thread. Particularly useful in non-preemptive
implementations.</dt>
</dl>
<h3><a name="class-thread_group"></a>Class <code>thread_group</code></h3>
<p>The <tt>thread_group</tt> class provides a container for easy grouping of threads
to simplify several common thread creation and management idioms.</p>
<p>All <tt>thread_group</tt> member functions are <a href=
"definitions.html#thread-safe">thread-safe</a>, except destruction.</p>
<h4><a name="class-thread_group-synopsis"></a>Class <code>thread_group</code>
synopsis</h4>
<pre>
namespace boost {
class thread_group : <a href=
"../../utility/utility.htm#Class noncopyable">boost::noncopyable</a>
{
public:
thread_group();
~thread_group();
thread* create_thread(const boost::function0&lt;void&gt;&amp; threadfunc);
void add_thread(thread* thrd);
void remove_thread(thread* thrd);
void join_all();
};
} // namespace boost
</pre>
<h4><a name="class-thread_group-ctors"></a>Class <code>thread_group</code> constructors
and destructor</h4>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructors</h3>
<pre>
thread_group();
thread();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs an empty <code>thread_group</code> container.</dt>
</dl>
<p><b>Effects:</b> Constructs a <code>thread</code> object representing the current thread
of execution.</p>
<p><b>Postcondition:</b> <code>*this</code> is non-joinable.</p>
<p><b>Danger:</b> <code>*this</code> is valid only within the current thread.</p>
<pre>
~thread_group();
thread(const <A href="../../function/index.html">boost::function0</A>&lt;void&gt;&amp; threadfunc);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Destroys each contained thread object. Destroys <code>*this</code>.</dt>
<dt><b>Notes:</b> Behavior is undefined if another thread references *this during
the execution of the destructor.</dt>
</dl>
<h4><a name="class-thread_group-modifiers"></a>Class <code>thread_group</code>
modifier functions</h4>
<p><b>Effects:</b> Starts a new thread of execution and constructs a <code>thread</code> object
representing it. Copies <code>threadfunc</code>
(which in turn copies the function object wrapped by <code>threadfunc</code>) to an
internal location which persists for the lifetime of the new thread of execution. Calls
<code>operator()</code> on the copy of the <code>threadfunc</code> function object in
the new thread of execution.</p>
<p><b>Postcondition:</b> <code>*this</code> is joinable.</p>
<p><b>Throws:</b> <code>boost::thread_resource_error</code> if a new thread of execution
cannot be started.</p>
<hr>
<h3>Destructor</h3>
<pre>
thread* create_thread(const boost::function0&lt;void&gt;&amp; threadfunc);
~thread();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Creates a new <tt>thread</tt> object that executes <tt>threadfunc</tt>
and adds it to the <tt>thread_group</tt> container object&#39;s list of managed
<tt>thread</tt> objects.</dt>
<dt><b>Returns:</b> Pointer to the newly created thread.</dt>
</dl>
<p><b>Effects:</b> Destroys <code>*this</code>. The actual thread of execution may
continue to execute after the <code>thread</code> object has been destroyed.</p>
<p><b>Notes:</b> If <code>*this</code> is joinable the actual thread of execution
becomes "detached". Any resources used by the thread will be reclaimed when the
thread of execution completes. To ensure such a thread of execution runs to completion
before the <code>thread</code> object is destroyed, call <code>join()</code>.</p>
<hr>
<h3>Comparison Operators</h3>
<pre>
void add_thread(thread* thrd);
bool operator==(const thread&amp; rhs);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Adds <tt>thrd</tt> to the <tt>thread_group</tt> object&#39;s
list of managed <tt>thread</tt> objects. The <tt>thrd</tt> object must have
been allocated via operator new and will be deleted when the group is destroyed.</dt>
</dl>
<p><b>Requires:</b> The thread is non-terminated or <code>*this</code> is joinable.</p>
<p><b>Returns:</b> <code>true</code> if <code>*this</code> and <code>rhs</code>
represent the same thread of execution.</p>
<pre>
Void remove_thread(thread* thrd);
bool operator!=(const thread&amp; rhs);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Removes <code>*this</code>&#39;s list of managed <tt>thread</tt>
objects.</dt>
<dt><b>Throws:</b> ? if <tt>thrd</tt> is not it <code>*this</code>&#39;s list
of managed <tt>thread</tt> objects.</dt>
</dl>
<p><b>Returns:</b> <code>!(*this==rhs)</code>.</p>
<hr>
<h3>join</h3>
<pre>
Void join_all();
void join();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Calls <code>join()</code> on each of the managed <tt>thread</tt>
objects.</dt>
</dl>
<h2><a name="functions"></a>Functions</h2>
<p><b>Requires:</b> <code>*this</code> is joinable.</p>
<p><b>Effects:</b> The current thread of execution blocks until the initial function of
the thread of execution represented by <code>*this</code> finishes and all resources
are reclaimed.</p>
<p><b>Postcondition:</b> <code>*this</code> is non-joinable.</p>
<p><b>Note:</b></p> If <code>*this == thread()</code> the result is implementation defined.
If the implementation doesn't detect this the result will be
<a href="definitions.html#Deadlock">deadlock</a>.</p>
<hr>
<h3>sleep</h3>
<pre>
<a name="function-spec"></a>{{function}}
static void sleep(const <a href="xtime.html">xtime</a>&amp; xt);
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> {{text}}</dt>
<dt><b>Effects:</b> {{text}}</dt>
<dt><b>Postconditions:</b> {{text}}</dt>
<dt><b>Returns:</b> {{text}}</dt>
<dt><b>Throws:</b> {{text}}</dt>
<dt><b>Complexity:</b> {{text}}</dt>
<dt><b>Rationale:</b> {{text}}</dt>
</dl>
<h2><a name="objects"></a>Objects</h2>
<p><a name="object-spec"></a>{{Object specifications}}</p>
<h2><a name="examples"></a>Example(s)</h2>
<h3><a name="example-thread"></a>Simple usage of <code>boost::thread</code></h3>
<p><a href="../example/thread.cpp">libs/thread/example/thread.cpp</a></p>
<p><b>Effects:</b> The current thread of execution blocks until <code>xt</code> is
reached.</p>
<hr>
<h3>yield</h3>
<pre>
static void yield();
</pre>
<p><b>Effects:</b> The current thread of execution is placed in the "ready" state.</p>
<p><b>Notes:</b> Allow the current thread to give up the rest of its time slice
(or other scheduling quota) to another thread. Particularly useful in non-preemptive
implementations.</p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include &lt;boost/thread/thread.hpp&gt;
#include &lt;iostream&gt;
struct thread_alarm
{
thread_alarm(int secs) : m_secs(secs) { }
void operator()()
{
boost::xtime xt;
boost::xtime_get(&amp;xt, boost::TIME_UTC);
xt.sec += m_secs;
boost::thread::sleep(xt);
std::cout &lt;&lt; &quot;alarm sounded...&quot; &lt;&lt; std::endl;
}
int m_secs;
};
int main(int argc, char* argv[])
{
int secs = 5;
std::cout &lt;&lt; &quot;setting alarm for 5 seconds...&quot; &lt;&lt; std::endl;
boost::thread thrd(thread_alarm(secs));
thrd.join();
}
</pre>
<p>The output is:</p>
<pre>
setting alarm for 5 seconds...
alarm sounded...
</pre>
<h3><a name="example-thread_group"></a>Simple usage of <code>boost::thread_group</code></h3>
<p><a href="../example/thread_group.cpp">libs/thread/example/thread_group.cpp</a></p>
<p>The output is:</p>
<pre>
count = 1
count = 2
count = 3
count = 4
count = 5
count = 6
count = 7
count = 8
count = 9
count = 10
</pre>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <A href="mailto:williamkempf@hotmail.com">William E. Kempf</A>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, thread_group</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">thread_group</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <tt>thread_group</tt> class provides a container for easy grouping of threads to simplify several
common thread creation and management idioms.</p>
<p>All <tt>thread_group</tt> member functions are <a href="definitions.html#thread-safe">thread-safe</a>,
except destruction.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost
{
class thread_group : <a href="../../utility/utility.htm#noncopyable">boost::noncopyable</a>
{
public:
thread_group();
~thread_group();
thread* create_thread(const boost::function0&lt;void&gt;&amp; threadfunc);
void add_thread(thread* thrd);
void remove_thread(thread* thrd);
void join_all();
};
}
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
thread_group();
</pre>
<p><b>Effects:</b> Constructs an empty <tt>thread_group</tt> container.</p>
<hr>
<h3>Destructor</h3>
<pre>
~thread_group();
</pre>
<p><b>Effects:</b> Destroys each contained thread object.&nbsp; Destroys <code>*this</code>.</p>
<p><b>Notes:</b> Behavior is undefined if another thread references *this during
the execution of the destructor.</p>
<hr>
<h3>create_thread</h3>
<pre>
thread* create_thread(const boost::function0&lt;void&gt;&amp; threadfunc);
</pre>
<p><b>Effects:</b> Creates a new <tt>thread</tt> object that executes <tt>threadfunc</tt> and adds it to the
<tt>thread_group</tt> container object's list of managed <tt>thread</tt> objects.</p>
<p><b>Returns:</b> Pointer to the newly created thread.</p>
<hr>
<h3>add_thread</h3>
<pre>
void add_thread(thread* thrd);
</pre>
<p><b>Effects:</b> Adds <tt>thrd</tt> to the <tt>thread_group</tt> object's list of managed <tt>thread</tt>
objects. The <tt>thrd</tt> object must have been allocated via operator new and will
be deleted when the group is destroyed.</p>
<hr>
<h3>remove_thread</h3>
<pre>
void remove_thread(thread* thrd);
</pre>
<p><b>Effects:</b> Removes <code>*this</code>'s list of managed <tt>thread</tt>
objects.</p>
<p><b>Throws: </b>? if <tt>thrd</tt> is not it <code>*this</code>'s list of managed <tt>thread</tt>
objects.</p>
<hr>
<h3>join_all</h3>
<pre>
void join_all();
</pre>
<p><b>Effects:</b> Calls <code> join()</code> on each of the managed <tt>thread</tt> objects.</p>
<hr>
<h2><a name="Example">Example</a> Usage</h2>
<pre>
#include &lt;boost/thread/thread.hpp&gt;
#include &lt;iostream&gt;
int count = 0;
boost::mutex mutex;
void increment_count()
{
boost::mutex::lock lock(mutex);
std::cout &lt;&lt; &quot;count = &quot; &lt;&lt; ++count &lt;&lt; std::endl;
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i = 0; i &lt; 10; ++i)
threads.create_thread(&amp;increment_count);
threads.join_all();
}
</pre>
<p>The output is:</p>
<pre>
count = 1
count = 2
count = 3
count = 4
count = 5
count = 6
count = 7
count = 8
count = 9
count = 10
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->06 August, 2001<!--webbot bot="Timestamp" endspan i-checksum="34352" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/thread_pool.hpp&gt;</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/thread_pool.hpp">boost/thread/thread_pool.hpp</a>&gt;</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-thread_pool">Class <code>thread_pool</code></a></dt>
<dl class="page-index">
<dt><a href="#class-thread_pool-synopsis">Class <code>thread_pool</code> synopsis</a></dt>
<dt><a href="#class-thread_pool-ctors">Class <code>thread_pool</code> constructors and destructor</a></dt>
<dt><a href="#class-thread_pool-modifiers">Class <code>thread_pool</code> modifier functions</a></dt>
</dl>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>Include the header &lt;<a href="../../../boost/thread/thread_pool.hpp">boost/thread/thread_pool.hpp</a>&gt;
to define the <a href="#class-thread_pool">thread_pool</a> class.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-thread_pool"></a>Class <code>thread_pool</code></h3>
<p>The <tt>thread_pool</tt> class provides&nbsp;an interface for&nbsp;running
jobs on a dynamically managed set&nbsp;of worker threads called a pool.&nbsp;
When a job is added, it can execute on any&nbsp;available thread in the pool.&nbsp;
This class controls&nbsp;both the maximum and minimum number of threads&nbsp;in
the pool.&nbsp; If a thread in the pool is sitting idle&nbsp;for a period&nbsp;of
time, it&nbsp;will exit unless by exiting the number of threads would dip below
the minimum. Thread pools provide an optimization over creating a new thread
for each job since the pool can often remove the overhead of thread creation.</p>
<h4><a name="class-thread_pool-synopsis"></a>Class <code>thread_pool</code> synopsis</h4>
<pre>
namespace boost
{
class thread_pool : <a href="../../utility/utility.htm#Class noncopyable">boost::noncopyable</a> // Exposition only.
// Class thread meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
{
public:
thread_pool(int max_threads=std::numeric_limits&lt;int&gt;::max(),
int min_threads=0,
int timeout_secs=5);
~thread_pool();
void add(const boost::function0&lt;void&gt; &amp;job);
void join();
void cancel();
void detach();
};
};
</pre>
<h4><a name="class-spec-ctors"></a>Class <code>thread_pool</code> constructors and destructor</h4>
<pre>
thread_pool(int max_threads=std::numeric_limits&lt;int&gt;::max(),
int min_threads=0,
int timeout_secs=5);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs a thread pool object and starts min_threads threads
running in the pool.</dt>
</dl>
<pre>
~thread_pool();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Calls join() if neither join() nor detach() were called
previously for this thread_pool.&nbsp; If detach() was not called, destroys all
resources associated with the threads in the pool and with the queue of jobs
still waiting to be executed.</dt>
</dl>
<h4><a name="class-spec-modifiers"></a>Class <code>thread_pool</code> modifier
functions</h4>
<pre>
void add(const boost::function0&lt;void&gt;&amp; job);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Adds <tt>job</tt> to the <tt>thread_pool</tt> object's list of
jobs waiting to be executed.&nbsp; If any threads in the pool are idle, the job
will be execute as soon as the idle thread is scheduled by the operating
system.&nbsp; If no threads are idle and the number of threads in the pool is
less than the maximum number provided to the constructor, an additional thread
is created and added to the pool.&nbsp; That new thread will execute this job
as soon as it is scheduled by the operating system.&nbsp; If no threads are
idle and&nbsp;the thread count is at the maximum, this job will be queued until
a thread becomes available.&nbsp; Currently, queued jobs are processed in FIFO
order.</dt>
<dt><b>Throws:</b> std::runtime_error if join() or detach() have
previously been called for this thread_pool object.</dt>
</dl>
<pre>
void detach();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Relinquishes control of the pool of threads by this thread_pool
object.&nbsp; Any threads in the pool will continue to run and continue to
process any queued jobs, but no new threads will be created, and any subsequent
attempts to add new jobs will result in an exception.</dt>
<dt><b>Throws:</b> std::runtime_error if join()&nbsp;has previously
been called for this thread_pool object.</dt>
</dl>
<pre>
void cancel();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Removes all queued jobs from the thread_pool's internal queue,
and calls cancel() on all boost::thread objects in the pool.&nbsp; The specific
behavior of those threads will be dictated by their cancellation behavior - the
pool threads may be executing a user's job that deferrs cancellation, for
example.</dt>
<dt><b>Throws:</b> std::runtime_error if join() or detach() have
previously been called for this thread_pool object.</dt>
<dt><b>Note:</b> for the current version (1.27.0) of Boost.Threads, thread::cancel() is
not provided.&nbsp; This function -will- clear out all queued jobs, but any
currently executing jobs will not be cancelled.</dt>
</dl>
<pre>
void join();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Waits until all queued jobs are completed by the thread pool,
and then join()s will all of the threads in the pool.&nbsp; When join()
returns, no running threads will remain in the pool, and this object is invalid
for anything except destruction.&nbsp; Any calls to cancel(), join(), detach(),
or add() will result in an exception.</dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<pre>
#include &lt;boost/thread/thread_pool.hpp&gt;
#include &lt;boost/thread/mutex.hpp&gt;
#include &lt;iostream&gt;
boost::mutex io_mutex;
class job_adapter {
public:
job_adapter(void (*func)(int), int param) :
_func(func), _param(param){ }
void operator()() const { _func(_param); }
private:
void (*_func)(int);
int _param;
};
void simple_job(int param)
{
boost::mutex::scoped_lock l(io_mutex);
std::cout &lt;&lt; param &lt;&lt; " squared is " &lt;&lt; (param*param) &lt;&lt; "\n";
}
int main(int argc, char* argv[])
{
boost::thread_pool tp;
for (int i = 1; i &lt;= 10; ++i)
tp.add(simple_job);
tp.join();
return 0;
}
</pre>
<p>Typical output would be:</p>
<pre>
1 squared is 1
2 squared is 4
3 squared is 9
4 squared is 16
5 squared is 25
7 squared is 49
6 squared is 36
8 squared is 64
10 squared is 100
9 squared is 81
</pre>
<P>While the jobs are dispatched in the order they are received, the scheduling of
the individual threads in the pool is platform-dependent.</P>
<P>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a>, David Moore 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, BTL, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, thread_resource_error</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">thread_resource_error</h2>
</td>
</tr>
</table>
<hr>
<p><a href="#Introduction">Introduction</a><br>
<a href="#Header">Header</a><br>
<a href="#Synopsis">Synopsis</a><br>
<a href="#Members">Members</a><br>
<a href="#Example">Example</a></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>thread_resource_error</code> class defines an exception type that is thrown
by constructors in the <b>Boost.Threads</b> library when thread related resources
can not be
acquired. This does not include memory allocation failures which instead throw
std::bad_alloc.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/exceptions.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost
{
class thread_resource_error : public std::runtime_error
{
public:
thread_resource_error();
};
}
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
thread_resource_error();
</pre>
<p>Constructs a <code>thread_resource_error</code> object.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->04 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39335" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="threads, Boost.Threads, thread library, C++">
<link rel="stylesheet" type="text/css" href="styles.css">
<title>Boost.Threads, thread_specific_ptr</title>
</head>
<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%">
<tr>
<td valign="top" width="300">
<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">thread_specific_ptr</h2>
</td>
</tr>
</table>
<hr>
<p><A href="#Introduction">Introduction</A><br>
<A href="#Header">Header</A><br>
<A href="#Synopsis">Synopsis</A><br>
<A href="#Members">Members</A><br>
<A href="#Example">Example</A></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>thread_specific_ptr</code> class defines an interface for using thread
specific storage. Thread specific storage is data associated with individual threads
and is often used to make operations
<a href="definitions.html#Thread-safe">thread-safe</a> that rely on global data.</p>
<p>Template <code>thread_specific_ptr</code> stores a pointer to an object obtained via
<code>new</code> on a thread-by-thread basis and calls delete on the contained pointer
when the thread terminates. Each thread initially stores the null pointer in each
<code>thread_specific_ptr</code> instance.</p>
<p>The template <code>thread_specific_ptr</code> is useful in the following cases:</p>
<ul>
<li>An interface was original written assuming a single thread of control and is
being ported to a multi-threaded environment.</li>
<li>Each thread of control invokes sequences of methods that share data that must be
logically accessed through a globally visible access point, but are physically
unique for each thread, instead of being explicitly passed.</li>
</ul>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/tss.hpp">&lt;boost/thread/tss.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
template &lt;typename T&gt;
class thread_specific_ptr : private boost::noncopyable // Exposition only.
// Class thread_specific_ptr meets the <a href="overview.html#NonCopyable">NonCopyable</a> requirement.
{
public:
thread_specific_ptr();
~thread_specific_ptr();
T* get() const;
T* operator-&gt;() const;
T&amp; operator*() const;
T* release();
void reset(T* p=0);
};
} // namespace boost
</pre>
<h2><a name="Members">Members</a></h2>
<hr>
<h3>Constructor</h3>
<pre>
thread_specific_ptr();
</pre>
<p><b>Postconditions:</b> A thread specific storage has been reserved for use by *this
in all threads, with each thread initially storing a null pointer.</p>
<p><b>Requires:</b> The expression <code>delete get()</code> is well formed.</p>
<p><b>Throws:</b> <code>boost::thread_resource_error</code> if the necessary resources
can not be obtained.</p>
<p><b>Notes:</b> There is an implementation specific limit to the number of thread
specific storage objects that can be created, and this limit may be small.</p>
<hr>
<h3>Destructor</h3>
<pre>
~thread_specific_ptr();
</pre>
<p><b>Notes:</b> Does not destroy any data that may be stored in any thread's thread
specific storage. For this reason you should not destroy a
<code>thread_specific_ptr</code> object until you are certain there are no threads
running that have made use of its thread specific storage.</p>
<hr>
<h3>get</h3>
<pre>
T* get() const;
</pre>
<p><b>Returns:</b> The object stored in thread specific storage for the current thread
for *this.</p>
<p><b>Notes:</b> Each thread initially returns 0.</p>
<hr>
<h3>Smart Pointer Operations</h3>
<pre>
T* operator-&gt;() const;
</pre>
<p><b>Returns:</b> <code>get()</code></p>
<pre>
T&amp; operator*() const;
</pre>
<p><b>Returns:</b> <code>get()</code></p>
<p><b>Requires:</b> <code>get() != 0</code></p>
<hr>
<h3>Release</h3>
<pre>
T* release();
</pre>
<p><b>Returns:</b> <code>get()</code></p>
<p><b>Postcondition:</b> *this holds the null pointer for the current thread.</p>
<hr>
<h3>Reset</h3>
<pre>
void reset(T* p=0);
</pre>
<p><b>Effects:</b> If <code>get()!= p</code> then <code>delete get()</code>.</p>
<p><b>Postconditions:</b> <code>*this</code> holds the pointer <code>p</code> for
the current thread.</p>
<p><b>Notes:</b> The pointer will be deleted when the thread terminates.</p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include <a href="../../../boost/thread/tss.hpp">&lt;boost/thread/tss.hpp&gt;</a>
#include &lt;cassert&gt;
boost::thread_specific_ptr&lt;int&gt; value;
void increment()
{
int* p = value.get();
++*p;
}
void thread_proc()
{
value.reset(new int(0)); // initialize the thread's storage
for (int i=0; i&lt;10; ++i)
{
increment();
int* p = value.get();
assert(*p == i+1);
}
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i=0; i&lt;5; ++i)
threads.create_thread(&amp;thread_proc);
threads.join_all();
}
</pre>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->13 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39334" -->
</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/tss.hpp&gt;</title>
</head>
<body link="#0000ff" vlink="#800080">
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/tss.hpp">boost/thread/tss.hpp</a>&gt;</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-thread_specific_ptr">Class <code>thread_specific_ptr</code></a></dt>
<dl class="page-index">
<dt><a href="#class-thread_specific_ptr-synopsis">Class <code>thread_specific_ptr</code>
synopsis</a></dt>
<dt><a href="#class-thread_specific_ptr-ctors">Class <code>thread_specific_ptr</code>
constructors and destructor</a></dt>
<dt><a href="#class-thread_specific_ptr-modifiers">Class <code>thread_specific_ptr</code>
modifier functions</a></dt>
<dt><a href="#class-thread_specific_ptr-observers">Class <code>thread_specific_ptr</code>
observer functions</a></dt>
</dl>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>The header &lt;<a href="../../../boost/thread/tss.hpp">boost/thread/tss.hpp</a>&gt;
defines the class <a href="#class-thread_specific_ptr">thread_specific_ptr</a>
which is used to manage data associated with specific thread instances.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-thread_specific_ptr"></a>Class <code>thread_specific_ptr</code></h3>
<p>The <code>thread_specific_ptr</code> class defines an interface for using thread
specific storage. Thread specific storage is data associated with individual
threads and is often used to make operations <a href="definitions.html#Thread-safe">thread-safe</a>
that rely on global data.</p>
<p>Template <code>thread_specific_ptr</code> stores a pointer to an object obtained
via <code>new</code> on a thread-by-thread basis and calls a specified cleanup
handler on the contained pointer when the thread terminates. The cleanup handlers
are called in the reverse order of construction of the <code>thread_specific_ptr</code>s,
and for the initial thread are called by the destructor, providing the same
ordering gaurantees as for normal declarations. Each thread initially stores
the null pointer in each <code> thread_specific_ptr</code> instance.</p>
<p>The template <code>thread_specific_ptr</code> is useful in the following cases:</p>
<ul>
<li>An interface was originally written assuming a single thread of control
and is being ported to a multithreaded environment.</li>
<li>Each thread of control invokes sequences of methods that share data that
must be logically accessed through a globally visible access point, but are
physically unique for each thread, instead of being explicitly passed.</li>
</ul>
<h4><a name="class-thread_specific_ptr-synopsis"></a>Class <code>thread_specific_ptr</code>
synopsis</h4>
<pre>
namespace boost
{
template &lt;typename T&gt;
class thread_specific_ptr : private boost::noncopyable // Exposition only.
// Class thread_specific_ptr meets the <a href="overview.html#non-copyable">NonCopyable</a> requirement.
{
public:
thread_specific_ptr();
~thread_specific_ptr();
T* get() const;
T* operator-&gt;() const;
T&amp; operator*() const;
T* release();
void reset(T* p=0);
};
};
</pre>
<h4><a name="class-thread_specific_ptr-ctors"></a>Class <code>thread_specific_ptr</code>
constructors and destructor</h4>
<pre>
thread_specific_ptr();
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> The expression <code>delete get()</code> is well formed.</dt>
<dt><b>Effects:</b> A thread-specific data key is allocated and visible to all
threads in the process. Upon creation, the value <code>NULL</code> will be
associated with the new key in all active threads. Upon thread creation, the
value <code>NULL</code> will be associated with all defined keys in the new
thread. A cleanup method is registered with the key that will call <code>delete</code>
on the value associated with the key for a thread when it exits. When a thread
exits, if a key has a registered cleanup method and the thread has a non-<code>NULL</code>
value associated with that key, the value of the key is set to <code>NULL</code>
and then the cleanup method is called with the previously associated value
as its sole argument. The order in which registered cleanup methods are called
when a thread exits is undefined. If after all the cleanup methods have been
called for all non-<code>NULL</code> values, there are still some non-<code>NULL</code>
values with associated cleanup handlers the result is undefined behavior.</dt>
<dt><b>Throws:</b> <code>boost::thread_resource_error</code> if the necessary
resources can not be obtained.</dt>
<dt><b>Note:</b> There may be an implementation specific limit to the number
of thread specific storage objects that can be created, and this limit may
be small.</dt>
<dt><b>Rationale:</b> The most common need for cleanup will be to call <code>delete</code>
on the associated value. If other forms of cleanup are required the overloaded
constructor should be called instead.</dt>
</dl>
<pre>
thread_specific_ptr(void (*cleanup)(void*));
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> A thread-specific data key is allocated and visible to all
threads in the process. Upon creation, the value <code>NULL</code> will be
associated with the new key in all active threads. Upon thread creation, the
value <code>NULL</code> will be associated with all defined keys in the new
thread. The <code>cleanup</code> method is registered with the key and will
be called for a thread with the value associated with the key for that thread
when it exits. When a thread exits, if a key has a registered cleanup method
and the thread has a non-<code>NULL</code> value associated with that key,
the value of the key is set to <code>NULL</code> and then the cleanup method
is called with the previously associated value as its sole argument. The order
in which registered cleanup methods are called when a thread exits is undefined.
If after all the cleanup methods have been called for all non-<code>NULL</code>
values, there are still some non-<code>NULL</code> values with associated
cleanup handlers the result is undefined behavior.</dt>
<dt><b>Throws:</b> <code>boost::thread_resource_error</code> if the necessary
resources can not be obtained.</dt>
<dt><b>Note:</b> There may be an implementation specific limit to the number
of thread specific storage objects that can be created, and this limit may
be small.</dt>
<dt><b>Rationale:</b> There is the occasional need to register specialized cleanup
methods, or to register no cleanup method at all (done by passing <code>NULL</code>
to this constructor.</dt>
</dl>
<pre>
~thread_specific_ptr();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Deletes the thread-specific data key allocated by the constructor.
The thread-specific data values associated with the key need not be <code>NULL</code>.
It is the responsibility of the application to perform any cleanup actions
for data associated with the key.</dt>
<dt><b>Note:</b> Does not destroy any data that may be stored in any thread&#39;s
thread specific storage. For this reason you should not destroy a <code>thread_specific_ptr</code>
object until you are certain there are no threads running that have made use
of its thread specific storage.</dt>
<dt><b>Rationale:</b> Associated data is not cleaned up because registered cleanup
methods need to be run in the thread that allocated the associated data to
be gauranteed to work correctly. There's no safe way to inject the call into
another thread's execution path, making it impossible to call the cleanup
methods safely.</dt>
</dl>
<h4><a name="class-thread_specific_ptr-modifiers"></a>Class <code>thread_specific_ptr</code>
modifier functions</h4>
<pre>
T* release();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> holds the null pointer for the
current thread.</dt>
<dt><b>Returns:</b> <code>this-&gt;get()</code> prior to the call.</dt>
<dt><b>Rationale:</b> This method provides a mechanism for the user to relinquish
control of the data associated with the thread-specific key.</dt>
</dl>
<pre>
void reset(T* p=0);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> If <code>this-&gt;get()!= p &amp;&amp; p != NULL</code>
then call the associated cleanup function. </dt>
<dt><b>Postconditions:</b> <code>*this</code> holds the pointer <code> p</code>
for the current thread.</dt>
</dl>
<h4><a name="class-thread_specific_ptr-observers"></a>Class <code>thread_specific_ptr</code>
observer functions</h4>
<pre>
T* get() const;
</pre>
<dl class="function-semantics">
<dt><b>Returns:</b> The object stored in thread specific storage for the current
thread for <code>*this</code>.</dt>
<dt><b>Note:</b> Each thread initially returns 0.</dt>
</dl>
<pre>
T* operator-&gt;() const;
</pre>
<dl class="function-semantics">
<dt><b>Returns:</b> <code>this-&gt;get()</code>.</dt>
</dl>
<pre>
T& operator*() const;
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>this-&gt;get() != 0</code></dt>
<dt><b>Returns:</b> <code>this-&gt;get()</code>.</dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<p><a href="../example/tss.cpp">libs/thread/example/tss.cpp</a></p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
</body>
</html>

View File

@@ -1,110 +1,141 @@
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="../../../boost.css">
<title>Boost.Threads - Header &lt;boost/thread/xtime.hpp&gt;</title>
<meta name="keywords" content="threads, Boost.Threads, thread library, C++">
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<title>Boost.Threads, xtime</title>
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"header">
<tr>
<td valign="top" width="300">
<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">Header &lt;<a href="../../../boost/thread/xtime.hpp">boost/thread/xtime.hpp</a>&gt;</h2>
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<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
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<h3><img src="../../../c++boost.gif" alt="C++ Boost" width="277" height="86"></h3>
</td>
<td valign="top">
<h1 align="center">Boost.Threads</h1>
<h2 align="center">xtime</h2>
</td>
</tr>
</table>
<hr>
<h2>Contents</h2>
<dl class="page-index">
<dt><a href="#introduction">Introduction</a></dt>
<dt><a href="#values">Values</a></dt>
<dl class="page-index">
<dt><a href="#value-spec">TIME_UTC</a></dt>
</dl>
<dt><a href="#classes">Classes</a></dt>
<dl class="page-index">
<dt><a href="#class-spec">Struct <code>xtime</code></a></dt>
<dl class="page-index">
<dt><a href="#class-xtime-synopsis">Struct <code>xtime</code> synopsis</a></dt>
</dl>
</dl>
<dt><a href="#functions">Functions</a></dt>
<dl class="page-index">
<dt><a href="#function-xtime_get"><code>xtime_get</code></a></dt>
</dl>
<dt><a href="#examples">Example(s)</a></dt>
</dl>
<hr>
<h2><a name="introduction"></a>Introduction</h2>
<p>The header &lt;<a href="../../../boost/thread/xtime.hpp">boost/thread/xtime.hpp</a>&gt;
defines functions and data types used to perform high-resolution time operations.
This is a temporary solution that will be replaced by a more robust time library
once available in Boost.</p>
<h2><a name="values"></a>Values</h2>
<pre><a name="value-spec"></a>
<p><A href="#Introduction">Introduction</A><br>
<A href="#Header">Header</A><br>
<A href="#Synopsis">Synopsis</A><br>
<A href="#Reference">Reference</A><br>
<A href="#Example">Example</A></p>
<h2><a name="Introduction">Introduction</a></h2>
<p>The <code>xtime</code> type is used to represent a point on some time scale or
a duration in time. This type may be proposed for the C standard by Markus Kuhn.
<b>Boost.Threads</b> provides only a very minimal implementation of this proposal
and it's expected that a full implementation will be provided in Boost as a separate
library, at which time <b>Boost.Threads</b> will deprecate its implementation.</p>
<h2><a name="Header">Header</a></h2>
<pre>
#include <a href="../../../boost/thread/xtime.hpp">&lt;boost/thread/xtime.hpp&gt;</a>
</pre>
<h2><a name="Synopsis">Synopsis</a></h2>
<pre>
namespace boost {
enum
{
TIME_UTC
TIME_UTC=1,
};
struct xtime
{
#if defined(BOOST_NO_INT64_T)
int_fast32_t sec;
#else
int_fast64_t sec;
#endif
int_fast32_t nsec;
};
int xtime_get(struct xtime* xtp, int clock_type);
} // namespace boost
</pre>
<h2><a name="Reference">Reference</a></h2>
<hr>
<h3>TIME_UTC</h3>
<p>The clock type for Coordinated Universal Time (UTC). The epoch for this clock type
is 1970-01-01 00:00:00. This is the only clock type supported by <b>Boost.Threads</b>.</p>
<hr>
<h3>xtime</h3>
<pre>
struct xtime
{
#if defined(BOOST_NO_INT64_T)
int_fast32_t sec;
#else
int_fast64_t sec;
#endif
int_fast32_t nsec;
};
</pre>
<p><b>sec</b> represents the whole seconds that have passed since the epoch.</p>
<p><b>nsec</b> represents the nanoseconds since <code>sec.</code>
<hr>
<h3>xtime_get</h3>
<pre>
int xtime_get(struct xtime* xtp, int clock_type);
</pre>
<p><b>Postcondition:</b> <code>xtp</code> represents the current point in time
as a duration since the epoch specified by the <code>clock_type</code>.</p>
<p><b>Returns:</b> <code>clock_type</code> if successful, otherwise 0.
<p><b>Notes:</b> The resolution is implementation specific. For many
implementations the best resolution of time is far more than one nanosecond, and
even when the resolution is reasonably good, the latency of a call to <code>xtime_get()</code>
may be significant. For maximum portability, avoid durations of less than
one second.</p>
<hr>
<h2><a name="Example">Example Usage</a></h2>
<pre>
#include <a href="../../../boost/thread/thread.hpp">&lt;boost/thread/thread.hpp&gt;</a>
#include <a href="../../../boost/thread/tss.hpp">&lt;boost/thread/xtime.hpp&gt;</a>
int main(int argc, char* argv[])
{
boost::xtime xt;
boost::xtime_get(&amp;xt, boost::TIME_UTC);
xt.sec += 1;
boost::thread::sleep(xt); // Sleep for 1 second
}
</pre>
<p>The clock type for Coordinated Universal Time (UTC). The epoch for this clock
type is 1970-01-01 00:00:00. This is the only clock type supported by <b>Boost.Threads</b>.</p>
<h2><a name="classes"></a>Classes</h2>
<h3><a name="class-xtime"></a>Struct <code>xtime</code></h3>
<p>The <code>xtime</code> type is used to represent a point on some time scale
or a duration in time. This type may be proposed for the C standard by Markus
Kuhn. <b>Boost.Threads</b> provides only a very minimal implementation of this
proposal and it&#39;s expected that a full implementation (or some other time
library) will be provided in Boost as a separate library, at which time <b>Boost.Threads</b>
will deprecate its implementation.</p>
<h4><a name="class-xtime-synopsis"></a>Struct <code>xtime</code> synopsis</h4>
<pre>
namespace boost
{
struct xtime
{
#if defined(BOOST_NO_INT64_T)
int_fast32_t sec;
#else
int_fast64_t sec;
#endif
int_fast32_t nsec;
};
};
</pre>
<h2><a name="functions"></a>Functions</h2>
<pre>
<a name="function-xtime_get"></a>int xtime_get(struct xtime* xtp, int clock_type);
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>xtp</code> represents the current point in
time as a duration since the epoch specified by the <code> clock_type</code>.</dt>
<dt><b>Returns:</b> <code>clock_type</code> if successful, otherwise 0.</dt>
<dt><b>Note:</b> The resolution is implementation specific. For many implementations
the best resolution of time is far more than one nanosecond, and even when
the resolution is reasonably good, the latency of a call to <code>xtime_get()</code>
may be significant. For maximum portability, avoid durations of less than
one second.</dt>
</dl>
<h2><a name="examples"></a>Example(s)</h2>
<p><a href="../example/xtime.cpp">libs/thread/example/xtime.cpp</a></p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
05 November, 2001
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->10 September, 2001<!--webbot bot="Timestamp" endspan i-checksum="39328" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.</i></p>
<p>Permission to use, copy, modify, distribute and sell this software and its
documentation for any purpose is hereby granted without fee, provided that the
above copyright notice appear in all copies and that both that copyright notice
and this permission notice appear in supporting documentation. William E. Kempf
makes no representations about the suitability of this software for any purpose.
It is provided &quot;as is&quot; without express or implied warranty.</p>
<p><i>© Copyright <a href="mailto:williamkempf@hotmail.com">William E. Kempf</a>
2001 all rights reserved.</i></p>
</body>
</html>

View File

@@ -1,2 +0,0 @@
bin
*.pdb

View File

@@ -2,33 +2,65 @@
# distribute this software is granted provided this copyright notice appears
# in all copies. This software is provided "as is" without express or implied
# warranty, and with no claim as to its suitability for any purpose.
#
# Boost.Threads build and test Jamfile
#
# Declares the following targets:
# 1. monitor, an example program.
# 2. starvephil, an example program.
# 3. tennis, an example program.
# Declare the location of this subproject relative to the root.
# declare the location of this subproject relative to the root
subproject libs/thread/example ;
# Include threads.jam for Boost.Threads global build information.
# This greatly simplifies the Jam code needed to configure the build
# for the various Win32 build types.
SEARCH on <module@>threads.jam = $(BOOST_ROOT)/libs/thread/build ;
include <module@>threads.jam ;
# Do some OS-specific setup
if $(NT)
{
BOOST_THREADMON_LIB = <lib>../build/libboost_threadmon ;
}
else
{
BOOST_THREADMON_LIB = ;
}
template example
## sources ##
: <template>thread_base <lib>../build/boost_thread <lib>../../test/build/unit_test_framework $(threadmon)
## requirements ##
:
## default build ##
: release <runtime-link>static
;
#######################
exe monitor : <template>example monitor.cpp ;
exe starvephil : <template>example starvephil.cpp ;
exe tennis : <template>example tennis.cpp ;
exe condition : <template>example condition.cpp ;
exe mutex : <template>example mutex.cpp ;
exe once : <template>example once.cpp ;
exe recursive_mutex : <template>example recursive_mutex.cpp ;
exe thread : <template>example thread.cpp ;
exe thread_group : <template>example thread_group.cpp ;
exe tss : <template>example tss.cpp ;
exe xtime : <template>example xtime.cpp ;
#
# Declare the Boost.Threads monitor example program.
#
exe monitor : monitor/monitor.cpp
<lib>../build/libboost_thread
$(BOOST_THREADMON_LIB)
# requirements
: <include>$(BOOST_ROOT)
<threading>multi
: debug release ;
#######################
#
# Declare the Boost.Threads starvephil example program.
#
exe starvephil : starvephil/starvephil.cpp
<lib>../build/libboost_thread
$(BOOST_THREADMON_LIB)
# requirements
: <include>$(BOOST_ROOT)
<threading>multi
: debug release ;
#######################
#
# Declare the Boost.Threads tennis example program.
#
exe tennis : tennis/tennis.cpp
<lib>../build/libboost_thread
$(BOOST_THREADMON_LIB)
# requirements
: <include>$(BOOST_ROOT)
<threading>multi
: debug release ;

View File

@@ -1,68 +0,0 @@
#include <iostream>
#include <vector>
#include <boost/utility.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
class bounded_buffer : private boost::noncopyable
{
public:
typedef boost::mutex::scoped_lock lock;
bounded_buffer(int n) : begin(0), end(0), buffered(0), circular_buf(n) { }
void send (int m) {
lock lk(monitor);
while (buffered == circular_buf.size())
buffer_not_full.wait(lk);
circular_buf[end] = m;
end = (end+1) % circular_buf.size();
++buffered;
buffer_not_empty.notify_one();
}
int receive() {
lock lk(monitor);
while (buffered == 0)
buffer_not_empty.wait(lk);
int i = circular_buf[begin];
begin = (begin+1) % circular_buf.size();
--buffered;
buffer_not_full.notify_one();
return i;
}
private:
int begin, end, buffered;
std::vector<int> circular_buf;
boost::condition buffer_not_full, buffer_not_empty;
boost::mutex monitor;
};
bounded_buffer buf(2);
void sender() {
int n = 0;
while (n < 100) {
buf.send(n);
std::cout << "sent: " << n << std::endl;
++n;
}
buf.send(-1);
}
void receiver() {
int n;
do {
n = buf.receive();
std::cout << "received: " << n << std::endl;
} while (n != -1); // -1 indicates end of buffer
}
int main(int, char*[])
{
boost::thread thrd1(&sender);
boost::thread thrd2(&receiver);
thrd1.join();
thrd2.join();
return 0;
}

View File

@@ -1,106 +0,0 @@
#include <vector>
#include <iostream>
#include <boost/thread/condition.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/recursive_mutex.hpp>
#include <boost/thread/thread.hpp>
namespace {
const int ITERS = 100;
boost::mutex io_mutex;
}
template <typename M>
class buffer_t
{
public:
typedef typename M::scoped_lock scoped_lock;
buffer_t(int n)
: p(0), c(0), full(0), buf(n)
{
}
void send(int m)
{
scoped_lock lk(mutex);
while (full == buf.size())
cond.wait(lk);
buf[p] = m;
p = (p+1) % buf.size();
++full;
cond.notify_one();
}
int receive()
{
scoped_lock lk(mutex);
while (full == 0)
cond.wait(lk);
int i = buf[c];
c = (c+1) % buf.size();
--full;
cond.notify_one();
return i;
}
static buffer_t& get_buffer()
{
static buffer_t buf(2);
return buf;
}
static void do_sender_thread()
{
for (int n = 0; n < ITERS; ++n)
{
{
boost::mutex::scoped_lock lock(io_mutex);
std::cout << "sending: " << n << std::endl;
}
get_buffer().send(n);
}
}
static void do_receiver_thread()
{
for (int x=0; x < (ITERS/2); ++x)
{
int n = get_buffer().receive();
{
boost::mutex::scoped_lock lock(io_mutex);
std::cout << "received: " << n << std::endl;
}
}
}
private:
M mutex;
boost::condition cond;
unsigned int p, c, full;
std::vector<int> buf;
};
template <typename M>
void do_test(M* dummy=0)
{
typedef buffer_t<M> buffer_type;
buffer_type::get_buffer();
boost::thread thrd1(&buffer_type::do_receiver_thread);
boost::thread thrd2(&buffer_type::do_receiver_thread);
boost::thread thrd3(&buffer_type::do_sender_thread);
thrd1.join();
thrd2.join();
thrd3.join();
}
void test_buffer()
{
do_test<boost::mutex>();
do_test<boost::recursive_mutex>();
}
int main()
{
test_buffer();
return 0;
}

View File

@@ -1 +0,0 @@
/*

View File

@@ -8,19 +8,19 @@
namespace {
const int ITERS = 100;
boost::mutex io_mutex;
}
};
template <typename M>
class buffer_t
{
public:
typedef typename M::scoped_lock scoped_lock;
buffer_t(int n)
: p(0), c(0), full(0), buf(n)
{
}
void send(int m)
{
scoped_lock lk(mutex);
@@ -29,7 +29,7 @@ public:
buf[p] = m;
p = (p+1) % buf.size();
++full;
cond.notify_one();
cond.notify_all();
}
int receive()
{
@@ -39,40 +39,41 @@ public:
int i = buf[c];
c = (c+1) % buf.size();
--full;
cond.notify_one();
cond.notify_all();
return i;
}
static buffer_t& get_buffer()
{
static buffer_t buf(2);
return buf;
}
static void do_sender_thread()
{
for (int n = 0; n < ITERS; ++n)
{
get_buffer().send(n);
{
boost::mutex::scoped_lock lock(io_mutex);
std::cout << "sending: " << n << std::endl;
std::cout << "sent: " << n << std::endl;
}
get_buffer().send(n);
}
}
static void do_receiver_thread()
{
for (int x=0; x < (ITERS/2); ++x)
int n;
do
{
int n = get_buffer().receive();
n = get_buffer().receive();
{
boost::mutex::scoped_lock lock(io_mutex);
std::cout << "received: " << n << std::endl;
}
}
} while (n < ITERS - 1);
}
private:
M mutex;
boost::condition cond;
@@ -85,12 +86,10 @@ void do_test(M* dummy=0)
{
typedef buffer_t<M> buffer_type;
buffer_type::get_buffer();
boost::thread thrd1(&buffer_type::do_receiver_thread);
boost::thread thrd1(&buffer_type::do_sender_thread);
boost::thread thrd2(&buffer_type::do_receiver_thread);
boost::thread thrd3(&buffer_type::do_sender_thread);
thrd1.join();
thrd2.join();
thrd3.join();
}
void test_buffer()

Binary file not shown.

View File

@@ -1,41 +0,0 @@
#include <boost/thread/mutex.hpp>
#include <boost/thread/thread.hpp>
#include <iostream>
boost::mutex io_mutex; // The iostreams are not guaranteed to be thread-safe!
class counter
{
public:
counter() : count(0) { }
int increment() {
boost::mutex::scoped_lock scoped_lock(mutex);
return ++count;
}
private:
boost::mutex mutex;
int count;
};
counter c;
void change_count()
{
int i = c.increment();
boost::mutex::scoped_lock scoped_lock(io_mutex);
std::cout << "count == " << i << std::endl;
}
int main(int, char*[])
{
const int num_threads = 4;
boost::thread_group thrds;
for (int i=0; i < num_threads; ++i)
thrds.create_thread(&change_count);
thrds.join_all();
return 0;
}

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@@ -1,25 +0,0 @@
#include <boost/thread/thread.hpp>
#include <boost/thread/once.hpp>
#include <cassert>
int value=0;
boost::once_flag once = BOOST_ONCE_INIT;
void init()
{
++value;
}
void thread_proc()
{
boost::call_once(&init, once);
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i=0; i<5; ++i)
threads.create_thread(&thread_proc);
threads.join_all();
assert(value == 1);
}

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@@ -1,43 +0,0 @@
#include <boost/thread/recursive_mutex.hpp>
#include <boost/thread/thread.hpp>
#include <iostream>
class counter
{
public:
counter() : count(0) { }
int add(int val) {
boost::recursive_mutex::scoped_lock scoped_lock(mutex);
count += val;
return count;
}
int increment() {
boost::recursive_mutex::scoped_lock scoped_lock(mutex);
return add(1);
}
private:
boost::recursive_mutex mutex;
int count;
};
counter c;
void change_count()
{
std::cout << "count == " << c.increment() << std::endl;
}
int main(int, char*[])
{
const int num_threads=4;
boost::thread_group threads;
for (int i=0; i < num_threads; ++i)
threads.create_thread(&change_count);
threads.join_all();
return 0;
}

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@@ -1,171 +0,0 @@
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
#include <iostream>
#include <time.h>
namespace
{
boost::mutex iomx;
}
class canteen
{
public:
canteen() : m_chickens(0) { }
void get(int id)
{
boost::mutex::scoped_lock lock(m_mutex);
while (m_chickens == 0)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": wot, no chickens? I'll WAIT ..." << std::endl;
}
m_condition.wait(lock);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": those chickens look good ... one please ..." << std::endl;
}
m_chickens--;
}
void put(int value)
{
boost::mutex::scoped_lock lock(m_mutex);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: ouch ... make room ... this dish is very hot ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 3;
boost::thread::sleep(xt);
m_chickens += value;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: more chickens ... " << m_chickens <<
" now available ... NOTIFYING ..." << std::endl;
}
m_condition.notify_all();
}
private:
boost::mutex m_mutex;
boost::condition m_condition;
int m_chickens;
};
canteen g_canteen;
void chef()
{
const int chickens = 4;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: starting ..." << std::endl;
}
for (;;)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: cooking ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 2;
boost::thread::sleep(xt);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: " << chickens
<< " chickens, ready-to-go ..." << std::endl;
}
g_canteen.put(chickens);
}
}
struct phil
{
phil(int id) : m_id(id) { }
void run() {
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id << ": starting ..." << std::endl;
}
for (;;)
{
if (m_id > 0)
{
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 3;
boost::thread::sleep(xt);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": gotta eat ..." << std::endl;
}
g_canteen.get(m_id);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": mmm ... that's good ..." << std::endl;
}
}
}
static void do_thread(void* param) {
static_cast<phil*>(param)->run();
}
int m_id;
};
struct thread_adapt
{
thread_adapt(void (*func)(void*), void* param) : _func(func), _param(param) { }
int operator()() const
{
_func(_param);
return 0;
}
void (*_func)(void*);
void* _param;
};
class thread_adapter
{
public:
thread_adapter(void (*func)(void*), void* param) : _func(func), _param(param) { }
void operator()() const { _func(_param); }
private:
void (*_func)(void*);
void* _param;
};
int main(int argc, char* argv[])
{
boost::thread thrd_chef(&chef);
phil p[] = { phil(0), phil(1), phil(2), phil(3), phil(4) };
boost::thread thrd_phil0(thread_adapter(&phil::do_thread, &p[0]));
boost::thread thrd_phil1(thread_adapter(&phil::do_thread, &p[1]));
boost::thread thrd_phil2(thread_adapter(&phil::do_thread, &p[2]));
boost::thread thrd_phil3(thread_adapter(&phil::do_thread, &p[3]));
boost::thread thrd_phil4(thread_adapter(&phil::do_thread, &p[4]));
thrd_chef.join();
thrd_phil0.join();
thrd_phil1.join();
thrd_phil2.join();
thrd_phil3.join();
thrd_phil4.join();
return 0;
}

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@@ -1 +0,0 @@
/*

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@@ -7,124 +7,124 @@
namespace
{
boost::mutex iomx;
}
boost::mutex iomx;
};
class canteen
{
public:
canteen() : m_chickens(0) { }
canteen() : m_chickens(0) { }
void get(int id)
{
boost::mutex::scoped_lock lock(m_mutex);
while (m_chickens == 0)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": wot, no chickens? I'll WAIT ..." << std::endl;
}
m_condition.wait(lock);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": those chickens look good ... one please ..." << std::endl;
}
m_chickens--;
}
void put(int value)
{
boost::mutex::scoped_lock lock(m_mutex);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: ouch ... make room ... this dish is very hot ..." << std::endl;
}
void get(int id)
{
boost::mutex::scoped_lock lock(m_mutex);
while (m_chickens == 0)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": wot, no chickens? I'll WAIT ..." << std::endl;
}
m_condition.wait(lock);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << id <<
": those chickens look good ... one please ..." << std::endl;
}
m_chickens--;
}
void put(int value)
{
boost::mutex::scoped_lock lock(m_mutex);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: ouch ... make room ... this dish is very hot ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 3;
boost::thread::sleep(xt);
m_chickens += value;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: more chickens ... " << m_chickens <<
" now available ... NOTIFYING ..." << std::endl;
}
m_condition.notify_all();
}
m_chickens += value;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() <<
") Chef: more chickens ... " << m_chickens <<
" now available ... NOTIFYING ..." << std::endl;
}
m_condition.notify_all();
}
private:
boost::mutex m_mutex;
boost::condition m_condition;
int m_chickens;
boost::mutex m_mutex;
boost::condition m_condition;
int m_chickens;
};
canteen g_canteen;
void chef()
{
const int chickens = 4;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: starting ..." << std::endl;
}
for (;;)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: cooking ..." << std::endl;
}
const int chickens = 4;
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: starting ..." << std::endl;
}
for (;;)
{
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: cooking ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 2;
boost::thread::sleep(xt);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: " << chickens
<< " chickens, ready-to-go ..." << std::endl;
}
g_canteen.put(chickens);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: " << chickens
<< " chickens, ready-to-go ..." << std::endl;
}
g_canteen.put(chickens);
}
}
struct phil
{
phil(int id) : m_id(id) { }
phil(int id) : m_id(id) { }
void run() {
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id << ": starting ..." << std::endl;
}
for (;;)
{
if (m_id > 0)
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id << ": starting ..." << std::endl;
}
for (;;)
{
if (m_id > 0)
{
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 3;
boost::thread::sleep(xt);
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": gotta eat ..." << std::endl;
}
g_canteen.get(m_id);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": mmm ... that's good ..." << std::endl;
}
}
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": gotta eat ..." << std::endl;
}
g_canteen.get(m_id);
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": mmm ... that's good ..." << std::endl;
}
}
}
static void do_thread(void* param) {
static void do_thread(void* param) {
static_cast<phil*>(param)->run();
}
}
int m_id;
int m_id;
};
struct thread_adapt

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@@ -1,120 +0,0 @@
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
#include <iostream>
#if defined(BOOST_HAS_WINTHREADS)
# include <windows.h>
# include <process.h>
#endif
enum game_state
{
START,
PLAYER_A,
PLAYER_B,
GAME_OVER,
ONE_PLAYER_GONE,
BOTH_PLAYERS_GONE
};
int state;
boost::mutex mutex;
boost::condition cond;
char* player_name(int state)
{
if (state == PLAYER_A)
return "PLAYER-A";
if (state == PLAYER_B)
return "PLAYER-B";
throw "bad player";
return 0;
}
void player(void* param)
{
boost::mutex::scoped_lock lock(mutex);
int active = (int)param;
int other = active == PLAYER_A ? PLAYER_B : PLAYER_A;
while (state < GAME_OVER)
{
std::cout << player_name(active) << ": Play." << std::endl;
state = other;
cond.notify_all();
do
{
cond.wait(lock);
if (state == other)
std::cout << "---" << player_name(active) << ": Spurious wakeup!" << std::endl;
} while (state == other);
}
++state;
std::cout << player_name(active) << ": Gone." << std::endl;
cond.notify_all();
}
struct thread_adapt
{
thread_adapt(void (*func)(void*), void* param) : _func(func), _param(param) { }
int operator()() const
{
_func(_param);
return 0;
}
void (*_func)(void*);
void* _param;
};
class thread_adapter
{
public:
thread_adapter(void (*func)(void*), void* param) : _func(func), _param(param) { }
void operator()() const { _func(_param); }
private:
void (*_func)(void*);
void* _param;
};
int main(int argc, char* argv[])
{
state = START;
boost::thread thrda(thread_adapter(&player, (void*)PLAYER_A));
boost::thread thrdb(thread_adapter(&player, (void*)PLAYER_B));
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 1;
boost::thread::sleep(xt);
{
boost::mutex::scoped_lock lock(mutex);
std::cout << "---Noise ON..." << std::endl;
}
for (int i = 0; i < 1000000; ++i)
cond.notify_all();
{
boost::mutex::scoped_lock lock(mutex);
std::cout << "---Noise OFF..." << std::endl;
state = GAME_OVER;
cond.notify_all();
do
{
cond.wait(lock);
} while (state != BOTH_PLAYERS_GONE);
}
std::cout << "GAME OVER" << std::endl;
thrda.join();
thrdb.join();
return 0;
}

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@@ -1 +0,0 @@
/*

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@@ -1,12 +1,13 @@
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/semaphore.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
#include <iostream>
#if defined(BOOST_HAS_WINTHREADS)
# include <windows.h>
# include <process.h>
# include <windows.h>
# include <process.h>
#endif
enum game_state

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@@ -1,29 +0,0 @@
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
#include <iostream>
struct thread_alarm
{
thread_alarm(int secs) : m_secs(secs) { }
void operator()()
{
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += m_secs;
boost::thread::sleep(xt);
std::cout << "alarm sounded..." << std::endl;
}
int m_secs;
};
int main(int argc, char* argv[])
{
int secs = 5;
std::cout << "setting alarm for 5 seconds..." << std::endl;
thread_alarm alarm(secs);
boost::thread thrd(alarm);
thrd.join();
}

View File

@@ -1,19 +0,0 @@
#include <boost/thread/thread.hpp>
#include <iostream>
int count = 0;
boost::mutex mutex;
void increment_count()
{
boost::mutex::scoped_lock lock(mutex);
std::cout << "count = " << ++count << std::endl;
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i = 0; i < 10; ++i)
threads.create_thread(&increment_count);
threads.join_all();
}

View File

@@ -1,30 +0,0 @@
#include <boost/thread/thread.hpp>
#include <boost/thread/tss.hpp>
#include <cassert>
boost::thread_specific_ptr<int> value;
void increment()
{
int* p = value.get();
++*p;
}
void thread_proc()
{
value.reset(new int(0)); // initialize the thread's storage
for (int i=0; i<10; ++i)
{
increment();
int* p = value.get();
assert(*p == i+1);
}
}
int main(int argc, char* argv[])
{
boost::thread_group threads;
for (int i=0; i<5; ++i)
threads.create_thread(&thread_proc);
threads.join_all();
}

View File

@@ -1,10 +0,0 @@
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>
int main(int argc, char* argv[])
{
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
xt.sec += 1;
boost::thread::sleep(xt); // Sleep for 1 second
}

View File

@@ -0,0 +1,61 @@
/*
*
* Copyright (C) 2001
* William E. Kempf
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. William E. Kempf makes no representations
* about the suitability of this software for any purpose.
* It is provided "as is" without express or implied warranty.
*
* Revision History (excluding minor changes for specific compilers)
* 8 Feb 01 Initial version.
*/
#ifndef BOOST_ATOMIC_HPP
#define BOOST_ATOMIC_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#if !defined(BOOST_HAS_WINTHREADS)
# include <boost/thread/mutex.hpp>
#endif
namespace boost {
class atomic_t
{
public:
typedef long value_type;
friend value_type read(const atomic_t&);
friend value_type increment(atomic_t&);
friend value_type decrement(atomic_t&);
friend value_type swap(atomic_t&, value_type);
friend value_type compare_swap(atomic_t&, value_type, value_type);
explicit atomic_t(value_type val=0)
: _value(val)
{
}
private:
volatile value_type _value;
#if !defined(BOOST_HAS_WINTHREADS)
mutex _mutex;
#endif
};
extern atomic_t::value_type read(const atomic_t&);
extern atomic_t::value_type increment(atomic_t&);
extern atomic_t::value_type decrement(atomic_t&);
extern atomic_t::value_type swap(atomic_t&, atomic_t::value_type);
extern atomic_t::value_type compare_swap(atomic_t&, atomic_t::value_type, atomic_t::value_type);
} // namespace boost
#endif // BOOST_ATOMIC_HPP

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@@ -1,38 +0,0 @@
// Copyright (C) 2002
// David Moore, William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_BARRIER_JDM030602_HPP
#define BOOST_BARRIER_JDM030602_HPP
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
namespace boost {
class barrier
{
public:
barrier(unsigned int count);
~barrier();
bool wait();
private:
mutex m_mutex;
condition m_cond;
unsigned int m_threshold;
unsigned int m_count;
unsigned int m_generation;
};
} // namespace boost
#endif

View File

@@ -6,7 +6,7 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_CONDITION_WEK070601_HPP
@@ -14,17 +14,14 @@
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
# error Thread support is unavailable!
#endif
#include <boost/thread/exceptions.hpp>
#include <boost/utility.hpp>
#include <boost/thread/detail/lock.hpp>
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
#elif defined(BOOST_HAS_MPTASKS)
# include "scoped_critical_region.hpp"
#endif
namespace boost {
@@ -36,7 +33,7 @@ class condition : private noncopyable
public:
condition();
~condition();
void notify_one();
void notify_all();
@@ -45,7 +42,7 @@ public:
{
if (!lock)
throw lock_error();
do_wait(lock.m_mutex);
}
@@ -54,7 +51,7 @@ public:
{
if (!lock)
throw lock_error();
while (!pred())
do_wait(lock.m_mutex);
}
@@ -64,7 +61,7 @@ public:
{
if (!lock)
throw lock_error();
return do_timed_wait(lock.m_mutex, xt);
}
@@ -73,7 +70,7 @@ public:
{
if (!lock)
throw lock_error();
while (!pred())
{
if (!do_timed_wait(lock.m_mutex, xt))
@@ -87,48 +84,46 @@ private:
template <typename M>
void do_wait(M& mutex)
{
#if (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#if defined(BOOST_HAS_WINTHREADS)
enter_wait();
#endif
typedef detail::thread::lock_ops<M> lock_ops;
typename lock_ops::lock_state state;
lock_ops::unlock(mutex, state);
typename M::cv_state state;
mutex.do_unlock(state);
#if defined(BOOST_HAS_PTHREADS)
do_wait(state.pmutex);
#elif (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#elif defined(BOOST_HAS_WINTHREADS)
do_wait();
#endif
lock_ops::lock(mutex, state);
mutex.do_lock(state);
}
template <typename M>
bool do_timed_wait(M& mutex, const xtime& xt)
{
#if (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#if defined(BOOST_HAS_WINTHREADS)
enter_wait();
#endif
typedef detail::thread::lock_ops<M> lock_ops;
typename lock_ops::lock_state state;
lock_ops::unlock(mutex, state);
typename M::cv_state state;
mutex.do_unlock(state);
bool ret = false;
#if defined(BOOST_HAS_PTHREADS)
ret = do_timed_wait(xt, state.pmutex);
#elif (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#elif defined(BOOST_HAS_WINTHREADS)
ret = do_timed_wait(xt);
#endif
lock_ops::lock(mutex, state);
mutex.do_lock(state);
return ret;
}
#if (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#if defined(BOOST_HAS_WINTHREADS)
void enter_wait();
void do_wait();
bool do_timed_wait(const xtime& xt);
@@ -138,24 +133,15 @@ private:
#endif
#if defined(BOOST_HAS_WINTHREADS)
void* m_gate;
void* m_queue;
void* m_mutex;
unsigned long m_gate;
unsigned long m_queue;
unsigned long m_mutex;
unsigned m_gone; // # threads that timed out and never made it to the m_queue
unsigned long m_blocked; // # threads m_blocked m_waiting for the condition
unsigned m_waiting; // # threads m_waiting no longer m_waiting for the condition but still
// m_waiting to be removed from the m_queue
#elif defined(BOOST_HAS_PTHREADS)
pthread_cond_t m_condition;
#elif defined(BOOST_HAS_MPTASKS)
MPSemaphoreID m_gate;
MPSemaphoreID m_queue;
threads::mac::detail::scoped_critical_region m_mutex;
threads::mac::detail::scoped_critical_region m_mutex_mutex;
unsigned m_gone; // # threads that timed out and never made it to the m_queue
unsigned long m_blocked; // # threads m_blocked m_waiting for the condition
unsigned m_waiting; // # threads m_waiting no longer m_waiting for the condition but still
// m_waiting to be removed from the m_queue
#endif
};

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@@ -0,0 +1,100 @@
// Copyright (C) 2001
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
// This file is used to configure Boost.Threads during development
// in order to decouple dependency on any Boost release. Once
// accepted into Boost these contents will be moved to <boost/config>
// or some other appropriate build configuration and all
// #include <boost/thread/config.hpp> statements will be changed
// accordingly.
#ifndef BOOST_THREAD_CONFIG_WEK070601_HPP
#define BOOST_THREAD_CONFIG_WEK070601_HPP
#include <boost/config.hpp>
#error "Included <boost/thread/config.hpp>"
/*// Define if threading support is enabled for the toolset.
#undef BOOST_HAS_THREADS
// Define if threading should be implemented in terms of Win32 threads.
#undef BOOST_HAS_WINTHREADS
// Define if threading should be implemented in terms of POSIX threads.
#undef BOOST_HAS_PTHREADS
// Define if BOOST_HAS_PTHREADS and pthread_delay_np() exists.
#undef BOOST_HAS_PTHREAD_DELAY_NP
// Define if BOOST_HAS_PTHREADS and not BOOST_HAS_PTHREAD_DELAY_NP
// but nanosleep can be used instead.
#undef BOOST_HAS_NANOSLEEP
// Define if BOOST_HAS_PTHREADS and pthread_yield() exists.
#undef BOOST_HAS_PTHREAD_YIELD
// Define if BOOST_HAS_PTHREADS and not BOOST_HAS_PTHREAD_YIELD and
// sched_yield() exists.
#undef BOOST_HAS_SCHED_YIELD
// Define if gettimeofday() exists.
#undef BOOST_HAS_GETTIMEOFDAY
// Define if not BOOST_HAS_GETTIMEOFDAY and clock_gettime() exists.
#undef BOOST_HAS_CLOCK_GETTIME
// Define if not BOOST_HAS_GETTIMEOFDAY and not BOOST_HAS_CLOCK_GETTIME and
// GetSystemTimeAsFileTime() can be called with an FTIME structure.
#undef BOOST_HAS_FTIME
// Define if pthread_mutexattr_settype and pthread_mutexattr_gettype exist.
#undef BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
// Here we'll set up known compiler options.
#if defined(BOOST_MSVC)
# if defined(_MT)
# define BOOST_HAS_THREADS
# endif
# define BOOST_HAS_WINTHREADS // comment out this to test pthreads-win32.
# if !defined(BOOST_HAS_WINTHREADS)
# define BOOST_HAS_PTHREADS
# define BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
# define PtW32NoCatchWarn
# pragma comment(lib, "pthreadVCE.lib")
# endif
# define BOOST_HAS_FTIME
// pdm: this is for linux - is there a better #define to #if on?
// wek: not sure how else to do this, but GNU CC on Win32 should probably
// use BOOST_HAS_WINTHREADS, and I expect there will be other
// platform specific variations for this compiler toolset. Need
// to decide how to handle this.
#elif defined( __GNUC__ )
# define BOOST_HAS_THREADS
# define BOOST_HAS_PTHREADS
# define BOOST_HAS_NANOSLEEP
# define BOOST_HAS_GETTIMEOFDAY
// pdm: From the pthread.h header, one of these macros
// must be defined for this stuff to exist.
// wek: This seems like a harmless enough method to determine these
// switches, but one should note that some implementations may not
// use these. Notably, pthreads-win32 doesn't define either
// __USE_UNIX98 or __USE_GNU.
# if defined( __USE_UNIX98 )
# define BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
# elif defined( __USE_GNU )
# define BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
# define BOOST_HAS_PTHREAD_YIELD
# endif
#endif*/
#endif // BOOST_THREAD_CONFIG_WEK070601_HPP

View File

@@ -1,44 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#ifndef BOOST_FORCE_CAST_MJM012402_HPP
#define BOOST_FORCE_CAST_MJM012402_HPP
namespace boost {
namespace detail {
namespace thread {
// force_cast will convert anything to anything.
// general case
template<class Return_Type, class Argument_Type>
inline Return_Type &force_cast(Argument_Type &rSrc)
{ return(*reinterpret_cast<Return_Type *>(&rSrc)); }
// specialization for const
template<class Return_Type, class Argument_Type>
inline const Return_Type &force_cast(const Argument_Type &rSrc)
{ return(*reinterpret_cast<const Return_Type *>(&rSrc)); }
} // namespace thread
} // namespace detail
} // namespace boost
#endif // BOOST_FORCE_CAST_MJM012402_HPP

View File

@@ -6,7 +6,7 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_XLOCK_WEK070601_HPP
@@ -22,47 +22,12 @@ struct xtime;
namespace detail { namespace thread {
template <typename Mutex>
class lock_ops : private noncopyable
{
private:
lock_ops() { }
public:
typedef typename Mutex::cv_state lock_state;
static void lock(Mutex& m)
{
m.do_lock();
}
static bool trylock(Mutex& m)
{
return m.do_trylock();
}
static bool timedlock(Mutex& m, const xtime& xt)
{
return m.do_timedlock(xt);
}
static void unlock(Mutex& m)
{
m.do_unlock();
}
static void lock(Mutex& m, lock_state& state)
{
m.do_lock(state);
}
static void unlock(Mutex& m, lock_state& state)
{
m.do_unlock(state);
}
};
template <typename Mutex>
class scoped_lock : private noncopyable
{
public:
typedef Mutex mutex_type;
explicit scoped_lock(Mutex& mx, bool initially_locked=true)
: m_mutex(mx), m_locked(false)
{
@@ -72,26 +37,26 @@ struct xtime;
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<Mutex>::lock(m_mutex);
m_mutex.do_lock();
m_locked = true;
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<Mutex>::unlock(m_mutex);
m_mutex.do_unlock();
m_locked = false;
}
bool locked() const { return m_locked; }
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
Mutex& m_mutex;
bool m_locked;
};
@@ -101,7 +66,7 @@ struct xtime;
{
public:
typedef TryMutex mutex_type;
explicit scoped_try_lock(TryMutex& mx)
: m_mutex(mx), m_locked(false)
{
@@ -116,31 +81,31 @@ struct xtime;
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<TryMutex>::lock(m_mutex);
m_mutex.do_lock();
m_locked = true;
}
bool try_lock()
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TryMutex>::trylock(m_mutex));
return (m_locked = m_mutex.do_trylock());
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<TryMutex>::unlock(m_mutex);
m_mutex.do_unlock();
m_locked = false;
}
bool locked() const { return m_locked; }
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
TryMutex& m_mutex;
bool m_locked;
};
@@ -150,7 +115,7 @@ struct xtime;
{
public:
typedef TimedMutex mutex_type;
scoped_timed_lock(TimedMutex& mx, const xtime& xt)
: m_mutex(mx), m_locked(false)
{
@@ -165,31 +130,31 @@ struct xtime;
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<TimedMutex>::lock(m_mutex);
m_mutex.do_lock();
m_locked = true;
}
bool timed_lock(const xtime& xt)
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TimedMutex>::timedlock(m_mutex, xt));
return (m_locked = m_mutex.do_timedlock(xt));
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<TimedMutex>::unlock(m_mutex);
m_mutex.do_unlock();
m_locked = false;
}
bool locked() const { return m_locked; }
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
private:
friend class boost::condition;
TimedMutex& m_mutex;
bool m_locked;
};

View File

@@ -1,334 +0,0 @@
// Copyright (C) 2002
// David Moore
//
// Original scoped_lock implementation
// Copyright (C) 2001
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. David Moore makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_XRWLOCK_JDM031002_HPP
#define BOOST_XRWLOCK_JDM031002_HPP
#include <boost/utility.hpp>
#include <boost/thread/exceptions.hpp>
namespace boost {
class condition;
struct xtime;
typedef enum
{
NO_LOCK=0,
SHARED_LOCK=1,
EXCL_LOCK=2
} rw_lock_state;
namespace detail { namespace thread {
template <typename Mutex>
class rw_lock_ops : private noncopyable
{
private:
rw_lock_ops() { }
public:
static void wrlock(Mutex& m)
{
m.do_wrlock();
}
static void rdlock(Mutex& m)
{
m.do_rdlock();
}
static void wrunlock(Mutex& m)
{
m.do_wrunlock();
}
static void rdunlock(Mutex &m)
{
m.do_rdunlock();
}
static bool try_wrlock(Mutex &m)
{
return m.do_try_wrlock();
}
static bool try_rdlock(Mutex &m)
{
return m.do_try_rdlock();
}
static bool timed_wrlock(Mutex &m,const xtime &xt)
{
return m.do_timed_wrlock(xt);
}
static bool timed_rdlock(Mutex &m,const xtime &xt)
{
return m.do_timed_rdlock(xt);
}
};
template <typename RWMutex>
class scoped_rw_lock : private noncopyable
{
public:
typedef RWMutex mutex_type;
explicit scoped_rw_lock(RWMutex& mx, rw_lock_state initial_state=SHARED_LOCK)
: m_mutex(mx), m_locked(NO_LOCK)
{
if(initial_state == SHARED_LOCK)
rdlock();
else if(initial_state == EXCL_LOCK)
wrlock();
}
~scoped_rw_lock()
{
if(m_locked != NO_LOCK)
unlock();
}
void rdlock()
{
if (m_locked != NO_LOCK) throw lock_error();
rw_lock_ops<RWMutex>::rdlock(m_mutex);
m_locked = SHARED_LOCK;
}
void wrlock()
{
if(m_locked != NO_LOCK) throw lock_error();
rw_lock_ops<RWMutex>::wrlock(m_mutex);
m_locked = EXCL_LOCK;
}
void unlock()
{
if (m_locked == NO_LOCK) throw lock_error();
if(m_locked == SHARED_LOCK)
rw_lock_ops<RWMutex>::rdunlock(m_mutex);
else
rw_lock_ops<RWMutex>::wrunlock(m_mutex);
m_locked = NO_LOCK;
}
bool locked() const
{
return m_locked != NO_LOCK;
}
operator const void*() const
{
return (m_locked != NO_LOCK) ? this : 0;
}
rw_lock_state state() const
{
return m_locked;
}
private:
RWMutex& m_mutex;
rw_lock_state m_locked;
};
template <typename TryRWMutex>
class scoped_try_rw_lock : private noncopyable
{
public:
typedef TryRWMutex mutex_type;
explicit scoped_try_rw_lock(TryRWMutex& mx)
: m_mutex(mx), m_locked(NO_LOCK)
{
try_rdlock();
}
scoped_try_rw_lock(TryRWMutex& mx, rw_lock_state initial_state)
: m_mutex(mx), m_locked(NO_LOCK)
{
if(initial_state == SHARED_LOCK)
rdlock();
else if(initial_state == EXCL_LOCK)
wrlock();
}
~scoped_try_rw_lock()
{
if(m_locked != NO_LOCK)
unlock();
}
void rdlock()
{
if (m_locked != NO_LOCK) throw lock_error();
rw_lock_ops<TryRWMutex>::rdlock(m_mutex);
m_locked = SHARED_LOCK;
}
bool try_rdlock()
{
if (m_locked != NO_LOCK) throw lock_error();
if(rw_lock_ops<TryRWMutex>::try_rdlock(m_mutex))
{
m_locked = SHARED_LOCK;
return true;
}
return false;
}
void wrlock()
{
if(m_locked != NO_LOCK) throw lock_error();
rw_lock_ops<TryRWMutex>::wrlock(m_mutex);
m_locked = EXCL_LOCK;
}
bool try_wrlock()
{
if (m_locked != NO_LOCK) throw lock_error();
if(rw_lock_ops<TryRWMutex>::try_wrlock(m_mutex))
{
m_locked = EXCL_LOCK;
return true;
}
return false;
}
void unlock()
{
if (m_locked == NO_LOCK) throw lock_error();
if(m_locked == SHARED_LOCK)
rw_lock_ops<TryRWMutex>::rdunlock(m_mutex);
else
rw_lock_ops<TryRWMutex>::wrunlock(m_mutex);
m_locked = NO_LOCK;
}
bool locked() const
{
return m_locked != NO_LOCK;
}
operator const void*() const
{
return (m_locked != NO_LOCK) ? this : 0;
}
rw_lock_state state() const
{
return m_locked;
}
private:
TryRWMutex& m_mutex;
rw_lock_state m_locked;
};
template <typename TimedRWMutex>
class scoped_timed_rw_lock : private noncopyable
{
public:
typedef TimedRWMutex mutex_type;
explicit scoped_timed_rw_lock(TimedRWMutex& mx, const xtime &xt)
: m_mutex(mx), m_locked(NO_LOCK)
{
timed_sharedlock(xt);
}
scoped_timed_rw_lock(TimedRWMutex& mx, rw_lock_state initial_state)
: m_mutex(mx), m_locked(NO_LOCK)
{
if(initial_state == SHARED_LOCK)
rdlock();
else if(initial_state == EXCL_LOCK)
wrlock();
}
~scoped_timed_rw_lock()
{
if(m_locked != NO_LOCK)
unlock();
}
void rdlock()
{
if (m_locked != NO_LOCK) throw lock_error();
rw_lock_ops<TimedRWMutex>::rdlock(m_mutex);
m_locked = SHARED_LOCK;
}
bool timed_rdlock(const xtime &xt)
{
if (m_locked != NO_LOCK) throw lock_error();
if(rw_lock_ops<TimedRWMutex>::timed_rdlock(m_mutex,xt))
{
m_locked = SHARED_LOCK;
return true;
}
return false;
}
void wrlock()
{
if(m_locked != NO_LOCK) throw lock_error();
rw_lock_ops<TimedRWMutex>::wrlock(m_mutex);
m_locked = EXCL_LOCK;
}
bool timed_wrlock(const xtime &xt)
{
if (m_locked != NO_LOCK) throw lock_error();
if(rw_lock_ops<TimedRWMutex>::timed_wrlock(m_mutex,xt))
{
m_locked = EXCL_LOCK;
return true;
}
return false;
}
void unlock()
{
if (m_locked == NO_LOCK) throw lock_error();
if(m_locked == SHARED_LOCK)
rw_lock_ops<TimedRWMutex>::rdunlock(m_mutex);
else
rw_lock_ops<TimedRWMutex>::wrunlock(m_mutex);
m_locked = NO_LOCK;
}
bool locked() const
{
return m_locked != NO_LOCK;
}
operator const void*() const
{
return (m_locked != NO_LOCK) ? this : 0;
}
rw_lock_state state() const
{
return m_locked;
}
private:
TimedRWMutex& m_mutex;
rw_lock_state m_locked;
};
} // namespace thread
} // namespace detail
} // namespace boost
// Change Log:
// 03/10/02 Initial version
#endif

View File

@@ -1,64 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#ifndef BOOST_SINGLETON_MJM012402_HPP
#define BOOST_SINGLETON_MJM012402_HPP
namespace boost {
namespace detail {
namespace thread {
// class singleton has the same goal as all singletons: create one instance of a
// class on demand, then dish it out as requested.
template<class T>
class singleton: private T
{
private:
singleton();
~singleton();
public:
static T &instance();
};
template<class T>
inline singleton<T>::singleton()
{ /* no-op */ }
template<class T>
inline singleton<T>::~singleton()
{ /* no-op */ }
template<class T>
/*static*/ T &singleton<T>::instance()
{
// function-local static to force this to work correctly at static initialization
// time.
static singleton<T> s_oT;
return(s_oT);
}
} // namespace thread
} // namespace detail
} // namespace boost
#endif // BOOST_SINGLETON_MJM012402_HPP

View File

@@ -9,6 +9,13 @@
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
// This file is used to configure Boost.Threads during development
// in order to decouple dependency on any Boost release. Once
// accepted into Boost these contents will be moved to <boost/config>
// or some other appropriate build configuration and all
// #include <boost/thread/config.hpp> statements will be changed
// accordingly.
#ifndef BOOST_THREAD_EXCEPTIONS_PDM070801_H
#define BOOST_THREAD_EXCEPTIONS_PDM070801_H
@@ -22,16 +29,16 @@
namespace boost {
class lock_error : public std::logic_error
class lock_error : public std::runtime_error
{
public:
lock_error();
lock_error() : std::runtime_error("thread lock error") { }
};
class thread_resource_error : public std::runtime_error
{
public:
thread_resource_error();
thread_resource_error() : std::runtime_error("thread resource error") { }
};
} // namespace boost

View File

@@ -6,7 +6,7 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_MUTEX_WEK070601_HPP
@@ -14,7 +14,7 @@
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
# error Thread support is unavailable!
#endif
#include <boost/utility.hpp>
@@ -24,24 +24,22 @@
# include <pthread.h>
#endif
#if defined(BOOST_HAS_MPTASKS)
# include "scoped_critical_region.hpp"
#endif
namespace boost {
class condition;
struct xtime;
class mutex : private noncopyable
{
public:
friend class detail::thread::lock_ops<mutex>;
friend class detail::thread::scoped_lock<mutex>;
friend class condition;
typedef detail::thread::scoped_lock<mutex> scoped_lock;
mutex();
~mutex();
private:
#if defined(BOOST_HAS_WINTHREADS)
typedef void* cv_state;
@@ -50,10 +48,6 @@ private:
{
pthread_mutex_t* pmutex;
};
#elif defined(BOOST_HAS_MPTASKS)
struct cv_state
{
};
#endif
void do_lock();
void do_unlock();
@@ -61,26 +55,25 @@ private:
void do_unlock(cv_state& state);
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
unsigned long m_mutex;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
#elif defined(BOOST_HAS_MPTASKS)
threads::mac::detail::scoped_critical_region m_mutex;
threads::mac::detail::scoped_critical_region m_mutex_mutex;
#endif
};
class try_mutex : private noncopyable
{
public:
friend class detail::thread::lock_ops<try_mutex>;
friend class detail::thread::scoped_lock<try_mutex>;
friend class detail::thread::scoped_try_lock<try_mutex>;
friend class condition;
typedef detail::thread::scoped_lock<try_mutex> scoped_lock;
typedef detail::thread::scoped_try_lock<try_mutex> scoped_try_lock;
try_mutex();
~try_mutex();
private:
#if defined(BOOST_HAS_WINTHREADS)
typedef void* cv_state;
@@ -89,10 +82,6 @@ private:
{
pthread_mutex_t* pmutex;
};
#elif defined(BOOST_HAS_MPTASKS)
struct cv_state
{
};
#endif
void do_lock();
bool do_trylock();
@@ -101,27 +90,27 @@ private:
void do_unlock(cv_state& state);
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
unsigned long m_mutex;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
#elif defined(BOOST_HAS_MPTASKS)
threads::mac::detail::scoped_critical_region m_mutex;
threads::mac::detail::scoped_critical_region m_mutex_mutex;
#endif
};
class timed_mutex : private noncopyable
{
public:
friend class detail::thread::lock_ops<timed_mutex>;
friend class detail::thread::scoped_lock<timed_mutex>;
friend class detail::thread::scoped_try_lock<timed_mutex>;
friend class detail::thread::scoped_timed_lock<timed_mutex>;
friend class condition;
typedef detail::thread::scoped_lock<timed_mutex> scoped_lock;
typedef detail::thread::scoped_try_lock<timed_mutex> scoped_try_lock;
typedef detail::thread::scoped_timed_lock<timed_mutex> scoped_timed_lock;
timed_mutex();
~timed_mutex();
private:
#if defined(BOOST_HAS_WINTHREADS)
typedef void* cv_state;
@@ -130,10 +119,6 @@ private:
{
pthread_mutex_t* pmutex;
};
#elif defined(BOOST_HAS_MPTASKS)
struct cv_state
{
};
#endif
void do_lock();
bool do_trylock();
@@ -141,16 +126,13 @@ private:
void do_unlock();
void do_lock(cv_state& state);
void do_unlock(cv_state& state);
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
unsigned long m_mutex;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
pthread_cond_t m_condition;
bool m_locked;
#elif defined(BOOST_HAS_MPTASKS)
threads::mac::detail::scoped_critical_region m_mutex;
threads::mac::detail::scoped_critical_region m_mutex_mutex;
#endif
};

View File

@@ -6,7 +6,7 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_ONCE_WEK080101_HPP
@@ -14,7 +14,7 @@
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
# error Thread support is unavailable!
#endif
#if defined(BOOST_HAS_PTHREADS)
@@ -26,12 +26,12 @@ namespace boost {
#if defined(BOOST_HAS_PTHREADS)
typedef pthread_once_t once_flag;
#define BOOST_ONCE_INIT PTHREAD_ONCE_INIT
const once_flag once_init = PTHREAD_ONCE_INIT;
#elif (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#elif defined(BOOST_HAS_WINTHREADS)
typedef long once_flag;
#define BOOST_ONCE_INIT 0
typedef bool once_flag;
const once_flag once_init = false;
#endif

View File

@@ -6,7 +6,7 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_RECURSIVE_MUTEX_WEK070601_HPP
@@ -14,7 +14,7 @@
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
# error Thread support is unavailable!
#endif
#include <boost/utility.hpp>
@@ -22,26 +22,26 @@
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
#elif defined(BOOST_HAS_MPTASKS)
# include "scoped_critical_region.hpp"
#endif
namespace boost {
class condition;
struct xtime;
class recursive_mutex : private noncopyable
{
public:
friend class detail::thread::lock_ops<recursive_mutex>;
friend class detail::thread::scoped_lock<recursive_mutex>;
friend class condition;
typedef detail::thread::scoped_lock<recursive_mutex> scoped_lock;
recursive_mutex();
~recursive_mutex();
private:
#if (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#if defined(BOOST_HAS_WINTHREADS)
typedef std::size_t cv_state;
#elif defined(BOOST_HAS_PTHREADS)
struct cv_state
@@ -56,7 +56,7 @@ private:
void do_unlock(cv_state& state);
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
unsigned long m_mutex;
unsigned long m_count;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
@@ -66,26 +66,24 @@ private:
pthread_t m_thread_id;
bool m_valid_id;
# endif
#elif defined(BOOST_HAS_MPTASKS)
threads::mac::detail::scoped_critical_region m_mutex;
threads::mac::detail::scoped_critical_region m_mutex_mutex;
std::size_t m_count;
#endif
};
class recursive_try_mutex : private noncopyable
{
public:
friend class detail::thread::lock_ops<recursive_try_mutex>;
friend class detail::thread::scoped_lock<recursive_try_mutex>;
friend class detail::thread::scoped_try_lock<recursive_try_mutex>;
friend class condition;
typedef detail::thread::scoped_lock<recursive_try_mutex> scoped_lock;
typedef detail::thread::scoped_try_lock<recursive_try_mutex> scoped_try_lock;
recursive_try_mutex();
~recursive_try_mutex();
private:
#if (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#if defined(BOOST_HAS_WINTHREADS)
typedef std::size_t cv_state;
#elif defined(BOOST_HAS_PTHREADS)
struct cv_state
@@ -99,9 +97,9 @@ private:
void do_unlock();
void do_lock(cv_state& state);
void do_unlock(cv_state& state);
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
unsigned long m_mutex;
unsigned long m_count;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
@@ -111,27 +109,26 @@ private:
pthread_t m_thread_id;
bool m_valid_id;
# endif
#elif defined(BOOST_HAS_MPTASKS)
threads::mac::detail::scoped_critical_region m_mutex;
threads::mac::detail::scoped_critical_region m_mutex_mutex;
std::size_t m_count;
#endif
};
class recursive_timed_mutex : private noncopyable
{
public:
friend class detail::thread::lock_ops<recursive_timed_mutex>;
friend class detail::thread::scoped_lock<recursive_timed_mutex>;
friend class detail::thread::scoped_try_lock<recursive_timed_mutex>;
friend class detail::thread::scoped_timed_lock<recursive_timed_mutex>;
friend class condition;
typedef detail::thread::scoped_lock<recursive_timed_mutex> scoped_lock;
typedef detail::thread::scoped_try_lock<recursive_timed_mutex> scoped_try_lock;
typedef detail::thread::scoped_timed_lock<recursive_timed_mutex> scoped_timed_lock;
recursive_timed_mutex();
~recursive_timed_mutex();
private:
#if (defined(BOOST_HAS_WINTHREADS) || defined(BOOST_HAS_MPTASKS))
#if defined(BOOST_HAS_WINTHREADS)
typedef std::size_t cv_state;
#elif defined(BOOST_HAS_PTHREADS)
struct cv_state
@@ -146,9 +143,9 @@ private:
void do_unlock();
void do_lock(cv_state& state);
void do_unlock(cv_state& state);
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
unsigned long m_mutex;
unsigned long m_count;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
@@ -156,10 +153,6 @@ private:
pthread_t m_thread_id;
bool m_valid_id;
unsigned m_count;
#elif defined(BOOST_HAS_MPTASKS)
threads::mac::detail::scoped_critical_region m_mutex;
threads::mac::detail::scoped_critical_region m_mutex_mutex;
std::size_t m_count;
#endif
};

View File

@@ -1,214 +0,0 @@
// Copyright (C) 2002
// David Moore
//
// Original mutex design and implementation
// Copyright (C) 2001
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. David Moore makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
//
//
// A Boost::threads implementation of a synchronization
// primitive which can allow multiple readers or a single
// writer to have access to a shared resource.
#ifndef BOOST_RW_MUTEX_JDM030602_HPP
#define BOOST_RW_MUTEX_JDM030602_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/utility.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/detail/lock.hpp>
#include <boost/thread/detail/rw_lock.hpp>
#include <boost/thread/condition.hpp>
namespace boost {
typedef enum
{
sp_writer_priority,
sp_reader_priority,
sp_alternating_many_reads,
sp_alternating_single_reads
} rw_scheduling_policy;
namespace detail { namespace thread {
// Shared implementation construct for explicit Scheduling Policies
//
// This implementation is susceptible to self-deadlock, though....
template<typename Mutex>
struct rw_mutex_impl
{
typedef detail::thread::scoped_lock<Mutex> scoped_lock;
typedef detail::thread::scoped_try_lock<Mutex> scoped_try_lock;
typedef detail::thread::scoped_timed_lock<Mutex> scoped_timed_lock;
rw_mutex_impl(rw_scheduling_policy sp) :
m_num_waiting_writers(0),
m_num_waiting_readers(0),
m_num_waiting_promotion(0),
m_state(0),
m_sp(sp),
m_readers_next(1)
{}
Mutex m_prot;
condition m_waiting_writers;
condition m_waiting_readers;
int m_num_waiting_writers;
int m_num_waiting_readers;
condition m_waiting_promotion;
int m_num_waiting_promotion;
int m_state; // -1 = excl locked
// 0 = unlocked
// 1-> INT_MAX - shared locked
rw_scheduling_policy m_sp;
// For alternating priority policies, who goes next?
int m_readers_next;
void do_rdlock();
void do_wrlock();
void do_wrunlock();
void do_rdunlock();
bool do_try_wrlock();
bool do_try_rdlock();
bool do_timed_wrlock(const xtime &xt);
bool do_timed_rdlock(const xtime &xt);
bool do_try_promote_rdlock();
void do_wakeups();
};
}// namespace detail
}// namespace thread
class rw_mutex : private noncopyable
{
public:
rw_mutex(rw_scheduling_policy sp) :
m_impl(sp)
{
}
~rw_mutex(){}
rw_scheduling_policy policy() const {return m_impl.m_sp;}
friend class detail::thread::rw_lock_ops<rw_mutex>;
typedef detail::thread::scoped_rw_lock<rw_mutex> scoped_rw_lock;
typedef detail::thread::scoped_try_rw_lock<rw_mutex> scoped_try_rw_lock;
private:
// Operations that will eventually be done only
// via lock types
void do_wrlock();
void do_rdlock();
void do_wrunlock();
void do_rdunlock();
detail::thread::rw_mutex_impl<mutex> m_impl;
};
class try_rw_mutex : private noncopyable
{
public:
try_rw_mutex(rw_scheduling_policy sp) :
m_impl(sp)
{
}
~try_rw_mutex(){}
rw_scheduling_policy policy() const {return m_impl.m_sp;}
friend class detail::thread::rw_lock_ops<try_rw_mutex>;
typedef detail::thread::scoped_rw_lock<try_rw_mutex> scoped_rw_lock;
typedef detail::thread::scoped_try_rw_lock<try_rw_mutex> scoped_try_rw_lock;
private:
// Operations that will eventually be done only
// via lock types
void do_wrlock();
void do_rdlock();
void do_wrunlock();
void do_rdunlock();
bool do_try_wrlock();
bool do_try_rdlock();
detail::thread::rw_mutex_impl<try_mutex> m_impl;
};
class timed_rw_mutex : private noncopyable
{
public:
timed_rw_mutex(rw_scheduling_policy sp) :
m_impl(sp)
{
}
~timed_rw_mutex(){}
rw_scheduling_policy policy() const {return m_impl.m_sp;}
friend class detail::thread::rw_lock_ops<timed_rw_mutex>;
typedef detail::thread::scoped_rw_lock<timed_rw_mutex> scoped_rw_lock;
typedef detail::thread::scoped_try_rw_lock<timed_rw_mutex> scoped_try_rw_lock;
typedef detail::thread::scoped_timed_rw_lock<timed_rw_mutex> scoped_timed_rw_lock;
private:
// Operations that will eventually be done only
// via lock types
void do_wrlock();
void do_rdlock();
void do_wrunlock();
void do_rdunlock();
bool do_try_wrlock();
bool do_try_rdlock();
bool do_timed_wrlock(const xtime &xt);
bool do_timed_rdlock(const xtime &xt);
detail::thread::rw_mutex_impl<timed_mutex> m_impl;
};
} // namespace boost
#endif

View File

@@ -0,0 +1,57 @@
// Copyright (C) 2001
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_SEMAPHORE_WEK070601_HPP
#define BOOST_SEMAPHORE_WEK070601_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/utility.hpp>
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
#endif
namespace boost {
struct xtime;
class semaphore : private noncopyable
{
public:
explicit semaphore(unsigned count=0, unsigned max=0);
~semaphore();
bool up(unsigned count=1, unsigned* prev=0);
void down();
bool down(const xtime& xt);
private:
#if defined(BOOST_HAS_WINTHREADS)
unsigned long m_sema;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
pthread_cond_t m_condition;
unsigned m_available;
unsigned m_max;
#endif
};
} // namespace boost
// Change Log:
// 8 Feb 01 WEKEMPF Initial version.
// 22 May 01 WEKEMPF Modified to use xtime for time outs.
#endif // BOOST_SEMAPHORE_WEK070601_HPP

View File

@@ -1,56 +0,0 @@
// Copyright (C) 2002
// William E. Kempf, David Moore
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_MUTEX_JDM062402_HPP
#define BOOST_MUTEX_JDM062402_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/utility.hpp>
#include <boost/function.hpp>
#include <boost/thread/exceptions.hpp>
#include <string>
namespace boost {
class shared_memory
{
public:
// Obtain a shared memory block len bytes long, zero initialized
shared_memory(const char *name,size_t len);
// Obtain a shared memory block and initialize it with initfunc
shared_memory(const char *name,size_t len,const boost::function2<void,void *,size_t> &initfunc);
~shared_memory();
void *get(){return m_ptr;}
private:
void create(const char *name,
size_t len);
void *m_ptr; // Pointer to shared memory block
int m_mem_obj; // Platform specific handle to shared memory block
void *m_h_event; // Platform specific handle to event saying block initialized.
size_t m_len;
boost::function2<void,void *,size_t> m_initfunc;
};
}; // namespace boost
#endif

View File

@@ -6,7 +6,7 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_THREAD_WEK070601_HPP
@@ -14,7 +14,7 @@
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
# error Thread support is unavailable!
#endif
#include <boost/utility.hpp>
@@ -26,25 +26,15 @@
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
# include <boost/thread/condition.hpp>
#elif defined(BOOST_HAS_MPTASKS)
# include <Multiprocessing.h>
#endif
namespace boost {
struct xtime;
class thread_cancel
{
public:
thread_cancel() { }
};
class thread : private noncopyable
{
public:
enum category_type { boost, native, adopted };
thread();
explicit thread(const function0<void>& threadfunc);
~thread();
@@ -52,16 +42,20 @@ public:
bool operator==(const thread& other) const;
bool operator!=(const thread& other) const;
category_type category() const;
void join();
void cancel();
static void test_cancel();
static void sleep(const xtime& xt);
static void yield();
private:
void* m_handle;
#if defined(BOOST_HAS_WINTHREADS)
unsigned long m_thread;
unsigned int m_id;
#elif defined(BOOST_HAS_PTHREADS)
private:
pthread_t m_thread;
#endif
bool m_joinable;
};
class thread_group : private noncopyable
@@ -73,7 +67,6 @@ public:
thread* create_thread(const function0<void>& threadfunc);
void add_thread(thread* thrd);
void remove_thread(thread* thrd);
thread* thread_group::find(thread& thrd);
void join_all();
private:

View File

@@ -1,52 +0,0 @@
// Copyright (C) 2002 David Moore
//
// Based on Boost.Threads
// Copyright (C) 2001
// William E. Kempf
//
// Derived loosely from work queue manager in "Programming POSIX Threads"
// by David Butenhof.
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_THREAD_POOL_JDM031802_HPP
#define BOOST_THREAD_POOL_JDM031802_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/function.hpp>
#include <boost/limits.hpp>
namespace boost {
class thread_pool
{
public:
thread_pool(int max_threads=std::numeric_limits<int>::max(),
int min_threads=0,
int timeout_secs=5,
int timeout_nsecs=0);
~thread_pool();
void add(const boost::function0<void> &job);
void join();
void cancel();
void detach();
private:
class impl;
impl* m_pimpl;
};
} // namespace boost
#endif

View File

@@ -6,7 +6,7 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_TSS_WEK070601_HPP
@@ -14,84 +14,59 @@
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
# error Thread support is unavailable!
#endif
#include <boost/utility.hpp>
#include <boost/function.hpp>
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
#elif defined(BOOST_HAS_MPTASKS)
# include <Multiprocessing.h>
#endif
namespace boost {
namespace detail {
class tss_ref
{
public:
tss_ref();
};
namespace detail {
class tss : private noncopyable
{
public:
tss(boost::function1<void, void*> cleanup);
tss(void (*cleanup)(void*)=0);
~tss();
void* get() const;
void set(void* value);
void cleanup(void* p);
bool set(void* value);
private:
int m_slot;
int m_generation;
#if defined(BOOST_HAS_WINTHREADS)
unsigned long m_key;
void (*m_cleanup)(void*);
#elif defined(BOOST_HAS_PTHREADS)
pthread_key_t m_key;
#endif
};
#if defined(BOOST_HAS_MPTASKS)
void thread_cleanup();
#endif
struct tss_adapter
{
tss_adapter(boost::function1<void, void*> cleanup) : m_cleanup(cleanup) { }
void operator()(void* p) { m_cleanup(p); }
boost::function1<void, void*> m_cleanup;
};
} // namespace detail
}
template <typename T>
class thread_specific_ptr : private noncopyable
{
public:
thread_specific_ptr() : m_tss(detail::tss_adapter(&thread_specific_ptr<T>::cleanup)) { }
thread_specific_ptr(void (*clean)(void*)) : m_tss(detail::tss_adapter(clean)) { }
~thread_specific_ptr() { reset(); }
thread_specific_ptr() : m_tss(&thread_specific_ptr<T>::cleanup) { }
T* get() const { return static_cast<T*>(m_tss.get()); }
T* operator->() const { return get(); }
T& operator*() const { return *get(); }
T* release() { T* temp = get(); m_tss.set(0); return temp; }
void reset(T* p=0) { T* cur = get(); if (cur == p) return; m_tss.set(p); if (cur) m_tss.cleanup(cur); }
void reset(T* p=0) { T* cur = get(); if (cur == p) return; delete cur; m_tss.set(p); }
private:
static void cleanup(void* p) { delete static_cast<T*>(p); }
detail::tss m_tss;
mutable detail::tss m_tss;
};
} // namespace boost
namespace {
// This injects a tss_ref into every namespace and helps to insure we get a proper
// value for the "main" thread
boost::detail::tss_ref _tss_ref__7BAFF4714CFC42ae9C425F60CE3714D8;
}
// Change Log:
// 6 Jun 01 WEKEMPF Initial version.
// 30 May 02 WEKEMPF Added interface to set specific cleanup handlers. Removed TLS slot limits
// from most implementations.
#endif // BOOST_TSS_WEK070601_HPP

View File

@@ -6,7 +6,7 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#ifndef BOOST_XTIME_WEK070601_HPP
@@ -40,13 +40,6 @@ struct xtime
};
int xtime_get(struct xtime* xtp, int clock_type);
inline int xtime_cmp(const xtime& xt1, const xtime& xt2)
{
int res = (int)(xt1.sec - xt2.sec);
if (res == 0)
res = (int)(xt1.nsec - xt2.nsec);
return res;
}
} // namespace boost

View File

@@ -1,8 +0,0 @@
<html>
<head>
<meta http-equiv="refresh" content="0; URL=doc/index.html">
</head>
<body>
Automatic redirection failed, please go to <a href="doc/index.html">doc/index.html</a>
</body>
</html>

80
src/_atomic.cpp Normal file
View File

@@ -0,0 +1,80 @@
/*
*
* Copyright (C) 2001
* William E. Kempf
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. William E. Kempf makes no representations
* about the suitability of this software for any purpose.
* It is provided "as is" without express or implied warranty.
*
* Revision History (excluding minor changes for specific compilers)
* 8 Feb 01 Initial version.
*/
#include <boost/thread/atomic.hpp>
#if defined(BOOST_HAS_WINTHREADS)
# include <windows.h>
#endif
namespace boost {
atomic_t::value_type read(const atomic_t& x)
{
return x._value;
}
#if defined(BOOST_HAS_WINTHREADS)
atomic_t::value_type increment(atomic_t& x)
{
return InterlockedIncrement(const_cast<long*>(&x._value));
}
atomic_t::value_type decrement(atomic_t& x)
{
return InterlockedDecrement(const_cast<long*>(&x._value));
}
atomic_t::value_type swap(atomic_t& x, atomic_t::value_type y)
{
return InterlockedExchange(const_cast<long*>(&x._value), y);
}
atomic_t::value_type compare_swap(atomic_t& x, atomic_t::value_type y, atomic_t::value_type z)
{
return InterlockedCompareExchange(const_cast<long*>(&x._value), y, z);
}
#else
atomic_t::value_type increment(atomic_t& x)
{
mutex::lock lock(x._mutex);
return ++x._value;
}
atomic_t::value_type decrement(atomic_t& x)
{
mutex::lock lock(x._mutex);
return --x._value;
}
atomic_t::value_type swap(atomic_t& x, atomic_t::value_type y)
{
mutex::lock lock(x._mutex);
atomic_t::value_type temp = x._value;
x._value = y;
return temp;
}
atomic_t::value_type compare_swap(atomic_t& x, atomic_t::value_type y, atomic_t::value_type z)
{
mutex::lock lock(x._mutex);
atomic_t::value_type temp = x._value;
if (temp == z)
x._value = y;
return temp;
}
#endif
} // namespace boost

View File

@@ -1,45 +0,0 @@
// Copyright (C) 2002
// David Moore, William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/barrier.hpp>
namespace boost {
barrier::barrier(unsigned int count)
: m_threshold(count), m_count(count), m_generation(0)
{
if (count == 0)
throw std::invalid_argument("count cannot be zero.");
}
barrier::~barrier()
{
}
bool barrier::wait()
{
boost::mutex::scoped_lock lock(m_mutex);
unsigned int gen = m_generation;
if (--m_count == 0)
{
m_generation++;
m_count = m_threshold;
m_cond.notify_all();
return true;
}
while (gen == m_generation)
m_cond.wait(lock);
return false;
}
} // namespace boost

View File

@@ -6,28 +6,22 @@
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/condition.hpp>
#include <boost/thread/xtime.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/exceptions.hpp>
#include <boost/limits.hpp>
#include <cassert>
#include "timeconv.inl"
#if defined(BOOST_HAS_WINTHREADS)
# ifndef NOMINMAX
# define NOMINMAX
# endif
# define NOMINMAX
# include <windows.h>
#elif defined(BOOST_HAS_PTHREADS)
# include <errno.h>
#elif defined(BOOST_HAS_MPTASKS)
# include <MacErrors.h>
# include "mac/init.hpp"
# include "mac/safe.hpp"
#endif
namespace boost {
@@ -36,28 +30,28 @@ namespace boost {
condition::condition()
: m_gone(0), m_blocked(0), m_waiting(0)
{
m_gate = reinterpret_cast<void*>(CreateSemaphore(0, 1, 1, 0));
m_queue = reinterpret_cast<void*>(CreateSemaphore(0, 0, std::numeric_limits<long>::max(), 0));
m_mutex = reinterpret_cast<void*>(CreateMutex(0, 0, 0));
m_gate = reinterpret_cast<unsigned long>(CreateSemaphore(0, 1, 1, 0));
m_queue = reinterpret_cast<unsigned long>(CreateSemaphore(0, 0, std::numeric_limits<long>::max(), 0));
m_mutex = reinterpret_cast<unsigned long>(CreateMutex(0, 0, 0));
if (!m_gate || !m_queue || !m_mutex)
{
int res = 0;
if (m_gate)
{
res = CloseHandle(reinterpret_cast<HANDLE>(m_gate));
assert(res);
}
if (m_queue)
{
res = CloseHandle(reinterpret_cast<HANDLE>(m_queue));
assert(res);
}
if (m_mutex)
{
res = CloseHandle(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
}
if (m_gate)
{
res = CloseHandle(reinterpret_cast<HANDLE>(m_gate));
assert(res);
}
if (m_queue)
{
res = CloseHandle(reinterpret_cast<HANDLE>(m_queue));
assert(res);
}
if (m_mutex)
{
res = CloseHandle(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
}
throw thread_resource_error();
}
@@ -93,7 +87,6 @@ void condition::notify_one()
++m_waiting;
--m_blocked;
signals = 1;
}
else
{
@@ -114,15 +107,15 @@ void condition::notify_one()
res = ReleaseSemaphore(reinterpret_cast<HANDLE>(m_gate), 1, 0);
assert(res);
}
}
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (signals)
{
res = ReleaseSemaphore(reinterpret_cast<HANDLE>(m_queue), signals, 0);
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (signals)
{
res = ReleaseSemaphore(reinterpret_cast<HANDLE>(m_queue), signals, 0);
assert(res);
}
}
}
@@ -192,7 +185,7 @@ void condition::do_wait()
int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_queue), INFINITE);
assert(res == WAIT_OBJECT_0);
unsigned was_waiting=0;
unsigned was_gone=0;
@@ -244,29 +237,15 @@ void condition::do_wait()
bool condition::do_timed_wait(const xtime& xt)
{
bool ret = false;
unsigned int res = 0;
unsigned milliseconds;
to_duration(xt, milliseconds);
for (;;)
{
int milliseconds;
to_duration(xt, milliseconds);
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_queue), milliseconds);
assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
ret = (res == WAIT_OBJECT_0);
if (res == WAIT_TIMEOUT)
{
xtime cur;
xtime_get(&cur, TIME_UTC);
if (xtime_cmp(xt, cur) > 0)
continue;
}
break;
}
int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_queue), milliseconds);
assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
bool ret = (res == WAIT_OBJECT_0);
unsigned was_waiting=0;
unsigned was_gone=0;
@@ -372,285 +351,6 @@ bool condition::do_timed_wait(const xtime& xt, pthread_mutex_t* pmutex)
return res != ETIMEDOUT;
}
#elif defined(BOOST_HAS_MPTASKS)
using threads::mac::detail::safe_enter_critical_region;
using threads::mac::detail::safe_wait_on_semaphore;
condition::condition()
: m_gone(0), m_blocked(0), m_waiting(0)
{
threads::mac::detail::thread_init();
OSStatus lStatus = noErr;
lStatus = MPCreateSemaphore(1, 1, &m_gate);
if(lStatus == noErr)
lStatus = MPCreateSemaphore(ULONG_MAX, 0, &m_queue);
if(lStatus != noErr || !m_gate || !m_queue)
{
if (m_gate)
{
lStatus = MPDeleteSemaphore(m_gate);
assert(lStatus == noErr);
}
if (m_queue)
{
lStatus = MPDeleteSemaphore(m_queue);
assert(lStatus == noErr);
}
throw thread_resource_error();
}
}
condition::~condition()
{
OSStatus lStatus = noErr;
lStatus = MPDeleteSemaphore(m_gate);
assert(lStatus == noErr);
lStatus = MPDeleteSemaphore(m_queue);
assert(lStatus == noErr);
}
void condition::notify_one()
{
unsigned signals = 0;
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
assert(lStatus == noErr);
if (m_waiting != 0) // the m_gate is already closed
{
if (m_blocked == 0)
{
lStatus = MPExitCriticalRegion(m_mutex);
assert(lStatus == noErr);
return;
}
++m_waiting;
--m_blocked;
}
else
{
lStatus = safe_wait_on_semaphore(m_gate, kDurationForever);
assert(lStatus == noErr);
if (m_blocked > m_gone)
{
if (m_gone != 0)
{
m_blocked -= m_gone;
m_gone = 0;
}
signals = m_waiting = 1;
--m_blocked;
}
else
{
lStatus = MPSignalSemaphore(m_gate);
assert(lStatus == noErr);
}
lStatus = MPExitCriticalRegion(m_mutex);
assert(lStatus == noErr);
while (signals)
{
lStatus = MPSignalSemaphore(m_queue);
assert(lStatus == noErr);
--signals;
}
}
}
void condition::notify_all()
{
unsigned signals = 0;
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
assert(lStatus == noErr);
if (m_waiting != 0) // the m_gate is already closed
{
if (m_blocked == 0)
{
lStatus = MPExitCriticalRegion(m_mutex);
assert(lStatus == noErr);
return;
}
m_waiting += (signals = m_blocked);
m_blocked = 0;
}
else
{
lStatus = safe_wait_on_semaphore(m_gate, kDurationForever);
assert(lStatus == noErr);
if (m_blocked > m_gone)
{
if (m_gone != 0)
{
m_blocked -= m_gone;
m_gone = 0;
}
signals = m_waiting = m_blocked;
m_blocked = 0;
}
else
{
lStatus = MPSignalSemaphore(m_gate);
assert(lStatus == noErr);
}
lStatus = MPExitCriticalRegion(m_mutex);
assert(lStatus == noErr);
while (signals)
{
lStatus = MPSignalSemaphore(m_queue);
assert(lStatus == noErr);
--signals;
}
}
}
void condition::enter_wait()
{
OSStatus lStatus = noErr;
lStatus = safe_wait_on_semaphore(m_gate, kDurationForever);
assert(lStatus == noErr);
++m_blocked;
lStatus = MPSignalSemaphore(m_gate);
assert(lStatus == noErr);
}
void condition::do_wait()
{
OSStatus lStatus = noErr;
lStatus = safe_wait_on_semaphore(m_queue, kDurationForever);
assert(lStatus == noErr);
unsigned was_waiting=0;
unsigned was_gone=0;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
assert(lStatus == noErr);
was_waiting = m_waiting;
was_gone = m_gone;
if (was_waiting != 0)
{
if (--m_waiting == 0)
{
if (m_blocked != 0)
{
lStatus = MPSignalSemaphore(m_gate); // open m_gate
assert(lStatus == noErr);
was_waiting = 0;
}
else if (m_gone != 0)
m_gone = 0;
}
}
else if (++m_gone == (std::numeric_limits<unsigned>::max() / 2))
{
// timeout occured, normalize the m_gone count
// this may occur if many calls to wait with a timeout are made and
// no call to notify_* is made
lStatus = safe_wait_on_semaphore(m_gate, kDurationForever);
assert(lStatus == noErr);
m_blocked -= m_gone;
lStatus = MPSignalSemaphore(m_gate);
assert(lStatus == noErr);
m_gone = 0;
}
lStatus = MPExitCriticalRegion(m_mutex);
assert(lStatus == noErr);
if (was_waiting == 1)
{
for (/**/ ; was_gone; --was_gone)
{
// better now than spurious later
lStatus = safe_wait_on_semaphore(m_queue, kDurationForever);
assert(lStatus == noErr);
}
lStatus = MPSignalSemaphore(m_gate);
assert(lStatus == noErr);
}
}
bool condition::do_timed_wait(const xtime& xt)
{
int milliseconds;
to_duration(xt, milliseconds);
OSStatus lStatus = noErr;
lStatus = safe_wait_on_semaphore(m_queue, milliseconds);
assert(lStatus == noErr || lStatus == kMPTimeoutErr);
bool ret = (lStatus == noErr);
unsigned was_waiting=0;
unsigned was_gone=0;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
assert(lStatus == noErr);
was_waiting = m_waiting;
was_gone = m_gone;
if (was_waiting != 0)
{
if (!ret) // timeout
{
if (m_blocked != 0)
--m_blocked;
else
++m_gone; // count spurious wakeups
}
if (--m_waiting == 0)
{
if (m_blocked != 0)
{
lStatus = MPSignalSemaphore(m_gate); // open m_gate
assert(lStatus == noErr);
was_waiting = 0;
}
else if (m_gone != 0)
m_gone = 0;
}
}
else if (++m_gone == (std::numeric_limits<unsigned>::max() / 2))
{
// timeout occured, normalize the m_gone count
// this may occur if many calls to wait with a timeout are made and
// no call to notify_* is made
lStatus = safe_wait_on_semaphore(m_gate, kDurationForever);
assert(lStatus == noErr);
m_blocked -= m_gone;
lStatus = MPSignalSemaphore(m_gate);
assert(lStatus == noErr);
m_gone = 0;
}
lStatus = MPExitCriticalRegion(m_mutex);
assert(lStatus == noErr);
if (was_waiting == 1)
{
for (/**/ ; was_gone; --was_gone)
{
// better now than spurious later
lStatus = safe_wait_on_semaphore(m_queue, kDurationForever);
assert(lStatus == noErr);
}
lStatus = MPSignalSemaphore(m_gate);
assert(lStatus == noErr);
}
return ret;
}
#endif
} // namespace boost

View File

@@ -1,25 +0,0 @@
// Copyright (C) 2001
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. William E. Kempf makes no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/exceptions.hpp>
#include <string>
namespace boost {
lock_error::lock_error() : std::logic_error("thread lock error")
{
}
thread_resource_error::thread_resource_error() : std::runtime_error("thread resource error")
{
}
} // namespace boost

View File

@@ -1,14 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#define TARGET_CARBON 1

View File

@@ -1,72 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#include "delivery_man.hpp"
#include "os.hpp"
#include "execution_context.hpp"
namespace boost {
namespace threads {
namespace mac {
namespace detail {
delivery_man::delivery_man():
m_pPackage(NULL),
m_pSemaphore(kInvalidID),
m_bPackageWaiting(false)
{
assert(at_st());
OSStatus lStatus = MPCreateSemaphore(1UL, 0UL, &m_pSemaphore);
// TODO - throw on error here
assert(lStatus == noErr);
}
delivery_man::~delivery_man()
{
assert(m_bPackageWaiting == false);
OSStatus lStatus = MPDeleteSemaphore(m_pSemaphore);
assert(lStatus == noErr);
}
void delivery_man::accept_deliveries()
{
if(m_bPackageWaiting)
{
assert(m_pPackage != NULL);
m_pPackage->accept();
m_pPackage = NULL;
m_bPackageWaiting = false;
// signal to the thread making the call that we're done
OSStatus lStatus = MPSignalSemaphore(m_pSemaphore);
assert(lStatus == noErr);
}
}
} // namespace detail
} // namespace mac
} // namespace threads
} // namespace boost

View File

@@ -1,90 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#ifndef BOOST_DELIVERY_MAN_MJM012402_HPP
#define BOOST_DELIVERY_MAN_MJM012402_HPP
#include <boost/function.hpp>
#include <boost/utility.hpp>
#include <boost/thread/mutex.hpp>
#include "package.hpp"
#include <Multiprocessing.h>
namespace boost {
namespace threads {
namespace mac {
namespace detail {
// class delivery_man is intended to move boost::function objects from MP tasks to
// other execution contexts (such as deferred task time or system task time).
class delivery_man: private noncopyable
{
public:
delivery_man();
~delivery_man();
public:
template<class R>
R deliver(function<R> &rFunctor);
void accept_deliveries();
private:
base_package *m_pPackage;
mutex m_oMutex;
MPSemaphoreID m_pSemaphore;
bool m_bPackageWaiting;
};
template<class R>
R delivery_man::deliver(function<R> &rFunctor)
{
assert(at_mp());
// lock our mutex
mutex::scoped_lock oLock(m_oMutex);
// create a package and save it
package<R> oPackage(rFunctor);
m_pPackage = &oPackage;
m_bPackageWaiting = true;
// wait on the semaphore
OSStatus lStatus = MPWaitOnSemaphore(m_pSemaphore, kDurationForever);
assert(lStatus == noErr);
return(oPackage.return_value());
}
} // namespace detail
} // namespace mac
} // namespace threads
} // namespace boost
#endif // BOOST_DELIVERY_MAN_MJM012402_HPP

View File

@@ -1,99 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#include "dt_scheduler.hpp"
#include "ot_context.hpp"
#include <boost/thread/detail/singleton.hpp>
#include <OpenTransportProtocol.h>
namespace boost {
namespace threads {
namespace mac {
namespace detail {
const OTTimeout k_ulTimerTaskDelay = 1UL;
dt_scheduler::dt_scheduler():
m_bReschedule(false),
m_uppTask(NULL),
m_lTask(0UL)
{
using ::boost::detail::thread::singleton;
ot_context &rContext(singleton<ot_context>::instance());
m_uppTask = NewOTProcessUPP(task_entry);
m_lTask = OTCreateTimerTaskInContext(m_uppTask, this, rContext.get_context());
}
dt_scheduler::~dt_scheduler()
{
OTDestroyTimerTask(m_lTask);
m_lTask = 0UL;
DisposeOTProcessUPP(m_uppTask);
m_uppTask = NULL;
}
void dt_scheduler::start_polling()
{
m_bReschedule = true;
schedule_task();
}
void dt_scheduler::stop_polling()
{
m_bReschedule = false;
}
void dt_scheduler::schedule_task()
{
if(m_bReschedule)
{
OTScheduleTimerTask(m_lTask, k_ulTimerTaskDelay);
}
}
/*static*/ pascal void dt_scheduler::task_entry(void *pRefCon)
{
dt_scheduler *pThis = reinterpret_cast<dt_scheduler *>(pRefCon);
assert(pThis != NULL);
pThis->task();
}
void dt_scheduler::task()
{
periodic_function();
schedule_task();
}
} // namespace detail
} // namespace mac
} // namespace threads
} // namespace boost

View File

@@ -1,69 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#ifndef BOOST_DT_SCHEDULER_MJM012402_HPP
#define BOOST_DT_SCHEDULER_MJM012402_HPP
#include "periodical.hpp"
#include <OpenTransport.h>
namespace boost {
namespace threads {
namespace mac {
namespace detail {
// class dt_scheduler calls its pure-virtual periodic_function method periodically at
// deferred task time. This is generally 1kHz under Mac OS 9.
class dt_scheduler
{
public:
dt_scheduler();
virtual ~dt_scheduler();
protected:
void start_polling();
void stop_polling();
private:
virtual void periodic_function() = 0;
private:
void schedule_task();
static pascal void task_entry(void *pRefCon);
void task();
private:
bool m_bReschedule;
OTProcessUPP m_uppTask;
long m_lTask;
};
} // namespace detail
} // namespace mac
} // namespace threads
} // namespace boost
#endif // BOOST_DT_SCHEDULER_MJM012402_HPP

View File

@@ -1,66 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#include <Debugging.h>
#include <Multiprocessing.h>
#include "execution_context.hpp"
#include "init.hpp"
namespace boost {
namespace threads {
namespace mac {
execution_context_t execution_context()
{
// make sure that MP services are available the first time through
static bool bIgnored = detail::thread_init();
// first check if we're an MP task
if(MPTaskIsPreemptive(kInvalidID))
{
return(k_eExecutionContextMPTask);
}
#if TARGET_CARBON
// Carbon has TaskLevel
UInt32 ulLevel = TaskLevel();
if(ulLevel == 0UL)
{
return(k_eExecutionContextSystemTask);
}
if(ulLevel & kInDeferredTaskMask)
{
return(k_eExecutionContextDeferredTask);
}
return(k_eExecutionContextOther);
#else
// this can be implemented using TaskLevel if you don't mind linking against
// DebugLib (and therefore breaking Mac OS 8.6 support), or CurrentExecutionLevel.
# error execution_context unimplimented
#endif
}
} // namespace mac
} // namespace threads
} // namespace boost

View File

@@ -1,53 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#ifndef BOOST_EXECUTION_CONTEXT_MJM012402_HPP
#define BOOST_EXECUTION_CONTEXT_MJM012402_HPP
namespace boost {
namespace threads {
namespace mac {
// utility functions for figuring out what context your code is executing in.
// Bear in mind that at_mp and in_blue are the only functions guarenteed by
// Apple to work. There is simply no way of being sure that you will not get
// false readings about task level at interrupt time in blue.
typedef enum {
k_eExecutionContextSystemTask,
k_eExecutionContextDeferredTask,
k_eExecutionContextMPTask,
k_eExecutionContextOther
} execution_context_t;
execution_context_t execution_context();
inline bool at_st()
{ return(execution_context() == k_eExecutionContextSystemTask); }
inline bool at_mp()
{ return(execution_context() == k_eExecutionContextMPTask); }
inline bool in_blue()
{ return(!at_mp()); }
} // namespace mac
} // namespace threads
} // namespace boost
#endif // BOOST_EXECUTION_CONTEXT_MJM012402_HPP

View File

@@ -1,64 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#include "init.hpp"
#include "remote_call_manager.hpp"
#include <boost/thread/detail/singleton.hpp>
#include <Multiprocessing.h>
namespace boost {
namespace threads {
namespace mac {
namespace detail {
namespace {
// force these to get called by the end of static initialization time.
static bool g_bInitialized = (thread_init() && create_singletons());
}
bool thread_init()
{
static bool bResult = MPLibraryIsLoaded();
return(bResult);
}
bool create_singletons()
{
using ::boost::detail::thread::singleton;
singleton<remote_call_manager>::instance();
return(true);
}
} // namespace detail
} // namespace mac
} // namespace threads
} // namespace boost

View File

@@ -1,40 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#ifndef BOOST_INIT_MJM012402_HPP
#define BOOST_INIT_MJM012402_HPP
namespace boost {
namespace threads {
namespace mac {
namespace detail {
bool thread_init();
bool create_singletons();
} // namespace detail
} // namespace mac
} // namespace threads
} // namespace boost
#endif // BOOST_INIT_MJM012402_HPP

View File

@@ -1,30 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
#include <cassert>
#include <cstdio>
#include <MacTypes.h>
#include "remote_calls.hpp"
// this function will be called when an assertion fails. We redirect the assertion
// to DebugStr (MacsBug under Mac OS 1.x-9.x, Console under Mac OS X).
void __assertion_failed(char const *pszAssertion, char const *pszFile, int nLine)
{
using std::snprintf;
unsigned char strlDebug[sizeof(Str255) + 1];
char *pszDebug = reinterpret_cast<char *>(&strlDebug[1]);
strlDebug[0] = snprintf(pszDebug, sizeof(Str255), "assertion failed: \"%s\", %s, line %d", pszAssertion, pszFile, nLine);
boost::threads::mac::dt_remote_call(DebugStr, static_cast<ConstStringPtr>(strlDebug));
}

View File

@@ -1,134 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
//
// includes
//
#include <abort_exit.h>
#include <console.h>
#include <console_io.h>
#include <misc_io.h>
#include <SIOUX.h>
#include "remote_calls.hpp"
//
// using declarations
//
using std::__file_handle;
using std::__idle_proc;
using std::__io_error;
using std::__no_io_error;
using std::size_t;
using boost::threads::mac::st_remote_call;
//
// prototypes
//
static bool check_console();
static int do_read_console(__file_handle ulHandle, unsigned char *pBuffer, size_t *pCount, __idle_proc pfnIdleProc);
static int do_write_console(__file_handle ulHandle, unsigned char *pBuffer, size_t *pCount, __idle_proc pfnIdleProc);
//
// MSL function replacements
//
// these two functions are called by cin and cout, respectively, as well as by (all?)
// other functions in MSL that do console I/O. All that they do is as the remote
// call manager to ensure that their guts are called at system task time.
int __read_console(__file_handle handle, unsigned char * buffer, size_t * count, __idle_proc idle_proc)
{
return(st_remote_call(do_read_console, handle, buffer, count, idle_proc));
}
int __write_console(__file_handle handle, unsigned char * buffer, size_t * count, __idle_proc idle_proc)
{
return(st_remote_call(do_write_console, handle, buffer, count, idle_proc));
}
//
// implementations
//
static bool check_console()
{
static bool s_bHaveConsole(false);
static bool s_bWontHaveConsole(false);
if(s_bHaveConsole)
{
return(true);
}
if(s_bWontHaveConsole == false)
{
__stdio_atexit();
if(InstallConsole(0) != 0)
{
s_bWontHaveConsole = true;
return(false);
}
__console_exit = RemoveConsole;
s_bHaveConsole = true;
return(true);
}
return(false);
}
int do_read_console(__file_handle /*ulHandle*/, unsigned char *pBuffer, size_t *pCount, __idle_proc /*pfnIdleProc*/)
{
assert(pCount != NULL);
assert(pBuffer != NULL || *pCount == 0UL);
if(check_console() == false)
{
return(__io_error);
}
std::fflush(stdout);
long lCount = ReadCharsFromConsole(reinterpret_cast<char *>(pBuffer), static_cast<long>(*pCount));
*pCount = static_cast<size_t>(lCount);
if(lCount == -1L)
{
return(__io_error);
}
return(__no_io_error);
}
int do_write_console(__file_handle /*ulHandle*/, unsigned char *pBuffer, size_t *pCount, __idle_proc /*pfnIdleProc*/)
{
if(check_console() == false)
{
return(__io_error);
}
long lCount = WriteCharsToConsole(reinterpret_cast<char *>(pBuffer), static_cast<long>(*pCount));
*pCount = static_cast<size_t>(lCount);
if(lCount == -1L)
{
return(__io_error);
}
return(__no_io_error);
}

View File

@@ -1,58 +0,0 @@
// Copyright (C) 2001
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. Mac Murrett makes no representations
// about the suitability of this software for any purpose. It is
// provided "as is" without express or implied warranty.
//
// See http://www.boost.org for most recent version including documentation.
//
// includes
//
#include <cstdlib>
#include <Multiprocessing.h>
//
// using declarations
//
using std::size_t;
extern "C" {
//
// prototypes
//
void *malloc(size_t ulSize);
void free(void *pBlock);
}
//
// MSL function replacements
//
// all allocation/deallocation currently goes through MPAllocateAligned/MPFree. This
// solution is sub-optimal at best, but will have to do for now.
void *malloc(size_t ulSize)
{
static bool bIgnored = MPLibraryIsLoaded();
return(MPAllocateAligned(ulSize, kMPAllocateDefaultAligned, 0UL));
}
void free(void *pBlock)
{
if(pBlock == NULL) return;
MPFree(pBlock);
}

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