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110 Commits

Author SHA1 Message Date
Michael Glassford
9f9292e2e3 Fix compile errors: some compilers don't like an enum and the namespace it is in to have the same name; missing typename; _sntprintf not in namespace std for cw. Fix warnings on some compilers. Clean up scheduling algorithms to pass unit tests and hopefully eliminate reported deadlocks. Still needs work, but should be better than before.
[SVN r23859]
2004-07-20 21:33:13 +00:00
Michael Glassford
0a88a53a33 Fix compile errors: some compilers don't like an enum and the namespace it is in to have the same name.
[SVN r23858]
2004-07-20 21:29:39 +00:00
Michael Glassford
0bce1befd9 Remove line-continuation inside #if (cwpro8 seemed not to like it).
[SVN r23857]
2004-07-20 21:24:00 +00:00
Michael Glassford
9f354c98ab Renamed add_thread_exit() to at_thread_exit(), a better name.
[SVN r23856]
2004-07-20 21:22:55 +00:00
Michael Glassford
274b04bcf7 Add hooks for users to provide their own tss cleanup in win32 statically linked builds.
[SVN r23586]
2004-07-15 15:19:08 +00:00
Michael Glassford
539d19468d Add try_lock() method to scoped_timed_lock.
[SVN r23585]
2004-07-15 14:30:42 +00:00
Michael Glassford
fff6d9eddd Changes for WinCE.
[SVN r23584]
2004-07-15 14:27:50 +00:00
Michael Glassford
5472ebdfde Add hooks for users to provide their own tss cleanup in win32 statically linked builds.
[SVN r23583]
2004-07-15 14:26:10 +00:00
Michael Glassford
50c034f650 Fix enum definition.
[SVN r23582]
2004-07-15 14:23:19 +00:00
Michael Glassford
2a5e1a36b5 Add read_lock and write_lock and related classes; modify lock constructors; add promote() that throws exception if it fails; fix enum definition.
[SVN r23581]
2004-07-15 14:21:37 +00:00
Michael Glassford
2e10da00ba Add cancellation guard.
[SVN r23417]
2004-07-09 09:52:39 +00:00
Michael Glassford
af4b2d5d2a Changes for WinCE.
[SVN r23416]
2004-07-09 09:50:44 +00:00
Michael Glassford
a89ec945c0 Apply patch for SGI MIPSpro compiler.
[SVN r23406]
2004-07-08 14:42:04 +00:00
Michael Glassford
08eb9eed48 Add title.
[SVN r23405]
2004-07-08 13:52:15 +00:00
Michael Glassford
7ed1a79ab8 Apply min/max fixes from main branch.
[SVN r23196]
2004-06-25 20:45:38 +00:00
Michael Glassford
18974b3cb4 Remove rw* files that have been renamed to read_write_*
[SVN r23195]
2004-06-25 20:41:54 +00:00
Michael Glassford
c973faf627 Fix enums, constructors; TimedReadWriteLock concept refines TryReadWriteLock; cleanup: always #include <boost/thread/detail/config.hpp> first; eliminate tabs; etc.
[SVN r23194]
2004-06-25 20:40:34 +00:00
Michael Glassford
6ffcde749a Remove HTML files that have been converted to BoostBook format.
[SVN r23193]
2004-06-25 20:40:21 +00:00
Michael Glassford
42840199aa Update release notes.
[SVN r23192]
2004-06-25 20:33:13 +00:00
Michael Glassford
1addb6ad9b Cleanup: always #include <boost/thread/detail/config.hpp> first; eliminate tabs; etc.
[SVN r23188]
2004-06-25 20:04:34 +00:00
Michael Glassford
1dbdb77ed7 Add option to build as static library.
[SVN r23187]
2004-06-25 19:52:44 +00:00
Michael Glassford
430ebf66f9 Apply min/max fixes from main branch.
[SVN r23186]
2004-06-25 19:49:44 +00:00
Michael Glassford
97562928a8 Cleanup: always #include <boost/thread/detail/config.hpp> first; eliminate tabs; etc.
[SVN r23185]
2004-06-25 19:36:47 +00:00
Michael Glassford
45aabefb4d Cleanup: always #include <boost/thread/detail/config.hpp> first.
[SVN r23184]
2004-06-25 19:22:18 +00:00
Michael Glassford
b0e970863b Proofreeding changes.
[SVN r23183]
2004-06-25 19:19:17 +00:00
Michael Glassford
3468fb61bc Convert documentation to BoostBook format.
[SVN r23182]
2004-06-25 19:17:49 +00:00
Michael Glassford
5982a97bdf Renamed from rw_* to read_write*.
[SVN r23161]
2004-06-22 22:17:17 +00:00
Michael Glassford
ffef009696 Renamed from test_rw_mutex.cpp.
[SVN r23160]
2004-06-22 22:16:47 +00:00
Michael Glassford
c8f181e461 Renamed from rw_mutex.cpp.
[SVN r23159]
2004-06-22 22:14:45 +00:00
Michael Glassford
7b84d69915 Renamed from rw_mutex-ref.xml.
[SVN r23158]
2004-06-22 22:06:21 +00:00
Michael Glassford
bbb8efe58f Renamed from rw_lock.hpp.
[SVN r23157]
2004-06-22 21:59:09 +00:00
Michael Glassford
63209e3c69 Renamed from rw_mutex.hpp.
[SVN r23156]
2004-06-22 21:57:38 +00:00
Michael Glassford
2272c322f9 Proofreeding changes.
[SVN r23155]
2004-06-22 21:37:24 +00:00
Michael Glassford
36acb80412 Add read/write mutex and related concepts.
[SVN r23154]
2004-06-22 21:36:32 +00:00
Michael Glassford
b72142cef7 Add entry for "undefined behavior".
[SVN r23153]
2004-06-22 21:35:11 +00:00
Michael Glassford
6dd6f51faa Remove documentation for unreleased thread pool.
[SVN r23152]
2004-06-22 21:33:55 +00:00
Michael Glassford
82630dc9bb Fix inconsistencies found while working on documentation.
[SVN r23151]
2004-06-22 21:28:53 +00:00
Michael Glassford
3402aea7c1 Change enumeration from anonymous to xtime_clock_types and remove unused clock types.
[SVN r23150]
2004-06-22 21:25:58 +00:00
Michael Glassford
5c4bd8e9c9 Finish conversion of documentation to BoostBook format.
[SVN r23122]
2004-06-18 21:30:19 +00:00
Michael Glassford
a11748d187 Finish conversion of documentation to BoostBook format.
[SVN r23048]
2004-06-07 21:45:26 +00:00
Michael Glassford
dc906613dc Finish conversion of documentation to BoostBook format.
[SVN r23047]
2004-06-07 19:04:02 +00:00
Michael Glassford
b69bdd3918 Finish conversion of documentation to BoostBook format.
[SVN r23046]
2004-06-07 16:01:05 +00:00
Michael Glassford
d90ef5eeef Finish conversion of documentation to BoostBook format.
[SVN r23045]
2004-06-07 14:42:24 +00:00
Michael Glassford
641d658a10 Finish conversion of documentation to BoostBook format.
[SVN r23044]
2004-06-07 14:30:36 +00:00
Michael Glassford
fef99d3db2 Finish conversion of documentation to BoostBook format.
[SVN r23021]
2004-06-03 16:36:57 +00:00
Michael Glassford
0fc8d8897d Finish conversion of documentation to BoostBook format.
[SVN r23011]
2004-06-02 19:38:15 +00:00
Michael Glassford
ad9f6244b0 Finish conversion of documentation to BoostBook format.
[SVN r23010]
2004-06-02 19:29:37 +00:00
Michael Glassford
59d082202c Finish conversion of documentation to BoostBook format.
[SVN r23009]
2004-06-02 19:24:03 +00:00
Michael Glassford
b7549a5bae Finish conversion of documentation to BoostBook format.
[SVN r23008]
2004-06-02 19:12:58 +00:00
Michael Glassford
f0dce755bb Finish conversion of documentation to BoostBook format.
[SVN r22957]
2004-05-27 19:43:24 +00:00
Michael Glassford
c1261d6df3 Proofreeding changes.
[SVN r22956]
2004-05-27 19:42:22 +00:00
Michael Glassford
1fb0dac16d Proofreeding changes.
[SVN r22955]
2004-05-27 19:34:39 +00:00
Michael Glassford
424d02fafa Proofreeding changes.
[SVN r22954]
2004-05-27 19:21:12 +00:00
Michael Glassford
52717aaa75 Finish conversion of documentation to BoostBook format.
[SVN r22953]
2004-05-27 15:49:50 +00:00
Michael Glassford
335f85ad5b Allow a mutex to be named, which allows it to be shared between two or more processes; currently implemented only for Win32.
Win32: use critical section instead of mutex whenever possible; abstract common code into functions.


[SVN r22827]
2004-05-15 02:02:43 +00:00
Michael Glassford
7da456edca Restore unintentionallly deleted BOOST_THREAD_DECL.
[SVN r22742]
2004-05-05 02:27:45 +00:00
Michael Glassford
f50176946d * Add lock promotion and demotion.
* Rename to improve consistency and eliminate abbreviations:
* Change try lock & timed lock constructor parameters for consistency.
* Add many assertions to test validity of mutex state and operations.
See change log in file for more details.


[SVN r22741]
2004-05-05 02:17:29 +00:00
Michael Glassford
aeafcbb822 Added MPTasks implementation; added comments to change log.
[SVN r22545]
2004-03-23 17:55:16 +00:00
Michael Glassford
171b890972 Added change log, fixed errors in comments, removed "unused parameter" warning.
[SVN r22544]
2004-03-23 17:47:29 +00:00
Michael Glassford
89a9531d34 Add missing pthread_mutexattr_destroy() to recursive_mutex::recursive_mutex() and recursive_try_mutex::recursive_try_mutex().
[SVN r22527]
2004-03-19 21:24:50 +00:00
Michael Glassford
3259f681a4 Merge fixes from main branch.
[SVN r22321]
2004-02-19 01:10:56 +00:00
Michael Glassford
17f72cf580 Merge minor changes from main branch.
[SVN r22320]
2004-02-19 01:10:07 +00:00
Michael Glassford
e03f0ed008 Merge minor changes from main branch.
[SVN r22319]
2004-02-19 01:00:42 +00:00
Michael Glassford
0804944002 Merge auto link changes from main branch.
[SVN r22318]
2004-02-19 00:57:36 +00:00
Michael Glassford
8e5d5002cd Merge fixes from main branch into thread_dev branch.
[SVN r22306]
2004-02-18 00:45:51 +00:00
Michael Glassford
008aaeaeee Merge fixes from HEAD into thread_dev branch.
[SVN r22238]
2004-02-11 16:02:52 +00:00
William E. Kempf
c1283bb731 Fixed thread join bugs. Fixed mutex creation bugs.
[SVN r18176]
2003-04-03 22:56:50 +00:00
William E. Kempf
46b1a4d1e3 Documented conditions with BoostBook
[SVN r18159]
2003-04-02 21:37:26 +00:00
William E. Kempf
ff6e0df2bc Removed <a> link.
[SVN r18150]
2003-04-01 15:41:51 +00:00
William E. Kempf
9cb9224b3c More BoostBook changes.
[SVN r18149]
2003-04-01 15:29:55 +00:00
William E. Kempf
5ea5494172 Added catalog.xml to .cvsignore.
[SVN r18145]
2003-04-01 01:46:42 +00:00
William E. Kempf
e4c27981d0 Added .cvsignore in doc directory.
[SVN r18144]
2003-04-01 01:45:24 +00:00
William E. Kempf
fe61772d47 Further conversions to DocBook.
[SVN r18143]
2003-04-01 01:44:32 +00:00
William E. Kempf
a437d6d7f6 Started migrating to Boost.Book.
[SVN r18117]
2003-03-27 23:24:44 +00:00
William E. Kempf
c9f52098b9 More changes for named mutexes.
[SVN r18063]
2003-03-22 22:28:57 +00:00
William E. Kempf
a15a35a4b6 Factored out named object support and made mutex a named object.
[SVN r17981]
2003-03-18 23:30:51 +00:00
William E. Kempf
14c8137ba6 Fixed name encoding algorithm.
[SVN r17929]
2003-03-14 22:56:29 +00:00
William E. Kempf
5caf9ed169 Further changes for name mapping in shared_memory.
[SVN r17896]
2003-03-13 18:43:55 +00:00
William E. Kempf
5da4a7b105 Added portable name mapping.
[SVN r17868]
2003-03-12 23:47:36 +00:00
William E. Kempf
91c4af37ad Fixed POSIX issues for shared_memory.
[SVN r17817]
2003-03-11 16:08:51 +00:00
William E. Kempf
5848dc2f56 More shared_memory changes.
[SVN r17816]
2003-03-11 15:47:22 +00:00
William E. Kempf
efa12b1db9 More shared_memory changes.
[SVN r17802]
2003-03-10 23:10:13 +00:00
William E. Kempf
58b6eba0ea Updated shared_memory to compile on Linux.
[SVN r17801]
2003-03-10 20:55:29 +00:00
William E. Kempf
f73253fcf5 Udpated shared_memory.
[SVN r17800]
2003-03-10 20:14:12 +00:00
William E. Kempf
3627dfc3b7 Removed warnings.
[SVN r17606]
2003-02-23 18:09:27 +00:00
William E. Kempf
f8ebb9a127 Added timed_join() and cancelled()
[SVN r17309]
2003-02-10 17:08:04 +00:00
William E. Kempf
2a0f57a8de Reformatted code and updated copyrights
[SVN r17274]
2003-02-07 22:50:55 +00:00
William E. Kempf
da7278acef Removed obsolete files.
[SVN r17273]
2003-02-07 22:22:35 +00:00
William E. Kempf
b17eb23f2e Updated thread_group to use the new thread reference implementation
[SVN r17135]
2003-01-31 21:23:11 +00:00
William E. Kempf
8e01ac5d04 Updated Jamfile
[SVN r17133]
2003-01-31 20:00:27 +00:00
William E. Kempf
5d6a1633e0 merged with thread_bae
[SVN r17100]
2003-01-30 23:05:44 +00:00
William E. Kempf
2e6f9a785e Updated Jamfile
[SVN r17098]
2003-01-30 21:20:28 +00:00
William E. Kempf
4e1acef27e Merged thread_base
[SVN r17096]
2003-01-30 20:51:12 +00:00
William E. Kempf
73e482832d Added bjam.log to .cvsignore
[SVN r17092]
2003-01-30 16:44:15 +00:00
William E. Kempf
949b332337 Removed warning messages
[SVN r17091]
2003-01-30 16:42:39 +00:00
nobody
244cfd3f01 This commit was manufactured by cvs2svn to create branch 'thread_dev'.
[SVN r17055]
2003-01-27 22:44:08 +00:00
William E. Kempf
3239fe0c22 Updated test cases for thread::attributes.
[SVN r17001]
2003-01-22 23:08:26 +00:00
William E. Kempf
ca10110aa7 Updated tests for new thread design
[SVN r16984]
2003-01-21 22:57:30 +00:00
William E. Kempf
fd4c76c7a5 Add cancellation_guard and test cases.
[SVN r16964]
2003-01-20 20:20:21 +00:00
William E. Kempf
60d7c84aa2 Fixed creation bug.
[SVN r16925]
2003-01-17 23:17:54 +00:00
William E. Kempf
c043efa346 Updated exceptions and removed conditional compilation.
[SVN r16897]
2003-01-13 23:05:14 +00:00
William E. Kempf
dab1961b5a Fixed bug in internal id() when pthread_t isn't a pointer type.
[SVN r16844]
2003-01-09 22:51:24 +00:00
William E. Kempf
6f94d26c50 Added full support for 'id' semantics.
[SVN r16842]
2003-01-09 21:17:39 +00:00
William E. Kempf
83baf142f2 Added thread::attributes.
[SVN r16808]
2003-01-08 22:25:15 +00:00
William E. Kempf
88bb39e3ce Fixed bug with cleanup_slots definition order on POSIX implementations.
[SVN r16807]
2003-01-08 22:22:54 +00:00
William E. Kempf
48ad27558a Updated new classes to DLL implementation. Worked out tss issues. Started thread implementation.
[SVN r16791]
2003-01-07 23:16:54 +00:00
William E. Kempf
a0ba7f174c Updated new classes to DLL implementation. Worked out tss issues. Started thread implementation.
[SVN r16789]
2003-01-07 23:08:51 +00:00
William E. Kempf
6e60d33181 Merged thread_development with thread_dev
[SVN r16776]
2003-01-06 23:24:59 +00:00
William E. Kempf
bc69926604 Merged thread_development with thread_dev
[SVN r16775]
2003-01-06 22:47:51 +00:00
nobody
d90825f7f9 This commit was manufactured by cvs2svn to create branch 'thread_dev'.
[SVN r16771]
2003-01-06 16:06:38 +00:00
127 changed files with 14455 additions and 5346 deletions

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@@ -1,2 +1,3 @@
bin*
*.pdb
*.pdb
bjam.log

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@@ -1,18 +1,16 @@
# (C) Copyright William E. Kempf 2001. Permission to copy, use, modify,
# sell and 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.
# Copyright (C) 2001-2003
# 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.
#
# Boost.Threads build 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
@@ -29,46 +27,106 @@ 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 ;
import ./threads ;
template thread_libs
## sources ##
: <template>thread_base
## requirements ##
:
## default build ##
: debug release <runtime-link>static/dynamic
;
{
CPP_SOURCES =
barrier
condition
exceptions
mutex
named
once
recursive_mutex
read_write_mutex
shared_memory
thread
threadmon
thread_pool
tss
xtime
;
#######################
# Declare the Boost.Threads static link library libboost_thread.
# Base names of the source files for libboost_thread.
CPP_SOURCES = condition mutex recursive_mutex thread tss xtime once
exceptions threadmon ;
#if $(NT) && ! $(PTW32)
#{
dll boost_thread
: <template>thread_libs ../src/$(CPP_SOURCES).cpp
: <define>BOOST_THREAD_BUILD_DLL=1
template boost_thread_lib_base
: ## sources ##
<template>thread_base
../src/$(CPP_SOURCES).cpp
: ## requirements ##
<define>BOOST_THREAD_BUILD_LIB=1
<runtime-link>static
# the common names rule ensures that the library will
# be named according to the rules used by the install
# and auto-link features:
common-variant-tag
: ## default build ##
;
#}
#else
#{
# lib boost_thread
# : <template>thread_libs ../src/$(CPP_SOURCES).cpp
# ;
#}
#######################
# Stage the generated targets.
template thread_dll_base
: ## sources ##
<template>thread_base
../src/$(CPP_SOURCES).cpp
: ## requirements ##
<define>BOOST_THREAD_BUILD_DLL=1
<runtime-link>dynamic
# the common names rule ensures that the library will
# be named according to the rules used by the install
# and auto-link features:
common-variant-tag
: ## default build ##
;
#stage bin-stage
# : <lib>boost_thread $(threadmon)
# : <tag><runtime-link-static>"s"
# <tag><debug>"d"
# : debug release <runtime-link>static/dynamic
#;
lib $(boost_thread_lib_name)
: ## sources ##
<template>boost_thread_lib_base
: ## requirements ##
<define>BOOST_THREAD_LIB_NAME=$(boost_thread_lib_name)
: ## default build ##
;
dll $(boost_thread_lib_name)
: ## sources ##
<template>thread_dll_base
: ## requirements ##
<define>BOOST_THREAD_LIB_NAME=$(boost_thread_lib_name)
: ## default build ##
;
stage bin-stage
: <dll>$(boost_thread_lib_name)
<lib>$(boost_thread_lib_name)
;
install thread lib
: <dll>$(boost_thread_lib_name)
<lib>$(boost_thread_lib_name)
;
if $(boost_thread_lib_settings_ptw32)
{
lib $(boost_thread_lib_name_ptw32)
: ## sources ##
<template>boost_thread_lib_base
: ## requirements ##
<define>BOOST_THREAD_LIB_NAME=$(boost_thread_lib_name_ptw32)
$(pthreads-win32)
;
dll $(boost_thread_lib_name_ptw32)
: ## sources ##
<template>thread_dll_base
: ## requirements ##
<define>BOOST_THREAD_LIB_NAME=$(boost_thread_lib_name_ptw32)
$(pthreads-win32)
;
stage bin-stage
: <dll>$(boost_thread_lib_name_ptw32)
<lib>$(boost_thread_lib_name_ptw32)
;
install thread lib
: <dll>$(boost_thread_lib_name_ptw32)
<lib>$(boost_thread_lib_name_ptw32)
;
}
}

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@@ -1,7 +1,10 @@
# Declare the uses system library
lib pthread : : <name>pthread ;
project boost/thread
: source-location ../src
: use-requirements <find-library>pthread
: usage-requirements <library>pthread
;
CPP_SOURCES = condition mutex recursive_mutex thread tss xtime once exceptions ;

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@@ -1,28 +1,45 @@
# Copyright (C) 2001-2003
# 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.
# Do some OS-specific setup
threadmon = ;
pthreads-win32 = ;
if $(NT)
{
if $(PTW32)
#thread library name
boost_thread_lib_name = boost_thread ;
#thread library name with "pthreads-win32" library
boost_thread_lib_name_ptw32 = boost_thread_ptw32 ;
if $(NT)
{
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)
;
if $(PTW32_DIR)
{
if $(PTW32_LIB)
{
boost_thread_lib_settings_ptw32 =
<define>BOOST_HAS_PTHREADS
<define>PtW32NoCatchWarn
<include>$(PTW32_DIR)/pre-built/include
<library-file>$(PTW32_DIR)/pre-built/lib/$(PTW32_LIB)
;
}
}
}
}
template thread_base
## sources ##
:
## requirements ##
: <sysinclude>$(BOOST_ROOT) <threading>multi $(pthreads-win32)
## default build ##
:
;
template thread_base
: ## sources ##
: ## requirements ##
<sysinclude>$(BOOST_ROOT)
<threading>multi
<borland><*><cxxflags>-w-8004
<borland><*><cxxflags>-w-8057
: ## default build ##
;
}

3
doc/.cvsignore Normal file
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bin
html
catalog.xml

5
doc/Jamfile.v2 Normal file
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project boost/doc ;
import boostbook : boostbook ;
boostbook doc : thread.xml ;

64
doc/acknowledgements.xml Normal file
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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="thread.acknowledgements"
last-revision="$Date$">
<title>Acknowledgements</title>
<para>William E. Kempf was the architect, designer, and implementor of
&Boost.Threads;.</para>
<para>Mac OS Carbon implementation written by Mac Murrett.</para>
<para>Dave Moore provided initial submissions and further comments on the
<code>barrier</code>
,
<code>thread_pool</code>
,
<code>read_write_mutex</code>
,
<code>read_write_try_mutex</code>
and
<code>read_write_timed_mutex</code>
classes.</para>
<para>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).</para>
<para>Mike Glassford finished changes to &Boost.Threads; that were begun
by William Kempf and moved them into the main CVS branch.
He also addressed a number of issues that were brought up on the Boost
developer's mailing list and provided some additions and changes to the
read_write_mutex and related classes.</para>
<para>The documentation was written by William E. Kempf. Beman Dawes
provided additional documentation material and editing.
Mike Glassford finished William Kempf's conversion of the documentation to
BoostBook format and added a number of new sections.</para>
<para>Discussions on the boost.org mailing list were essential in the
development of &Boost.Threads;
. 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, 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.</para>
<para>Apologies for anyone inadvertently missed.</para>
</section>

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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>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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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/barrier.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="barrier">
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<purpose>
<para>An object of class <classname>barrier</classname> 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.</para>
</purpose>
<description>
<para>When a barrier is created, it is initialized with a thread count N.
The first N-1 calls to <code>wait()</code> will all cause their threads to be blocked.
The Nth call to <code>wait()</code> will allow all of the waiting threads, including
the Nth thread, to be placed in a ready state. The Nth call will also "reset"
the barrier such that, if an additional N+1th call is made to <code>wait()</code>,
it will be as though this were the first call to <code>wait()</code>; in other
words, the N+1th to 2N-1th calls to <code>wait()</code> will cause their
threads to be blocked, and the 2Nth call to <code>wait()</code> will allow all of
the waiting threads, including the 2Nth thread, to be placed in a ready state
and reset the barrier. 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.</para>
<para>See <xref linkend="threads.glossary"/> for definitions of thread
states <link linkend="threads.glossary.thread-state">blocked</link>
and <link linkend="threads.glossary.thread-state">ready</link>.
Note that "waiting" is a synonym for blocked.</para>
</description>
<constructor>
<parameter name="count">
<paramtype>size_t</paramtype>
</parameter>
<effects><simpara>Constructs a <classname>barrier</classname> object that
will cause <code>count</code> threads to block on a call to <code>wait()</code>.
</simpara></effects>
</constructor>
<destructor>
<effects><simpara>Destroys <code>*this</code>. If threads are still executing
their <code>wait()</code> operations, the behavior for these threads is undefined.
</simpara></effects>
</destructor>
<method-group name="waiting">
<method name="wait">
<type>bool</type>
<effects><simpara>Wait until N threads call <code>wait()</code>, where
N equals the <code>count</code> provided to the constructor for the
barrier object.</simpara>
<simpara><emphasis role="bold">Note</emphasis> that if the barrier is
destroyed before <code>wait()</code> can return, the behavior is
undefined.</simpara></effects>
<returns>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.</returns>
</method>
</method-group>
</class>
</namespace>
</header>

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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 - Bibliography</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">Bibliography</h2>
</td>
</tr>
</table>
<hr>
<table summary="Bibliography" 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="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>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Hoare-74">Hoare 74</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>
</td>
</tr>
<tr>
<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> <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.</p>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Schmidt">Schmidt</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>
</td>
</tr>
<tr>
<td width="102" valign="top" align="left"><b>[<a name=
"Schmidt-00">Schmidt 00</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>
</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>
</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>
<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> 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>
</body>
</html>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<bibliography id="threads.bibliography"
last-revision="$Date$">
<title>Bibliography</title>
<biblioentry id="threads.bib.AndrewsSchneider83">
<abbrev id="threads.bib.AndrewsSchneider83.abbrev">AndrewsSchnieder83</abbrev>
<biblioset relation="journal">
<title>ACM Computing Surveys</title>
<volumenum>Vol. 15</volumenum>
<issuenum>No. 1</issuenum>
<date>March, 1983</date>
</biblioset>
<biblioset relation="article">
<authorgroup>
<author>
<firstname>Gregory</firstname>
<othername>R.</othername>
<surname>Andrews</surname>
</author>
<author>
<firstname>Fred</firstname>
<othername>B.</othername>
<surname>Schneider</surname>
</author>
</authorgroup>
<title>
<ulink
url="http://www.acm.org/pubs/citations/journals/surveys/1983-15-1/p3-andrews/"
>Concepts and Notations for Concurrent Programming</ulink>
</title>
</biblioset>
<para>Good general background reading. Includes descriptions of Path
Expressions, Message Passing, and Remote Procedure Call in addition to the
basics</para>
</biblioentry>
<biblioentry id="threads.bib.Boost">
<abbrev id="threads.bib.Boost.abbrev">Boost</abbrev>
<bibliomisc>The <emphasis>Boost</emphasis> world wide web site.
<ulink url="http:/www.boost.org">http://www.boost.org</ulink></bibliomisc>
<para>&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.</para>
</biblioentry>
<biblioentry id="threads.bib.Hansen73">
<abbrev id="threads.bib.Hansen73.abbrev">Hansen73</abbrev>
<biblioset relation="journal">
<title>ACM Computing Surveys</title>
<volumenum>Vol. 5</volumenum>
<issuenum>No. 4</issuenum>
<date>December, 1983</date>
</biblioset>
<biblioset relation="article">
<author>0-201-63392-2
<firstname>Per Brinch</firstname>
<lastname>Hansen</lastname>
</author>
<title>
<ulink
url="http://www.acm.org/pubs/articles/journals/surveys/1973-5-4/p223-hansen/"
>Concurrent Programming Concepts</ulink>
</title>
</biblioset>
<para>"This paper describes the evolution of language features for
multiprogramming from event queues and semaphores to critical regions and
monitors." Includes analysis of why events 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.</para>
</biblioentry>
<biblioentry id="threads.bib.Butenhof97">
<abbrev id="threads.bib.Butenhof97.abbrev">Butenhof97</abbrev>
<title>
<ulink url="http://cseng.aw.com/book/0,3828,0201633922,00.html"
>Programming with POSIX Threads </ulink>
</title>
<author>
<firstname>David</firstname>
<othername>R.</othername>
<surname>Butenhof</surname>
</author>
<publisher>Addison-Wesley</publisher>
<copyright><year>1997</year></copyright>
<isbn>ISNB: 0-201-63392-2</isbn>
<para>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</para>
</biblioentry>
<biblioentry id="threads.bib.Hoare74">
<abbrev id="threads.bib.Hoare74.abbrev">Hoare74</abbrev>
<biblioset relation="journal">
<title>Communications of the ACM</title>
<volumenum>Vol. 17</volumenum>
<issuenum>No. 10</issuenum>
<date>October, 1974</date>
</biblioset>
<biblioset relation="article">
<title>
<ulink url=" http://www.acm.org/classics/feb96/"
>Monitors: An Operating System Structuring Concept</ulink>
</title>
<author>
<firstname>C.A.R.</firstname>
<surname>Hoare</surname>
</author>
<pagenums>549-557</pagenums>
</biblioset>
<para>Hoare and Brinch Hansen'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.</para>
</biblioentry>
<biblioentry id="threads.bib.ISO98">
<abbrev id="threads.bib.ISO98.abbrev">ISO98</abbrev>
<title>
<ulink url="http://www.ansi.org">Programming Language C++</ulink>
</title>
<orgname>ISO/IEC</orgname>
<releaseinfo>14882:1998(E)</releaseinfo>
<para>This is the official C++ Standards document. Available from the ANSI
(American National Standards Institute) Electronic Standards Store.</para>
</biblioentry>
<biblioentry id="threads.bib.McDowellHelmbold89">
<abbrev id="threads.bib.McDowellHelmbold89.abbrev">McDowellHelmbold89</abbrev>
<biblioset relation="journal">
<title>Communications of the ACM</title>
<volumenum>Vol. 21</volumenum>
<issuenum>No. 2</issuenum>
<date>December, 1989</date>
</biblioset>
<biblioset>
<author>
<firstname>Charles</firstname>
<othername>E.</othername>
<surname>McDowell</surname>
</author>
<author>
<firstname>David</firstname>
<othername>P.</othername>
<surname>Helmbold</surname>
</author>
<title>
<ulink
url="http://www.acm.org/pubs/citations/journals/surveys/1989-21-4/p593-mcdowell/"
>Debugging Concurrent Programs</ulink>
</title>
</biblioset>
<para>Identifies many of the unique failure modes and debugging difficulties
associated with concurrent programs.</para>
</biblioentry>
<biblioentry id="threads.bib.SchmidtPyarali">
<abbrev id="threads.bib.SchmidtPyarali.abbrev">SchmidtPyarali</abbrev>
<title>
<ulink url="http://www.cs.wustl.edu/~schmidt/win32-cv-1.html8"
>Strategies for Implementing POSIX Condition Variables on Win32</ulink>
</title>
<authorgroup>
<author>
<firstname>Douglas</firstname>
<othername>C.</othername>
<surname>Schmidt</surname>
</author>
<author>
<firstname>Irfan</firstname>
<surname>Pyarali</surname>
</author>
</authorgroup>
<orgname>Department of Computer Science, Washington University, St. Louis,
Missouri</orgname>
<para>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.</para>
</biblioentry>
<biblioentry id="threads.bib.SchmidtStalRohnertBuschmann">
<abbrev
id="threads.bib.SchmidtStalRohnertBuschmann.abbrev">SchmidtStalRohnertBuschmann</abbrev>
<title>
<ulink
url="http://www.wiley.com/Corporate/Website/Objects/Products/0,9049,104671,00.html"
>Pattern-Oriented Architecture Volume 2</ulink>
</title>
<subtitle>Patterns for Concurrent and Networked Objects</subtitle>
<titleabbrev>POSA2</titleabbrev>
<authorgroup>
<author>
<firstname>Douglas</firstname>
<othername>C.</othername>
<surname>Schmidt</surname>
</author>
<author>
<firstname>Michael</firstname>
<lastname>Stal</lastname>
</author>
<author>
<firstname>Hans</firstname>
<surname>Rohnert</surname>
</author>
<author>
<firstname>Frank</firstname>
<surname>Buschmann</surname>
</author>
</authorgroup>
<publisher>Wiley</publisher>
<copyright><year>2000</year></copyright>
<para>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 &Boost.Threads;
documentation.</para>
</biblioentry>
<biblioentry id="threads.bib.Stroustrup">
<abbrev id="threads.bib.Stroustrup.abbrev">Stroustrup</abbrev>
<title>
<ulink url="http://cseng.aw.com/book/0,3828,0201700735,00.html"
>The C++ Programming Language</ulink>
</title>
<edition>Special Edition</edition>
<publisher>Addison-Wesley</publisher>
<copyright><year>2000</year></copyright>
<isbn>ISBN: 0-201-70073-5</isbn>
<para>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.</para>
</biblioentry>
</bibliography>

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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>
</body>
</html>

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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="thread.build" last-revision="$Date$">
<title>Build</title>
<para>
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 &Boost.Build;.
In general you should refer to the documentation for &Boost.Build;.
This document will only supply you with some simple usage examples for how to
use <emphasis>bjam</emphasis> to build and test &Boost.Threads;. In addition, this document
will try to 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;.
</para>
<section id="thread.build.building">
<title>Building the &Boost.Threads; Libraries</title>
<para>
To build the &Boost.Threads; libraries using &Boost.Build;, simply change to the
directory <emphasis>boost_root</emphasis>/libs/thread/build and execute the command:
<programlisting>bjam -sTOOLS=<emphasis>toolset</emphasis></programlisting>
This will create the debug and the release builds of the &Boost.Threads; library.
<note>Invoking the above command in <emphasis>boost_root</emphasis> will build all of
the Boost distribution, including &Boost.Threads;.</note>
</para>
<para>
The Jamfile supplied with &Boost.Threads; produces a dynamic link library named
<emphasis>boost_thread{build-specific-tags}.{extension}</emphasis>, where the build-specific
tags indicate the toolset used to build the library, whether it's a debug or release
build, what version of Boost was used, etc.; and the extension is the appropriate extension
for a dynamic link library for the platform for which &Boost.Threads; is being built.
For instance, a debug library built for Win32 with VC++ 7.1 using Boost 1.31 would
be named <emphasis>boost_thread-vc71-mt-gd-1_31.dll</emphasis>.
</para>
<para>
The source files that are used to create the &Boost.Threads; library
are all of the *.cpp files found in <emphasis>boost_root</emphasis>/libs/thread/src.
These need 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.
</para>
</section>
<section id="thread.build.testing">
<title>Testing the &Boost.Threads; Libraries</title>
<para>
To test the &Boost.Threads; libraries using &Boost.Build;, simply change to the
directory <emphasis>boost_root</emphasis>/libs/thread/test and execute the command:
<programlisting>bjam -sTOOLS=<emphasis>toolset</emphasis> test</programlisting>
</para>
</section>
</section>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/condition.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="condition">
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<purpose>
<para>An object of class <classname>condition</classname> is a
synchronization primitive used to cause a thread to wait until a
particular shared-data condition (or time) is met.</para>
</purpose>
<description>
<para>A <classname>condition</classname> object is always used in
conjunction with a <link linkend="threads.concepts.mutexes">mutex</link>
object (an object whose type is a model of a <link
linkend="threads.concepts.Mutex">Mutex</link> or one of its
refinements). The mutex object must be locked prior to waiting on the
condition, which is verified by passing a lock object (an object whose
type is a model of <link linkend="threads.concepts.Lock">Lock</link> or
one of its refinements) to the <classname>condition</classname> object's
wait functions. Upon blocking on the <classname>condition</classname>
object, the thread unlocks the mutex object. When the thread returns
from a call to one of the <classname>condition</classname> object's wait
functions the mutex object is again locked. The tricky unlock/lock
sequence is performed automatically by the
<classname>condition</classname> object's wait functions.</para>
<para>The <classname>condition</classname> type is often used to
implement the Monitor Object and other important patterns (see
&cite.SchmidtStalRohnertBuschmann; and &cite.Hoare74;). Monitors are one
of the most important patterns for creating reliable multithreaded
programs.</para>
<para>See <xref linkend="threads.glossary"/> for definitions of <link
linkend="threads.glossary.thread-state">thread states</link>
blocked and ready. Note that "waiting" is a synonym for blocked.</para>
</description>
<constructor>
<effects><simpara>Constructs a <classname>condition</classname>
object.</simpara></effects>
</constructor>
<destructor>
<effects><simpara>Destroys <code>*this</code>.</simpara></effects>
</destructor>
<method-group name="notification">
<method name="notify_one">
<type>void</type>
<effects><simpara>If there is a thread waiting on <code>*this</code>,
change that thread's state to ready. Otherwise there is no
effect.</simpara></effects>
<notes><simpara>If more than one thread is waiting on <code>*this</code>,
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 <classname>condition</classname>
object's wait functions.)</simpara></notes>
</method>
<method name="notify_all">
<type>void</type>
<effects><simpara>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.</simpara></effects>
</method>
</method-group>
<method-group name="waiting">
<method name="wait">
<template>
<template-type-parameter name="ScopedLock"/>
</template>
<type>void</type>
<parameter name="lock">
<paramtype>ScopedLock&amp;</paramtype>
</parameter>
<requires><simpara><code>ScopedLock</code> meets the <link
linkend="threads.concepts.ScopedLock">ScopedLock</link>
requirements.</simpara></requires>
<effects><simpara>Releases the lock on the <link
linkend="threads.concepts.mutexes">mutex object</link>
associated with <code>lock</code>, blocks the current thread of execution
until readied by a call to <code>this->notify_one()</code>
or<code> this->notify_all()</code>, and then reacquires the
lock.</simpara></effects>
<throws><simpara><classname>lock_error</classname> if
<code>!lock.locked()</code></simpara></throws>
</method>
<method name="wait">
<template>
<template-type-parameter name="ScopedLock"/>
<template-type-parameter name="Pred"/>
</template>
<type>void</type>
<parameter name="lock">
<paramtype>ScopedLock&amp;</paramtype>
</parameter>
<parameter name="pred">
<paramtype>Pred</paramtype>
</parameter>
<requires><simpara><code>ScopedLock</code> meets the <link
linkend="threads.concepts.ScopedLock">ScopedLock</link>
requirements and the return from <code>pred()</code> is
convertible to <code>bool</code>.</simpara></requires>
<effects><simpara>As if: <code>while (!pred())
wait(lock)</code></simpara></effects>
<throws><simpara><classname>lock_error</classname> if
<code>!lock.locked()</code></simpara></throws>
</method>
<method name="timed_wait">
<template>
<template-type-parameter name="ScopedLock"/>
</template>
<type>bool</type>
<parameter name="lock">
<paramtype>ScopedLock&amp;</paramtype>
</parameter>
<parameter name="xt">
<paramtype>const <classname>boost::xtime</classname>&amp;</paramtype>
</parameter>
<requires><simpara><code>ScopedLock</code> meets the <link
linkend="threads.concepts.ScopedLock">ScopedLock</link>
requirements.</simpara></requires>
<effects><simpara>Releases the lock on the <link
linkend="threads.concepts.mutexes">mutex object</link>
associated with <code>lock</code>, blocks the current thread of execution
until readied by a call to <code>this->notify_one()</code>
or<code> this->notify_all()</code>, or until time <code>xt</code>
is reached, and then reacquires the lock.</simpara></effects>
<returns><simpara><code>false</code> if time <code>xt</code> is reached,
otherwise <code>true</code>.</simpara></returns>
<throws><simpara><classname>lock_error</classname> if
<code>!lock.locked()</code></simpara></throws>
</method>
<method name="timed_wait">
<template>
<template-type-parameter name="ScopedLock"/>
<template-type-parameter name="Pred"/>
</template>
<type>bool</type>
<parameter name="lock">
<paramtype>ScopedLock&amp;</paramtype>
</parameter>
<parameter name="pred">
<paramtype>Pred</paramtype>
</parameter>
<requires><simpara><code>ScopedLock</code> meets the <link
linkend="threads.concepts.ScopedLock">ScopedLock</link>
requirements and the return from <code>pred()</code> is
convertible to <code>bool</code>.</simpara></requires>
<effects><simpara>As if: <code>while (!pred()) { if (!timed_wait(lock,
xt)) return false; } return true;</code></simpara></effects>
<returns><simpara><code>false</code> if <code>xt</code> is reached,
otherwise <code>true</code>.</simpara></returns>
<throws><simpara><classname>lock_error</classname> if
<code>!lock.locked()</code></simpara></throws>
</method>
</method-group>
</class>
</namespace>
</header>

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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/condition.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/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);
};
};
</pre>
<h4><a name="class-condition-ctors"></a>Class <code>condition</code> constructors
and destructor</h4>
<pre>
condition();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs a <code>condition</code> object.</dt>
</dl>
<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>
<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>
<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>
<pre>
template &lt;typename ScopedLock&gt;
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>
<pre>
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>
<pre>
template &lt;typename ScopedLock&gt;
bool timed_wait(ScopedLock&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>
<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);
</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())
{
if (!timed_wait(lock, XT))
return false;
}
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
received: 0
received: 1
sent: 2
sent: 3
received: 2
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" -->
</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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<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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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="thread.configuration" last-revision="$Date$">
<title>Configuration</title>
<para>&Boost.Threads; uses several configuration macros in &lt;boost/config.hpp&gt;,
as well as configuration macros meant to be supplied by the application. These
macros are documented here.
</para>
<section id="thread.configuration.public">
<title>Library Defined Public Macros</title>
<para>
These macros are defined by &Boost.Threads; but are expected to be used
by application code.
</para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>Macro</entry>
<entry>Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry>BOOST_HAS_THREADS</entry>
<entry>
Indicates that threading support is available. This means both that there
is a platform specific implementation for &Boost.Threads; and that
threading support has been enabled in a platform specific manner. For instance,
on the Win32 platform there&#39;s an implementation for &Boost.Threads;
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.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</section>
<section id="thread.configuration.implementation">
<title>Library Defined Implementation Macros</title>
<para>
These macros are defined by &Boost.Threads; and are implementation details
of interest only to implementors.
</para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>Macro</entry>
<entry>Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry>BOOST_HAS_WINTHREADS</entry>
<entry>
Indicates that the platform has the Microsoft Win32 threading libraries,
and that they should be used to implement &Boost.Threads;.
</entry>
</row>
<row>
<entry>BOOST_HAS_PTHREADS</entry>
<entry>
Indicates that the platform has the POSIX pthreads libraries, and that
they should be used to implement &Boost.Threads;.
</entry>
</row>
<row>
<entry>BOOST_HAS_FTIME</entry>
<entry>
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().
</entry>
</row>
<row>
<entry>BOOST_HAS_GETTTIMEOFDAY</entry>
<entry>
Indicates that the implementation should use gettimeofday() to calculate
the current time. This is an implementation detail used by boost::detail::getcurtime().
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</section>
</section>

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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 - Definitions</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">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>
<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>
</ul>
<ul>
<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>
</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>
</ul>
<p>Each thread has its own:</p>
<ul>
<li>Registers and current execution sequence (program counter) [1.9/5].</li>
</ul>
<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>
<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">
<tr>
<td><b>State</b></td>
<td><b>Description</b></td>
</tr>
<tr>
<td>Ready</td>
<td>Ready to run, but waiting for a processor.</td>
</tr>
<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>
</tr>
<tr>
<td>Blocked</td>
<td>Waiting for some resource other than a processor which is not currently
available, or for the completion of calls to library functions [1.9/6].
The term &quot;waiting&quot; is synonymous for &quot;blocked&quot;</td>
</tr>
<tr>
<td>Terminated</td>
<td>Finished execution but not yet detached or joined.</td>
</tr>
</table>
<p>Thread state transitions shall occur only as specified:</p>
<table summary="state transitions" border="1" cellpadding="5">
<tr>
<td><b>From</b></td>
<td><b>To</b></td>
<td><b>Cause</b></td>
</tr>
<tr>
<td>
<p align="left">[none]</p>
</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>
</tr>
<tr>
<td>Ready</td>
<td>Running</td>
<td>Processor becomes available.</td>
</tr>
<tr>
<td>Running</td>
<td>Ready</td>
<td>Thread preempted.</td>
</tr>
<tr>
<td>Running</td>
<td>Blocked</td>
<td>Thread calls a library function which waits for a resource or for the
completion of I/O.</td>
</tr>
<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>
</tr>
<tr>
<td>Blocked</td>
<td>Ready</td>
<td>The resource being waited for becomes available, or the blocking library
function completes.</td>
</tr>
<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>
</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>
<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>
<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">
<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>
</tr>
<tr>
<td>The sequence point at a call to a library function which locks a mutex,
directly or by waiting for a condition variable.</td>
<td>The sequence point after a call to a library function which unlocks the
same mutex.</td>
</tr>
<tr>
<td>The last sequence point before thread termination.</td>
<td>The sequence point after a call to a library function which joins the
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>
</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>
<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>
<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>
<p>This document was originally written by Beman Dawes, and then much improved by the incorporation of comments from
William Kempf, who now maintains the contents.</p>
<p>The visibility rules are based on <a href=
"bibliography.html#Butenhof-97">[Butenhof 97]</a>.</p>
<hr>
<p>Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->06 October, 2002<!--webbot bot="Timestamp" endspan i-checksum="38429" -->
</p>
<p><i>&copy; Copyright <a href="mailto:wekempf@cox.net">William E. Kempf</a> 2001-2002.
All Rights Reserved.<br>
</i>© Copyright Beman Dawes, 2001</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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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="threads.design" last-revision="$Date$">
<title>Design</title>
<para>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 concepts unique to C++, such as
exceptions.</para>
<para>The &Boost.Threads; library is an attempt to define a portable interface
for writing parallel processes in C++.</para>
<section id="threads.design.goals">
<title>Goals</title>
<para>The &Boost.Threads; 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.
<variablelist>
<varlistentry>
<term>Portability</term>
<listitem>
<para>&Boost.Threads; 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.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Safety</term>
<listitem>
<para>&Boost.Threads; was designed to be as safe as possible. Writing
<link linkend="threads.glossary.thread-safe">thread-safe</link>
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:
<itemizedlist>
<listitem>
<para>C++ language features are used to make correct usage easy
(if possible) and error-prone usage impossible or at least more
difficult. For example, see the <link
linkend="threads.concepts.Mutex">Mutex</link> and <link
linkend="threads.concepts.Lock">Lock</link> designs, and note
how they interact.</para>
</listitem>
<listitem>
<para>Certain traditional concurrent programming features are
considered so error-prone that they are not provided at all. For
example, see <xref linkend="threads.rationale.events" />.</para>
</listitem>
<listitem>
<para>Dangerous features, or features which may be misused, are
identified as such in the documentation to make users aware of
potential pitfalls.</para>
</listitem>
</itemizedlist></para>
</listitem>
</varlistentry>
<varlistentry>
<term>Flexibility</term>
<listitem>
<para>&Boost.Threads; was designed to be flexible. This goal is often
at odds with <emphasis>safety</emphasis>. When functionality might be
compromised by the desire to keep the interface safe, &Boost.Threads;
has been designed to provide the functionality, but to make it'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.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Efficiency</term>
<listitem>
<para>&Boost.Threads; 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. &Boost.Threads; 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 <emphasis>safety</emphasis>. Every
effort was made to ensure efficient implementations, but when in
conflict <emphasis>safety</emphasis> has always taken
precedence.</para>
</listitem>
</varlistentry>
</variablelist></para>
</section>
<section>
<title>Iterative Phases</title>
<para>Another goal of &Boost.Threads; 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 it is very difficult to use them safely or to provide formal
proofs for constructs built on top of them. There has been a lot of research
into other concepts, such as in "Communicating Sequential Processes."
&Boost.Threads; was designed in iterative steps, with each step providing
the building blocks necessary for the next step and giving the researcher
the tools necessary to explore new concepts in a portable manner.</para>
<para>Given the goal of following a dynamic, iterative approach
&Boost.Threads; shall go through several growth cycles. Each phase in its
development shall be roughly documented here.</para>
</section>
<section>
<title>Phase 1, Synchronization Primitives</title>
<para>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 therefore not
much help to a programmer who wants to use the library in his multithreaded
application. So there's a very great need for portable primitives that will
allow the library developer to create <link
linkend="threads.glossary.thread-safe">thread-safe</link>
implementations. This need far out weighs the need for portable methods to
create and manage threads.</para>
<para>Because of this need, the first phase of &Boost.Threads; focuses
solely on providing portable primitive concepts for thread
synchronization. Types provided in this phase include the
<classname>boost::mutex</classname>,
<classname>boost::try_mutex</classname>,
<classname>boost::timed_mutex</classname>,
<classname>boost::recursive_mutex</classname>,
<classname>boost::recursive_try_mutex</classname>,
<classname>boost::recursive_timed_mutex</classname>, and
<classname>boost::lock_error</classname>. These are considered the "core"
synchronization primitives, though there are others that will be added in
later phases.</para>
</section>
<section id="threads.design.phase2">
<title>Phase 2, Thread Management and Thread Specific Storage</title>
<para>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 &Boost.Threads; adds the <classname>boost::thread</classname> and
<classname>boost::thread_specific_ptr</classname> types. With these
additions the &Boost.Threads; library can be considered minimal but
complete.</para>
</section>
<section>
<title>The Next Phase</title>
<para>The next phase will address more advanced synchronization concepts,
such as read/write mutexes and barriers.</para>
</section>
</section>

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<!ENTITY Boost.Threads "<emphasis role='bold'>Boost.Threads</emphasis>">
<!ENTITY Boost.Build "<emphasis role='bold'>Boost.Build</emphasis>">
<!ENTITY cite.AndrewsSchneider83 "<citation><xref
linkend='threads.bib.AndrewsSchneider83'
endterm='threads.bib.AndrewsSchneider83.abbrev'/></citation>">
<!ENTITY cite.Boost "<citation><xref linkend='threads.bib.Boost'
endterm='threads.bib.Boost.abbrev'/></citation>">
<!ENTITY cite.Hansen73 "<citation><xref linkend='threads.bib.Hansen73'
endterm='threads.bib.Hansen73.abbrev'/></citation>">
<!ENTITY cite.Butenhof97 "<citation><xref linkend='threads.bib.Butenhof97'
endterm='threads.bib.Butenhof97.abbrev'/></citation>">
<!ENTITY cite.Hoare74 "<citation><xref linkend='threads.bib.Hoare74'
endterm='threads.bib.Hoare74.abbrev'/></citation>">
<!ENTITY cite.ISO98 "<citation><xref linkend='threads.bib.ISO98'
endterm='threads.bib.ISO98.abbrev'/></citation>">
<!ENTITY cite.McDowellHelmbold89 "<citation><xref
linkend='threads.bib.McDowellHelmbold89'
endterm='threads.bib.McDowellHelmbold89.abbrev'/></citation>">
<!ENTITY cite.SchmidtPyarali "<citation><xref
linkend='threads.bib.SchmidtPyarali'
endterm='threads.bib.SchmidtPyarali.abbrev'/></citation>">
<!ENTITY cite.SchmidtStalRohnertBuschmann "<citation><xref
linkend='threads.bib.SchmidtStalRohnertBuschmann'
endterm='threads.bib.SchmidtStalRohnertBuschmann.abbrev'/></citation>">
<!ENTITY cite.Stroustrup "<citation><xref linkend='threads.bib.Stroustrup'
endterm='threads.bib.Stroustrup.abbrev'/></citation>">

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/exceptions.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="lock_error">
<purpose>
<simpara>The lock_error class defines an exception type thrown
to indicate a locking related error has been detected.</simpara>
</purpose>
<description>
<simpara>Examples of errors indicated by a lock_error exception
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.</simpara>
</description>
<inherit access="public">
<type><classname>std::logical_error</classname></type>
</inherit>
<constructor>
<effects><simpara>Constructs a <code>lock_error</code> object.
</simpara></effects>
</constructor>
</class>
<class name="thread_resource_error">
<purpose>
<simpara>The <classname>thread_resource_error</classname> class
defines an exception type that is thrown by constructors in the
&Boost.Threads; library when thread-related resources can not be
acquired.</simpara>
</purpose>
<description>
<simpara><classname>thread_resource_error</classname> is used
only when thread-related resources cannot be acquired; memory
allocation failures are indicated by
<classname>std::bad_alloc</classname>.</simpara>
</description>
<inherit access="public">
<type><classname>std::runtime_error</classname></type>
</inherit>
<constructor>
<effects><simpara>Constructs a <code>thread_resource_error</code>
object.</simpara></effects>
</constructor>
</class>
</namespace>
</header>

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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">
<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/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>

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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 - FAQ</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">Frequently Asked Questions (FAQs)</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>
<pre>
class counter
{
public:
// Doesn't need synchronization since there can be no references to *this
// until after it's constructed!
explicit counter(int initial_value)
: m_value(initial_value)
{
}
// We only need to synchronize 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);
return m_value;
}
int increment()
{
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>
<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>
<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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doc/faq.xml Normal file
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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="threads.faq" last-revision="$Date$">
<title>Frequently Asked Questions</title>
<qandaset>
<qandaentry>
<question>
<para>Are lock objects <link
linkend="threads.glossary.thread-safe">thread safe</link>?</para>
</question>
<answer>
<para><emphasis role="bold">No!</emphasis> 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 anyway.
Share <link linkend="threads.concepts.mutexes">Mutexes</link>, not
Locks. For more information see the <link
linkend="threads.rationale.locks">rationale</link> behind the
design for lock objects.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why was &Boost.Threads; modeled after (specific library
name)?</para>
</question>
<answer>
<para>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 the Win32
threading API. But the &Boost.Threads; design is very much in the spirit
of C++, and thus doesn't model such C based APIs.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why wasn't &Boost.Threads; modeled after (specific library
name)?</para>
</question>
<answer>
<para>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, the WIN32 thread API lacks condition
variables, even though these are critical for the important Monitor
pattern &cite.SchmidtStalRohnertBuschmann;.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why do <link linkend="threads.concepts.mutexes">Mutexes</link>
have noncopyable semantics?</para>
</question>
<answer>
<para>To ensure that <link
linkend="threads.glossary.deadlock">deadlocks</link> 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).</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>How can you prevent <link
linkend="threads.glossary.deadlock">deadlock</link> from occurring when
a thread must lock multiple mutexes?</para>
</question>
<answer>
<para>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.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Don't noncopyable <link
linkend="threads.concepts.mutexes">Mutex</link> semantics mean that a
class with a mutex member will be noncopyable as well?</para>
</question>
<answer>
<para>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 <emphasis role="bold">good thing</emphasis>,
however, since the compiler generated operations would not be <link
linkend="threads.glossary.thread-safe">thread-safe</link>. The following
is a simple example of a class with copyable semantics and internal
synchronization through a mutex member.</para>
<programlisting>
class counter
{
public:
// Doesn't need synchronization since there can be no references to *this
// until after it's constructed!
explicit counter(int initial_value)
: m_value(initial_value)
{
}
// We only need to synchronize 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);
return m_value;
}
int increment()
{
boost::mutex::scoped_lock scoped_lock(m_mutex);
return ++m_value;
}
private:
mutable boost::mutex m_mutex;
int m_value;
};
</programlisting>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>How can you lock a <link
linkend="threads.concepts.mutexes">Mutex</link> member in a const member
function, in order to implement the Monitor Pattern?</para>
</question>
<answer>
<para>The Monitor Pattern &cite.SchmidtStalRohnertBuschmann; mutex
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.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why supply <classname>boost::condition</classname> variables rather than
event variables?</para>
</question>
<answer>
<para>Condition variables result in user code much less prone to <link
linkend="threads.glossary.race-condition">race conditions</link> than
event variables. See <xref linkend="threads.rationale.events" />
for analysis. Also see &cite.Hoare74; and &cite.SchmidtStalRohnertBuschmann;.
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why isn't thread cancellation or termination provided?</para>
</question>
<answer>
<para>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.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Is it safe for threads to share automatic storage duration (stack)
objects via pointers or references?</para>
</question>
<answer>
<para>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).</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Why has class semaphore disappeared?</para>
</question>
<answer>
<para>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.</para>
</answer>
</qandaentry>
</qandaset>
</section>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<glossary id="threads.glossary" last-revision="$Date$">
<title>Glossary</title>
<para>Definitions are given in terms of the C++ Standard
&cite.ISO98;. References to the standard are in the form [1.2.3/4], which
represents the section number, with the paragraph number following the
"/".</para>
<para>Because the definitions are written in something akin to "standardese",
they can be difficult to understand. 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.</para>
<glossentry id="threads.glossary.thread">
<glossterm>Thread</glossterm>
<glossdef>
<para>Thread is short for "thread of execution". 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.</para>
<para>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:</para>
<itemizedlist>
<listitem><para>Static storage duration (static, extern) objects
[3.7.1].</para></listitem>
<listitem><para>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.</para></listitem>
<listitem><para>Automatic storage duration (stack) objects [3.7.2]
accessed via pointer or reference from another thread.</para></listitem>
<listitem><para>Resources provided by the operating system. For example,
files.</para></listitem>
<listitem><para>The program itself. In other words, each thread is
executing some function of the same program, not a totally different
program.</para></listitem>
</itemizedlist>
<para>Each thread has its own:</para>
<itemizedlist>
<listitem><para>Registers and current execution sequence (program
counter) [1.9/5].</para></listitem>
<listitem><para>Automatic storage duration (stack) objects
[3.7.2].</para></listitem>
</itemizedlist>
</glossdef>
</glossentry>
<glossentry id="threads.glossary.thread-safe">
<glossterm>Thread-safe</glossterm>
<glossdef>
<para>A program is thread-safe if it has no <link
linkend="threads.glossary.race-condition">race conditions</link>, does
not <link linkend="threads.glossary.deadlock">deadlock</link>, and has
no <link linkend="threads.glossary.priority-failure">priority
failures</link>.</para>
<para>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.</para>
</glossdef>
</glossentry>
<glossentry id="threads.glossary.thread-state">
<glossterm>Thread State</glossterm>
<glossdef>
<para>During the lifetime of a thread, it shall be in one of the following
states:</para>
<table>
<title>Thread States</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>State</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>Ready</entry>
<entry>Ready to run, but waiting for a processor.</entry>
</row>
<row>
<entry>Running</entry>
<entry>Currently executing on a processor. Zero or more threads
may be running at any time, with a maximum equal to the number of
processors.</entry>
</row>
<row>
<entry>Blocked</entry>
<entry>Waiting for some resource other than a processor which is
not currently available, or for the completion of calls to library
functions [1.9/6]. The term "waiting" is synonymous with
"blocked"</entry>
</row>
<row>
<entry>Terminated</entry>
<entry>Finished execution but not yet detached or joined.</entry>
</row>
</tbody>
</tgroup>
</table>
<para>Thread state transitions shall occur only as specified:</para>
<table>
<title>Thread States Transitions</title>
<tgroup cols="3" align="left">
<thead>
<row>
<entry>From</entry>
<entry>To</entry>
<entry>Cause</entry>
</row>
</thead>
<tbody>
<row>
<entry>[none]</entry>
<entry>Ready</entry>
<entry><para>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].</para></entry>
</row>
<row>
<entry>Ready</entry>
<entry>Running</entry>
<entry><para>Processor becomes available.</para></entry>
</row>
<row>
<entry>Running</entry>
<entry>Ready</entry>
<entry>Thread preempted.</entry>
</row>
<row>
<entry>Running</entry>
<entry>Blocked</entry>
<entry>Thread calls a library function which waits for a resource or
for the completion of I/O.</entry>
</row>
<row>
<entry>Running</entry>
<entry>Terminated</entry>
<entry>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.</entry>
</row>
<row>
<entry>Blocked</entry>
<entry>Ready</entry>
<entry>The resource being waited for becomes available, or the
blocking library function completes.</entry>
</row>
<row>
<entry>Terminated</entry>
<entry>[none]</entry>
<entry>Thread is detached or joined by some other thread calling the
appropriate library function, or by program termination
[3.6.3].</entry>
</row>
</tbody>
</tgroup>
</table>
<para>[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.]</para>
</glossdef>
</glossentry>
<glossentry id="threads.glossary.race-condition">
<glossterm>Race Condition</glossterm>
<glossdef>
<para>A race condition is what occurs when multiple threads read from 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't even a valid value for the data type. A race condition
results in undefined behavior [1.3.12].</para>
<para>Race conditions can be prevented by serializing memory access using
the tools provided by &Boost.Threads;.</para>
</glossdef>
</glossentry>
<glossentry id="threads.glossary.deadlock">
<glossterm>Deadlock</glossterm>
<glossdef>
<para>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.</para>
</glossdef>
</glossentry>
<glossentry id="threads.glossary.starvation">
<glossterm>Starvation</glossterm>
<glossdef>
<para>The condition in which a thread is not making sufficient progress in
its work during a given time interval.</para>
</glossdef>
</glossentry>
<glossentry id="threads.glossary.priority-failure">
<glossterm>Priority Failure</glossterm>
<glossdef>
<para>A priority failure (such as priority inversion or infinite overtaking)
occurs when threads are executed in such a sequence that required work is not
performed in time to be useful.</para>
</glossdef>
</glossentry>
<glossentry id="threads.glossary.undefined-behavior">
<glossterm>Undefined Behavior</glossterm>
<glossdef>
<para>The result of certain operations in &Boost.Threads; is undefined;
this means that those operations can invoke almost any behavior when
they are executed.</para>
<para>An operation whose behavior is undefined can work "correctly"
in some implementations (i.e., do what the programmer thought it
would do), while in other implementations it may exhibit almost
any "incorrect" behavior--such as returning an invalid value,
throwing an exception, generating an access violation, or terminating
the process.</para>
<para>Executing a statement whose behavior is undefined is a
programming error.</para>
</glossdef>
</glossentry>
<glossentry id="threads.glossary.memory-visibility">
<glossterm>Memory Visibility</glossterm>
<glossdef>
<para>An address [1.7] shall always point to the same memory byte,
regardless of the thread or processor dereferencing the address.</para>
<para>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.</para>
<para>For an object accessible from multiple threads, the value of the
object accessed from one thread may be indeterminate or different from 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
"sequence point at a call" is the sequence point after the evaluation of all
function arguments [1.9/17], while the "sequence point after a call" is the
sequence point after the copying of the returned value... [1.9/17].</para>
<table>
<title>Memory Visibility</title>
<tgroup cols="2">
<thead>
<row>
<entry>Thread A</entry>
<entry>Thread B</entry>
</row>
</thead>
<tbody>
<row>
<entry>The sequence point at a call to a library thread-creation
function.</entry>
<entry>The first sequence point of the initial function in the new
thread created by the Thread A call.</entry>
</row>
<row>
<entry>The sequence point at a call to a library function which
locks a mutex, directly or by waiting for a condition
variable.</entry>
<entry>The sequence point after a call to a library function which
unlocks the same mutex.</entry>
</row>
<row>
<entry>The last sequence point before thread termination.</entry>
<entry>The sequence point after a call to a library function which
joins the terminated thread.</entry>
</row>
<row>
<entry>The sequence point at a call to a library function which
signals or broadcasts a condition variable.</entry>
<entry>The sequence point after the call to the library function
which was waiting on that same condition variable or signal.</entry>
</row>
</tbody>
</tgroup>
</table>
<para>The architecture of the execution environment and the observable
behavior of the abstract machine [1.9] shall be the same on all
processors.</para>
<para>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.</para>
<para>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.</para>
</glossdef>
</glossentry>
<section>
<title>Acknowledgements</title>
<para>This document was originally written by Beman Dawes, and then much
improved by the incorporation of comments from William Kempf, who now
maintains the contents.</para>
<para>The visibility rules are based on &cite.Butenhof97;.</para>
</section>
</glossary>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="threads.implementation_notes" last-revision="$Date$">
<title>Implementation Notes</title>
<section id="threads.implementation_notes.win32">
<title>Win32</title>
<para>
In the current Win32 implementation, creating a boost::thread object
during dll initialization will result in deadlock because the thread
class constructor causes the current thread to wait on the thread that
is being created until it signals that it has finished its initialization,
and, as stated in the
<ulink url="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/dllmain.asp">MSDN Library, "DllMain" article, "Remarks" section</ulink>,
"Because DLL notifications are serialized, entry-point functions should not
attempt to communicate with other threads or processes. Deadlocks may occur as a result."
(Also see <ulink url="http://www.microsoft.com/msj/archive/S220.aspx">"Under the Hood", January 1996</ulink>
for a more detailed discussion of this issue).
</para>
<para>
The following non-exhaustive list details some of the situations that
should be avoided until this issue can be addressed:
<itemizedlist>
<listitem>Creating a boost::thread object in DllMain() or in any function called by it.</listitem>
<listitem>Creating a boost::thread object in the constructor of a global static object or in any function called by one.</listitem>
<listitem>Creating a boost::thread object in MFC's CWinApp::InitInstance() function or in any function called by it.</listitem>
<listitem>Creating a boost::thread object in the function pointed to by MFC's _pRawDllMain function pointer or in any function called by it.</listitem>
</itemizedlist>
</para>
</section>
</section>

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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</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">Index</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="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>
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<dt><a href="exceptions.html"><code>&lt;boost/thread/exceptions.hpp&gt;</code></a></dt>
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<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>
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<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>
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<dt><a href="once.html"><code>&lt;boost/thread/once.hpp&gt;</code></a></dt>
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<dt><a href="once.html#macros">Macros</a></dt>
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<dt><a href="once.html#macro-BOOST_ONCE_INIT"><code>BOOST_ONCE_INIT</code></a></dt>
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<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>
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<dt><a href="recursive_mutex.html#classes">Classes</a></dt>
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<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>
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<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>
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<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>
</dl>
<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>
<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>
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@@ -1,159 +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 - Introduction to Design</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">Introduction to Design</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>
<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>
</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>
<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>
<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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<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 - ScopedLock 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">ScopedLock Concept</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">
<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 mutex object 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>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>
</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>
</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">
<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>
</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>
</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">
<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>
</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>
</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>
</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">
<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>
</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>
</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>
</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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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/mutex.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="mutex">
<purpose>
<para>The <classname>mutex</classname> class is a model of the
<link linkend="threads.concepts.Mutex">Mutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>mutex</classname> class is a model of the
<link linkend="threads.concepts.Mutex">Mutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>try_mutex</classname> and <classname>timed_mutex</classname>.</para>
<para>For <link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics, see <classname>recursive_mutex</classname>,
<classname>recursive_try_mutex</classname>, and <classname>recursive_timed_mutex</classname>.
</para>
<para>The <classname>mutex</classname> class supplies the following typedef,
which <link linkend="threads.concepts.lock-models">models</link>
the specified locking strategy:
<informaltable>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedLock">ScopedLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>mutex</classname> class uses an
<link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
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.</para>
<para>Like all
<link linkend="threads.concepts.mutex-models">mutex models</link>
in &Boost.Threads;, <classname>mutex</classname> leaves the
<link linkend="threads.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="threads.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="try_mutex">
<purpose>
<para>The <classname>try_mutex</classname> class is a model of the
<link linkend="threads.concepts.TryMutex">TryMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>try_mutex</classname> class is a model of the
<link linkend="threads.concepts.TryMutex">TryMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>mutex</classname> and <classname>timed_mutex</classname>.</para>
<para>For <link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics, see <classname>recursive_mutex</classname>,
<classname>recursive_try_mutex</classname>, and <classname>recursive_timed_mutex</classname>.
</para>
<para>The <classname>try_mutex</classname> class supplies the following typedefs,
which <link linkend="threads.concepts.lock-models">model</link>
the specified locking strategies:
<informaltable>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="threads.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>try_mutex</classname> class uses an
<link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>try_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
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.</para>
<para>Like all
<link linkend="threads.concepts.mutex-models">mutex models</link>
in &Boost.Threads;, <classname>try_mutex</classname> leaves the
<link linkend="threads.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="threads.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>try_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>try_mutex</classname> object.
</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="timed_mutex">
<purpose>
<para>The <classname>timed_mutex</classname> class is a model of the
<link linkend="threads.concepts.TimedMutex">TimedMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>timed_mutex</classname> class is a model of the
<link linkend="threads.concepts.TimedMutex">TimedMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>mutex</classname> and <classname>try_mutex</classname>.</para>
<para>For <link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics, see <classname>recursive_mutex</classname>,
<classname>recursive_try_mutex</classname>, and <classname>recursive_timed_mutex</classname>.
</para>
<para>The <classname>timed_mutex</classname> class supplies the following typedefs,
which <link linkend="threads.concepts.lock-models">model</link>
the specified locking strategies:
<informaltable>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="threads.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
<row>
<entry>scoped_timed_lock</entry>
<entry><link linkend="threads.concepts.ScopedTimedLock">ScopedTimedLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>timed_mutex</classname> class uses an
<link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>timed_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
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.</para>
<para>Like all
<link linkend="threads.concepts.mutex-models">mutex models</link>
in &Boost.Threads;, <classname>timed_mutex</classname> leaves the
<link linkend="threads.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="threads.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_timed_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>timed_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>timed_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
</namespace>
</header>

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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/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/mutex.hpp">boost/thread/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="#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>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">
<tr>
<td><b>Mutex Class</b></td>
<td><b>Lock name</b></td>
<td><b>Lock Concept</b></td>
</tr>
<tr>
<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>
</tr>
<tr>
<td valign="top"><code><a href="#try_mutex Synopsis"> 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>
</tr>
<tr>
<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>
</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>
<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.
{
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>
<pre>
mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<pre>
~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>
<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.
{
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>
<pre>
try_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<pre>
~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>
<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.
{
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>
<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>
<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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<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 - Mutex 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"> <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>
</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>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">
<tr>
<td><b>Expression</b></td>
<td><b>Effects</b></td>
</tr>
<tr>
<td><code>M m;</code></td>
<td>Constructs a mutex object m. Post-condition: m is unlocked.</td>
</tr>
<tr>
<td><code>(&amp;m)-&gt;~M();</code></td>
<td>Precondition: m is unlocked. Destroys a mutex object m.</td>
</tr>
<tr>
<td><code>M::scoped_lock</code></td>
<td>A model of <a href="lock_concept.html#ScopedLock">ScopedLock</a>.</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">
<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>
</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">
<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>
</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">
<tr>
<td><b>Concept</b></td>
<td><b>Refines</b></td>
<td><b>Models</b></td>
</tr>
<tr>
<td valign="top"><a href="#Mutex-concept">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>
</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>
</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>
</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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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/once.hpp"
last-revision="$Date$">
<macro name="BOOST_ONCE_INIT">
<purpose>The <functionname>call_once</functionname> function and
<code>once_flag</code> type (statically initialized to
<macroname>BOOST_ONCE_INIT</macroname>) can be used to run a
routine exactly once. This can be used to initialize data in a
<link linkend="threads.glossary.thread-safe">thread-safe</link>
manner.</purpose>
<description>The implementation-defined macro
<macroname>BOOST_ONCE_INIT</macroname> is a constant value used to
initialize <code>once_flag</code> instances to indicate that the
logically associated routine has not been run yet. See
<functionname>call_once</functionname> for more details.</description>
</macro>
<namespace name="boost">
<typedef name="once_flag">
<purpose>The <functionname>call_once</functionname> function and
<code>once_flag</code> type (statically initialized to
<macroname>BOOST_ONCE_INIT</macroname>) can be used to run a
routine exactly once. This can be used to initialize data in a
<link linkend="threads.glossary.thread-safe">thread-safe</link>
manner.</purpose>
<description>The implementation-defined type <code>once_flag</code>
is used as a flag to insure a routine is called only once.
Instances of this type should be statically initialized to
<macroname>BOOST_ONCE_INIT</macroname>. See
<functionname>call_once</functionname> for more details.
</description>
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<function name="call_once">
<purpose>The <functionname>call_once</functionname> function and
<code>once_flag</code> type (statically initialized to
<macroname>BOOST_ONCE_INIT</macroname>) can be used to run a
routine exactly once. This can be used to initialize data in a
<link linkend="threads.glossary.thread-safe">thread-safe</link>
manner.</purpose>
<description>
<para>Example usage is as follows:</para>
<para>
<programlisting>//Example usage:
boost::once_flag once = BOOST_ONCE_INIT;
void init()
{
//...
}
void thread_proc()
{
boost::call_once(&amp;init, once);
}</programlisting>
</para></description>
<parameter name="func">
<paramtype>void (*func)()</paramtype>
</parameter>
<parameter name="flag">
<paramtype>once_flag&amp;</paramtype>
</parameter>
<requires>The function <code>func</code> shall not throw
exceptions.</requires>
<effects>As if (in an atomic fashion):
<code>if (flag == BOOST_ONCE_INIT) func();</code></effects>
<postconditions><code>flag != BOOST_ONCE_INIT</code>
</postconditions>
</function>
</namespace>
</header>

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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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<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>
</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>
</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>
<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>
</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>
</ul>
<ul>
<li>Some program designs may be easier to formulate using a multithreaded approach.
After all, the real world is asynchronous!</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>
<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>
(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>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>
<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>
</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>
<ul>
<li>rand</li>
<li>strtok</li>
<li>asctime</li>
<li>ctime</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>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>
<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>
<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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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="threads.overview" last-revision="$Date$">
<title>Overview</title>
<section id="threads.introduction">
<title>Introduction</title>
<para>&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. The <link
linkend="threads.glossary">glossary</link> gives a more complete description
of the multithreading execution environment.</para>
<para>Multithreading provides several advantages:
<itemizedlist>
<listitem>
<para>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.</para>
</listitem>
<listitem>
<para>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 than single-threaded programs.</para>
</listitem>
<listitem>
<para>Some program designs may be easier to formulate using a
multithreaded approach. After all, the real world is
asynchronous!</para>
</listitem>
</itemizedlist></para>
</section>
<section>
<title>Dangers</title>
<section>
<title>General considerations</title>
<para>Beyond the errors which can occur in single-threaded programs,
multithreaded programs are subject to additional errors:
<itemizedlist>
<listitem>
<para><link linkend="threads.glossary.race-condition">Race
conditions</link></para>
</listitem>
<listitem>
<para><link linkend="threads.glossary.deadlock">Deadlock</link>
(sometimes called "deadly embrace")</para>
</listitem>
<listitem>
<para><link linkend="threads.glossary.priority-failure">Priority
failures</link> (priority inversion, infinite overtaking, starvation,
etc.)</para>
</listitem>
</itemizedlist></para>
<para>Every multithreaded program must be designed carefully to avoid these
errors. These aren'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.</para>
<para>The <link linkend="threads.design">&Boost.Threads; design</link>
attempts to minimize these errors, but they will still occur unless the
programmer proactively designs to avoid them.</para>
<note>Please also see <xref linkend="threads.implementation_notes"/>
for additional, implementation-specific considerations.</note>
</section>
<section>
<title>Testing and debugging considerations</title>
<para>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:
<itemizedlist>
<listitem>
<para>Failures are often not repeatable.</para>
</listitem>
<listitem>
<para>Probe effect causes debuggers to produce very different results
from non-debug uses.</para>
</listitem>
<listitem>
<para>Debuggers require special support to show thread state.</para>
</listitem>
<listitem>
<para>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.</para>
</listitem>
<listitem>
<para>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.</para>
</listitem>
</itemizedlist></para>
</section>
<section>
<title>Getting a head start</title>
<para>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.</para>
<para>Design patterns for reliable multithreaded programs, including the
important <emphasis>monitor</emphasis> pattern, are presented in
<emphasis>Pattern-Oriented Software Architecture Volume 2 - Patterns for
Concurrent and Networked Objects</emphasis>
&cite.SchmidtStalRohnertBuschmann;. Many important multithreading programming
considerations (independent of threading library) are discussed in
<emphasis>Programming with POSIX Threads</emphasis> &cite.Butenhof97;.</para>
<para>Doing some reading before attempting multithreaded designs will
give you a head start toward reliable multithreaded programs.</para>
</section>
</section>
<section>
<title>C++ Standard Library usage in multithreaded programs</title>
<section>
<title>Runtime libraries</title>
<para>
<emphasis role="bold">Warning:</emphasis> Multithreaded programs such as
those using &Boost.Threads; must link to <link
linkend="threads.glossary.thread-safe">thread-safe</link> versions of
all runtime libraries used by the program, including the runtime library
for the C++ Standard Library. Failure to do so will cause <link
linkend="threads.glossary.race-condition">race conditions</link> to occur
when multiple threads simultaneously execute runtime library functions for
<code>new</code>, <code>delete</code>, or other language features which
imply shared state.</para>
</section>
<section>
<title>Potentially non-thread-safe functions</title>
<para>Certain C++ Standard Library functions inherited from C are
particular problems because they hold internal state between
calls:
<itemizedlist>
<listitem>
<para><code>rand</code></para>
</listitem>
<listitem>
<para><code>strtok</code></para>
</listitem>
<listitem>
<para><code>asctime</code></para>
</listitem>
<listitem>
<para><code>ctime</code></para>
</listitem>
<listitem>
<para><code>gmtime</code></para>
</listitem>
<listitem>
<para><code>localtime</code></para>
</listitem>
</itemizedlist></para>
<para>It is possible to write thread-safe implementations of these by
using thread specific storage (see
<classname>boost::thread_specific_ptr</classname>), and several C++
compiler vendors do just that. The technique is well-know and is explained
in &cite.Butenhof97;.</para>
<para>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.</para>
<para><emphasis role="bold">Recommendation:</emphasis> For the most
portable, yet thread-safe code, use Boost replacements for the problem
functions. See the <libraryname>Boost Random Number Library</libraryname>
and <libraryname>Boost Tokenizer Library</libraryname>.</para>
</section>
</section>
<section>
<title>Common guarantees for all &Boost.Threads; components</title>
<section>
<title>Exceptions</title>
<para>&Boost.Threads; destructors never
throw exceptions. Unless otherwise specified, other
&Boost.Threads; functions that do not have
an exception-specification may throw implementation-defined
exceptions.</para>
<para>In particular, &Boost.Threads;
reports failure to allocate storage by throwing an exception of type
<code>std::bad_alloc</code> or a class derived from
<code>std::bad_alloc</code>, failure to obtain thread resources other than
memory by throwing an exception of type
<classname>boost::thread_resource_error</classname>, and certain lock
related failures by throwing an exception of type
<classname>boost::lock_error</classname>.</para>
<para><emphasis role="bold">Rationale:</emphasis> Follows the C++ Standard
Library practice of allowing all functions except destructors or other
specified functions to throw exceptions on errors.</para>
</section>
<section>
<title>NonCopyable requirement</title>
<para>&Boost.Threads; 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 <classname>boost::noncopyable</classname>. Users
should not depend on this derivation, however, as implementations are free
to meet the NonCopyable requirement in other ways.</para>
</section>
</section>
</section>

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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 - Rationale</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">Rationale</h2>
</td>
</tr>
</table>
<hr>
<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>
<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()
{
thread = create_thread(&amp;bar);
join(thread);
}
</pre>
<h3>3. Simple creation of several threads in a loop.</h3>
<pre>
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()
{
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].join();
}
</pre>
<h3>5. Creation of a thread whose ownership is passed to another object/method.</h3>
<pre>
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>
<pre>
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>
<h3>1.</h3>
<pre>
void foo()
{
thread thrd(&amp;bar);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
}
</pre>
<h3>2.</h3>
<pre>
void foo()
{
thread thrd(&amp;bar);
thrd.join();
}
void foo()
{
thread_ref thrd =
create_thread(&amp;bar);thrd-&gt;join();
}
</pre>
<h3>3.</h3>
<pre>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
thread thrd(&amp;bar);
}
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
thread_ref thrd = create_thread(&amp;bar);
}
</pre>
<h3>4.</h3>
<pre>
void foo()
{
std::auto_ptr&lt;thread&gt; threads[NUM_THREADS];
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = std::auto_ptr&lt;thread&gt;(new thread(&amp;bar));
for (int i= 0; i&lt;NUM_THREADS;
++i)threads[i]-&gt;join();
}
void foo()
{
thread_ref threads[NUM_THREADS];
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();
}
</pre>
<h3>5.</h3>
<pre>
void foo()
{
thread thrd* = new thread(&amp;bar);
manager.owns(thread);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
manager.owns(thrd);
}
</pre>
<h3>6.</h3>
<pre>
void foo()
{
boost::shared_ptr&lt;thread&gt; thrd(new thread(&amp;bar));
manager1.add(thrd);
manager2.add(thrd);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
manager1.add(thrd);
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>
<pre>
void foo()
{
thread_group threads;
for (int i=0; i&lt;NUM_THREADS; ++i)
threads.create_thread(&amp;bar);
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>[Note that Graphical User Interface <i>events</i> are a different concept,
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>
<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>
</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>[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>
<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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@@ -0,0 +1,434 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="threads.rationale" last-revision="$Date$">
<title>Rationale</title>
<para>This page explains the rationale behind various design decisions in the
&Boost.Threads; 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.</para>
<section id="threads.rationale.Boost.Threads">
<title>Rationale for the Creation of &Boost.Threads;</title>
<para>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
multithreaded programming are quite well known to most modern programmers,
yet the C++ language doesn't directly support this concept.</para>
<para>Many platforms support multithreaded 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.</para>
<para>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.</para>
<para>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.</para>
<para>The &Boost.Threads; library was developed to provide a C++ developer
with a portable interface for writing multithreaded 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.</para>
</section>
<section id="threads.rationale.primitives">
<title>Rationale for the Low Level Primitives Supported in &Boost.Threads;</title>
<para>The &Boost.Threads; library supplies a set of low level primitives for
writing multithreaded programs, such as 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 it's difficult 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?</para>
<para>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.</para>
<para>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's
hard to prove that their usage is correct. Since many users will be familiar
with these lower level concepts but unfamiliar with any of the higher
level concepts, supporting the lower level concepts provides
greater accessibility.</para>
</section>
<section id="threads.rationale.locks">
<title>Rationale for the Lock Design</title>
<para>Programmers who are used to multithreaded programming issues will
quickly note that the &Boost.Threads; design for mutex lock concepts is not
<link linkend="threads.glossary.thread-safe">thread-safe</link> (this is
clearly documented as well). At first this may seem like a serious design
flaw. Why have a multithreading primitive that's not thread-safe
itself?</para>
<para>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 (in fact, to do so would likely be an
error). Nor are there any cases when such usage would be required.</para>
<para>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.</para>
<para>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
multithreading issues.</para>
</section>
<section id="threads.rationale.non-copyable">
<title>Rationale for NonCopyable Thread Type</title>
<para>Programmers who are used to C libraries for multithreaded programming
are likely to wonder why &Boost.Threads; uses a noncopyable design for
<classname>boost::thread</classname>. 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.</para>
<para>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's an API for acquiring the resource and an API for releasing
the resource. 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.</para>
<para>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.</para>
<para>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 than
wrappers (such as boost::shared_ptr) around a noncopyable thread
concept. Analysis of whether or not these arguments would hold true doesn'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.</para>
<section id="threads.rationale.non-copyable.simple">
<title>1. Use case: Simple creation of a thread.</title>
<programlisting>
void foo()
{
create_thread(&amp;bar);
}
</programlisting>
</section>
<section id="threads.rationale.non-copyable.joined">
<title>2. Use case: Creation of a thread that's later joined.</title>
<programlisting>
void foo()
{
thread = create_thread(&amp;bar);
join(thread);
}
</programlisting>
</section>
<section id="threads.rationale.non-copyable.loop">
<title>3. Use case: Simple creation of several threads in a loop.</title>
<programlisting>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
create_thread(&amp;bar);
}
</programlisting>
</section>
<section id="threads.rationale.non-copyable.loop-join">
<title>4. Use case: Creation of several threads in a loop which are later joined.</title>
<programlisting>
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].join();
}
</programlisting>
</section>
<section id="threads.rationale.non-copyable.pass">
<title>5. Use case: Creation of a thread whose ownership is passed to another object/method.</title>
<programlisting>
void foo()
{
thread = create_thread(&amp;bar);
manager.owns(thread);
}
</programlisting>
</section>
<section id="threads.rationale.non-copyable.shared">
<title>6. Use case: Creation of a thread whose ownership is shared between multiple
objects.</title>
<programlisting>
void foo()
{
thread = create_thread(&amp;bar);
manager1.add(thread);
manager2.add(thread);
}
</programlisting>
</section>
<para>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.</para>
<para>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.</para>
<para>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.</para>
<para>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.</para>
<section id="threads.rationale_comparison.non-copyable.simple">
<title>1. Comparison: simple creation of a thread.</title>
<programlisting>
void foo()
{
thread thrd(&amp;bar);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
}
</programlisting>
</section>
<section id="threads.rationale_comparison.non-copyable.joined">
<title>2. Comparison: creation of a thread that's later joined.</title>
<programlisting>
void foo()
{
thread thrd(&amp;bar);
thrd.join();
}
void foo()
{
thread_ref thrd =
create_thread(&amp;bar);thrd-&gt;join();
}
</programlisting>
</section>
<section id="threads.rationale_comparison.non-copyable.loop">
<title>3. Comparison: simple creation of several threads in a loop.</title>
<programlisting>
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
thread thrd(&amp;bar);
}
void foo()
{
for (int i=0; i&lt;NUM_THREADS; ++i)
thread_ref thrd = create_thread(&amp;bar);
}
</programlisting>
</section>
<section id="threads.rationale_comparison.non-copyable.loop-join">
<title>4. Comparison: creation of several threads in a loop which are later joined.</title>
<programlisting>
void foo()
{
std::auto_ptr&lt;thread&gt; threads[NUM_THREADS];
for (int i=0; i&lt;NUM_THREADS; ++i)
threads[i] = std::auto_ptr&lt;thread&gt;(new thread(&amp;bar));
for (int i= 0; i&lt;NUM_THREADS;
++i)threads[i]-&gt;join();
}
void foo()
{
thread_ref threads[NUM_THREADS];
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();
}
</programlisting>
</section>
<section id="threads.rationale_comparison.non-copyable.pass">
<title>5. Comparison: creation of a thread whose ownership is passed to another object/method.</title>
<programlisting>
void foo()
{
thread thrd* = new thread(&amp;bar);
manager.owns(thread);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
manager.owns(thrd);
}
</programlisting>
</section>
<section id="threads.rationale_comparison.non-copyable.shared">
<title>6. Comparison: creation of a thread whose ownership is shared
between multiple objects.</title>
<programlisting>
void foo()
{
boost::shared_ptr&lt;thread&gt; thrd(new thread(&amp;bar));
manager1.add(thrd);
manager2.add(thrd);
}
void foo()
{
thread_ref thrd = create_thread(&amp;bar);
manager1.add(thrd);
manager2.add(thrd);
}
</programlisting>
</section>
<para>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
<link linkend="threads.rationale_comparison.non-copyable.loop-join">(4)</link>,
<link linkend="threads.rationale_comparison.non-copyable.pass">(5)</link>, and
<link linkend="threads.rationale_comparison.non-copyable.shared">(6)</link>;
and the use of std::auto_ptr and boost::shared_ptr in
<link linkend="threads.rationale_comparison.non-copyable.loop-join">(4)</link> and
<link linkend="threads.rationale_comparison.non-copyable.shared">(6)</link>
respectively. However, that's not really
much added complexity, and C++ programmers are used to using these idioms
anyway. 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
<link linkend="threads.rationale_comparison.non-copyable.loop-join">(4)</link>
down to:</para>
<programlisting>
void foo()
{
thread_group threads;
for (int i=0; i&lt;NUM_THREADS; ++i)
threads.create_thread(&amp;bar);
threads.join_all();
}
</programlisting>
<para>So ease of use is really a wash and not much help in picking a
design.</para>
<para>So what about performance? Looking at the above code examples,
we can analyze the theoretical impact to performance that both designs
have. For <link linkend="threads.rationale_comparison.non-copyable.simple">(1)</link>
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 <link linkend="threads.rationale_comparison.non-copyable.joined">(2)</link>
and <link linkend="threads.rationale_comparison.non-copyable.loop">(3)</link>
the performance impact will be identical to
<link linkend="threads.rationale_comparison.non-copyable.simple">(1)</link>.
For <link linkend="threads.rationale_comparison.non-copyable.loop-join">(4)</link>
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
<link linkend="threads.rationale_comparison.non-copyable.pass">(5)</link> we see
the same impact as we do for
<link linkend="threads.rationale_comparison.non-copyable.loop-join">(4)</link>.
For <link linkend="threads.rationale_comparison.non-copyable.shared">(6)</link>
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
<link linkend="threads.rationale_comparison.non-copyable.simple">(1)</link>,
<link linkend="threads.rationale_comparison.non-copyable.joined">(2)</link> and
<link linkend="threads.rationale_comparison.non-copyable.loop">(3)</link>; with
<link linkend="threads.rationale_comparison.non-copyable.loop-join">(4)</link>
and <link linkend="threads.rationale_comparison.non-copyable.pass">(5)</link> the
winner depending on the implementation and the platform but with the thread design
probably having a better chance; and with
<link linkend="threads.rationale_comparison.non-copyable.shared">(6)</link>
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.</para>
<para>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.</para>
</section>
<section id="threads.rationale.events">
<title>Rationale for not providing <emphasis>Event Variables</emphasis></title>
<para><emphasis>Event variables</emphasis> are simply far too
error-prone. <classname>boost::condition</classname> variables are a much safer
alternative. [Note that Graphical User Interface <emphasis>events</emphasis> are
a different concept, and are not what is being discussed here.]</para>
<para>Event variables were one of the first synchronization primitives. They
are still used today, for example, in the native Windows multithreading
API. 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.</para>
<para>Per Brinch Hansen &cite.Hansen73; analyzed event variables in some
detail, pointing out [emphasis his] that "<emphasis>event operations force
the programmer to be aware of the relative speeds of the sending and
receiving processes</emphasis>". His summary:</para>
<blockquote>
<para>We must therefore conclude that event variables of the previous type
are impractical for system design. <emphasis>The effect of an interaction
between two processes must be independent of the speed at which it is
carried out.</emphasis></para>
</blockquote>
<para>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 <link
linkend="threads.glossary.race-condition">race condition</link> 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.</para>
<para>The decision to exclude event variables from &Boost.Threads; 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 "goto considered harmful" 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 will be less likely to contain latent defects.</para>
<para>[Rationale provided by Beman Dawes]</para>
</section>
</section>

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@@ -0,0 +1,362 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/read_write_mutex.hpp"
last-revision="$Date$">
<namespace name="boost">
<namespace name="read_write_scheduling_policy">
<enum name="read_write_scheduling_policy">
<enumvalue name="writer_priority" />
<enumvalue name="reader_priority" />
<enumvalue name="alternating_many_reads" />
<enumvalue name="alternating_single_read" />
<purpose>
<para>Specifies the
<link linkend="threads.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
to use when a set of threads try to obtain different types of
locks simultaneously.</para>
</purpose>
<description>
<para>The only clock type supported by &Boost.Threads; is
<code>TIME_UTC</code>. The epoch for <code>TIME_UTC</code>
is 1970-01-01 00:00:00.</para>
</description>
</enum>
</namespace>
<class name="read_write_mutex">
<purpose>
<para>The <classname>read_write_mutex</classname> class is a model of the
<link linkend="threads.concepts.ReadWriteMutex">ReadWriteMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>read_write_mutex</classname> class is a model of the
<link linkend="threads.concepts.ReadWriteMutex">ReadWriteMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>try_read_write_mutex</classname> and <classname>timed_read_write_mutex</classname>.</para>
<para>The <classname>read_write_mutex</classname> class supplies the following typedef,
which <link linkend="threads.concepts.read-write-lock-models">models</link>
the specified locking strategy:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedReadWriteLock">ScopedReadWriteLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>read_write_mutex</classname> class uses an
<link linkend="threads.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>read_write_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
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.</para>
<para>Like all
<link linkend="threads.concepts.read-write-mutex-models">read/write mutex models</link>
in &Boost.Threads;, <classname>read_write_mutex</classname> has two types of
<link linkend="threads.concepts.read-write-scheduling-policies">scheduling policies</link>, an
<link linkend="threads.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
between threads trying to obtain different types of locks and an
<link linkend="threads.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link>
between threads trying to obtain the same type of lock.
The <classname>read_write_mutex</classname> class allows the
programmer to choose what
<link linkend="threads.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
will be used; however, like all read/write mutex models,
<classname>read_write_mutex</classname> leaves the
<link linkend="threads.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link> as
<link linkend="threads.concepts.read-write-locking-strategies.unspecified">Unspecified</link>.
</para>
<note>Self-deadlock is virtually guaranteed if a thread tries to
lock the same <classname>read_write_mutex</classname> multiple times
unless all locks are read-locks (but see below)</note>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<parameter name="count">
<paramtype>boost::read_write_scheduling_policy</paramtype>
</parameter>
<effects>Constructs a <classname>read_write_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>read_write_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="try_read_write_mutex">
<purpose>
<para>The <classname>try_read_write_mutex</classname> class is a model of the
<link linkend="threads.concepts.TryReadWriteMutex">TryReadWriteMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>try_read_write_mutex</classname> class is a model of the
<link linkend="threads.concepts.TryReadWriteMutex">TryReadWriteMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>read_write_mutex</classname> and <classname>timed_read_write_mutex</classname>.</para>
<para>The <classname>try_read_write_mutex</classname> class supplies the following typedefs,
which <link linkend="threads.concepts.read-write-lock-models">model</link>
the specified locking strategy:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedReadWriteLock">ScopedReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="threads.concepts.ScopedTryReadWriteLock">ScopedTryReadWriteLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>try_read_write_mutex</classname> class uses an
<link linkend="threads.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>try_read_write_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
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.</para>
<para>Like all
<link linkend="threads.concepts.read-write-mutex-models">read/write mutex models</link>
in &Boost.Threads;, <classname>try_read_write_mutex</classname> has two types of
<link linkend="threads.concepts.read-write-scheduling-policies">scheduling policies</link>, an
<link linkend="threads.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
between threads trying to obtain different types of locks and an
<link linkend="threads.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link>
between threads trying to obtain the same type of lock.
The <classname>try_read_write_mutex</classname> class allows the
programmer to choose what
<link linkend="threads.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
will be used; however, like all read/write mutex models,
<classname>try_read_write_mutex</classname> leaves the
<link linkend="threads.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link> as
<link linkend="threads.concepts.unspecified-scheduling-policy">Unspecified</link>.
</para>
<note>Self-deadlock is virtually guaranteed if a thread tries to
lock the same <classname>try_read_write_mutex</classname> multiple times
unless all locks are read-locks (but see below)</note>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<parameter name="count">
<paramtype>boost::read_write_scheduling_policy</paramtype>
</parameter>
<effects>Constructs a <classname>try_read_write_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>try_read_write_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="timed_read_write_mutex">
<purpose>
<para>The <classname>timed_read_write_mutex</classname> class is a model of the
<link linkend="threads.concepts.TimedReadWriteMutex">TimedReadWriteMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>timed_read_write_mutex</classname> class is a model of the
<link linkend="threads.concepts.TimedReadWriteMutex">TimedReadWriteMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>read_write_mutex</classname> and <classname>try_read_write_mutex</classname>.</para>
<para>The <classname>timed_read_write_mutex</classname> class supplies the following typedefs,
which <link linkend="threads.concepts.read-write-lock-models">model</link>
the specified locking strategy:
<informaltable>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedReadWriteLock">ScopedReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="threads.concepts.ScopedTryReadWriteLock">ScopedTryReadWriteLock</link></entry>
</row>
<row>
<entry>scoped_timed_lock</entry>
<entry><link linkend="threads.concepts.ScopedTimedReadWriteLock">ScopedTimedReadWriteLock</link></entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
<para>The <classname>timed_read_write_mutex</classname> class uses an
<link linkend="threads.concepts.read-write-locking-strategies.unspecified">Unspecified</link>
locking strategy, so attempts to recursively lock a <classname>timed_read_write_mutex</classname>
object or attempts to unlock one by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.
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.</para>
<para>Like all
<link linkend="threads.concepts.read-write-mutex-models">read/write mutex models</link>
in &Boost.Threads;, <classname>timed_read_write_mutex</classname> has two types of
<link linkend="threads.concepts.read-write-scheduling-policies">scheduling policies</link>, an
<link linkend="threads.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
between threads trying to obtain different types of locks and an
<link linkend="threads.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link>
between threads trying to obtain the same type of lock.
The <classname>timed_read_write_mutex</classname> class allows the
programmer to choose what
<link linkend="threads.concepts.read-write-scheduling-policies.inter-class">inter-class sheduling policy</link>
will be used; however, like all read/write mutex models,
<classname>timed_read_write_mutex</classname> leaves the
<link linkend="threads.concepts.read-write-scheduling-policies.intra-class">intra-class sheduling policy</link> as
<link linkend="threads.concepts.unspecified-scheduling-policy">Unspecified</link>.
</para>
<note>Self-deadlock is virtually guaranteed if a thread tries to
lock the same <classname>timed_read_write_mutex</classname> multiple times
unless all locks are read-locks (but see below)</note>
</description>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_timed_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<parameter name="count">
<paramtype>boost::read_write_scheduling_policy</paramtype>
</parameter>
<effects>Constructs a <classname>timed_read_write_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>timed_read_write_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
</namespace>
</header>

302
doc/recursive_mutex-ref.xml Normal file
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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/recursive_mutex.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="recursive_mutex">
<purpose>
<para>The <classname>recursive_mutex</classname> class is a model of the
<link linkend="threads.concepts.Mutex">Mutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>recursive_mutex</classname> class is a model of the
<link linkend="threads.concepts.Mutex">Mutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>recursive_try_mutex</classname> and <classname>recursive_timed_mutex</classname>.</para>
<para>For <link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics, see <classname>mutex</classname>,
<classname>try_mutex</classname>, and <classname>timed_mutex</classname>.
</para>
<para>The <classname>recursive_mutex</classname> class supplies the following typedef,
which models the specified locking strategy:
<table>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedLock">ScopedLock</link></entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>The <classname>recursive_mutex</classname> class uses a
<link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking strategy, so attempts to recursively lock a
<classname>recursive_mutex</classname> object
succeed and an internal "lock count" is maintained.
Attempts to unlock a <classname>recursive_mutex</classname> object
by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.</para>
<para>Like all
<link linkend="threads.concepts.mutex-models">mutex models</link>
in &Boost.Threads;, <classname>recursive_mutex</classname> leaves the
<link linkend="threads.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="threads.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>recursive_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>recursive_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="recursive_try_mutex">
<purpose>
<para>The <classname>recursive_try_mutex</classname> class is a model of the
<link linkend="threads.concepts.TryMutex">TryMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>recursive_try_mutex</classname> class is a model of the
<link linkend="threads.concepts.TryMutex">TryMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>recursive_mutex</classname> and <classname>recursive_timed_mutex</classname>.</para>
<para>For <link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics, see <classname>mutex</classname>,
<classname>try_mutex</classname>, and <classname>timed_mutex</classname>.
</para>
<para>The <classname>recursive_try_mutex</classname> class supplies the following typedefs,
which model the specified locking strategies:
<table>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="threads.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>The <classname>recursive_try_mutex</classname> class uses a
<link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking strategy, so attempts to recursively lock a
<classname>recursive_try_mutex</classname> object
succeed and an internal "lock count" is maintained.
Attempts to unlock a <classname>recursive_mutex</classname> object
by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.</para>
<para>Like all
<link linkend="threads.concepts.mutex-models">mutex models</link>
in &Boost.Threads;, <classname>recursive_try_mutex</classname> leaves the
<link linkend="threads.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="threads.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>recursive_try_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>recursive_try_mutex</classname> object.
</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
<class name="recursive_timed_mutex">
<purpose>
<para>The <classname>recursive_timed_mutex</classname> class is a model of the
<link linkend="threads.concepts.TimedMutex">TimedMutex</link> concept.</para>
</purpose>
<description>
<para>The <classname>recursive_timed_mutex</classname> class is a model of the
<link linkend="threads.concepts.TimedMutex">TimedMutex</link> concept.
It should be used to synchronize access to shared resources using
<link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking mechanics.</para>
<para>For classes that model related mutex concepts, see
<classname>recursive_mutex</classname> and <classname>recursive_try_mutex</classname>.</para>
<para>For <link linkend="threads.concepts.unspecified-locking-strategy">Unspecified</link>
locking mechanics, see <classname>mutex</classname>,
<classname>try_mutex</classname>, and <classname>timed_mutex</classname>.
</para>
<para>The <classname>recursive_timed_mutex</classname> class supplies the following typedefs,
which model the specified locking strategies:
<table>
<title>Supported Lock Types</title>
<tgroup cols="2" align="left">
<thead>
<row>
<entry>Lock Name</entry>
<entry>Lock Concept</entry>
</row>
</thead>
<tbody>
<row>
<entry>scoped_lock</entry>
<entry><link linkend="threads.concepts.ScopedLock">ScopedLock</link></entry>
</row>
<row>
<entry>scoped_try_lock</entry>
<entry><link linkend="threads.concepts.ScopedTryLock">ScopedTryLock</link></entry>
</row>
<row>
<entry>scoped_timed_lock</entry>
<entry><link linkend="threads.concepts.ScopedTimedLock">ScopedTimedLock</link></entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>The <classname>recursive_timed_mutex</classname> class uses a
<link linkend="threads.concepts.recursive-locking-strategy">Recursive</link>
locking strategy, so attempts to recursively lock a
<classname>recursive_timed_mutex</classname> object
succeed and an internal "lock count" is maintained.
Attempts to unlock a <classname>recursive_mutex</classname> object
by threads that don't own a lock on it result in
<emphasis role="bold">undefined behavior</emphasis>.</para>
<para>Like all
<link linkend="threads.concepts.mutex-models">mutex models</link>
in &Boost.Threads;, <classname>recursive_timed_mutex</classname> leaves the
<link linkend="threads.concepts.sheduling-policies">scheduling policy</link>
as <link linkend="threads.concepts.unspecified-scheduling-policy">Unspecified</link>.
Programmers should make no assumptions about the order in which
waiting threads acquire a lock.</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<typedef name="scoped_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_try_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<typedef name="scoped_timed_lock">
<type><emphasis>implementation-defined</emphasis></type>
</typedef>
<constructor>
<effects>Constructs a <classname>recursive_timed_mutex</classname> object.
</effects>
<postconditions><code>*this</code> is in an unlocked state.
</postconditions>
</constructor>
<destructor>
<effects>Destroys a <classname>recursive_timed_mutex</classname> object.</effects>
<requires><code>*this</code> is in an unlocked state.</requires>
<notes><emphasis role="bold">Danger:</emphasis> Destruction of a
locked mutex is a serious programming error resulting in undefined
behavior such as a program crash.</notes>
</destructor>
</class>
</namespace>
</header>

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@@ -1,244 +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/recursive_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/recursive_mutex.hpp">boost/thread/recursive_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="#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">
<tr>
<td><b>Mutex Class</b></td>
<td><b>Lock name</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="middle"><code>scoped_lock</code></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="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>
</tr>
<tr>
<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>
</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>
<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;
recursive_mutex();
~recursive_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>
<pre>
recursive_try_mutex();
</pre>
<dl class="function-semantics">
<dt><b>Postconditions:</b> <code>*this</code> is in an unlocked state.</dt>
</dl>
<pre>
~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>
<pre>
namespace boost
{
class recursive_timed_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;
typedef [implementation defined; see Introduction] scoped_timed_lock;
recursive_timed_mutex();
~recursive_timed_mutex();
};
};
</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>
<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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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<library-reference id="threads.reference"
last-revision="$Date$"
xmlns:xi="http://www.w3.org/2001/XInclude">
<xi:include href="barrier-ref.xml"/>
<xi:include href="condition-ref.xml"/>
<xi:include href="exceptions-ref.xml"/>
<xi:include href="mutex-ref.xml"/>
<xi:include href="once-ref.xml"/>
<xi:include href="recursive_mutex-ref.xml"/>
<xi:include href="read_write_mutex-ref.xml"/>
<xi:include href="thread-ref.xml"/>
<xi:include href="tss-ref.xml"/>
<xi:include href="xtime-ref.xml"/>
</library-reference>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<section id="threads.release_notes" last-revision="$Date$">
<title>Release Notes</title>
<section id="threads.release_notes.boost_1_32_0">
<title>Boost 1.32.0</title>
<section id="threads.release_notes.boost_1_32_0.change_log.documentation">
<title>Documentation converted to BoostBook</title>
<para>The documentation was converted to BoostBook format,
and a number of errors and inconsistencies were
fixed in the process.
Since this was a fairly large task, there are likely to be
more errors and inconsistencies remaining. If you find any,
please report them!</para>
</section>
<section id="threads.release_notes.boost_1_32_0.change_log.static_link">
<title>Static-link build option added</title>
<para>The option to link &Boost.Threads; as a static
library has been added back with some limitations.
This feature was originally removed because
<classname>boost::thread_specific_ptr</classname> required
that &Boost.Threads; be dynamically linked in order for its
cleanup functionality to work on Win32 platforms.
Several options are currently being explored to resolve
this issue. In the meantime, the ability to link
&Boost.Threads; statically has been added back
<emphasis>with <classname>boost::thread_specific_ptr</classname>
support removed</emphasis> from the statically linked version.
The decision to add it back was made because its lack is
one of the most frequent complaints about &Boost.Threads;
and because the other approaches that are being investigated
to deal with <classname>boost::thread_specific_ptr</classname>
cleanup look fairly promising.
<note>&Boost.Threads; is still dynamically linked by default.
In order to force it to be statically linked, it is necessary to
#define BOOST_THREAD_USE_LIB before any of the &Boost.Threads;
header files are #included.</note>
<note>If the <classname>boost::thread_specific_ptr</classname> cleanup
issue cannot be resolved by some other means, it is highly
likely that the option to statically link &Boost.Threads;
will be removed again in a future version of Boost, at least
for Win32 platforms. This is because the
<classname>boost::thread_specific_ptr</classname> functionality
will be increasingly used by &Boost.Threads; itself,
so that proper cleanup will become essential
in future versions of &Boost.Threads;.</note>
</para>
</section>
<section id="threads.release_notes.boost_1_32_0.change_log.barrier">
<title>Barrier functionality added</title>
<para>A new class, <classname>boost::barrier</classname>, was added.</para>
</section>
<section id="threads.release_notes.boost_1_32_0.change_log.read_write_mutex">
<title>Read/write mutex functionality added</title>
<para>New classes,
<classname>boost::read_write_mutex</classname>,
<classname>boost::try_read_write_mutex</classname>, and
<classname>boost::timed_read_write_mutex</classname>
were added.</para>
</section>
<section id="threads.release_notes.boost_1_32_0.change_log.thread_specific_ptr">
<title>Thread-specific pointer functionality changed</title>
<para>The <classname>boost::thread_specific_ptr</classname>
constructor now takes an optional pointer to a cleanup function that
is called to release the thread-specific data that is being pointed
to by <classname>boost::thread_specific_ptr</classname> objects.</para>
<para>Fixed: the number of available thread-specific storage "slots"
is too small on some platforms.</para>
<para>Fixed: <functionname>thread_specific_ptr::reset()</functionname>
doesn't check error returned by <functionname>tss::set()</functionname>
(the <functionname>tss::set()</functionname> function now throws
if it fails instead of returning an error code).</para>
<para>Fixed: calling
<functionname>boost::thread_specific_ptr::reset()</functionname> or
<functionname>boost::thread_specific_ptr::release()</functionname>
causes double-delete: once when
<functionname>boost::thread_specific_ptr::reset()</functionname> or
<functionname>boost::thread_specific_ptr::release()</functionname>
is called and once when
<functionname>boost::thread_specific_ptr::~thread_specific_ptr()</functionname>
is called.</para>
</section>
<section id="threads.release_notes.boost_1_32_0.change_log.mutex">
<title>Mutex implementation changed for Win32</title>
<para>On Win32, <classname>boost::mutex</classname>,
<classname>boost::try_mutex</classname>, <classname>boost::recursive_mutex</classname>,
and <classname>boost::recursive_try_mutex</classname> now use a Win32 critical section
whenever possible; otherwise they use a Win32 mutex. As before,
<classname>boost::timed_mutex</classname> and
<classname>boost::recursive_timed_mutex</classname> use a Win32 mutex.</para>
</section>
</section>
</section>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/thread.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="thread">
<purpose>
<para>The <classname>thread</classname> class represents threads of
execution, and provides the functionality to create and manage
threads within the &Boost.Threads; library. See
<xref linkend="threads.glossary"/> for a precise description of
<link linkend="threads.glossary.thread">thread of execution</link>,
and for definitions of threading-related terms and of thread states such as
<link linkend="threads.glossary.thread-state">blocked</link>.</para>
</purpose>
<description>
<para>A <link linkend="threads.glossary.thread">thread of execution</link>
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 <classname>thread</classname> object's constructor.</para>
<para>A thread of execution is said to be &quot;finished&quot;
or to have &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.</para>
<para>A thread object has an associated state which is either
&quot;joinable&quot; or &quot;non-joinable&quot;.</para>
<para>Except as described below, the policy used by an implementation
of &Boost.Threads; to schedule transitions between thread states is
unspecified.</para>
<para><note>Just as the lifetime of a file may be different from the
lifetime of an <code>iostream</code> object which represents the file, the lifetime
of a thread of execution may be different from the
<classname>thread</classname> 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
<classname>thread</classname> object continues to exist until the
end of its normal lifetime. The converse is also possible; if
a <classname>thread</classname> object is destroyed without
<code>join()</code> first having been called, the thread of execution
continues until its initial function completes.</note></para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<constructor>
<effects>Constructs a <classname>thread</classname> object
representing the current thread of execution.</effects>
<postconditions><code>*this</code> is non-joinable.</postconditions>
<notes><emphasis role="bold">Danger:</emphasis>
<code>*this</code> is valid only within the current thread.</notes>
</constructor>
<constructor specifiers="explicit">
<parameter name="threadfunc">
<paramtype>const boost::function0&lt;void&gt;&amp;</paramtype>
</parameter>
<effects>
Starts a new thread of execution and constructs a
<classname>thread</classname> 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.
</effects>
<postconditions><code>*this</code> is joinable.</postconditions>
<throws><code>boost::thread_resource_error</code> if a new thread
of execution cannot be started.</throws>
</constructor>
<destructor>
<effects>Destroys <code>*this</code>. The actual thread of
execution may continue to execute after the
<classname>thread</classname> object has been destroyed.
</effects>
<notes>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 <classname>thread</classname> object is destroyed, call
<code>join()</code>.</notes>
</destructor>
<method-group name="comparison">
<method name="operator==" cv="const">
<type>bool</type>
<parameter name="rhs">
<type>const thread&amp;</type>
</parameter>
<requires>The thread is non-terminated or <code>*this</code>
is joinable.</requires>
<returns><code>true</code> if <code>*this</code> and
<code>rhs</code> represent the same thread of
execution.</returns>
</method>
<method name="operator!=" cv="const">
<type>bool</type>
<parameter name="rhs">
<type>const thread&amp;</type>
</parameter>
<requires>The thread is non-terminated or <code>*this</code>
is joinable.</requires>
<returns><code>!(*this==rhs)</code>.</returns>
</method>
</method-group>
<method-group name="modifier">
<method name="join">
<type>void</type>
<requires><code>*this</code> is joinable.</requires>
<effects>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.</effects>
<postcondition><code>*this</code> is non-joinable.</postcondition>
<notes>If <code>*this == thread()</code> the result is
implementation-defined. If the implementation doesn't
detect this the result will be
<link linkend="threads.glossary.deadlock">deadlock</link>.
</notes>
</method>
</method-group>
<method-group name="static">
<method name="sleep" specifiers="static">
<type>void</type>
<parameter name="xt">
<paramtype>const <classname>xtime</classname>&amp;</paramtype>
</parameter>
<effects>The current thread of execution blocks until
<code>xt</code> is reached.</effects>
</method>
<method name="yield" specifiers="static">
<type>void</type>
<effects>The current thread of execution is placed in the
<link linkend="threads.glossary.thread-state">ready</link>
state.</effects>
<notes>
<simpara>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.</simpara>
</notes>
</method>
</method-group>
</class>
<class name="thread_group">
<purpose>
The <classname>thread_group</classname> class provides a container
for easy grouping of threads to simplify several common thread
creation and management idioms.
</purpose>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<constructor>
<effects>Constructs an empty <classname>thread_group</classname>
container.</effects>
</constructor>
<destructor>
<effects>Destroys each contained thread object. Destroys <code>*this</code>.</effects>
<notes>Behavior is undefined if another thread references
<code>*this </code> during the execution of the destructor.
</notes>
</destructor>
<method-group name="modifier">
<method name="create_thread">
<type><classname>thread</classname>*</type>
<parameter name="threadfunc">
<paramtype>const boost::function0&lt;void&gt;&amp;</paramtype>
</parameter>
<effects>Creates a new <classname>thread</classname> object
that executes <code>threadfunc</code> and adds it to the
<code>thread_group</code> container object's list of managed
<classname>thread</classname> objects.</effects>
<returns>Pointer to the newly created
<classname>thread</classname> object.</returns>
</method>
<method name="add_thread">
<type>void</type>
<parameter name="thrd">
<paramtype><classname>thread</classname>* thrd</paramtype>
</parameter>
<effects>Adds <code>thrd</code> to the
<classname>thread_group</classname> object's list of managed
<classname>thread</classname> objects. The <code>thrd</code>
object must have been allocated via <code>operator new</code> and will
be deleted when the group is destroyed.</effects>
</method>
<method name="remove_thread">
<type>void</type>
<parameter name="thrd">
<paramtype><classname>thread</classname>* thrd</paramtype>
</parameter>
<effects>Removes <code>thread</code> from <code>*this</code>'s
list of managed <classname>thread</classname> objects.</effects>
<throws><emphasis role="bold">???</emphasis> if
<code>thrd</code> is not in <code>*this</code>'s list
of managed <classname>thread</classname> objects.</throws>
</method>
<method name="join_all">
<type>void</type>
<effects>Calls <code>join()</code> on each of the managed
<classname>thread</classname> objects.</effects>
</method>
</method-group>
</class>
</namespace>
</header>

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@@ -1,323 +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 - &lt;boost/thread.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.hpp">boost/thread.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">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>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>
<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.
{
public:
thread();
explicit thread(const boost::function0&lt;void&gt;&amp; threadfunc);
~thread();
bool operator==(const thread&amp; rhs) const;
bool operator!=(const thread&amp; rhs) const;
void join();
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>
<pre>
thread_group();
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> Constructs an empty <code>thread_group</code> container.</dt>
</dl>
<pre>
~thread_group();
</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>
<pre>
thread* create_thread(const boost::function0&lt;void&gt;&amp; threadfunc);
</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>
<pre>
void add_thread(thread* thrd);
</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>
<pre>
Void remove_thread(thread* thrd);
</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>
<pre>
Void join_all();
</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>
<pre>
<a name="function-spec"></a>{{function}}
</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>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>
<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>

54
doc/thread.xml Normal file
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@@ -0,0 +1,54 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<library name="Threads" dirname="thread" id="threads"
last-revision="$Date$"
xmlns:xi="http://www.w3.org/2001/XInclude">
<libraryinfo>
<author>
<firstname>William</firstname>
<othername>E.</othername>
<surname>Kempf</surname>
</author>
<copyright>
<year>2001</year>
<year>2002</year>
<year>2003</year>
<holder>William E. Kempf</holder>
</copyright>
<legalnotice>
<para>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.</para>
</legalnotice>
<librarypurpose>Portable C++ multi-threading</librarypurpose>
<librarycategory name="category:concurrent" />
<title>Boost.Threads</title>
</libraryinfo>
<title>&Boost.Threads;</title>
<xi:include href="overview.xml"/>
<xi:include href="design.xml"/>
<xi:include href="concepts.xml"/>
<xi:include href="rationale.xml"/>
<xi:include href="reference.xml"/>
<xi:include href="faq.xml"/>
<xi:include href="configuration.xml"/>
<xi:include href="build.xml"/>
<xi:include href="implementation_notes.xml"/>
<xi:include href="release_notes.xml"/>
<xi:include href="glossary.xml"/>
<xi:include href="acknowledgements.xml"/>
<xi:include href="bibliography.xml"/>
</library>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/thread_pool.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="thread_pool">
</class>
</namespace>
</header>

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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>
</body>
</html>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/tss.hpp"
last-revision="$Date$">
<namespace name="boost">
<class name="thread_specific_ptr">
<purpose>
The <classname>thread_specific_ptr</classname> class defines
an interface for using thread specific storage.
</purpose>
<description>
<para>Thread specific storage is data associated with
individual threads and is often used to make operations
that rely on global data
<link linkend="threads.glossary.thread-safe">thread-safe</link>.
</para>
<para>Template <classname>thread_specific_ptr</classname>
stores a pointer to an object obtained 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
<classname>thread_specific_ptr</classname>s, and for the
initial thread are called by the destructor, providing the
same ordering guarantees as for normal declarations. Each
thread initially stores the null pointer in each
<classname>thread_specific_ptr</classname> instance.</para>
<para>The template <classname>thread_specific_ptr</classname>
is useful in the following cases:
<itemizedlist>
<listitem>An interface was originally written assuming
a single thread of control and it is being ported to a
multithreaded environment.</listitem>
<listitem>Each thread of control invokes sequences of
methods that share data that are physically unique
for each thread, but must be logically accessed
through a globally visible access point instead of
being explicitly passed.</listitem>
</itemizedlist>
</para>
</description>
<inherit access="private">
<type><classname>boost::noncopyable</classname></type>
<purpose>Exposition only</purpose>
</inherit>
<constructor>
<requires>The expression <code>delete get()</code> is well
formed.</requires>
<effects>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. 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.</effects>
<throws><classname>boost::thread_resource_error</classname> if
the necessary resources can not be obtained.</throws>
<notes>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.</notes>
<rationale>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.</rationale>
</constructor>
<constructor>
<parameter name="cleanup">
<paramtype>void (*cleanup)(void*)</paramtype>
</parameter>
<effects>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. 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.</effects>
<throws><classname>boost::thread_resource_error</classname> if
the necessary resources can not be obtained.</throws>
<notes>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.</notes>
<rationale>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.
</rationale>
</constructor>
<destructor>
<effects>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.</effects>
<notes>Does not destroy any data that may be stored in any
thread's thread specific storage. For this reason you should
not destroy a <classname>thread_specific_ptr</classname> object
until you are certain there are no threads running that have
made use of its thread specific storage.</notes>
<rationale>Associated data is not cleaned up because registered
cleanup methods need to be run in the thread that allocated the
associated data to be guarranteed 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.
</rationale>
</destructor>
<method-group name="modifier functions">
<method name="release">
<type>T*</type>
<postconditions><code>*this</code> holds the null pointer
for the current thread.</postconditions>
<returns><code>this-&gt;get()</code> prior to the call.</returns>
<rationale>This method provides a mechanism for the user to
relinquish control of the data associated with the
thread-specific key.</rationale>
</method>
<method name="reset">
<type>void</type>
<parameter name="p">
<paramtype>T*</paramtype>
<default>0</default>
</parameter>
<effects>If <code>this-&gt;get() != p &amp;&amp;
this-&gt;get() != NULL</code> then call the
associated cleanup function.</effects>
<postconditions><code>*this</code> holds the pointer
<code>p</code> for the current thread.</postconditions>
</method>
</method-group>
<method-group name="observer functions">
<method name="get" cv="const">
<type>T*</type>
<returns>The object stored in thread specific storage for
the current thread for <code>*this</code>.</returns>
<notes>Each thread initially returns 0.</notes>
</method>
<method name="operator-&gt;" cv="const">
<type>T*</type>
<returns><code>this-&gt;get()</code>.</returns>
</method>
<method name="operator*()" cv="const">
<type>T&amp;</type>
<requires><code>this-&gt;get() != 0</code></requires>
<returns><code>this-&gt;get()</code>.</returns>
</method>
</method-group>
</class>
</namespace>
</header>

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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 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 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>Postconditions:</b> A thread specific storage has been reserved for use
by <code>*this</code> in all threads, with each thread initially storing a
null pointer.</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 is an implementation specific limit to the number of
thread specific storage objects that can be created, and this limit may be
small.</dt>
</dl>
<pre>
~thread_specific_ptr();
</pre>
<dl class="function-semantics">
<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>
</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>
</dl>
<pre>
void reset(T* p=0);
</pre>
<dl class="function-semantics">
<dt><b>Effects:</b> If <code>this-&gt;get()!= p</code> then <code>delete this-&gt;get()</code>.
</dt>
<dt><b>Postconditions:</b> <code>*this</code> holds the pointer <code> p</code>
for the current thread.</dt>
<dt><b>Note:</b> The pointer will be deleted when the thread terminates.</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-&lt;get()</code>.</dt>
</dl>
<pre>
T& operator*() const;
</pre>
<dl class="function-semantics">
<dt><b>Requires:</b> <code>this-&lt;get() != 0</code></dt>
<dt><b>Returns:</b> <code>this-&lt;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>

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
"http://www.boost.org/tools/boostbook/dtd/boostbook.dtd" [
<!ENTITY % threads.entities SYSTEM "entities.xml">
%threads.entities;
]>
<header name="boost/thread/xtime.hpp"
last-revision="$Date$">
<namespace name="boost">
<enum name="xtime_clock_types">
<enumvalue name="TIME_UTC" />
<purpose>
<para>Specifies the clock type to use when creating
an object of type <classname>xtime</classname>.</para>
</purpose>
<description>
<para>The only clock type supported by &Boost.Threads; is
<code>TIME_UTC</code>. The epoch for <code>TIME_UTC</code>
is 1970-01-01 00:00:00.</para>
</description>
</enum>
<struct name="xtime">
<purpose>
<simpara>An object of type <classname>xtime</classname>
defines a time that is 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.</simpara>
</purpose>
<description>
<simpara>The <classname>xtime</classname> 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. &Boost.Threads; provides only a very minimal implementation of this
proposal; it is expected that a full implementation (or some other time
library) will be provided in Boost as a separate library, at which time &Boost.Threads;
will deprecate its own implementation.</simpara>
<simpara><emphasis role="bold">Note</emphasis> that 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.</simpara>
</description>
<free-function-group name="creation">
<function name="xtime_get">
<type>int</type>
<parameter name="xtp">
<paramtype><classname>xtime</classname>*</paramtype>
</parameter>
<parameter name="clock_type">
<paramtype>int</paramtype>
</parameter>
<postconditions>
<simpara><code>xtp</code> represents the current point in
time as a duration since the epoch specified by
<code>clock_type</code>.</simpara>
</postconditions>
<returns>
<simpara><code>clock_type</code> if successful, otherwise 0.</simpara>
</returns>
</function>
</free-function-group>
<data-member name="sec">
<type><emphasis>platform-specific-type</emphasis></type>
</data-member>
</struct>
</namespace>
</header>

View File

@@ -1,110 +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/xtime.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/xtime.hpp">boost/thread/xtime.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="#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>
enum
{
TIME_UTC
}
</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>
<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

@@ -1,7 +1,25 @@
# (C) Copyright William E. Kempf 2001. Permission to copy, use, modify, sell and
# 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.
# Copyright (C) 2001-2003
# 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.
#
# Boost.Threads example Jamfile
#
# 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"
# Declare the location of this subproject relative to the root.
subproject libs/thread/example ;
@@ -9,28 +27,28 @@ 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 ;
import ../build/threads ;
template example
## sources ##
: <template>thread_base
<dll>../build/boost_thread
$(threadmon)
## requirements ##
:
## default build ##
: release <runtime-link>dynamic
;
{
template example
## sources ##
: <template>thread_base
<dll>../build/boost_thread
## requirements ##
:
## default build ##
:
;
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 ;
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 ;
}

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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 <iostream>
#include <vector>
#include <boost/utility.hpp>
@@ -43,9 +54,9 @@ bounded_buffer buf(2);
void sender() {
int n = 0;
while (n < 100) {
buf.send(n);
std::cout << "sent: " << n << std::endl;
++n;
buf.send(n);
std::cout << "sent: " << n << std::endl;
++n;
}
buf.send(-1);
}
@@ -53,8 +64,8 @@ void sender() {
void receiver() {
int n;
do {
n = buf.receive();
std::cout << "received: " << n << std::endl;
n = buf.receive();
std::cout << "received: " << n << std::endl;
} while (n != -1); // -1 indicates end of buffer
}

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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 <vector>
#include <iostream>
#include <boost/thread/condition.hpp>
@@ -6,9 +17,9 @@
#include <boost/thread/thread.hpp>
namespace {
const int ITERS = 100;
boost::mutex io_mutex;
}
const int ITERS = 100;
boost::mutex io_mutex;
} // namespace
template <typename M>
class buffer_t

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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/mutex.hpp>
#include <boost/thread/thread.hpp>
#include <iostream>

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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/thread.hpp>
#include <boost/thread/once.hpp>
#include <cassert>
@@ -12,14 +23,14 @@ void init()
void thread_proc()
{
boost::call_once(&init, once);
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);
boost::thread_group threads;
for (int i=0; i<5; ++i)
threads.create_thread(&thread_proc);
threads.join_all();
assert(value == 1);
}

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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/recursive_mutex.hpp>
#include <boost/thread/thread.hpp>
#include <iostream>

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
@@ -7,7 +18,7 @@
namespace
{
boost::mutex iomx;
boost::mutex iomx;
}
class canteen
@@ -39,8 +50,9 @@ public:
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;
std::cout << "(" << clock()
<< ") Chef: ouch ... make room ... this dish is "
<< "very hot ..." << std::endl;
}
boost::xtime xt;
boost::xtime_get(&xt, boost::TIME_UTC);
@@ -84,7 +96,7 @@ void chef()
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Chef: " << chickens
<< " chickens, ready-to-go ..." << std::endl;
<< " chickens, ready-to-go ..." << std::endl;
}
g_canteen.put(chickens);
}
@@ -96,7 +108,8 @@ struct phil
void run() {
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id << ": starting ..." << std::endl;
std::cout << "(" << clock() << ") Phil" << m_id
<< ": starting ..." << std::endl;
}
for (;;)
{
@@ -110,13 +123,13 @@ struct phil
{
boost::mutex::scoped_lock lock(iomx);
std::cout << "(" << clock() << ") Phil" << m_id
<< ": gotta eat ..." << std::endl;
<< ": 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;
<< ": mmm ... that's good ..." << std::endl;
}
}
}
@@ -129,7 +142,10 @@ struct phil
struct thread_adapt
{
thread_adapt(void (*func)(void*), void* param) : _func(func), _param(param) { }
thread_adapt(void (*func)(void*), void* param)
: _func(func), _param(param)
{
}
int operator()() const
{
_func(_param);
@@ -143,7 +159,10 @@ struct thread_adapt
class thread_adapter
{
public:
thread_adapter(void (*func)(void*), void* param) : _func(func), _param(param) { }
thread_adapter(void (*func)(void*), void* param)
: _func(func), _param(param)
{
}
void operator()() const { _func(_param); }
private:
void (*_func)(void*);

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/thread.hpp>
@@ -49,7 +60,10 @@ void player(void* param)
{
cond.wait(lock);
if (state == other)
std::cout << "---" << player_name(active) << ": Spurious wakeup!" << std::endl;
{
std::cout << "---" << player_name(active)
<< ": Spurious wakeup!" << std::endl;
}
} while (state == other);
}
@@ -60,7 +74,10 @@ void player(void* param)
struct thread_adapt
{
thread_adapt(void (*func)(void*), void* param) : _func(func), _param(param) { }
thread_adapt(void (*func)(void*), void* param)
: _func(func), _param(param)
{
}
int operator()() const
{
_func(_param);
@@ -74,7 +91,10 @@ struct thread_adapt
class thread_adapter
{
public:
thread_adapter(void (*func)(void*), void* param) : _func(func), _param(param) { }
thread_adapter(void (*func)(void*), void* param)
: _func(func), _param(param)
{
}
void operator()() const { _func(_param); }
private:
void (*_func)(void*);

View File

@@ -1,29 +1,40 @@
// Copyright (C) 2001-2003
// 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/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;
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);
boost::thread::sleep(xt);
std::cout << "alarm sounded..." << std::endl;
}
std::cout << "alarm sounded..." << std::endl;
}
int m_secs;
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();
int secs = 5;
std::cout << "setting alarm for 5 seconds..." << std::endl;
thread_alarm alarm(secs);
boost::thread thrd(alarm);
thrd.join();
}

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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/thread.hpp>
#include <iostream>
@@ -6,14 +17,14 @@ boost::mutex mutex;
void increment_count()
{
boost::mutex::scoped_lock lock(mutex);
std::cout << "count = " << ++count << std::endl;
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();
boost::thread_group threads;
for (int i = 0; i < 10; ++i)
threads.create_thread(&increment_count);
threads.join_all();
}

View File

@@ -1,3 +1,14 @@
// Copyright (C) 2001-2003
// 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/thread.hpp>
#include <boost/thread/tss.hpp>
#include <cassert>
@@ -6,25 +17,25 @@ boost::thread_specific_ptr<int> value;
void increment()
{
int* p = value.get();
++*p;
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);
}
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();
boost::thread_group threads;
for (int i=0; i<5; ++i)
threads.create_thread(&thread_proc);
threads.join_all();
}

View File

@@ -1,10 +1,21 @@
// Copyright (C) 2001-2003
// 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/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
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 +1,40 @@
// Copyright (C) 2002-2003
// 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/detail/config.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
namespace boost {
class BOOST_THREAD_DECL 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

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,15 +12,11 @@
#ifndef BOOST_CONDITION_WEK070601_HPP
#define BOOST_CONDITION_WEK070601_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/thread/detail/config.hpp>
#include <boost/thread/exceptions.hpp>
#include <boost/utility.hpp>
#include <boost/thread/detail/lock.hpp>
#include <boost/thread/detail/config.hpp>
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
@@ -143,9 +139,9 @@ private:
typedef detail::thread::lock_ops<M>
#if defined(__HP_aCC) && __HP_aCC <= 33900 && !defined(BOOST_STRICT_CONFIG)
# define lock_ops lock_ops_ // HP confuses lock_ops witht the template
#endif
#endif
lock_ops;
typename lock_ops::lock_state state;
lock_ops::unlock(mutex, state);
@@ -169,9 +165,9 @@ private:
typedef detail::thread::lock_ops<M>
#if defined(__HP_aCC) && __HP_aCC <= 33900 && !defined(BOOST_STRICT_CONFIG)
# define lock_ops lock_ops_ // HP confuses lock_ops witht the template
#endif
#endif
lock_ops;
typename lock_ops::lock_state state;
lock_ops::unlock(mutex, state);

View File

@@ -1,14 +1,60 @@
// Copyright (C) 2001-2003
// 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_THREAD_CONFIG_WEK01032003_HPP
#define BOOST_THREAD_CONFIG_WEK01032003_HPP
#include <boost/config.hpp>
// insist on threading support being available:
#include <boost/config/requires_threads.hpp>
#if defined(BOOST_HAS_WINTHREADS)
# if defined(BOOST_THREAD_BUILD_DLL)
# if defined(BOOST_THREAD_BUILD_DLL) //Build dll
# define BOOST_THREAD_DECL __declspec(dllexport)
# else
# elif defined(BOOST_THREAD_BUILD_LIB) //Build lib
# define BOOST_THREAD_DECL
# elif defined(BOOST_THREAD_USE_LIB) //Use lib
# define BOOST_THREAD_DECL
# else //Use dll
# define BOOST_THREAD_DECL __declspec(dllimport)
# define BOOST_DYN_LINK
# endif
#else
# define BOOST_THREAD_DECL
#endif // BOOST_THREAD_SHARED_LIB
# if defined(BOOST_THREAD_USE_LIB) //Use lib
# else //Use dll
# define BOOST_DYN_LINK
# endif
#endif // BOOST_HAS_WINTHREADS
//
// Automatically link to the correct build variant where possible.
//
#if !defined(BOOST_ALL_NO_LIB) && !defined(BOOST_THREAD_NO_LIB) && !defined(BOOST_THREAD_BUILD_DLL) && !defined(BOOST_THREAD_BUILD_LIB)
//
// Set the name of our library, this will get undef'ed by auto_link.hpp
// once it's done with it:
//
#if defined(BOOST_THREAD_LIB_NAME)
# define BOOST_LIB_NAME BOOST_THREAD_LIB_NAME
#else
# define BOOST_LIB_NAME boost_thread
#endif
//
// If we're importing code from a dll, then tell auto_link.hpp about it:
//
// And include the header that does the work:
//
#include <boost/config/auto_link.hpp>
#endif // auto-linking disabled
#endif // BOOST_THREAD_CONFIG_WEK1032003_HPP

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
@@ -14,31 +14,30 @@
#ifndef BOOST_FORCE_CAST_MJM012402_HPP
#define BOOST_FORCE_CAST_MJM012402_HPP
#include <boost/thread/detail/config.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)); }
{
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)); }
{
return(*reinterpret_cast<const Return_Type *>(&rSrc));
}
} // namespace thread
} // namespace detail
} // namespace boost
#endif // BOOST_FORCE_CAST_MJM012402_HPP

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,6 +12,8 @@
#ifndef BOOST_XLOCK_WEK070601_HPP
#define BOOST_XLOCK_WEK070601_HPP
#include <boost/thread/detail/config.hpp>
#include <boost/utility.hpp>
#include <boost/thread/exceptions.hpp>
@@ -20,188 +22,193 @@ namespace boost {
class condition;
struct xtime;
namespace detail { namespace thread {
namespace detail { namespace thread {
template <typename Mutex>
class lock_ops : private noncopyable
template <typename Mutex>
class lock_ops : private noncopyable
{
private:
lock_ops() { }
public:
typedef typename Mutex::cv_state lock_state;
static void lock(Mutex& m)
{
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
m.do_lock();
}
static bool trylock(Mutex& m)
{
public:
typedef Mutex mutex_type;
explicit scoped_lock(Mutex& mx, bool initially_locked=true)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<Mutex>::lock(m_mutex);
m_locked = true;
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<Mutex>::unlock(m_mutex);
m_locked = false;
}
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;
};
template <typename TryMutex>
class scoped_try_lock : private noncopyable
return m.do_trylock();
}
static bool timedlock(Mutex& m, const xtime& xt)
{
public:
typedef TryMutex mutex_type;
explicit scoped_try_lock(TryMutex& mx)
: m_mutex(mx), m_locked(false)
{
try_lock();
}
scoped_try_lock(TryMutex& mx, bool initially_locked)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_try_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<TryMutex>::lock(m_mutex);
m_locked = true;
}
bool try_lock()
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TryMutex>::trylock(m_mutex));
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<TryMutex>::unlock(m_mutex);
m_locked = false;
}
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;
};
template <typename TimedMutex>
class scoped_timed_lock : private noncopyable
return m.do_timedlock(xt);
}
static void unlock(Mutex& m)
{
public:
typedef TimedMutex mutex_type;
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);
}
};
scoped_timed_lock(TimedMutex& mx, const xtime& xt)
: m_mutex(mx), m_locked(false)
{
timed_lock(xt);
}
scoped_timed_lock(TimedMutex& mx, bool initially_locked)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_timed_lock()
{
if (m_locked) unlock();
}
template <typename Mutex>
class scoped_lock : private noncopyable
{
public:
typedef Mutex mutex_type;
void lock()
{
if (m_locked) throw lock_error();
lock_ops<TimedMutex>::lock(m_mutex);
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));
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<TimedMutex>::unlock(m_mutex);
m_locked = false;
}
explicit scoped_lock(Mutex& mx, bool initially_locked=true)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_lock()
{
if (m_locked) unlock();
}
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
void lock()
{
if (m_locked) throw lock_error();
lock_ops<Mutex>::lock(m_mutex);
m_locked = true;
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<Mutex>::unlock(m_mutex);
m_locked = false;
}
private:
friend class boost::condition;
bool locked() const { return m_locked; }
operator const void*() const { return m_locked ? this : 0; }
TimedMutex& m_mutex;
bool m_locked;
};
private:
friend class boost::condition;
} // namespace thread
} // namespace detail
Mutex& m_mutex;
bool m_locked;
};
template <typename TryMutex>
class scoped_try_lock : private noncopyable
{
public:
typedef TryMutex mutex_type;
explicit scoped_try_lock(TryMutex& mx)
: m_mutex(mx), m_locked(false)
{
try_lock();
}
scoped_try_lock(TryMutex& mx, bool initially_locked)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_try_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<TryMutex>::lock(m_mutex);
m_locked = true;
}
bool try_lock()
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TryMutex>::trylock(m_mutex));
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<TryMutex>::unlock(m_mutex);
m_locked = false;
}
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;
};
template <typename TimedMutex>
class scoped_timed_lock : private noncopyable
{
public:
typedef TimedMutex mutex_type;
scoped_timed_lock(TimedMutex& mx, const xtime& xt)
: m_mutex(mx), m_locked(false)
{
timed_lock(xt);
}
scoped_timed_lock(TimedMutex& mx, bool initially_locked)
: m_mutex(mx), m_locked(false)
{
if (initially_locked) lock();
}
~scoped_timed_lock()
{
if (m_locked) unlock();
}
void lock()
{
if (m_locked) throw lock_error();
lock_ops<TimedMutex>::lock(m_mutex);
m_locked = true;
}
bool try_lock()
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TimedMutex>::trylock(m_mutex));
}
bool timed_lock(const xtime& xt)
{
if (m_locked) throw lock_error();
return (m_locked = lock_ops<TimedMutex>::timedlock(m_mutex, xt));
}
void unlock()
{
if (!m_locked) throw lock_error();
lock_ops<TimedMutex>::unlock(m_mutex);
m_locked = false;
}
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;
};
} // namespace thread
} // namespace detail
} // namespace boost
#endif // BOOST_XLOCK_WEK070601_HPP
// Change Log:
// 8 Feb 01 WEKEMPF Initial version.
// 22 May 01 WEKEMPF Modified to use xtime for time outs.
// 30 Jul 01 WEKEMPF Moved lock types into boost::detail::thread. Renamed some types.
// Added locked() methods.
#endif // BOOST_XLOCK_WEK070601_HPP
// 30 Jul 01 WEKEMPF Moved lock types into boost::detail::thread. Renamed
// some types. Added locked() methods.

View File

@@ -0,0 +1,38 @@
// Copyright (C) 2001-2003
// 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_NAMED_WEK031703_HPP
#define BOOST_NAMED_WEK031703_HPP
#include <boost/thread/detail/config.hpp>
namespace boost {
namespace detail {
class named_object
{
protected:
named_object(const char* name=0);
~named_object();
public:
const char* name() const;
const char* effective_name() const;
protected:
char* m_name;
char* m_ename;
};
} // namespace detail
} // namespace boost
#endif // BOOST_NAMED_WEK031703_HPP

File diff suppressed because it is too large Load Diff

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@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// Mac Murrett
//
// Permission to use, copy, modify, distribute and sell this software
@@ -14,51 +14,50 @@
#ifndef BOOST_SINGLETON_MJM012402_HPP
#define BOOST_SINGLETON_MJM012402_HPP
#include <boost/thread/detail/config.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.
// 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
template <class T>
class singleton : private T
{
private:
private:
singleton();
~singleton();
public:
public:
static T &instance();
};
template<class T>
template <class T>
inline singleton<T>::singleton()
{ /* no-op */ }
{
/* no-op */
}
template<class T>
template <class T>
inline singleton<T>::~singleton()
{ /* no-op */ }
{
/* no-op */
}
template<class T>
template <class T>
/*static*/ T &singleton<T>::instance()
{
// function-local static to force this to work correctly at static initialization
// time.
// 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

@@ -1,14 +1,35 @@
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
// Copyright (C) 2001-2003
// 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_THREADMON_WEK062504_HPP
#define BOOST_THREADMON_WEK062504_HPP
#include <boost/thread/detail/config.hpp>
#ifdef BOOST_HAS_WINTHREADS
#include <boost/thread/detail/config.hpp>
extern "C" BOOST_THREAD_DECL int at_thread_exit(void (__cdecl * func)(void));
//Add a function to the list of thread-exit functions
extern "C" BOOST_THREAD_DECL int on_thread_exit(void (__cdecl * func)(void));
extern "C" BOOST_THREAD_DECL void on_process_enter(void);
//To be called when the process starts, when the dll is loaded, etc.
//Called automatically by Boost.Thread when possible
extern "C" BOOST_THREAD_DECL void on_thread_exit(void);
//To be called for each thread when it exits
//Must be called in the context of the thread that is exiting
//Called automatically by Boost.Thread when possible
extern "C" BOOST_THREAD_DECL void on_process_exit(void);
//To be called when the process exits, when the dll is unloaded, etc.
//Called automatically by Boost.Thread when possible
#endif // BOOST_HAS_WINTHREADS
#endif // BOOST_THREADMON_WEK062504_HPP

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,7 +12,6 @@
#ifndef BOOST_THREAD_EXCEPTIONS_PDM070801_H
#define BOOST_THREAD_EXCEPTIONS_PDM070801_H
#include <boost/config.hpp>
#include <boost/thread/detail/config.hpp>
// pdm: Sorry, but this class is used all over the place & I end up
@@ -25,21 +24,77 @@
namespace boost {
class BOOST_THREAD_DECL lock_error : public std::logic_error
class BOOST_THREAD_DECL thread_exception : public std::exception
{
protected:
thread_exception();
thread_exception(int sys_err_code);
public:
~thread_exception() throw();
int native_error() const { return m_sys_err; }
const char* message() const;
private:
int m_sys_err;
};
class BOOST_THREAD_DECL lock_error : public thread_exception
{
public:
lock_error();
lock_error(int sys_err_code);
~lock_error() throw();
virtual const char* what() const throw();
};
class BOOST_THREAD_DECL thread_resource_error : public std::runtime_error
class BOOST_THREAD_DECL thread_resource_error : public thread_exception
{
public:
thread_resource_error();
thread_resource_error(int sys_err_code);
~thread_resource_error() throw();
virtual const char* what() const throw();
};
class BOOST_THREAD_DECL unsupported_thread_option : public thread_exception
{
public:
unsupported_thread_option();
unsupported_thread_option(int sys_err_code);
~unsupported_thread_option() throw();
virtual const char* what() const throw();
};
class BOOST_THREAD_DECL invalid_thread_argument : public thread_exception
{
public:
invalid_thread_argument();
invalid_thread_argument(int sys_err_code);
~invalid_thread_argument() throw();
virtual const char* what() const throw();
};
class BOOST_THREAD_DECL thread_permission_error : public thread_exception
{
public:
thread_permission_error();
thread_permission_error(int sys_err_code);
~thread_permission_error() throw();
virtual const char* what() const throw();
};
} // namespace boost
#endif // BOOST_THREAD_CONFIG_PDM070801_H
// Change log:
// 3 Jan 03 WEKEMPF Modified for DLL implementation.
#endif // BOOST_THREAD_CONFIG_PDM070801_H

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@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,14 +12,11 @@
#ifndef BOOST_MUTEX_WEK070601_HPP
#define BOOST_MUTEX_WEK070601_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/thread/detail/config.hpp>
#include <boost/utility.hpp>
#include <boost/thread/detail/lock.hpp>
#include <boost/thread/detail/config.hpp>
#include <boost/thread/detail/named.hpp>
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
@@ -33,14 +30,16 @@ namespace boost {
struct xtime;
class BOOST_THREAD_DECL mutex : private noncopyable
class BOOST_THREAD_DECL mutex
: private noncopyable
, public boost::detail::named_object
{
public:
friend class detail::thread::lock_ops<mutex>;
typedef detail::thread::scoped_lock<mutex> scoped_lock;
mutex();
mutex(const char* name=0);
~mutex();
private:
@@ -63,6 +62,7 @@ private:
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
bool m_critical_section;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
#elif defined(BOOST_HAS_MPTASKS)
@@ -71,7 +71,9 @@ private:
#endif
};
class BOOST_THREAD_DECL try_mutex : private noncopyable
class BOOST_THREAD_DECL try_mutex
: private noncopyable
, public boost::detail::named_object
{
public:
friend class detail::thread::lock_ops<try_mutex>;
@@ -79,7 +81,7 @@ public:
typedef detail::thread::scoped_lock<try_mutex> scoped_lock;
typedef detail::thread::scoped_try_lock<try_mutex> scoped_try_lock;
try_mutex();
try_mutex(const char* name=0);
~try_mutex();
private:
@@ -103,6 +105,7 @@ private:
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
bool m_critical_section;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
#elif defined(BOOST_HAS_MPTASKS)
@@ -111,7 +114,9 @@ private:
#endif
};
class BOOST_THREAD_DECL timed_mutex : private noncopyable
class BOOST_THREAD_DECL timed_mutex
: private noncopyable
, public boost::detail::named_object
{
public:
friend class detail::thread::lock_ops<timed_mutex>;
@@ -120,7 +125,7 @@ public:
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(const char* name=0);
~timed_mutex();
private:

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@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,11 +12,6 @@
#ifndef BOOST_ONCE_WEK080101_HPP
#define BOOST_ONCE_WEK080101_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/thread/detail/config.hpp>
#if defined(BOOST_HAS_PTHREADS)

View File

@@ -0,0 +1,271 @@
// Copyright (C) 2002-2003
// 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. 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_READ_WRITE_MUTEX_JDM030602_HPP
#define BOOST_READ_WRITE_MUTEX_JDM030602_HPP
#include <boost/thread/detail/config.hpp>
#include <boost/utility.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/detail/lock.hpp>
#include <boost/thread/detail/read_write_lock.hpp>
#include <boost/thread/condition.hpp>
namespace boost {
namespace read_write_scheduling_policy {
enum read_write_scheduling_policy_enum
{
writer_priority, //Prefer writers; can starve readers
reader_priority, //Prefer readers; can starve writers
alternating_many_reads, //Alternate readers and writers; before a writer, release all queued readers
alternating_single_read //Alternate readers and writers; before a writer, release only on queued reader
};
} // namespace read_write_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 read_write_mutex_impl
{
typedef Mutex mutex_type;
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;
read_write_mutex_impl(read_write_scheduling_policy::read_write_scheduling_policy_enum sp)
: m_num_waiting_writers(0),
m_num_waiting_readers(0),
m_num_readers_to_wake(0),
m_state_waiting_promotion(false),
m_state(0),
m_sp(sp),
m_readers_next(true) { }
Mutex m_prot;
boost::condition m_waiting_writers;
boost::condition m_waiting_readers;
int m_num_waiting_writers;
int m_num_waiting_readers;
int m_num_readers_to_wake;
boost::condition m_waiting_promotion;
bool m_state_waiting_promotion;
int m_state; // -1 = excl locked
// 0 = unlocked
// 1-> INT_MAX - shared locked
const read_write_scheduling_policy::read_write_scheduling_policy_enum m_sp;
bool m_readers_next;
void do_read_lock();
void do_write_lock();
void do_write_unlock();
void do_read_unlock();
bool do_try_write_lock();
bool do_try_read_lock();
bool do_timed_write_lock(const xtime &xt);
bool do_timed_read_lock(const xtime &xt);
void do_demote_to_read_lock();
bool do_try_demote_to_read_lock();
bool do_timed_demote_to_read_lock(const xtime &xt);
void do_promote_to_write_lock();
bool do_try_promote_to_write_lock();
bool do_timed_promote_to_write_lock(const xtime &xt);
bool locked();
read_write_lock_state::read_write_lock_state_enum state();
private:
void do_unlock_scheduling_impl();
void do_demote_scheduling_impl();
void do_scheduling_impl();
bool do_demote_to_read_lock_impl();
};
} // namespace detail
} // namespace thread
class BOOST_THREAD_DECL read_write_mutex : private noncopyable
{
public:
read_write_mutex(read_write_scheduling_policy::read_write_scheduling_policy_enum sp) : m_impl(sp) { }
~read_write_mutex() { }
read_write_scheduling_policy::read_write_scheduling_policy_enum policy() const { return m_impl.m_sp; }
friend class detail::thread::read_write_lock_ops<read_write_mutex>;
typedef detail::thread::scoped_read_write_lock<
read_write_mutex> scoped_read_write_lock;
typedef detail::thread::scoped_read_lock<
read_write_mutex> scoped_read_lock;
typedef detail::thread::scoped_write_lock<
read_write_mutex> scoped_write_lock;
private:
// Operations that will eventually be done only
// via lock types
void do_write_lock();
void do_read_lock();
void do_write_unlock();
void do_read_unlock();
void do_demote_to_read_lock();
void do_promote_to_write_lock();
bool locked();
read_write_lock_state::read_write_lock_state_enum state();
detail::thread::read_write_mutex_impl<mutex> m_impl;
};
class BOOST_THREAD_DECL try_read_write_mutex : private noncopyable
{
public:
try_read_write_mutex(read_write_scheduling_policy::read_write_scheduling_policy_enum sp) : m_impl(sp) { }
~try_read_write_mutex() { }
read_write_scheduling_policy::read_write_scheduling_policy_enum policy() const { return m_impl.m_sp; }
friend class detail::thread::read_write_lock_ops<try_read_write_mutex>;
typedef detail::thread::scoped_read_write_lock<
try_read_write_mutex> scoped_read_write_lock;
typedef detail::thread::scoped_try_read_write_lock<
try_read_write_mutex> scoped_try_read_write_lock;
typedef detail::thread::scoped_read_lock<
try_read_write_mutex> scoped_read_lock;
typedef detail::thread::scoped_try_read_lock<
try_read_write_mutex> scoped_try_read_lock;
typedef detail::thread::scoped_write_lock<
try_read_write_mutex> scoped_write_lock;
typedef detail::thread::scoped_try_write_lock<
try_read_write_mutex> scoped_try_write_lock;
private:
// Operations that will eventually be done only
// via lock types
void do_write_lock();
void do_read_lock();
void do_write_unlock();
void do_read_unlock();
bool do_try_write_lock();
bool do_try_read_lock();
void do_demote_to_read_lock();
bool do_try_demote_to_read_lock();
void do_promote_to_write_lock();
bool do_try_promote_to_write_lock();
bool locked();
read_write_lock_state::read_write_lock_state_enum state();
detail::thread::read_write_mutex_impl<try_mutex> m_impl;
};
class BOOST_THREAD_DECL timed_read_write_mutex : private noncopyable
{
public:
timed_read_write_mutex(read_write_scheduling_policy::read_write_scheduling_policy_enum sp) : m_impl(sp) { }
~timed_read_write_mutex() { }
read_write_scheduling_policy::read_write_scheduling_policy_enum policy() const { return m_impl.m_sp; }
friend class detail::thread::read_write_lock_ops<timed_read_write_mutex>;
typedef detail::thread::scoped_read_write_lock<
timed_read_write_mutex> scoped_read_write_lock;
typedef detail::thread::scoped_try_read_write_lock<
timed_read_write_mutex> scoped_try_read_write_lock;
typedef detail::thread::scoped_timed_read_write_lock<
timed_read_write_mutex> scoped_timed_read_write_lock;
typedef detail::thread::scoped_read_lock<
timed_read_write_mutex> scoped_read_lock;
typedef detail::thread::scoped_try_read_lock<
timed_read_write_mutex> scoped_try_read_lock;
typedef detail::thread::scoped_timed_read_lock<
timed_read_write_mutex> scoped_timed_read_lock;
typedef detail::thread::scoped_write_lock<
timed_read_write_mutex> scoped_write_lock;
typedef detail::thread::scoped_try_write_lock<
timed_read_write_mutex> scoped_try_write_lock;
typedef detail::thread::scoped_timed_write_lock<
timed_read_write_mutex> scoped_timed_write_lock;
private:
// Operations that will eventually be done only
// via lock types
void do_write_lock();
void do_read_lock();
void do_write_unlock();
void do_read_unlock();
bool do_try_write_lock();
bool do_try_read_lock();
bool do_timed_write_lock(const xtime &xt);
bool do_timed_read_lock(const xtime &xt);
void do_demote_to_read_lock();
bool do_try_demote_to_read_lock();
bool do_timed_demote_to_read_lock(const xtime &xt);
void do_promote_to_write_lock();
bool do_try_promote_to_write_lock();
bool do_timed_promote_to_write_lock(const xtime &xt);
bool locked();
read_write_lock_state::read_write_lock_state_enum state();
detail::thread::read_write_mutex_impl<timed_mutex> m_impl;
};
} // namespace boost
#endif
// Change Log:
// 10 Mar 02
// Original version.
// 4 May 04 GlassfordM
// Implement lock promotion and demotion.
// Add locked() and state() member functions for debugging
// (should these be made public?).
// Rename to improve consistency and eliminate abbreviations:
// Use "read" and "write" instead of "shared" and "exclusive".
// Change "rd" to "read", "wr" to "write", "rw" to "read_write".
// Add mutex_type typdef.

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,18 +12,17 @@
#ifndef BOOST_RECURSIVE_MUTEX_WEK070601_HPP
#define BOOST_RECURSIVE_MUTEX_WEK070601_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/thread/detail/config.hpp>
#include <boost/utility.hpp>
#include <boost/thread/detail/lock.hpp>
#include <boost/thread/detail/config.hpp>
#include <boost/thread/detail/named.hpp>
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
#elif defined(BOOST_HAS_MPTASKS)
#endif
#if defined(BOOST_HAS_MPTASKS)
# include "scoped_critical_region.hpp"
#endif
@@ -31,14 +30,16 @@ namespace boost {
struct xtime;
class BOOST_THREAD_DECL recursive_mutex : private noncopyable
class BOOST_THREAD_DECL recursive_mutex
: private noncopyable
, public boost::detail::named_object
{
public:
friend class detail::thread::lock_ops<recursive_mutex>;
typedef detail::thread::scoped_lock<recursive_mutex> scoped_lock;
recursive_mutex();
recursive_mutex(const char* name=0);
~recursive_mutex();
private:
@@ -58,6 +59,7 @@ private:
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
bool m_critical_section;
unsigned long m_count;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
@@ -74,15 +76,18 @@ private:
#endif
};
class BOOST_THREAD_DECL recursive_try_mutex : private noncopyable
class BOOST_THREAD_DECL recursive_try_mutex
: private noncopyable
, public boost::detail::named_object
{
public:
friend class detail::thread::lock_ops<recursive_try_mutex>;
typedef detail::thread::scoped_lock<recursive_try_mutex> scoped_lock;
typedef detail::thread::scoped_try_lock<recursive_try_mutex> scoped_try_lock;
typedef detail::thread::scoped_try_lock<
recursive_try_mutex> scoped_try_lock;
recursive_try_mutex();
recursive_try_mutex(const char* name=0);
~recursive_try_mutex();
private:
@@ -103,6 +108,7 @@ private:
#if defined(BOOST_HAS_WINTHREADS)
void* m_mutex;
bool m_critical_section;
unsigned long m_count;
#elif defined(BOOST_HAS_PTHREADS)
pthread_mutex_t m_mutex;
@@ -119,16 +125,20 @@ private:
#endif
};
class BOOST_THREAD_DECL recursive_timed_mutex : private noncopyable
class BOOST_THREAD_DECL recursive_timed_mutex
: private noncopyable
, public boost::detail::named_object
{
public:
friend class detail::thread::lock_ops<recursive_timed_mutex>;
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;
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(const char* name=0);
~recursive_timed_mutex();
private:
@@ -166,12 +176,11 @@ private:
} // namespace boost
#endif // BOOST_RECURSIVE_MUTEX_WEK070601_HPP
// Change Log:
// 8 Feb 01 WEKEMPF Initial version.
// 1 Jun 01 WEKEMPF Modified to use xtime for time outs. Factored out
// to three classes, mutex, try_mutex and timed_mutex.
// 11 Jun 01 WEKEMPF Modified to use PTHREAD_MUTEX_RECURSIVE if available.
// 3 Jan 03 WEKEMPF Modified for DLL implementation.
#endif // BOOST_RECURSIVE_MUTEX_WEK070601_HPP
// 3 Jan 03 WEKEMPF Modified for DLL implementation.

View File

@@ -0,0 +1,58 @@
// Copyright (C) 2002-2003
// 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/thread/detail/config.hpp>
#include <boost/utility.hpp>
#include <boost/function.hpp>
#include <boost/thread/exceptions.hpp>
#include <boost/thread/detail/named.hpp>
#include <string>
namespace boost {
class shared_memory : public boost::detail::named_object
{
public:
enum {
write=0x1,
create=0x2,
exclusive=0x4,
};
shared_memory(const char *name, std::size_t len, int flags);
shared_memory(const char *name, std::size_t len, int flags,
const boost::function1<void,void *>& initfunc);
~shared_memory();
void* get() const { return m_ptr; }
private:
void init(std::size_t len, int flags,
const boost::function1<void, void*>* initfunc);
void *m_ptr; // Pointer to shared memory block
#if defined(BOOST_HAS_WINTHREADS)
void* m_hmap;
#elif defined(BOOST_HAS_PTHREADS)
std::size_t m_len;
int m_hmap;
#endif
};
} // namespace boost
#endif

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,15 +12,11 @@
#ifndef BOOST_THREAD_WEK070601_HPP
#define BOOST_THREAD_WEK070601_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/thread/detail/config.hpp>
#include <boost/utility.hpp>
#include <boost/function.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/detail/config.hpp>
#include <iostream>
#include <list>
#include <memory>
@@ -35,56 +31,163 @@ namespace boost {
struct xtime;
class BOOST_THREAD_DECL thread : private noncopyable
class BOOST_THREAD_DECL thread_cancel
{
public:
thread_cancel();
~thread_cancel();
};
class BOOST_THREAD_DECL cancellation_guard
{
public:
cancellation_guard();
~cancellation_guard();
private:
void* m_handle;
};
#if defined(BOOST_HAS_WINTHREADS)
struct sched_param
{
int priority;
};
enum { sched_fifo, sched_round_robin, sched_other };
enum { scope_process, scope_system };
#elif defined(BOOST_HAS_PTHREADS)
using ::sched_param;
enum
{
sched_fifo = SCHED_FIFO,
sched_round_robin = SCHED_RR,
sched_other = SCHED_OTHER
};
enum
{
scope_process = PTHREAD_SCOPE_PROCESS,
scope_system = PTHREAD_SCOPE_SYSTEM
};
#endif
class BOOST_THREAD_DECL thread
{
public:
class BOOST_THREAD_DECL attributes
{
public:
attributes();
~attributes();
attributes& set_stack_size(size_t size);
size_t get_stack_size() const;
attributes& set_stack_address(void* addr);
void* get_stack_address() const;
attributes& inherit_scheduling(bool inherit);
bool inherit_scheduling() const;
attributes& set_schedule(int policy, const sched_param& param);
void get_schedule(int& policy, sched_param& param);
attributes& scope(int scope);
int scope() const;
private:
friend class thread;
#if defined(BOOST_HAS_WINTHREADS)
size_t m_stacksize;
bool m_schedinherit;
sched_param m_schedparam;
#elif defined(BOOST_HAS_PTHREADS)
pthread_attr_t m_attr;
#endif
};
thread();
explicit thread(const function0<void>& threadfunc);
explicit thread(const function0<void>& threadfunc,
const attributes& attr=attributes());
thread(const thread& other);
~thread();
thread& operator=(const thread& other);
bool operator==(const thread& other) const;
bool operator!=(const thread& other) const;
bool operator<(const thread& other) const;
void join();
bool timed_join(const xtime& xt);
void cancel();
bool cancelled() const;
void set_scheduling_parameter(int policy, const sched_param& param);
void get_scheduling_parameter(int& policy, sched_param& param) const;
static int max_priority(int policy);
static int min_priority(int policy);
static void test_cancel();
static void sleep(const xtime& xt);
static void yield();
private:
static const int stack_min;
#if defined(BOOST_HAS_WINTHREADS)
void* m_thread;
unsigned int m_id;
#elif defined(BOOST_HAS_PTHREADS)
private:
pthread_t m_thread;
#elif defined(BOOST_HAS_MPTASKS)
MPQueueID m_pJoinQueueID;
MPTaskID m_pTaskID;
typedef unsigned int id_type;
#else
typedef const void* id_type;
#endif
bool m_joinable;
id_type id() const;
private:
void* m_handle;
};
template <typename charT, typename Traits>
std::basic_ostream<charT, Traits>& operator<<(
std::basic_ostream<charT, Traits>& os, const thread& thrd)
{
if (!os.good()) return os;
typename std::basic_ostream<charT, Traits>::sentry opfx(os);
if (opfx)
os << thrd.id();
return os;
}
class BOOST_THREAD_DECL thread_group : private noncopyable
{
public:
thread_group();
~thread_group();
thread* create_thread(const function0<void>& threadfunc);
void add_thread(thread* thrd);
void remove_thread(thread* thrd);
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:
std::list<thread*> m_threads;
std::list<thread> m_threads;
mutex m_mutex;
};
} // namespace boost
#endif // BOOST_THREAD_WEK070601_HPP
// Change Log:
// 8 Feb 01 WEKEMPF Initial version.
// 1 Jun 01 WEKEMPF Added boost::thread initial implementation.
// 3 Jul 01 WEKEMPF Redesigned boost::thread to be noncopyable.
#endif // BOOST_THREAD_WEK070601_HPP

View File

@@ -0,0 +1,44 @@
// Copyright (C) 2002-2003
// 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.
// Derived loosely from work queue manager in "Programming POSIX Threads"
// by David Butenhof.
#ifndef BOOST_THREAD_POOL_JDM031802_HPP
#define BOOST_THREAD_POOL_JDM031802_HPP
#include <boost/thread/detail/config.hpp>
#include <boost/function.hpp>
#include <boost/limits.hpp>
namespace boost {
class BOOST_THREAD_DECL 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

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,13 +12,11 @@
#ifndef BOOST_TSS_WEK070601_HPP
#define BOOST_TSS_WEK070601_HPP
#include <boost/config.hpp>
#ifndef BOOST_HAS_THREADS
# error Thread support is unavailable!
#endif
#include <boost/thread/detail/config.hpp>
#include <boost/utility.hpp>
#include <boost/thread/detail/config.hpp>
#include <boost/function.hpp>
#include <boost/thread/exceptions.hpp>
#if defined(BOOST_HAS_PTHREADS)
# include <pthread.h>
@@ -28,55 +26,96 @@
namespace boost {
namespace detail {
class BOOST_THREAD_DECL tss : private noncopyable
namespace detail {
class BOOST_THREAD_DECL tss : private noncopyable
{
public:
tss(boost::function1<void, void*>* pcleanup) {
if (pcleanup == 0) throw boost::thread_resource_error();
try
{
public:
tss(void (*cleanup)(void*)=0);
~tss();
void* get() const;
bool set(void* value);
private:
#if defined(BOOST_HAS_WINTHREADS)
unsigned long m_key;
void (*m_cleanup)(void*);
#elif defined(BOOST_HAS_PTHREADS)
pthread_key_t m_key;
#elif defined(BOOST_HAS_MPTASKS)
TaskStorageIndex m_key;
void (*m_cleanup)(void*);
#endif
};
#if defined(BOOST_HAS_MPTASKS)
void thread_cleanup();
#endif
init(pcleanup);
}
catch (...)
{
delete pcleanup;
throw boost::thread_resource_error();
}
}
void* get() const;
void set(void* value);
void cleanup(void* p);
private:
unsigned int m_slot; //This is a "pseudo-slot", not a native slot
void init(boost::function1<void, void*>* pcleanup);
};
#if defined(BOOST_HAS_MPTASKS)
void thread_cleanup();
#endif
template <typename T>
struct tss_adapter
{
template <typename F>
tss_adapter(const F& cleanup) : m_cleanup(cleanup) { }
void operator()(void* p) { m_cleanup(static_cast<T*>(p)); }
boost::function1<void, T*> m_cleanup;
};
} // namespace detail
template <typename T>
class thread_specific_ptr : private noncopyable
{
public:
thread_specific_ptr() : m_tss(&thread_specific_ptr<T>::cleanup) { }
thread_specific_ptr()
: m_tss(new boost::function1<void, void*>(
boost::detail::tss_adapter<T>(
&thread_specific_ptr<T>::cleanup)))
{
}
thread_specific_ptr(void (*clean)(T*))
: m_tss(new boost::function1<void, void*>(
boost::detail::tss_adapter<T>(clean)))
{
}
~thread_specific_ptr() { reset(); }
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; delete cur; m_tss.set(p); }
T* release() { T* temp = get(); if (temp) 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);
}
private:
static void cleanup(void* p) { delete static_cast<T*>(p); }
mutable detail::tss m_tss;
static void cleanup(T* p) { delete p; }
detail::tss m_tss;
};
} // namespace boost
#endif //BOOST_TSS_WEK070601_HPP
// Change Log:
// 6 Jun 01 WEKEMPF Initial version.
#endif // BOOST_TSS_WEK070601_HPP
// 6 Jun 01
// WEKEMPF Initial version.
// 30 May 02 WEKEMPF
// Added interface to set specific cleanup handlers.
// Removed TLS slot limits from most implementations.
// 22 Mar 04 GlassfordM for WEKEMPF
// Fixed: thread_specific_ptr::reset() doesn't check error returned
// by tss::set(); tss::set() now throws if it fails.
// Fixed: calling thread_specific_ptr::reset() or
// thread_specific_ptr::release() causes double-delete: once on
// reset()/release() and once on ~thread_specific_ptr().

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -12,22 +12,22 @@
#ifndef BOOST_XTIME_WEK070601_HPP
#define BOOST_XTIME_WEK070601_HPP
#include <boost/config.hpp>
#include <boost/cstdint.hpp>
#include <boost/thread/detail/config.hpp>
#include <boost/cstdint.hpp>
namespace boost {
enum
enum xtime_clock_types
{
TIME_UTC=1,
TIME_TAI,
TIME_MONOTONIC,
TIME_PROCESS,
TIME_THREAD,
TIME_LOCAL,
TIME_SYNC,
TIME_RESOLUTION
TIME_UTC=1
// TIME_TAI,
// TIME_MONOTONIC,
// TIME_PROCESS,
// TIME_THREAD,
// TIME_LOCAL,
// TIME_SYNC,
// TIME_RESOLUTION
};
struct xtime

49
src/barrier.cpp Normal file
View File

@@ -0,0 +1,49 @@
// Copyright (C) 2002-2003
// 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/detail/config.hpp>
#include <boost/thread/barrier.hpp>
#include <boost/thread/thread.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;
}
boost::cancellation_guard guard;
while (gen == m_generation)
m_cond.wait(lock);
return false;
}
} // namespace boost

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -9,6 +9,8 @@
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/xtime.hpp>
#include <boost/thread/thread.hpp>
@@ -25,9 +27,9 @@
#elif defined(BOOST_HAS_PTHREADS)
# include <errno.h>
#elif defined(BOOST_HAS_MPTASKS)
# include <MacErrors.h>
# include "mac/init.hpp"
# include "mac/safe.hpp"
# include <MacErrors.h>
# include "mac/init.hpp"
# include "mac/safe.hpp"
#endif
namespace boost {
@@ -39,8 +41,8 @@ condition_impl::condition_impl()
: 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_queue = reinterpret_cast<void*>(
CreateSemaphore(0, 0, (std::numeric_limits<long>::max)(), 0));
m_mutex = reinterpret_cast<void*>(CreateMutex(0, 0, 0));
if (!m_gate || !m_queue || !m_mutex)
@@ -168,15 +170,15 @@ void condition_impl::notify_all()
res = ReleaseSemaphore(reinterpret_cast<HANDLE>(m_gate), 1, 0);
assert(res);
}
}
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (signals)
{
res = ReleaseSemaphore(reinterpret_cast<HANDLE>(m_queue), signals, 0);
assert(res);
if (signals)
{
res = ReleaseSemaphore(reinterpret_cast<HANDLE>(m_queue), signals, 0);
assert(res);
}
}
}
@@ -218,7 +220,7 @@ void condition_impl::do_wait()
m_gone = 0;
}
}
else if (++m_gone == (std::numeric_limits<unsigned>::max() / 2))
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
@@ -302,7 +304,7 @@ bool condition_impl::do_timed_wait(const xtime& xt)
m_gone = 0;
}
}
else if (++m_gone == (std::numeric_limits<unsigned>::max() / 2))
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
@@ -427,7 +429,8 @@ void condition_impl::notify_one()
unsigned signals = 0;
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
if (m_waiting != 0) // the m_gate is already closed
@@ -479,7 +482,8 @@ void condition_impl::notify_all()
unsigned signals = 0;
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
if (m_waiting != 0) // the m_gate is already closed
@@ -545,7 +549,8 @@ void condition_impl::do_wait()
unsigned was_waiting=0;
unsigned was_gone=0;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
was_waiting = m_waiting;
was_gone = m_gone;
@@ -563,7 +568,7 @@ void condition_impl::do_wait()
m_gone = 0;
}
}
else if (++m_gone == (std::numeric_limits<unsigned>::max() / 2))
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
@@ -605,7 +610,8 @@ bool condition_impl::do_timed_wait(const xtime& xt)
unsigned was_waiting=0;
unsigned was_gone=0;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
was_waiting = m_waiting;
was_gone = m_gone;
@@ -630,7 +636,7 @@ bool condition_impl::do_timed_wait(const xtime& xt)
m_gone = 0;
}
}
else if (++m_gone == (std::numeric_limits<unsigned>::max() / 2))
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

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -9,17 +9,174 @@
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/exceptions.hpp>
#include <cstring>
#include <string>
# ifdef BOOST_NO_STDC_NAMESPACE
namespace std { using ::strerror; }
# endif
// BOOST_POSIX or BOOST_WINDOWS specify which API to use.
# if !defined( BOOST_WINDOWS ) && !defined( BOOST_POSIX )
# if defined(_WIN32) || defined(__WIN32__) || defined(WIN32) || defined(__CYGWIN__)
# define BOOST_WINDOWS
# else
# define BOOST_POSIX
# endif
# endif
# if defined( BOOST_WINDOWS )
# include "windows.h"
# else
# include <errno.h> // for POSIX error codes
# endif
namespace
{
std::string system_message(int sys_err_code)
{
std::string str;
# ifdef BOOST_WINDOWS
LPVOID lpMsgBuf;
::FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
sys_err_code,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
(LPSTR)&lpMsgBuf,
0,
NULL);
str += static_cast<LPCSTR>(lpMsgBuf);
::LocalFree(lpMsgBuf); // free the buffer
while (str.size() && (str[str.size()-1] == '\n' ||
str[str.size()-1] == '\r'))
{
str.erase(str.size()-1);
}
# else
str += std::strerror(errno);
# endif
return str;
}
} // unnamed namespace
namespace boost {
lock_error::lock_error() : std::logic_error("thread lock error")
thread_exception::thread_exception()
: m_sys_err(0)
{
}
thread_resource_error::thread_resource_error() : std::runtime_error("thread resource error")
thread_exception::thread_exception(int sys_err_code)
: m_sys_err(sys_err_code)
{
}
thread_exception::~thread_exception() throw()
{
}
const char* thread_exception::message() const
{
if (m_sys_err != 0)
return system_message(m_sys_err).c_str();
return what();
}
lock_error::lock_error()
{
}
lock_error::lock_error(int sys_err_code)
: thread_exception(sys_err_code)
{
}
lock_error::~lock_error() throw()
{
}
const char* lock_error::what() const throw()
{
return "boost::lock_error";
}
thread_resource_error::thread_resource_error()
{
}
thread_resource_error::thread_resource_error(int sys_err_code)
: thread_exception(sys_err_code)
{
}
thread_resource_error::~thread_resource_error() throw()
{
}
const char* thread_resource_error::what() const throw()
{
return "boost::thread_resource_error";
}
unsupported_thread_option::unsupported_thread_option()
{
}
unsupported_thread_option::unsupported_thread_option(int sys_err_code)
: thread_exception(sys_err_code)
{
}
unsupported_thread_option::~unsupported_thread_option() throw()
{
}
const char* unsupported_thread_option::what() const throw()
{
return "boost::unsupported_thread_option";
}
invalid_thread_argument::invalid_thread_argument()
{
}
invalid_thread_argument::invalid_thread_argument(int sys_err_code)
: thread_exception(sys_err_code)
{
}
invalid_thread_argument::~invalid_thread_argument() throw()
{
}
const char* invalid_thread_argument::what() const throw()
{
return "boost::invalid_thread_argument";
}
thread_permission_error::thread_permission_error()
{
}
thread_permission_error::thread_permission_error(int sys_err_code)
: thread_exception(sys_err_code)
{
}
thread_permission_error::~thread_permission_error() throw()
{
}
const char* thread_permission_error::what() const throw()
{
return "boost::thread_permission_error";
}
} // namespace boost

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -9,6 +9,8 @@
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/xtime.hpp>
#include <boost/thread/thread.hpp>
@@ -16,17 +18,18 @@
#include <boost/limits.hpp>
#include <stdexcept>
#include <cassert>
#include <new>
#include "timeconv.inl"
#if defined(BOOST_HAS_WINTHREADS)
# include <new>
# include <boost/thread/once.hpp>
# include <windows.h>
# include <time.h>
# include "mutex.inl"
#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
@@ -34,28 +37,41 @@
namespace boost {
#if defined(BOOST_HAS_WINTHREADS)
mutex::mutex()
mutex::mutex(const char* name)
: boost::detail::named_object(name)
, m_mutex(0)
, m_critical_section(false)
{
m_mutex = reinterpret_cast<void*>(new(std::nothrow) CRITICAL_SECTION);
if (!m_mutex)
throw thread_resource_error();
InitializeCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
m_critical_section = !name;
if (m_critical_section)
m_mutex = new_critical_section();
else
m_mutex = new_mutex(effective_name()); //:add special name that creates a mutex instead of a critical section, but doesn't name the mutex?
}
mutex::~mutex()
{
DeleteCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
delete reinterpret_cast<LPCRITICAL_SECTION>(m_mutex);
if (m_critical_section)
delete_critical_section(m_mutex);
else
delete_mutex(m_mutex);
}
void mutex::do_lock()
{
EnterCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
if (m_critical_section)
wait_critical_section_infinite(m_mutex);
else
wait_mutex(m_mutex, INFINITE);
}
void mutex::do_unlock()
{
LeaveCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
void mutex::do_lock(cv_state&)
@@ -68,40 +84,48 @@ void mutex::do_unlock(cv_state&)
do_unlock();
}
try_mutex::try_mutex()
try_mutex::try_mutex(const char* name)
: boost::detail::named_object(name)
, m_mutex(0)
, m_critical_section(false)
{
m_mutex = reinterpret_cast<void*>(CreateMutex(0, 0, 0));
if (!m_mutex)
throw thread_resource_error();
m_critical_section = !name && has_TryEnterCriticalSection();
if (m_critical_section)
m_mutex = new_critical_section();
else
m_mutex = new_mutex(effective_name());
}
try_mutex::~try_mutex()
{
int res = 0;
res = CloseHandle(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (m_critical_section)
delete_critical_section(m_mutex);
else
delete_mutex(m_mutex);
}
void try_mutex::do_lock()
{
int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), INFINITE);
assert(res == WAIT_OBJECT_0);
if (m_critical_section)
wait_critical_section_infinite(m_mutex);
else
wait_mutex(m_mutex, INFINITE);
}
bool try_mutex::do_trylock()
{
unsigned int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), 0);
assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
return res == WAIT_OBJECT_0;
if (m_critical_section)
return wait_critical_section_try(m_mutex);
else
return wait_mutex(m_mutex, 0) == WAIT_OBJECT_0;
}
void try_mutex::do_unlock()
{
int res = 0;
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
void try_mutex::do_lock(cv_state&)
@@ -114,51 +138,42 @@ void try_mutex::do_unlock(cv_state&)
do_unlock();
}
timed_mutex::timed_mutex()
timed_mutex::timed_mutex(const char* name)
: boost::detail::named_object(name)
, m_mutex(0)
{
m_mutex = reinterpret_cast<void*>(CreateMutex(0, 0, 0));
if (!m_mutex)
throw thread_resource_error();
m_mutex = new_mutex(effective_name());
}
timed_mutex::~timed_mutex()
{
int res = 0;
res = CloseHandle(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
delete_mutex(m_mutex);
}
void timed_mutex::do_lock()
{
int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), INFINITE);
assert(res == WAIT_OBJECT_0);
wait_mutex(m_mutex, INFINITE);
}
bool timed_mutex::do_trylock()
{
unsigned int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), 0);
assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
return res == WAIT_OBJECT_0;
return wait_mutex(m_mutex, 0) == WAIT_OBJECT_0;
}
bool timed_mutex::do_timedlock(const xtime& xt)
{
unsigned int res = 0;
for (;;)
{
int milliseconds;
to_duration(xt, milliseconds);
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), milliseconds);
assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
int res = wait_mutex(m_mutex, milliseconds);
if (res == WAIT_TIMEOUT)
{
xtime cur;
xtime_get(&cur, TIME_UTC);
if (xtime_cmp(xt, cur) > 0)
boost::xtime cur;
boost::xtime_get(&cur, boost::TIME_UTC);
if (boost::xtime_cmp(xt, cur) > 0)
continue;
}
@@ -168,9 +183,7 @@ bool timed_mutex::do_timedlock(const xtime& xt)
void timed_mutex::do_unlock()
{
int res = 0;
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
release_mutex(m_mutex);
}
void timed_mutex::do_lock(cv_state&)
@@ -182,9 +195,13 @@ void timed_mutex::do_unlock(cv_state&)
{
do_unlock();
}
#elif defined(BOOST_HAS_PTHREADS)
mutex::mutex()
mutex::mutex(const char* name)
{
//:Use name parameter
int res = 0;
res = pthread_mutex_init(&m_mutex, 0);
if (res != 0)
@@ -223,8 +240,10 @@ void mutex::do_unlock(cv_state& state)
state.pmutex = &m_mutex;
}
try_mutex::try_mutex()
try_mutex::try_mutex(const char* name)
{
//:Use name parameter
int res = 0;
res = pthread_mutex_init(&m_mutex, 0);
if (res != 0)
@@ -272,9 +291,11 @@ void try_mutex::do_unlock(cv_state& state)
state.pmutex = &m_mutex;
}
timed_mutex::timed_mutex()
timed_mutex::timed_mutex(const char* name)
: m_locked(false)
{
//:Use name parameter
int res = 0;
res = pthread_mutex_init(&m_mutex, 0);
if (res != 0)
@@ -412,12 +433,14 @@ void timed_mutex::do_unlock(cv_state& state)
state.pmutex = &m_mutex;
}
#elif defined(BOOST_HAS_MPTASKS)
using threads::mac::detail::safe_enter_critical_region;
mutex::mutex()
mutex::mutex(const char* name)
{
//:Use name parameter
}
mutex::~mutex()
@@ -427,7 +450,8 @@ mutex::~mutex()
void mutex::do_lock()
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
}
@@ -448,8 +472,9 @@ void mutex::do_unlock(cv_state& /*state*/)
do_unlock();
}
try_mutex::try_mutex()
try_mutex::try_mutex(const char* name)
{
//:Use name parameter
}
try_mutex::~try_mutex()
@@ -459,7 +484,8 @@ try_mutex::~try_mutex()
void try_mutex::do_lock()
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
}
@@ -488,8 +514,9 @@ void try_mutex::do_unlock(cv_state& /*state*/)
do_unlock();
}
timed_mutex::timed_mutex()
timed_mutex::timed_mutex(const char* name)
{
//:Use name parameter
}
timed_mutex::~timed_mutex()
@@ -499,7 +526,8 @@ timed_mutex::~timed_mutex()
void timed_mutex::do_lock()
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
}
@@ -540,6 +568,7 @@ void timed_mutex::do_unlock(cv_state& /*state*/)
{
do_unlock();
}
#endif
} // namespace boost

124
src/mutex.inl Normal file
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@@ -0,0 +1,124 @@
// Copyright (C) 2001-2003
// 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.
namespace {
#if defined(BOOST_HAS_WINTHREADS)
//:PREVENT THIS FROM BEING DUPLICATED
typedef BOOL (WINAPI* TryEnterCriticalSection_type)(LPCRITICAL_SECTION lpCriticalSection);
TryEnterCriticalSection_type g_TryEnterCriticalSection = 0;
boost::once_flag once_init_TryEnterCriticalSection = BOOST_ONCE_INIT;
void init_TryEnterCriticalSection()
{
//TryEnterCriticalSection is only available on WinNT 4.0 or later;
//it is not available on Win9x.
OSVERSIONINFO version_info = {sizeof(OSVERSIONINFO)};
::GetVersionEx(&version_info);
if (version_info.dwPlatformId == VER_PLATFORM_WIN32_NT &&
version_info.dwMajorVersion >= 4)
{
if (HMODULE kernel_module = GetModuleHandle(TEXT("KERNEL32.DLL")))
g_TryEnterCriticalSection = reinterpret_cast<TryEnterCriticalSection_type>(GetProcAddress(kernel_module, "TryEnterCriticalSection"));
}
}
inline bool has_TryEnterCriticalSection()
{
boost::call_once(init_TryEnterCriticalSection, once_init_TryEnterCriticalSection);
return g_TryEnterCriticalSection != 0;
}
inline HANDLE mutex_cast(void* p)
{
return reinterpret_cast<HANDLE>(p);
}
inline LPCRITICAL_SECTION critical_section_cast(void* p)
{
return reinterpret_cast<LPCRITICAL_SECTION>(p);
}
inline void* new_critical_section()
{
try
{
LPCRITICAL_SECTION critical_section = new CRITICAL_SECTION;
if (critical_section == 0) throw boost::thread_resource_error();
InitializeCriticalSection(critical_section);
return critical_section;
}
catch(...)
{
throw boost::thread_resource_error();
}
}
inline void* new_mutex(const char* name)
{
#if defined(BOOST_NO_ANSI_APIS)
USES_CONVERSION;
HANDLE mutex = CreateMutexW(0, 0, A2CW(name));
#else
HANDLE mutex = CreateMutexA(0, 0, name);
#endif
if (mutex == 0 || mutex == INVALID_HANDLE_VALUE) //:xxx (check for both values?)
throw boost::thread_resource_error();
return reinterpret_cast<void*>(mutex);
}
inline void delete_critical_section(void* mutex)
{
DeleteCriticalSection(critical_section_cast(mutex));
delete critical_section_cast(mutex);
}
inline void delete_mutex(void* mutex)
{
int res = 0;
res = CloseHandle(mutex_cast(mutex));
assert(res);
}
inline void wait_critical_section_infinite(void* mutex)
{
EnterCriticalSection(critical_section_cast(mutex)); //:xxx Can throw an exception under low memory conditions
}
inline bool wait_critical_section_try(void* mutex)
{
BOOL res = g_TryEnterCriticalSection(critical_section_cast(mutex));
return res != 0;
}
inline int wait_mutex(void* mutex, int time)
{
unsigned int res = 0;
res = WaitForSingleObject(mutex_cast(mutex), time);
//:xxx assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
return res;
}
inline void release_critical_section(void* mutex)
{
LeaveCriticalSection(critical_section_cast(mutex));
}
inline void release_mutex(void* mutex)
{
BOOL res = FALSE;
res = ReleaseMutex(mutex_cast(mutex));
assert(res);
}
#endif
}

135
src/named.cpp Normal file
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@@ -0,0 +1,135 @@
// Copyright (C) 2001-2003
// 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/detail/config.hpp>
#include <boost/thread/detail/named.hpp>
#include <string.h>
#include <malloc.h>
namespace {
char* concat(char* result, const char* buf)
{
if (result == 0)
return strdup(buf);
int len = strlen(result) + strlen(buf) + 1;
result = (char*)realloc(result, len);
strcat(result, buf);
return result;
}
char* get_root()
{
#if defined(BOOST_HAS_WINTHREADS)
return "";
#elif defined(BOOST_HAS_PTHREADS)
return "/";
#else
return "";
#endif
}
char* encode(const char* str)
{
const char* digits="0123456789abcdef";
char* result=0;
static char buf[100];
char* ebuf = buf + 100;
char* p = buf;
*p = 0;
strcat(p, get_root());
p = p + strlen(p);
while (*str)
{
if (((*str >= '0') && (*str <= '9')) ||
((*str >= 'a') && (*str <= 'z')) ||
((*str >= 'A') && (*str <= 'Z')) ||
(*str == '/') || (*str == '.') || (*str == '_'))
{
*p = *str;
}
else if (*str == ' ')
{
*p = '+';
}
else
{
if (p + 3 >= ebuf)
{
*p = 0;
result = concat(result, buf);
p = buf;
}
*p = '%';
char* e = p + 2;
int v = *str;
while (e > p)
{
*e-- = digits[v % 16];
v /= 16;
}
p += 2;
}
if (++p == ebuf)
{
*p = 0;
result = concat(result, buf);
p = buf;
}
++str;
}
*p = 0;
result = concat(result, buf);
return result;
}
} // namespace
namespace boost {
namespace detail {
named_object::named_object(const char* name)
: m_name(0), m_ename(0)
{
if (name)
{
m_name = strdup(name);
if (*m_name == '%')
m_ename = m_name + 1;
else
m_ename = encode(name);
}
}
named_object::~named_object()
{
if (m_name)
{
if (*m_name != '%')
free(m_ename);
free(m_name);
}
}
const char* named_object::name() const
{
return m_name;
}
const char* named_object::effective_name() const
{
return m_ename;
}
} // namespace detail
} // namespace boost

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -9,6 +9,8 @@
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/once.hpp>
#include <cstdio>
#include <cassert>
@@ -17,14 +19,16 @@
# include <windows.h>
# if defined(BOOST_NO_STRINGSTREAM)
# include <strstream>
class unfreezer
{
public:
unfreezer(std::ostrstream& s) : m_stream(s) {}
~unfreezer() { m_stream.freeze(false); }
private:
std::ostrstream& m_stream;
};
class unfreezer
{
public:
unfreezer(std::ostrstream& s) : m_stream(s) {}
~unfreezer() { m_stream.freeze(false); }
private:
std::ostrstream& m_stream;
};
# else
# include <sstream>
# endif
@@ -33,7 +37,7 @@
#endif
#ifdef BOOST_NO_STDC_NAMESPACE
namespace std { using ::sprintf; }
namespace std { using ::sprintf; }
#endif
#if defined(BOOST_HAS_PTHREADS)
@@ -46,64 +50,70 @@ typedef void (*once_callback)();
extern "C" {
static void key_init()
{
pthread_key_create(&key, 0);
}
static void key_init()
{
pthread_key_create(&key, 0);
}
static void do_once()
{
once_callback* cb = reinterpret_cast<once_callback*>(pthread_getspecific(key));
(**cb)();
}
static void do_once()
{
once_callback* cb = reinterpret_cast<once_callback*>(
pthread_getspecific(key));
(**cb)();
}
}
#elif defined(BOOST_HAS_MPTASKS)
namespace {
void *remote_call_proxy(void *pData)
void *remote_call_proxy(void *pData)
{
std::pair<void (*)(), boost::once_flag *> &rData(
*reinterpret_cast<std::pair<void (*)(), boost::once_flag *> *>(pData));
if(*rData.second == false)
{
std::pair<void (*)(), boost::once_flag *> &rData(*reinterpret_cast<std::pair<void (*)(), boost::once_flag *> *>(pData));
if(*rData.second == false)
{
rData.first();
*rData.second = true;
}
return(NULL);
rData.first();
*rData.second = true;
}
return(NULL);
}
}
#elif defined(BOOST_HAS_WINTHREADS)
namespace {
// The signature for InterlockedCompareExchange has changed with the
// addition of Win64 support. I can't determine any (consistent and
// portable) way of using conditional compilation to detect this, so
// we use these type wrappers. Unfortunately, the various vendors
// use different calling conventions and other signature anamolies,
// and thus have unique types as well. This is known to work on VC6,
// VC7, Borland 5.5.2 and gcc 3.2. Are there other signatures for
// other platforms?
inline LONG ice_wrapper(LONG (__stdcall *ice)(LONG*, LONG, LONG), volatile LONG* dest, LONG exch, LONG cmp)
{
return (*ice)(const_cast<LONG*>(dest), exch, cmp);
}
// The signature for InterlockedCompareExchange has changed with the
// addition of Win64 support. I can't determine any (consistent and
// portable) way of using conditional compilation to detect this, so
// we use these type wrappers. Unfortunately, the various vendors
// use different calling conventions and other signature anamolies,
// and thus have unique types as well. This is known to work on VC6,
// VC7, Borland 5.5.2 and gcc 3.2. Are there other signatures for
// other platforms?
inline LONG ice_wrapper(LONG (__stdcall *ice)(LONG*, LONG, LONG),
volatile LONG* dest, LONG exch, LONG cmp)
{
return (*ice)(const_cast<LONG*>(dest), exch, cmp);
}
inline LONG ice_wrapper(LONG (__stdcall *ice)(volatile LONG*, LONG, LONG), volatile LONG* dest, LONG exch, LONG cmp)
{
return (*ice)(dest, exch, cmp);
}
inline LONG ice_wrapper(LONG (__stdcall *ice)(volatile LONG*, LONG, LONG),
volatile LONG* dest, LONG exch, LONG cmp)
{
return (*ice)(dest, exch, cmp);
}
inline LONG ice_wrapper(LPVOID (__stdcall *ice)(LPVOID*, LPVOID, LPVOID), volatile LONG* dest, LONG exch, LONG cmp)
{
return (LONG)(*ice)((LPVOID*)dest, (LPVOID)exch, (LPVOID)cmp);
}
inline LONG ice_wrapper(LPVOID (__stdcall *ice)(LPVOID*, LPVOID, LPVOID),
volatile LONG* dest, LONG exch, LONG cmp)
{
return (LONG)(*ice)((LPVOID*)dest, (LPVOID)exch, (LPVOID)cmp);
}
// The friendly form of InterlockedCompareExchange that defers
// according to the above function type wrappers.
inline LONG compare_exchange(volatile LPLONG dest, LONG exch, LONG cmp)
{
return ice_wrapper(&InterlockedCompareExchange, dest, exch, cmp);
}
// The friendly form of InterlockedCompareExchange that defers
// according to the above function type wrappers.
inline LONG compare_exchange(volatile LPLONG dest, LONG exch, LONG cmp)
{
return ice_wrapper(&InterlockedCompareExchange, dest, exch, cmp);
}
}
#endif
@@ -116,13 +126,34 @@ void call_once(void (*func)(), once_flag& flag)
{
#if defined(BOOST_NO_STRINGSTREAM)
std::ostrstream strm;
strm << "2AC1A572DB6944B0A65C38C4140AF2F4" << std::hex << GetCurrentProcessId() << &flag << std::ends;
strm << "2AC1A572DB6944B0A65C38C4140AF2F4"
<< std::hex
<< GetCurrentProcessId()
<< &flag
<< std::ends;
unfreezer unfreeze(strm);
HANDLE mutex = CreateMutex(NULL, FALSE, strm.str());
# if defined (BOOST_NO_ANSI_APIS)
USES_CONVERSION;
HANDLE mutex = CreateMutexW(NULL, FALSE, A2CW(strm.str()));
# else
HANDLE mutex = CreateMutexA(NULL, FALSE, strm.str());
# endif
#else
# if defined (BOOST_NO_ANSI_APIS)
std::wostringstream strm;
strm << L"2AC1A572DB6944B0A65C38C4140AF2F4"
<< std::hex
<< GetCurrentProcessId()
<< &flag;
HANDLE mutex = CreateMutexW(NULL, FALSE, strm.str().c_str());
# else
std::ostringstream strm;
strm << "2AC1A572DB6944B0A65C38C4140AF2F4" << std::hex << GetCurrentProcessId() << &flag;
strm << "2AC1A572DB6944B0A65C38C4140AF2F4"
<< std::hex
<< GetCurrentProcessId()
<< &flag;
HANDLE mutex = CreateMutexA(NULL, FALSE, strm.str().c_str());
# endif
#endif
assert(mutex != NULL);
@@ -132,7 +163,18 @@ void call_once(void (*func)(), once_flag& flag)
if (compare_exchange(&flag, 1, 1) == 0)
{
func();
try
{
func();
}
catch (...)
{
res = ReleaseMutex(mutex);
assert(res);
res = CloseHandle(mutex);
assert(res);
throw;
}
InterlockedExchange(&flag, 1);
}
@@ -148,7 +190,8 @@ void call_once(void (*func)(), once_flag& flag)
#elif defined(BOOST_HAS_MPTASKS)
if(flag == false)
{
// all we do here is make a remote call to blue, as blue is not reentrant.
// all we do here is make a remote call to blue, as blue is not
// reentrant.
std::pair<void (*)(), once_flag *> sData(func, &flag);
MPRemoteCall(remote_call_proxy, &sData, kMPOwningProcessRemoteContext);
assert(flag == true);

1146
src/read_write_mutex.cpp Normal file

File diff suppressed because it is too large Load Diff

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -9,6 +9,8 @@
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/recursive_mutex.hpp>
#include <boost/thread/xtime.hpp>
#include <boost/thread/thread.hpp>
@@ -18,50 +20,77 @@
#include "timeconv.inl"
#if defined(BOOST_HAS_WINTHREADS)
# include <new>
# include <boost/thread/once.hpp>
# include <windows.h>
# include <time.h>
# include "mutex.inl"
#elif defined(BOOST_HAS_PTHREADS)
# include <errno.h>
#elif defined(BOOST_HAS_MPTASKS)
# include <MacErrors.h>
# include "safe.hpp"
# include <MacErrors.h>
# include "safe.hpp"
#endif
namespace boost {
#if defined(BOOST_HAS_WINTHREADS)
recursive_mutex::recursive_mutex()
: m_count(0)
recursive_mutex::recursive_mutex(const char* name)
: boost::detail::named_object(name)
, m_mutex(0)
, m_count(0)
, m_critical_section(false)
{
m_mutex = reinterpret_cast<void*>(new(std::nothrow) CRITICAL_SECTION);
if (!m_mutex)
throw thread_resource_error();
InitializeCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
m_critical_section = !name;
if (m_critical_section)
m_mutex = new_critical_section();
else
m_mutex = new_mutex(effective_name()); //:add special name that creates a mutex instead of a critical section, but doesn't name the mutex?
}
recursive_mutex::~recursive_mutex()
{
DeleteCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
delete reinterpret_cast<LPCRITICAL_SECTION>(m_mutex);
if (m_critical_section)
delete_critical_section(m_mutex);
else
delete_mutex(m_mutex);
}
void recursive_mutex::do_lock()
{
EnterCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
if (m_critical_section)
wait_critical_section_infinite(m_mutex);
else
wait_mutex(m_mutex, INFINITE);
if (++m_count > 1)
LeaveCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
{
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
}
void recursive_mutex::do_unlock()
{
if (--m_count == 0)
LeaveCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
{
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
}
void recursive_mutex::do_lock(cv_state& state)
{
EnterCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
if (m_critical_section)
wait_critical_section_infinite(m_mutex);
else
wait_mutex(m_mutex, INFINITE);
m_count = state;
}
@@ -69,49 +98,66 @@ void recursive_mutex::do_unlock(cv_state& state)
{
state = m_count;
m_count = 0;
LeaveCriticalSection(reinterpret_cast<LPCRITICAL_SECTION>(m_mutex));
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
recursive_try_mutex::recursive_try_mutex()
: m_count(0)
recursive_try_mutex::recursive_try_mutex(const char* name)
: boost::detail::named_object(name)
, m_mutex(0)
, m_count(0)
, m_critical_section(false)
{
m_mutex = reinterpret_cast<void*>(CreateMutex(0, 0, 0));
if (!m_mutex)
throw thread_resource_error();
m_critical_section = !name && has_TryEnterCriticalSection();
if (m_critical_section)
m_mutex = new_critical_section();
else
m_mutex = new_mutex(effective_name());
}
recursive_try_mutex::~recursive_try_mutex()
{
int res = 0;
res = CloseHandle(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (m_critical_section)
delete_critical_section(m_mutex);
else
delete_mutex(m_mutex);
}
void recursive_try_mutex::do_lock()
{
int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), INFINITE);
assert(res == WAIT_OBJECT_0);
if (m_critical_section)
wait_critical_section_infinite(m_mutex);
else
wait_mutex(m_mutex, INFINITE);
if (++m_count > 1)
{
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
}
bool recursive_try_mutex::do_trylock()
{
unsigned int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), 0);
assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
bool res = false;
if (m_critical_section)
res = wait_critical_section_try(m_mutex);
else
res = wait_mutex(m_mutex, 0) == WAIT_OBJECT_0;
if (res == WAIT_OBJECT_0)
if (res)
{
if (++m_count > 1)
{
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
return true;
}
@@ -122,17 +168,19 @@ void recursive_try_mutex::do_unlock()
{
if (--m_count == 0)
{
int res = 0;
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
}
void recursive_try_mutex::do_lock(cv_state& state)
{
int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), INFINITE);
assert(res == WAIT_OBJECT_0);
if (m_critical_section)
wait_critical_section_infinite(m_mutex);
else
wait_mutex(m_mutex, INFINITE);
m_count = state;
}
@@ -142,52 +190,41 @@ void recursive_try_mutex::do_unlock(cv_state& state)
state = m_count;
m_count = 0;
int res = 0;
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
if (m_critical_section)
release_critical_section(m_mutex);
else
release_mutex(m_mutex);
}
recursive_timed_mutex::recursive_timed_mutex()
: m_count(0)
recursive_timed_mutex::recursive_timed_mutex(const char* name)
: boost::detail::named_object(name)
, m_mutex(0)
, m_count(0)
{
m_mutex = reinterpret_cast<void*>(CreateMutex(0, 0, 0));
if (!m_mutex)
throw thread_resource_error();
m_mutex = new_mutex(effective_name());
}
recursive_timed_mutex::~recursive_timed_mutex()
{
int res = 0;
res = CloseHandle(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
delete_mutex(m_mutex);
}
void recursive_timed_mutex::do_lock()
{
int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), INFINITE);
assert(res == WAIT_OBJECT_0);
wait_mutex(m_mutex, INFINITE);
if (++m_count > 1)
{
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
}
release_mutex(m_mutex);
}
bool recursive_timed_mutex::do_trylock()
{
unsigned int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), 0);
assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
bool res = wait_mutex(m_mutex, 0) == WAIT_OBJECT_0;
if (res == WAIT_OBJECT_0)
if (res)
{
if (++m_count > 1)
{
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
}
release_mutex(m_mutex);
return true;
}
return false;
@@ -200,9 +237,7 @@ bool recursive_timed_mutex::do_timedlock(const xtime& xt)
int milliseconds;
to_duration(xt, milliseconds);
unsigned int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), milliseconds);
assert(res != WAIT_FAILED && res != WAIT_ABANDONED);
unsigned int res = wait_mutex(m_mutex, milliseconds);
if (res == WAIT_TIMEOUT)
{
@@ -215,10 +250,7 @@ bool recursive_timed_mutex::do_timedlock(const xtime& xt)
if (res == WAIT_OBJECT_0)
{
if (++m_count > 1)
{
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
}
release_mutex(m_mutex);
return true;
}
@@ -229,18 +261,12 @@ bool recursive_timed_mutex::do_timedlock(const xtime& xt)
void recursive_timed_mutex::do_unlock()
{
if (--m_count == 0)
{
int res = 0;
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
}
release_mutex(m_mutex);
}
void recursive_timed_mutex::do_lock(cv_state& state)
{
int res = 0;
res = WaitForSingleObject(reinterpret_cast<HANDLE>(m_mutex), INFINITE);
assert(res == WAIT_OBJECT_0);
wait_mutex(m_mutex, INFINITE);
m_count = state;
}
@@ -250,20 +276,21 @@ void recursive_timed_mutex::do_unlock(cv_state& state)
state = m_count;
m_count = 0;
int res = 0;
res = ReleaseMutex(reinterpret_cast<HANDLE>(m_mutex));
assert(res);
release_mutex(m_mutex);
}
#elif defined(BOOST_HAS_PTHREADS)
recursive_mutex::recursive_mutex()
recursive_mutex::recursive_mutex(const char* name)
: m_count(0)
# if !defined(BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE)
, m_valid_id(false)
# endif
{
//:Use name parameter
pthread_mutexattr_t attr;
int res = 0;
res = pthread_mutexattr_init(&attr);
int res = pthread_mutexattr_init(&attr);
assert(res == 0);
# if defined(BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE)
@@ -272,6 +299,10 @@ recursive_mutex::recursive_mutex()
# endif
res = pthread_mutex_init(&m_mutex, &attr);
{
int res = pthread_mutexattr_destroy(&attr);
assert(res == 0);
}
if (res != 0)
throw thread_resource_error();
@@ -407,15 +438,16 @@ void recursive_mutex::do_unlock(cv_state& state)
state.count = m_count;
}
recursive_try_mutex::recursive_try_mutex()
recursive_try_mutex::recursive_try_mutex(const char* name)
: m_count(0)
# if !defined(BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE)
, m_valid_id(false)
# endif
{
//:Use name parameter
pthread_mutexattr_t attr;
int res = 0;
res = pthread_mutexattr_init(&attr);
int res = pthread_mutexattr_init(&attr);
assert(res == 0);
# if defined(BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE)
@@ -424,6 +456,10 @@ recursive_try_mutex::recursive_try_mutex()
# endif
res = pthread_mutex_init(&m_mutex, &attr);
{
int res = pthread_mutexattr_destroy(&attr);
assert(res == 0);
}
if (res != 0)
throw thread_resource_error();
@@ -603,9 +639,11 @@ void recursive_try_mutex::do_unlock(cv_state& state)
state.count = m_count;
}
recursive_timed_mutex::recursive_timed_mutex()
recursive_timed_mutex::recursive_timed_mutex(const char* name)
: m_valid_id(false), m_count(0)
{
//:Use name parameter
int res = 0;
res = pthread_mutex_init(&m_mutex, 0);
if (res != 0)
@@ -781,14 +819,16 @@ void recursive_timed_mutex::do_unlock(cv_state& state)
state.pmutex = &m_mutex;
state.count = m_count;
}
#elif defined(BOOST_HAS_MPTASKS)
using threads::mac::detail::safe_enter_critical_region;
recursive_mutex::recursive_mutex()
recursive_mutex::recursive_mutex(const char* name)
: m_count(0)
{
//:Use name parameter
}
recursive_mutex::~recursive_mutex()
@@ -798,7 +838,8 @@ recursive_mutex::~recursive_mutex()
void recursive_mutex::do_lock()
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
if (++m_count > 1)
@@ -821,7 +862,8 @@ void recursive_mutex::do_unlock()
void recursive_mutex::do_lock(cv_state& state)
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
m_count = state;
@@ -837,9 +879,10 @@ void recursive_mutex::do_unlock(cv_state& state)
assert(lStatus == noErr);
}
recursive_try_mutex::recursive_try_mutex()
recursive_try_mutex::recursive_try_mutex(const char* name)
: m_count(0)
{
//:Use name parameter
}
recursive_try_mutex::~recursive_try_mutex()
@@ -849,7 +892,8 @@ recursive_try_mutex::~recursive_try_mutex()
void recursive_try_mutex::do_lock()
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
if (++m_count > 1)
@@ -890,7 +934,8 @@ void recursive_try_mutex::do_unlock()
void recursive_try_mutex::do_lock(cv_state& state)
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
m_count = state;
@@ -906,9 +951,10 @@ void recursive_try_mutex::do_unlock(cv_state& state)
assert(lStatus == noErr);
}
recursive_timed_mutex::recursive_timed_mutex()
recursive_timed_mutex::recursive_timed_mutex(const char* name)
: m_count(0)
{
//:Use name parameter
}
recursive_timed_mutex::~recursive_timed_mutex()
@@ -918,7 +964,8 @@ recursive_timed_mutex::~recursive_timed_mutex()
void recursive_timed_mutex::do_lock()
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
if (++m_count > 1)
@@ -981,7 +1028,8 @@ void recursive_timed_mutex::do_unlock()
void recursive_timed_mutex::do_lock(cv_state& state)
{
OSStatus lStatus = noErr;
lStatus = safe_enter_critical_region(m_mutex, kDurationForever, m_mutex_mutex);
lStatus = safe_enter_critical_region(m_mutex, kDurationForever,
m_mutex_mutex);
assert(lStatus == noErr);
m_count = state;
@@ -996,6 +1044,7 @@ void recursive_timed_mutex::do_unlock(cv_state& state)
lStatus = MPExitCriticalRegion(m_mutex);
assert(lStatus == noErr);
}
#endif
} // namespace boost

191
src/shared_memory.cpp Normal file
View File

@@ -0,0 +1,191 @@
// 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.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/shared_memory.hpp>
#include <boost/thread/once.hpp>
#include <boost/thread/mutex.hpp>
#if defined(BOOST_HAS_WINTHREADS)
#include <windows.h>
#include <winbase.h>
// Next line should really be BOOST_HAS_POSIX_xxx
#elif defined(BOOST_HAS_PTHREADS)
//#include <sys/shm.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <semaphore.h>
#include <errno.h>
#endif
namespace boost {
shared_memory::shared_memory(const char *name, size_t len, int flags)
: boost::detail::named_object(name)
{
init(len, flags, 0);
}
shared_memory::shared_memory(const char *name, size_t len, int flags,
const boost::function1<void, void *>& initfunc)
: boost::detail::named_object(name)
{
init(len, flags & create, &initfunc);
}
shared_memory::~shared_memory()
{
if (m_ptr)
{
int res = 0;
#if defined(BOOST_HAS_WINTHREADS)
res = UnmapViewOfFile(m_ptr);
assert(res);
res = CloseHandle(reinterpret_cast<HANDLE>(m_hmap));
assert(res);
#elif defined(BOOST_HAS_PTHREADS)
res = munmap(reinterpret_cast<char*>(m_ptr), m_len);
assert(res == 0);
res = close(m_hmap);
assert(res == 0);
res = shm_unlink(effective_name());
assert(res == 0);
#endif
}
}
void shared_memory::init(size_t len, int flags,
const boost::function1<void,void *>* initfunc)
{
int res = 0;
bool should_init = false;
std::string ename = effective_name();
std::string mxname = ename + "mx94543CBD1523443dB128451E51B5103E";
#if defined(BOOST_HAS_WINTHREADS)
HANDLE mutex = CreateMutexA(0, FALSE, mxname.c_str());
if (mutex == INVALID_HANDLE_VALUE)
throw thread_resource_error();
res = WaitForSingleObject(mutex, INFINITE);
assert(res == WAIT_OBJECT_0);
if (flags & create)
{
DWORD protect = (flags & write) ? PAGE_READWRITE : PAGE_READONLY;
m_hmap = CreateFileMapping(INVALID_HANDLE_VALUE, NULL, protect,
0, len, ename.c_str());
if (m_hmap == INVALID_HANDLE_VALUE ||
((flags & exclusive) && GetLastError() == ERROR_ALREADY_EXISTS))
{
res = ReleaseMutex(mutex);
assert(res);
res = CloseHandle(mutex);
assert(res);
if (m_hmap != INVALID_HANDLE_VALUE)
{
res = CloseHandle(m_hmap);
assert(res);
}
throw thread_resource_error();
}
should_init = GetLastError() != ERROR_ALREADY_EXISTS;
}
else
{
DWORD protect = (flags & write) ? FILE_MAP_WRITE : FILE_MAP_READ;
m_hmap = OpenFileMapping(protect, FALSE, ename.c_str());
if (m_hmap == INVALID_HANDLE_VALUE)
{
res = ReleaseMutex(mutex);
assert(res);
res = CloseHandle(mutex);
assert(res);
throw thread_resource_error();
}
}
m_ptr = MapViewOfFile(m_hmap, FILE_MAP_WRITE, 0, 0, 0);
assert(m_ptr);
#elif defined(BOOST_HAS_PTHREADS)
m_len = len;
sem_t* sem = sem_open(mxname.c_str(), O_CREAT);
if (sem == SEM_FAILED)
throw thread_resource_error();
res = sem_wait(sem);
assert(res == 0);
int oflag = (flags & write) ? O_RDWR : O_RDONLY;
int cflag = (flags & create) ? O_CREAT|O_TRUNC|O_EXCL : 0;
for (;;)
{
m_hmap = shm_open(m_name.c_str(), oflag|cflag, 0);
if (m_hmap == -1)
{
if (errno != EEXIST || (flags & exclusive))
{
res = sem_post(sem);
assert(res == 0);
res = sem_close(sem);
assert(res == 0);
res = sem_unlink(mxname.c_str());
assert(res);
throw thread_resource_error();
}
m_hmap = shm_open(m_name.c_str(), oflag, 0);
if (m_hmap == -1)
{
if (errno == ENOENT)
continue;
res = sem_post(sem);
assert(res == 0);
res = sem_close(sem);
assert(res);
res = sem_unlink(mxname.c_str());
assert(res);
throw thread_resource_error();
}
}
else
should_init = true;
break;
}
ftruncate(m_hmap, len);
int prot = (flags & write) ? PROT_READ|PROT_WRITE : PROT_READ;
m_ptr = mmap(0, m_len, prot, MAP_SHARED, m_hmap, 0);
#endif
if (should_init && initfunc)
(*initfunc)(m_ptr);
#if defined(BOOST_HAS_WINTHREADS)
res = ReleaseMutex(mutex);
assert(res);
res = CloseHandle(mutex);
assert(res);
#elif defined(BOOST_HAS_PTHREADS)
res = sem_post(sem);
assert(res == 0);
res = sem_close(sem);
assert(res == 0);
res = sem_unlink(mxname.c_str());
assert(res == 0);
#endif
}
} // namespace boost

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321
src/thread_pool.cpp Normal file
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@@ -0,0 +1,321 @@
// Copyright (C) 2002-2003
// 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.
// Derived loosely from work queue manager in "Programming POSIX Threads"
// by David Butenhof.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/thread_pool.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/xtime.hpp>
#include <boost/bind.hpp>
#include <list>
#include <queue>
#include <stdexcept>
#include <cassert>
namespace boost {
class thread_pool::impl
{
public:
impl(int max_threads, int min_threads, int timeout_secs,
int timeout_nsecs);
~impl();
void add(const boost::function0<void> &job);
void join();
void cancel();
void detach();
void worker_harness();
private:
typedef enum
{
RUNNING,
CANCELLING,
JOINING,
JOINED,
DETACHED
} thread_pool_state;
typedef std::queue<boost::function0<void> > job_q;
condition m_more_work;
condition m_done;
mutex m_prot;
job_q m_jobs;
thread_group m_workers;
thread_pool_state m_state;
int m_max_threads; // Max threads allowed
int m_min_threads;
int m_thread_count; // Current number of threads
int m_idle_count; // Number of idle threads
int m_timeout_secs; // How long to keep idle threads
int m_timeout_nsecs;
};
thread_pool::impl::impl(int max_threads, int min_threads, int timeout_secs,
int timeout_nsecs)
: m_state(RUNNING), m_max_threads(max_threads), m_min_threads(min_threads),
m_thread_count(0), m_idle_count(0), m_timeout_secs(timeout_secs),
m_timeout_nsecs(timeout_nsecs)
{
// Immediately launch some worker threads.
//
// Not an exception safe implementation, yet.
while (min_threads-- > 0)
{
m_workers.create_thread(
bind(&thread_pool::impl::worker_harness, this));
m_thread_count++;
}
}
thread_pool::impl::~impl()
{
// Join in the destructor, unless they have already
// joined or detached.
mutex::scoped_lock lock(m_prot);
if (m_state == RUNNING)
{
lock.unlock();
join();
}
}
void thread_pool::impl::add(const boost::function0<void> &job)
{
mutex::scoped_lock lock(m_prot);
// Note - can never reach this point if m_state == CANCELLED
// because the m_prot is held during the entire cancel operation.
assert(m_state == RUNNING);
m_jobs.push(job);
if (m_idle_count > 0)
m_more_work.notify_one();
else if (m_thread_count < m_max_threads)
{
// No idle threads, and we're below our limit. Spawn a new
// worker.
// What we really need is thread::detach(), or "create suspended"
m_workers.create_thread(
bind(&thread_pool::impl::worker_harness, this));
m_thread_count++;
}
}
void thread_pool::impl::join()
{
mutex::scoped_lock lock(m_prot);
assert(m_state == RUNNING);
if (m_thread_count > 0)
{
m_state = JOINING;
// if any threads are idling, wake them.
if (m_idle_count > 0)
m_more_work.notify_all();
// Track the shutdown progress of the threads.
while (m_thread_count > 0)
m_done.wait(lock);
}
m_workers.join_all();
m_state = JOINED;
}
// This is a "weak" form of cancel which empties out the job queue and takes
// the thread count down to zero.
//
// Upon receiving more work, the thread count would grow back up to
// min_threads.
//
// Cancel will be much stronger once full thread cancellation is in place!
void thread_pool::impl::cancel()
{
mutex::scoped_lock lock(m_prot);
assert(m_state == RUNNING);
if (m_thread_count > 0)
{
m_state = CANCELLING;
// Cancelling kills any unexecuted jobs.
while (!m_jobs.empty())
m_jobs.pop();
/* If we had cancel, this would be something like....
m_workers.cancel_all();
while(m_cancel_count > 0)
m_all_cancelled.wait(lock);
*/
}
m_state = RUNNING; // Go back to accepting work.
}
void thread_pool::impl::detach()
{
mutex::scoped_lock lock(m_prot);
if (m_state == RUNNING)
{
m_min_threads = 0;
m_state = DETACHED;
}
else
{
// detach during/after a join has no effect - the join will
// complete.
}
}
void thread_pool::impl::worker_harness()
{
boost::thread me;
xtime timeout;
int timedout;
mutex::scoped_lock lock(m_prot);
for (;;)
{
timedout = 0;
xtime_get(&timeout, boost::TIME_UTC);
timeout.sec += m_timeout_secs;
timeout.nsec += m_timeout_nsecs;
while (m_jobs.empty() && (m_state == RUNNING))
{
m_idle_count++;
bool status = m_more_work.timed_wait(lock, timeout);
m_idle_count--;
if (!status)
{
timedout = 1;
return;
}
}
if (!m_jobs.empty() && m_state != CANCELLING)
{
boost::function0<void> jobfunc = m_jobs.front();
m_jobs.pop();
lock.unlock();
jobfunc();
lock.lock();
}
else if (m_jobs.empty() && m_state == JOINING)
{
m_thread_count--;
// If we are the last worker exiting, let everyone know about it!
if (m_thread_count == 0)
m_done.notify_all();
return;
}
else if (m_jobs.empty() && m_state == DETACHED)
{
m_thread_count--;
// If we are the last worker exiting, let everyone know about it!
if (m_thread_count == 0)
{
lock.unlock();
delete this;
}
return;
}
/*
* If there's no more work, and we wait for as long as
* we're allowed, then terminate this server thread.
*/
if (m_jobs.empty() && timedout)
{
if (m_thread_count > m_min_threads)
{
m_thread_count--;
if (m_state == DETACHED &&
m_thread_count == 0)
{
lock.unlock();
delete this;
return;
}
// We aren't in a JOINING or CANCELLING state, so trim
// down our resource usage and clean ourselves up.
// thread* thrd = m_workers.find(me);
m_workers.remove_thread(me);
// delete thrd;
return;
}
}
}
}
thread_pool::thread_pool(int max_threads, int min_threads, int timeout_secs,
int timeout_nsecs)
: m_pimpl(new impl(max_threads, min_threads, timeout_secs, timeout_nsecs))
{
}
thread_pool::~thread_pool()
{
if (m_pimpl != NULL)
delete m_pimpl;
}
void thread_pool::add(const boost::function0<void> &job)
{
assert(m_pimpl);
m_pimpl->add(job);
}
void thread_pool::join()
{
assert(m_pimpl);
m_pimpl->join();
}
void thread_pool::cancel()
{
assert(m_pimpl);
m_pimpl->cancel();
}
void thread_pool::detach()
{
assert(m_pimpl);
// Tell our implementation it is running detached.
m_pimpl->detach();
m_pimpl = NULL;
}
} // namespace boost

View File

@@ -1,165 +1,185 @@
// threadmon.cpp : Defines the entry point for the DLL application.
// Copyright (C) 2001-2003
// 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/config.hpp>
#include <boost/thread/detail/config.hpp>
#if defined(BOOST_HAS_WINTHREADS)
#if defined(BOOST_THREAD_BUILD_DLL)
#include <boost/thread/detail/threadmon.hpp>
#define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers
#include <windows.h>
#ifdef BOOST_MSVC
# pragma warning(disable : 4786)
#endif
#include <list>
#include <set>
#include <algorithm>
typedef void (__cdecl * handler)(void);
typedef std::list<handler> exit_handlers;
typedef std::set<exit_handlers*> registered_handlers;
namespace
{
CRITICAL_SECTION cs;
DWORD key;
registered_handlers registry;
}
#if defined(__BORLANDC__)
#define DllMain DllEntryPoint
#endif
extern "C"
BOOL WINAPI DllMain(HANDLE module, DWORD reason, LPVOID)
{
switch (reason)
extern "C" void tss_cleanup_implemented(void);
void require_tss_cleanup_implemented(void)
{
case DLL_PROCESS_ATTACH:
InitializeCriticalSection(&cs);
tss_cleanup_implemented();
}
#define WIN32_LEAN_AND_MEAN
//Exclude rarely-used stuff from Windows headers
#include <windows.h>
#ifdef BOOST_MSVC
# pragma warning(disable : 4786)
#endif
#include <list>
#include <boost/thread/detail/threadmon.hpp>
typedef void (__cdecl * handler)(void);
typedef std::list<handler> exit_handlers;
namespace
{
const DWORD invalid_key = TLS_OUT_OF_INDEXES;
static DWORD key = invalid_key;
}
extern "C"
BOOST_THREAD_DECL int at_thread_exit(void (__cdecl * func)(void))
{
//Get the exit handlers for the current thread,
//creating and registering one if it doesn't exist.
if (key == invalid_key)
key = TlsAlloc();
break;
case DLL_THREAD_ATTACH:
break;
case DLL_THREAD_DETACH:
{
// Call the thread's exit handlers.
exit_handlers* handlers =
static_cast<exit_handlers*>(TlsGetValue(key));
if (handlers)
{
for (exit_handlers::iterator it = handlers->begin();
it != handlers->end(); ++it)
{
(*it)();
}
// Remove the exit handler list from the registered lists
// and then destroy it.
EnterCriticalSection(&cs);
registry.erase(handlers);
LeaveCriticalSection(&cs);
delete handlers;
}
}
break;
case DLL_PROCESS_DETACH:
{
// Assume the main thread is ending (call its handlers) and
// all other threads have already ended. If this DLL is
// loaded and unloaded dynamically at run time
// this is a bad assumption, but this is the best we can do.
exit_handlers* handlers =
static_cast<exit_handlers*>(TlsGetValue(key));
if (handlers)
{
for (exit_handlers::iterator it = handlers->begin();
it != handlers->end(); ++it)
{
(*it)();
}
}
if (key == invalid_key)
return -1;
// Destroy any remaining exit handlers. Above we assumed
// there'd only be the main thread left, but to insure we
// don't get memory leaks we won't make that assumption
// here.
EnterCriticalSection(&cs);
for (registered_handlers::iterator it = registry.begin();
it != registry.end(); ++it)
{
delete (*it);
}
LeaveCriticalSection(&cs);
DeleteCriticalSection(&cs);
TlsFree(key);
}
break;
}
return TRUE;
}
exit_handlers* handlers =
static_cast<exit_handlers*>(TlsGetValue(key));
extern "C" BOOST_THREAD_DECL int on_thread_exit(void (__cdecl * func)(void))
{
// Get the exit handlers for the current thread, creating and registering
// one if it doesn't exist.
exit_handlers* handlers = static_cast<exit_handlers*>(TlsGetValue(key));
if (!handlers)
{
try
if (!handlers)
{
handlers = new exit_handlers;
// Handle broken implementations of operator new that don't throw.
if (!handlers)
try
{
handlers = new exit_handlers;
//Handle broken implementations
//of operator new that don't throw
if (!handlers)
return -1;
}
catch (...)
{
return -1;
}
catch (...)
{
return -1;
}
//Attempt to set a TLS value for the new handlers.
if (!TlsSetValue(key, handlers))
{
delete handlers;
return -1;
}
}
// Attempt to set a TLS value for the new handlers.
if (!TlsSetValue(key, handlers))
{
delete handlers;
return -1;
}
// Attempt to register this new handler so that memory can be properly
// cleaned up.
//Attempt to add the handler to the list of exit handlers.
try
{
EnterCriticalSection(&cs);
registry.insert(handlers);
LeaveCriticalSection(&cs);
handlers->push_front(func);
}
catch (...)
{
LeaveCriticalSection(&cs);
delete handlers;
return -1;
}
return 0;
}
extern "C" BOOST_THREAD_DECL void on_process_enter(void)
{
if (key == invalid_key)
key = TlsAlloc();
}
extern "C" BOOST_THREAD_DECL void on_thread_exit(void)
{
if (key == invalid_key)
return;
exit_handlers* handlers =
static_cast<exit_handlers*>(TlsGetValue(key));
if (handlers)
{
for (exit_handlers::iterator it = handlers->begin();
it != handlers->end();
++it)
{
//Call each exit handler
(*it)();
}
//Destroy the exit handlers
delete handlers;
}
}
// Attempt to add the handler to the list of exit handlers. If it's been
// previously added just report success and exit.
try
extern "C" BOOST_THREAD_DECL void on_process_exit(void)
{
handlers->push_front(func);
}
catch (...)
{
return -1;
if (key != invalid_key)
{
TlsFree(key);
key = invalid_key;
}
}
return 0;
}
#if defined(BOOST_THREAD_BUILD_DLL)
extern "C" void tss_cleanup_implemented(void)
{
//Don't need to do anything; this function's
//sole purpose is to cause a link error in cases
//where tss cleanup is not implemented by Boost.Threads
//as a reminder that user code is responsible for calling
//on_process_enter(), on_thread_exit(), and
//on_process_exit() at the appropriate times
//and implementing an empty tss_cleanup_implemented()
//function to eliminate the link error.
}
#endif // BOOST_THREAD_BUILD_DLL
#if defined(__BORLANDC__)
#define DllMain DllEntryPoint
#endif
extern "C"
BOOL WINAPI DllMain(HANDLE /*module*/, DWORD reason, LPVOID)
{
switch (reason)
{
case DLL_PROCESS_ATTACH:
{
on_process_enter();
break;
}
case DLL_THREAD_ATTACH:
{
break;
}
case DLL_THREAD_DETACH:
{
on_thread_exit();
break;
}
case DLL_PROCESS_DETACH:
{
on_thread_exit();
on_process_exit();
break;
}
}
return TRUE;
}
#endif // BOOST_THREAD_BUILD_DLL
#endif // BOOST_HAS_WINTHREADS
// Change Log:
// 20 Mar 04 GLASSFORM for WEKEMPF
// Removed uneccessary critical section:
// Windows already serializes calls to DllMain.
// Removed registered_handlers.

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -10,118 +10,119 @@
// It is provided "as is" without express or implied warranty.
namespace {
const int MILLISECONDS_PER_SECOND = 1000;
const int NANOSECONDS_PER_SECOND = 1000000000;
const int NANOSECONDS_PER_MILLISECOND = 1000000;
const int MILLISECONDS_PER_SECOND = 1000;
const int NANOSECONDS_PER_SECOND = 1000000000;
const int NANOSECONDS_PER_MILLISECOND = 1000000;
const int MICROSECONDS_PER_SECOND = 1000000;
const int NANOSECONDS_PER_MICROSECOND = 1000;
const int MICROSECONDS_PER_SECOND = 1000000;
const int NANOSECONDS_PER_MICROSECOND = 1000;
inline void to_time(int milliseconds, boost::xtime& xt)
inline void to_time(int milliseconds, boost::xtime& xt)
{
int res = 0;
res = boost::xtime_get(&xt, boost::TIME_UTC);
assert(res == boost::TIME_UTC);
xt.sec += (milliseconds / MILLISECONDS_PER_SECOND);
xt.nsec += ((milliseconds % MILLISECONDS_PER_SECOND) *
NANOSECONDS_PER_MILLISECOND);
if (xt.nsec > static_cast<const int>(NANOSECONDS_PER_SECOND))
{
int res = 0;
res = boost::xtime_get(&xt, boost::TIME_UTC);
assert(res == boost::TIME_UTC);
xt.sec += (milliseconds / MILLISECONDS_PER_SECOND);
xt.nsec += ((milliseconds % MILLISECONDS_PER_SECOND) * NANOSECONDS_PER_MILLISECOND);
if (xt.nsec > static_cast<const int>(NANOSECONDS_PER_SECOND))
{
++xt.sec;
xt.nsec -= NANOSECONDS_PER_SECOND;
}
++xt.sec;
xt.nsec -= NANOSECONDS_PER_SECOND;
}
}
#if defined(BOOST_HAS_PTHREADS)
inline void to_timespec(const boost::xtime& xt, timespec& ts)
inline void to_timespec(const boost::xtime& xt, timespec& ts)
{
ts.tv_sec = static_cast<int>(xt.sec);
ts.tv_nsec = static_cast<int>(xt.nsec);
if(ts.tv_nsec > static_cast<const int>(NANOSECONDS_PER_SECOND))
{
ts.tv_sec = static_cast<int>(xt.sec);
ts.tv_nsec = static_cast<int>(xt.nsec);
ts.tv_sec += ts.tv_nsec / NANOSECONDS_PER_SECOND;
ts.tv_nsec %= NANOSECONDS_PER_SECOND;
}
}
inline void to_time(int milliseconds, timespec& ts)
{
boost::xtime xt;
to_time(milliseconds, xt);
to_timespec(xt, ts);
}
inline void to_timespec_duration(const boost::xtime& xt, timespec& ts)
{
boost::xtime cur;
int res = 0;
res = boost::xtime_get(&cur, boost::TIME_UTC);
assert(res == boost::TIME_UTC);
if (boost::xtime_cmp(xt, cur) <= 0)
{
ts.tv_sec = 0;
ts.tv_nsec = 0;
}
else
{
ts.tv_sec = xt.sec - cur.sec;
ts.tv_nsec = xt.nsec - cur.nsec;
if( ts.tv_nsec < 0 )
{
ts.tv_sec -= 1;
ts.tv_nsec += NANOSECONDS_PER_SECOND;
}
if(ts.tv_nsec > static_cast<const int>(NANOSECONDS_PER_SECOND))
{
ts.tv_sec += ts.tv_nsec / NANOSECONDS_PER_SECOND;
ts.tv_nsec %= NANOSECONDS_PER_SECOND;
}
}
inline void to_time(int milliseconds, timespec& ts)
{
boost::xtime xt;
to_time(milliseconds, xt);
to_timespec(xt, ts);
}
inline void to_timespec_duration(const boost::xtime& xt, timespec& ts)
{
boost::xtime cur;
int res = 0;
res = boost::xtime_get(&cur, boost::TIME_UTC);
assert(res == boost::TIME_UTC);
if (boost::xtime_cmp(xt, cur) <= 0)
{
ts.tv_sec = 0;
ts.tv_nsec = 0;
}
else
{
ts.tv_sec = xt.sec - cur.sec;
ts.tv_nsec = xt.nsec - cur.nsec;
if( ts.tv_nsec < 0 )
{
ts.tv_sec -= 1;
ts.tv_nsec += NANOSECONDS_PER_SECOND;
}
if(ts.tv_nsec > static_cast<const int>(NANOSECONDS_PER_SECOND))
{
ts.tv_sec += ts.tv_nsec / NANOSECONDS_PER_SECOND;
ts.tv_nsec %= NANOSECONDS_PER_SECOND;
}
}
}
}
#endif
inline void to_duration(boost::xtime xt, int& milliseconds)
{
boost::xtime cur;
int res = 0;
res = boost::xtime_get(&cur, boost::TIME_UTC);
assert(res == boost::TIME_UTC);
inline void to_duration(boost::xtime xt, int& milliseconds)
{
boost::xtime cur;
int res = 0;
res = boost::xtime_get(&cur, boost::TIME_UTC);
assert(res == boost::TIME_UTC);
if (boost::xtime_cmp(xt, cur) <= 0)
milliseconds = 0;
else
if (boost::xtime_cmp(xt, cur) <= 0)
milliseconds = 0;
else
{
if (cur.nsec > xt.nsec)
{
if (cur.nsec > xt.nsec)
{
xt.nsec += NANOSECONDS_PER_SECOND;
--xt.sec;
}
milliseconds = ((xt.sec - cur.sec) * MILLISECONDS_PER_SECOND) +
(((xt.nsec - cur.nsec) + (NANOSECONDS_PER_MILLISECOND/2)) /
xt.nsec += NANOSECONDS_PER_SECOND;
--xt.sec;
}
milliseconds = (int)((xt.sec - cur.sec) * MILLISECONDS_PER_SECOND) +
(((xt.nsec - cur.nsec) + (NANOSECONDS_PER_MILLISECOND/2)) /
NANOSECONDS_PER_MILLISECOND);
}
}
}
inline void to_microduration(const boost::xtime& xt, int& microseconds)
inline void to_microduration(const boost::xtime& xt, int& microseconds)
{
boost::xtime cur;
int res = 0;
res = boost::xtime_get(&cur, boost::TIME_UTC);
assert(res == boost::TIME_UTC);
if (boost::xtime_get(&cur, boost::TIME_UTC) <= 0)
microseconds = 0;
else
{
boost::xtime cur;
int res = 0;
res = boost::xtime_get(&cur, boost::TIME_UTC);
assert(res == boost::TIME_UTC);
if (boost::xtime_get(&cur, boost::TIME_UTC) <= 0)
microseconds = 0;
else
{
microseconds = ((xt.sec - cur.sec) * MICROSECONDS_PER_SECOND) +
(((xt.nsec - cur.nsec) + (NANOSECONDS_PER_MICROSECOND/2)) /
microseconds = (int)((xt.sec - cur.sec) * MICROSECONDS_PER_SECOND) +
(((xt.nsec - cur.nsec) + (NANOSECONDS_PER_MICROSECOND/2)) /
NANOSECONDS_PER_MICROSECOND);
}
}
}
}
// Change Log:
// 1 Jun 01 Initial creation.

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -9,239 +9,206 @@
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/tss.hpp>
#ifndef BOOST_THREAD_NO_TSS_CLEANUP
#include <boost/thread/once.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/exceptions.hpp>
#include <vector>
#include <stdexcept>
#include <cassert>
#if defined(BOOST_HAS_WINTHREADS)
# include <windows.h>
# include <boost/thread/detail/threadmon.hpp>
#endif
namespace {
typedef std::vector<void*> tss_slots;
struct tss_data_t
{
boost::mutex mutex;
std::vector<boost::function1<void, void*>*> cleanup_handlers;
#if defined(BOOST_HAS_WINTHREADS)
#include <boost/thread/detail/threadmon.hpp>
#include <map>
namespace {
typedef std::pair<void(*)(void*), void*> cleanup_info;
typedef std::map<int, cleanup_info> cleanup_handlers;
DWORD key;
boost::once_flag once = BOOST_ONCE_INIT;
void init_cleanup_key()
{
key = TlsAlloc();
assert(key != 0xFFFFFFFF);
}
void __cdecl cleanup()
{
cleanup_handlers* handlers = static_cast<cleanup_handlers*>(TlsGetValue(key));
for (cleanup_handlers::iterator it = handlers->begin(); it != handlers->end(); ++it)
{
cleanup_info info = it->second;
if (info.second)
info.first(info.second);
}
delete handlers;
}
cleanup_handlers* get_handlers()
{
boost::call_once(&init_cleanup_key, once);
cleanup_handlers* handlers = static_cast<cleanup_handlers*>(TlsGetValue(key));
if (!handlers)
{
try
{
handlers = new cleanup_handlers;
}
catch (...)
{
return 0;
}
int res = 0;
res = TlsSetValue(key, handlers);
assert(res);
res = on_thread_exit(&cleanup);
assert(res == 0);
}
return handlers;
}
}
DWORD native_key;
#elif defined(BOOST_HAS_PTHREADS)
pthread_key_t native_key;
#elif defined(BOOST_HAS_MPTASKS)
#include <map>
namespace {
typedef std::pair<void(*)(void*), void*> cleanup_info;
typedef std::map<int, cleanup_info> cleanup_handlers;
TaskStorageIndex native_key;
#endif
};
TaskStorageIndex key;
boost::once_flag once = BOOST_ONCE_INIT;
tss_data_t* tss_data = 0;
boost::once_flag tss_data_once = BOOST_ONCE_INIT;
void init_cleanup_key()
extern "C" void cleanup_slots(void* p)
{
tss_slots* slots = static_cast<tss_slots*>(p);
for (tss_slots::size_type i = 0; i < slots->size(); ++i)
{
OSStatus lStatus = MPAllocateTaskStorageIndex(&key);
assert(lStatus == noErr);
}
cleanup_handlers* get_handlers()
{
boost::call_once(&init_cleanup_key, once);
cleanup_handlers* handlers = reinterpret_cast<cleanup_handlers*>(MPGetTaskStorageValue(key));
if (!handlers)
{
try
{
handlers = new cleanup_handlers;
}
catch (...)
{
return 0;
}
OSStatus lStatus = noErr;
lStatus = MPSetTaskStorageValue(key, reinterpret_cast<TaskStorageValue>(handlers));
assert(lStatus == noErr);
// TODO - create a generalized mechanism for registering thread exit functions
// and use it here.
}
return handlers;
boost::mutex::scoped_lock lock(tss_data->mutex);
(*tss_data->cleanup_handlers[i])((*slots)[i]);
(*slots)[i] = 0;
}
}
void init_tss_data()
{
std::auto_ptr<tss_data_t> temp(new tss_data_t);
#if defined(BOOST_HAS_WINTHREADS)
temp->native_key = TlsAlloc();
if (temp->native_key == 0xFFFFFFFF)
return;
#elif defined(BOOST_HAS_PTHREADS)
int res = pthread_key_create(&temp->native_key, &cleanup_slots);
if (res != 0)
return;
#elif defined(BOOST_HAS_MPTASKS)
OSStatus status = MPAllocateTaskStorageIndex(&temp->native_key);
if (status != noErr)
return;
#endif
// Intentional memory "leak"
// This is the only way to ensure the mutex in the global data
// structure is available when cleanup handlers are run, since the
// execution order of cleanup handlers is unspecified on any platform
// with regards to C++ destructor ordering rules.
tss_data = temp.release();
}
#if defined(BOOST_HAS_WINTHREADS)
tss_slots* get_slots(bool alloc);
void __cdecl tss_thread_exit()
{
tss_slots* slots = get_slots(false);
if (slots)
cleanup_slots(slots);
}
#endif
tss_slots* get_slots(bool alloc)
{
tss_slots* slots = 0;
#if defined(BOOST_HAS_WINTHREADS)
slots = static_cast<tss_slots*>(
TlsGetValue(tss_data->native_key));
#elif defined(BOOST_HAS_PTHREADS)
slots = static_cast<tss_slots*>(
pthread_getspecific(tss_data->native_key));
#elif defined(BOOST_HAS_MPTASKS)
slots = static_cast<tss_slots*>(
MPGetTaskStorageValue(tss_data->native_key));
#endif
if (slots == 0 && alloc)
{
std::auto_ptr<tss_slots> temp(new tss_slots);
#if defined(BOOST_HAS_WINTHREADS)
if (at_thread_exit(&tss_thread_exit) == -1)
return 0;
if (!TlsSetValue(tss_data->native_key, temp.get()))
return 0;
#elif defined(BOOST_HAS_PTHREADS)
if (pthread_setspecific(tss_data->native_key, temp.get()) != 0)
return 0;
#elif defined(BOOST_HAS_MPTASKS)
if (MPSetTaskStorageValue(tss_data->native_key, temp.get()) != noErr)
return 0;
#endif
slots = temp.release();
}
return slots;
}
} // namespace
namespace boost {
namespace detail {
void thread_cleanup()
void tss::init(boost::function1<void, void*>* pcleanup)
{
cleanup_handlers* handlers = reinterpret_cast<cleanup_handlers*>(MPGetTaskStorageValue(key));
if(handlers != NULL)
boost::call_once(&init_tss_data, tss_data_once);
if (tss_data == 0)
throw thread_resource_error();
boost::mutex::scoped_lock lock(tss_data->mutex);
try
{
for (cleanup_handlers::iterator it = handlers->begin(); it != handlers->end(); ++it)
tss_data->cleanup_handlers.push_back(pcleanup);
m_slot = tss_data->cleanup_handlers.size() - 1;
}
catch (...)
{
throw thread_resource_error();
}
}
void* tss::get() const
{
tss_slots* slots = get_slots(false);
if (!slots)
return 0;
if (m_slot >= slots->size())
return 0;
return (*slots)[m_slot];
}
void tss::set(void* value)
{
tss_slots* slots = get_slots(true);
if (!slots)
throw boost::thread_resource_error();
if (m_slot >= slots->size())
{
try
{
cleanup_info info = it->second;
if (info.second)
info.first(info.second);
slots->resize(m_slot + 1);
}
catch (...)
{
throw boost::thread_resource_error();
}
delete handlers;
}
(*slots)[m_slot] = value;
}
} // namespace detail
} // namespace boost
#endif
namespace boost { namespace detail {
#if defined(BOOST_HAS_WINTHREADS)
tss::tss(void (*cleanup)(void*))
void tss::cleanup(void* value)
{
m_key = TlsAlloc();
if (m_key == 0xFFFFFFFF)
throw thread_resource_error();
m_cleanup = cleanup;
boost::mutex::scoped_lock lock(tss_data->mutex);
(*tss_data->cleanup_handlers[m_slot])(value);
}
tss::~tss()
{
int res = 0;
res = TlsFree(m_key);
assert(res);
}
void* tss::get() const
{
return TlsGetValue(m_key);
}
bool tss::set(void* value)
{
if (value && m_cleanup)
{
cleanup_handlers* handlers = get_handlers();
assert(handlers);
if (!handlers)
return false;
cleanup_info info(m_cleanup, value);
(*handlers)[m_key] = info;
}
return !!TlsSetValue(m_key, value);
}
#elif defined(BOOST_HAS_PTHREADS)
tss::tss(void (*cleanup)(void*))
{
int res = 0;
res = pthread_key_create(&m_key, cleanup);
if (res != 0)
throw thread_resource_error();
}
tss::~tss()
{
int res = 0;
res = pthread_key_delete(m_key);
assert(res == 0);
}
void* tss::get() const
{
return pthread_getspecific(m_key);
}
bool tss::set(void* value)
{
return pthread_setspecific(m_key, value) == 0;
}
#elif defined(BOOST_HAS_MPTASKS)
tss::tss(void (*cleanup)(void*))
{
OSStatus lStatus = MPAllocateTaskStorageIndex(&m_key);
if(lStatus != noErr)
throw thread_resource_error();
m_cleanup = cleanup;
}
tss::~tss()
{
OSStatus lStatus = MPDeallocateTaskStorageIndex(m_key);
assert(lStatus == noErr);
}
void* tss::get() const
{
TaskStorageValue ulValue = MPGetTaskStorageValue(m_key);
return(reinterpret_cast<void *>(ulValue));
}
bool tss::set(void* value)
{
if (value && m_cleanup)
{
cleanup_handlers* handlers = get_handlers();
assert(handlers);
if (!handlers)
return false;
cleanup_info info(m_cleanup, value);
(*handlers)[m_key] = info;
}
OSStatus lStatus = MPSetTaskStorageValue(m_key, reinterpret_cast<TaskStorageValue>(value));
return(lStatus == noErr);
}
#endif
} // namespace detail
} // namespace boost
#endif //BOOST_THREAD_NO_TSS_CLEANUP
// Change Log:
// 6 Jun 01 WEKEMPF Initial version.
// 6 Jun 01
// WEKEMPF Initial version.
// 30 May 02 WEKEMPF
// Added interface to set specific cleanup handlers.
// Removed TLS slot limits from most implementations.
// 22 Mar 04 GlassfordM for WEKEMPF
// Fixed: thread_specific_ptr::reset() doesn't check error returned
// by tss::set(); tss::set() now throws if it fails.
// Fixed: calling thread_specific_ptr::reset() or
// thread_specific_ptr::release() causes double-delete: once on
// reset()/release() and once on ~thread_specific_ptr().

View File

@@ -1,4 +1,4 @@
// Copyright (C) 2001
// Copyright (C) 2001-2003
// William E. Kempf
//
// Permission to use, copy, modify, distribute and sell this software
@@ -9,6 +9,8 @@
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
#include <boost/thread/detail/config.hpp>
#include <boost/thread/xtime.hpp>
#if defined(BOOST_HAS_FTIME)
@@ -33,29 +35,30 @@ struct startup_time_info
{
startup_time_info()
{
// 1970 Jan 1 at 00:00:00
// 1970 Jan 1 at 00:00:00
static const DateTimeRec k_sUNIXBase = {1970, 1, 1, 0, 0, 0, 0};
static unsigned long s_ulUNIXBaseSeconds = 0UL;
if(s_ulUNIXBaseSeconds == 0UL)
{
// calculate the number of seconds between the Mac OS base and the UNIX base
// the first time we enter this constructor.
// calculate the number of seconds between the Mac OS base and the
// UNIX base the first time we enter this constructor.
DateToSeconds(&k_sUNIXBase, &s_ulUNIXBaseSeconds);
}
unsigned long ulSeconds;
// get the time in UpTime units twice, with the time in seconds in the middle.
// get the time in UpTime units twice, with the time in seconds in the
// middle.
uint64_t ullFirstUpTime = force_cast<uint64_t>(UpTime());
GetDateTime(&ulSeconds);
uint64_t ullSecondUpTime = force_cast<uint64_t>(UpTime());
// calculate the midpoint of the two UpTimes, and save that.
// calculate the midpoint of the two UpTimes, and save that.
uint64_t ullAverageUpTime = (ullFirstUpTime + ullSecondUpTime) / 2ULL;
m_sStartupAbsoluteTime = force_cast<AbsoluteTime>(ullAverageUpTime);
// save the number of seconds, recentered at the UNIX base.
// save the number of seconds, recentered at the UNIX base.
m_ulStartupSeconds = ulSeconds - s_ulUNIXBaseSeconds;
}
@@ -76,11 +79,22 @@ int xtime_get(struct xtime* xtp, int clock_type)
{
#if defined(BOOST_HAS_FTIME)
FILETIME ft;
# if defined(BOOST_NO_GETSYSTEMTIMEASFILETIME)
{
SYSTEMTIME st;
GetSystemTime(&st);
SystemTimeToFileTime(&st,&ft);
}
# else
GetSystemTimeAsFileTime(&ft);
const boost::uint64_t TIMESPEC_TO_FILETIME_OFFSET = ((boost::uint64_t)27111902UL << 32) + (boost::uint64_t)3577643008UL;
xtp->sec = (int)((*(__int64*)&ft - TIMESPEC_TO_FILETIME_OFFSET) / 10000000);
# endif
const boost::uint64_t TIMESPEC_TO_FILETIME_OFFSET =
((boost::uint64_t)27111902UL << 32) +
(boost::uint64_t)3577643008UL;
xtp->sec = (int)((*(__int64*)&ft - TIMESPEC_TO_FILETIME_OFFSET) /
10000000);
xtp->nsec = (int)((*(__int64*)&ft - TIMESPEC_TO_FILETIME_OFFSET -
((__int64)xtp->sec * (__int64)10000000)) * 100);
((__int64)xtp->sec * (__int64)10000000)) * 100);
return clock_type;
#elif defined(BOOST_HAS_GETTIMEOFDAY)
struct timeval tv;
@@ -96,12 +110,16 @@ int xtime_get(struct xtime* xtp, int clock_type)
return clock_type;
#elif defined(BOOST_HAS_MPTASKS)
using detail::thread::force_cast;
// the Mac OS does not have an MP-safe way of getting the date/time, so we use a
// delta from the startup time. We _could_ defer this and use something that is
// interrupt-safe, but this would be _SLOW_, and we need speed here.
// the Mac OS does not have an MP-safe way of getting the date/time,
// so we use a delta from the startup time. We _could_ defer this
// and use something that is interrupt-safe, but this would be _SLOW_,
// and we need speed here.
const uint64_t k_ullNanosecondsPerSecond(1000ULL * 1000ULL * 1000ULL);
AbsoluteTime sUpTime(UpTime());
uint64_t ullNanoseconds(force_cast<uint64_t>(AbsoluteDeltaToNanoseconds(sUpTime, detail::g_sStartupTimeInfo.m_sStartupAbsoluteTime)));
uint64_t ullNanoseconds(
force_cast<uint64_t>(
AbsoluteDeltaToNanoseconds(sUpTime,
detail::g_sStartupTimeInfo.m_sStartupAbsoluteTime)));
uint64_t ullSeconds = (ullNanoseconds / k_ullNanosecondsPerSecond);
ullNanoseconds -= (ullSeconds * k_ullNanosecondsPerSecond);
xtp->sec = detail::g_sStartupTimeInfo.m_ulStartupSeconds + ullSeconds;

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