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213 lines
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HTML
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213 lines
11 KiB
HTML
Executable File
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML>
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<HEAD>
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<TITLE>File Descriptor Devices</TITLE>
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<LINK REL='stylesheet' HREF='../../../../boost.css'>
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<LINK REL='stylesheet' HREF='../theme/iostreams.css'>
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<STYLE> H3 CODE { font-size: 110% } </STYLE>
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</HEAD>
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<BODY>
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<!-- Begin Banner -->
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<H1 CLASS='title'>File Descriptor Devices</H1>
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<HR CLASS='banner'>
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<DL class='page-index'>
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<DT><A href='#overview'>Overview</A></DT>
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<DT><A href='#acknowledgments'>Acknowledments</A></DT>
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<DT><A href='#installation'>Installation</A></DT>
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<DT><A href='#headers'>Headers</A></DT>
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<DT><A href='#reference'>Reference</A>
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<UL>
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<LI CLASS='square'><A href='#file_descriptor_source'>Class <CODE>file_descriptor_source</CODE></A></LI>
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<LI CLASS='square'><A href='#file_descriptor_sink'>Class <CODE>file_descriptor_sink</CODE></A></LI>
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<LI CLASS='square'><A href='#file_descriptor'>Class <CODE>file_descriptor</CODE></A></LI>
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</UL>
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</DT>
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</DL>
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<HR>
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<A NAME='overview'>
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<H2>Overview</H2>
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<P>
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The classes <CODE>file_descriptor_source</CODE>, <CODE>file_descriptor_sink</CODE> and <CODE>file_descriptor</CODE> provide file access via operating system file descriptors. These <A HREF="../concepts.html#device_concepts">Devices</A> behave much like the <A HREF="file.html">File Wrappers</A> <CODE>basic_file_source</CODE>, <CODE>basic_file_sink</CODE> and <CODE>basic_file</CODE>, with the following important differences:
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</P>
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<UL>
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<LI CLASS='square'>A file descriptor Device may be constructed from a file descriptor which is already open.
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<LI CLASS='square'>The only buffering is provded by the Boost Iostreams Library.
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<LI CLASS='square'>There is no automatic line-endings conversion.
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<LI CLASS='square'>Wide-character streams are not supported.
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</UL>
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<P>
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Line-ending conversion is available using the <A HREF='newline_filter.html'>Newline Filters</A>. Wide-character versions of the file descriptor Devices may be defined as follows, using the template <A HREF='converter.html'><CODE>converter</CODE></A>:
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<PRE CLASS='broken_ie'> <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS='header' HREF='../../../../boost/iostreams/converter.hpp'><SPAN CLASS="literal"><boost/iostreams/converter.hpp></SPAN></A>
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<SPAN CLASS="preprocessor">#include</SPAN> <A CLASS='header' HREF='../../../../boost/iostreams/device/file_descriptor.hpp'><SPAN CLASS="literal"><boost/iostreams/maped_file.hpp></SPAN></A>
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typedef converter<file_descriptor_source> <SPAN CLASS="defined">wfile_descriptor_source</SPAN>;
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typedef converter<file_descriptor_sink> <SPAN CLASS="defined">wfile_descriptor_sink</SPAN>;</PRE>
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</P>
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<P>
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When a file descriptor Device is copied, the result represents the same underlying file descriptor. The underlying file descriptor is <I>not</I> duplicated.
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</P>
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<P>
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Currently, file descriptor Devices do not work corectly with file descriptors opened in non-blocking mode.
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</P>
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<A NAME='acknowledgments'>
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<H2>Acknowledgments</H2>
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<P>
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The file descriptor Devices are based on work of Nicolai Josuttis (<A CLASS='bib_ref' HREF='../bibliography.html#josuttis1'>[Josuttis1]</A> <I>pp.</I> 672-3 and <A CLASS='bib_ref' HREF='../bibliography.html#josuttis2'>[Josuttis2]</A>).
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</P>
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<A NAME='installation'>
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<H2>Installation</H2>
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<P>
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The file descriptor Devices depends on the source file <A CLASS='header' HREF='../../src/file_descriptor.cpp'><CODE><libs/iostreams/src/file_descriptor.cpp></CODE></A>, which makes use of Windows or POSIX headers depending on the user's operating system. For installation instructions see <A HREF='../installation.html'>Installation</A>.
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</P>
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<A NAME='headers'>
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<H2>Headers</H2>
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<DL class='page-index'>
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<DT><A CLASS='header' HREF='../../../../boost/iostreams/device/file_descriptor.hpp'><CODE><boost/iostreams/device/file_descriptor.hpp></CODE></A></DT>
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</DL>
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<A NAME='reference'>
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<H2>Reference</H2>
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<A NAME='file_descriptor_source'>
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<H3>Class <CODE>file_descriptor_source</CODE></H3>
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<H4>Description</H4>
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<P>Model of <A HREF='../concepts/source.html'>Source</A> providing read-only access to a file through an operating system file descriptor.</P>
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<H4>Synopsis</H4>
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<PRE CLASS='broken_ie'><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
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<SPAN CLASS="keyword">class</SPAN> file_descriptor_source : <SPAN CLASS="keyword">public</SPAN> <A CLASS="documented" HREF="device.html#synopsis">source</A> { <SPAN CLASS="comment">// Exposition only</SPAN>
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<SPAN CLASS="keyword">public</SPAN>:
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<A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close = <SPAN CLASS="keyword">false</SPAN> );
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<A CLASS="documented" HREF="#file_descriptor_source_ctor">file_descriptor_source</A>( <SPAN CLASS="keyword">const</SPAN> std::string& pathname,
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std::ios_base::open_mode mode =
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std::ios_base::in );
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};
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} } // End namespace boost::io</PRE>
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<A NAME='file_descriptor_source_ctor'></A>
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<H4><CODE>file_descriptor_source::file_descriptor_source</CODE></H4>
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<A NAME='file_descriptor_source_ctor'></A>
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<PRE CLASS='broken_ie'> file_descriptor_source( <SPAN CLASS="keyword">int </SPAN>fd, <SPAN CLASS="keyword">bool</SPAN> close = <SPAN CLASS="keyword">false</SPAN>);
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file_descriptor_source( <SPAN CLASS="keyword">const</SPAN> std::string& pathname,
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std::ios_base::open_mode mode =
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std::ios_base::in );</PRE>
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<P>
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The first member constructs a <CODE>file_descriptor_source</CODE> to access the file with the given operating system file descriptor. If the second argument is <CODE>true</CODE>, the file descriptor is closed when the new <CODE>file_descriptor_source</CODE> — or one of its copies — is closed. The second member constructs a <CODE>file_descriptor_source</CODE> to access the file with the given pathname. The parameter <CODE>mode</CODE> has the same interpretation as <CODE>(mode | std::ios_base::in)</CODE> in <CODE>std::basic_filebuf::open</CODE>.<A CLASS='footnote_ref' NAME='note_1_ref' HREF='#note_1'><SUP>[1]</SUP>
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</P>
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<A NAME='file_descriptor_sink'>
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<H3>Class <CODE>file_descriptor_sink</CODE></H3>
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<H4>Description</H4>
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<P>Model of <A HREF='../concepts/sink.html'>Sink</A> providing write-only access to a file through an operating system file descriptor.
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<H4>Synopsis</H4>
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<PRE CLASS='broken_ie'><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
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<SPAN CLASS="keyword">class</SPAN> file_descriptor_sink : <SPAN CLASS="keyword">public</SPAN> <A CLASS="documented" HREF="device.html#synopsis">sink</A> { <SPAN CLASS="comment">// Exposition only</SPAN>
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<SPAN CLASS="keyword">public</SPAN>:
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<A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close = <SPAN CLASS="keyword">false</SPAN> );
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<A CLASS="documented" HREF="#file_descriptor_sink_ctor">file_descriptor_sink</A>( <SPAN CLASS="keyword">const</SPAN> std::string& pathname,
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std::ios_base::open_mode mode =
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std::ios_base::out );
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};
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} } // End namespace boost::io</PRE>
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<A NAME='file_descriptor_sink_ctor'></A>
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<H4><CODE>file_descriptor_sink::file_descriptor_sink</CODE></H4>
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<PRE CLASS='broken_ie'> file_descriptor_sink( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close = <SPAN CLASS="keyword">false</SPAN> );
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file_descriptor_sink( <SPAN CLASS="keyword">const</SPAN> std::string& pathname,
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std::ios_base::open_mode mode =
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std::ios_base::out );</PRE>
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<P>
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The first member constructs a <CODE>file_descriptor_sink</CODE> to access the file with the given operating system file descriptor. If the second argument is <CODE>true</CODE>, the file descriptor is closed when the new <CODE>file_descriptor_sink</CODE> — or one of its copies — is closed. The second member constructs a <CODE>file_descriptor_sink</CODE> to access the file with the given pathname. The parameter <CODE>mode</CODE> has the same interpretation as <CODE>(mode | std::ios_base::out)</CODE> in <CODE>std::basic_filebuf::open</CODE>.<A CLASS='footnote_ref' NAME='note_1_ref' HREF='#note_1'><SUP>[1]</SUP>
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</P>
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<A NAME='file_descriptor'>
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<H3>Class <CODE>file_descriptor</CODE></H3>
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<H4>Description</H4>
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<P>Model of <A HREF='../concepts/seekable_device.html'>SeekableDevice</A> providing read-write access to a file through an operating system file descriptor.
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<H4>Synopsis</H4>
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<PRE CLASS='broken_ie'><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
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<SPAN CLASS="keyword">class</SPAN> file_descriptor : <SPAN CLASS="keyword">public</SPAN> <A CLASS="documented" HREF="device.html">Device</A><seekable> { <SPAN CLASS="comment">// Exposition only</SPAN>
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<SPAN CLASS="keyword">public</SPAN>:
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<A CLASS="documented" HREF="#file_descriptor_ctor">file_descriptor</A>( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close = <SPAN CLASS="keyword">false</SPAN> );
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<A CLASS="documented" HREF="#file_descriptor_ctor">file_descriptor</A>( <SPAN CLASS="keyword">const</SPAN> std::string& pathname,
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std::ios_base::open_mode mode =
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std::ios_base::in | std::ios_base::out );
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};
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} } // End namespace boost::io</PRE>
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<A NAME='file_descriptor_constructor'></A>
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<H4><CODE>file_descriptor::file_descriptor</CODE></H4>
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<PRE CLASS='broken_ie'> file_descriptor( <SPAN CLASS="keyword">int</SPAN> fd, <SPAN CLASS="keyword">bool</SPAN> close = <SPAN CLASS="keyword">false</SPAN> );
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file_descriptor( <SPAN CLASS="keyword">const</SPAN> std::string& pathname,
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std::ios_base::open_mode mode =
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std::ios_base::in | std::ios_base::out );</PRE>
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<P>
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The first member constructs a <CODE>file_descriptor</CODE> to access the file with the given operating system file descriptor. If the second argument is <CODE>true</CODE>, the file descriptor is closed when the new <CODE>file_descriptor</CODE> — or one of its copies — is closed. The second member constructs a <CODE>file_descriptor</CODE> to access the file with the given pathname. The parameter <CODE>mode</CODE> has the same interpretation as in <CODE>std::basic_filebuf::open</CODE>.<A CLASS='footnote_ref' NAME='note_1_ref' HREF='#note_1'><SUP>[1]</SUP>
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</P>
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<!-- Begin Footnotes -->
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<HR>
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<P>
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<A CLASS='footnote_ref' NAME='note_1' HREF='#note_1_ref'><SUP>[1]</SUP></A><A CLASS='bib_ref' HREF='../bibliography.html#iso'>[I<SPAN STYLE='font-size:80%'>SO</SPAN>]</A>, Table 92.
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</P>
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<!-- End Footnotes -->
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<!-- Begin Footer -->
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<HR>
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<P CLASS='copyright'>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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20 May, 2004
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<!--webbot bot="Timestamp" endspan i-checksum="38504" -->
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</P>
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<P CLASS='copyright'>© Copyright Jonathan Turkanis, 2004</P>
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<P CLASS='copyright'>
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Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF='http://www.boost.org/LICENSE_1_0.txt'>http://www.boost.org/LICENSE_1_0.txt</A>)
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