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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML>
<HEAD>
<TITLE>Memory-Mapped Files</TITLE>
<LINK REL="stylesheet" HREF="../../../../boost.css">
<LINK REL="stylesheet" HREF="../theme/iostreams.css">
</HEAD>
<BODY>
<!-- Begin Banner -->
<H1 CLASS="title">Memory-Mapped Files</H1>
<HR CLASS="banner">
<!-- End Banner -->
<DL class="page-index">
<DT><A href="#overview">Overview</A></DT>
<DT><A href="#acknowledgments">Acknowledgments</A></DT>
<DT><A href="#installation">Installation</A></DT>
<DT><A href="#headers">Headers</A></DT>
<DT><A href="#reference">Reference</A>
<OL>
<LI CLASS="square"><A href="#mapped_file_params">Class <CODE>mapped_file_params</CODE></A></LI>
<LI CLASS="square"><A href="#mapped_file_source">Class <CODE>mapped_file_source</CODE></A></LI>
<LI CLASS="square"><A href="#mapped_file_sink">Class <CODE>mapped_file_sink</CODE></A></LI>
<LI CLASS="square"><A href="#mapped_file">Class <CODE>mapped_file</CODE></A></LI>
</OL>
</DT>
</DL>
<HR>
<A NAME="overview">
<H2>Overview</H2>
<P>
The classes <CODE>mapped_file_source</CODE>, <CODE>mapped_file_sink</CODE> and <CODE>mapped_file</CODE> provide access to memory-mapped files on Windows and POSIX systems. These <A HREF="../guide/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:
</P>
<UL>
<LI CLASS="square">By default, files must exist before being opened, and are not truncated; attempting to write past the end of a file results in an error. To map a file which does not yet exist, use <A HREF="#mapped_file_params_size"><CODE>mapped_file_params::new_file_size</CODE></A>.
<LI CLASS="square">Files are always opened in binary mode.
<LI CLASS="square">Wide-character streams are not supported.
</UL>
<P>
Wide-character versions of the memory-mapped file Devices may be defined as follows, using the template <A HREF="code_converter.html"><CODE>code_converter</CODE></A>:
<PRE CLASS="broken_ie"> <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/code_converter.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/code_converter.hpp&gt;</SPAN></A>
<SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/device/mapped_file.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/maped_file.hpp&gt;</SPAN></A>
<SPAN CLASS="keyword">typedef</SPAN> code_converter&lt;mapped_file_source&gt; <SPAN CLASS="defined">wmapped_file_source</SPAN>;
<SPAN CLASS="keyword">typedef</SPAN> code_converter&lt;mapped_file_sink&gt; <SPAN CLASS="defined">wmapped_file_sink</SPAN>;</PRE>
</P>
<A NAME="acknowledgments">
<H2>Acknowledgments</H2>
<P>
The memory-mapped file Devices are based on the work of Craig Henderson (<A CLASS="bib_ref" HREF="../bibliography.html#henderson">[Henderson]</A>). Additionals features were implemented by Jonathan Graehl.
</P>
<A NAME="installation">
<H2>Installation</H2>
<P>
The memory-mapped file Devices depend on the source file <A CLASS="header" HREF="../../src/mapped_file.cpp"><CODE>&lt;libs/iostreams/src/mapped_file.cpp&gt;</CODE></A>. This source file makes use of Windows or POSIX headers depending on the user's operating system. For installation instructions see <A HREF="../installation.html">Installation</A>.
</P>
<A NAME="headers">
<H2>Headers</H2>
<DL class="page-index">
<DT><A CLASS="header" HREF="../../../../boost/iostreams/device/mapped_file.hpp"><CODE>&lt;boost/iostreams/device/mapped_file.hpp&gt;</CODE></A></DT>
</DL>
<A NAME="reference">
<H2>Reference</H2>
<A NAME="mapped_file_params">
<H3>1. Class <CODE>mapped_file_params</CODE></H3>
<H4>Description</H4>
<P>Class encapsulating the parameters used to open a memory-mapped file.</P>
<H4>Synopsis</H4>
<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
<SPAN CLASS="keyword">struct</SPAN> <SPAN CLASS="defined">mapped_file_params</SPAN> {
<SPAN CLASS='keyword'>explicit</SPAN> mapped_file_params();
<SPAN CLASS='keyword'>explicit</SPAN> mapped_file_params(<SPAN CLASS='keyword'>const</SPAN> std::string& path);
std::string <A CLASS='documented' HREF='#mapped_file_params_hint'>path</A>;
std::ios_base::openmode <A CLASS='documented' HREF='#mapped_file_params_mode'>mode</A>;
stream_offset <A CLASS='documented' HREF='#mapped_file_params_offset'>offset</A>;
std::size_t <A CLASS='documented' HREF='#mapped_file_params_length'>length</A>;
stream_offset <A CLASS="documented" HREF="#mapped_file_params_size">new_file_size</A>;
<SPAN CLASS='keyword'>const</SPAN> <SPAN CLASS='keyword'>char</SPAN>* <A CLASS='documented' HREF='#mapped_file_params_hint'>hint</A>;
};
} } // End namespace boost::io</PRE>
<A NAME="mapped_file_params_path"></A>
<H4><CODE>mapped_file_params::path</CODE></H4>
<PRE CLASS="broken_ie"> std::string path;</PRE>
<P>The pathname of the file to map.</P>
<A NAME="mapped_file_params_mode"></A>
<H4><CODE>mapped_file_params::mode</CODE></H4>
<PRE CLASS="broken_ie"> std::ios_base::openmode mode;</PRE>
<P>Indicates whether the file should be opened with read-access, write-access or both. Ignored by <CODE>mapped_file_source</CODE> and <CODE>mapped_file_sink</CODE> .</P>
<A NAME="mapped_file_params_offset"></A>
<H4><CODE>mapped_file_params::offset</CODE></H4>
<PRE CLASS="broken_ie"> stream_offset offset;</PRE>
<P>The offset where the mapping is to begin. This value must be a multiple of the operating system's virtual memory allocation granularity, which can be abotained via the static member function <A HREF="#mapped_file_alignment"><CODE>alignment</CODE></A> of <CODE>mapped_file_source</CODE>, <CODE>mapped_file_sink</CODE> or <CODE>mapped_file</CODE>. Defaults to <CODE>0</CODE>.</P>
<A NAME="mapped_file_params_length"></A>
<H4><CODE>mapped_file_params::length</CODE></H4>
<PRE CLASS="broken_ie"> std::size_t length;</PRE>
<P>The number of bytes to map. If this parameter is not specified, the entire file is mapped.</P>
<A NAME="mapped_file_params_size"></A>
<H4><CODE>mapped_file_params::new_file_size</CODE></H4>
<PRE CLASS="broken_ie"> stream_offset new_file_size;</PRE>
<P>If this value is non-zero it specifies the size of a file to be created. If a file with pathname <I>path</I> already exists, it will be overwritten.</P>
<A NAME="mapped_file_params_hint"></A>
<H4><CODE>mapped_file_params::hint</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>const</SPAN> <SPAN CLASS='keyword'>char</SPAN>* hint;</PRE>
<P>Suggests a location in the process's address space for the mapping to begin.</P>
<A NAME="mapped_file_source">
<H3>2. Class <CODE>mapped_file_source</CODE></H3>
<H4>Description</H4>
<P>Model of <A HREF="../concepts/source.html">Source</A> providing read-only access to memory-mapped files on Windows and POSIX systems.</P>
<H4>Synopsis</H4>
<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
<SPAN CLASS="keyword">class</SPAN> <SPAN CLASS="defined">mapped_file_source</SPAN> {
<SPAN CLASS="keyword">public</SPAN>:
<SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='keyword'>char</SPAN> char_type;
<SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN> category;
<A CLASS='documented' HREF='#mapped_file_source_default_ctor'>mapped_file_source</A>();
<SPAN CLASS='keyword'>explicit</SPAN> <A CLASS='documented' HREF='#mapped_file_source_params_ctor'>mapped_file_source</A>(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);
<SPAN CLASS='keyword'>explicit</SPAN> <A CLASS='documented' HREF='#mapped_file_source_basic_ctor'>mapped_file_source</A>( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );
void <A CLASS='documented' HREF='#mapped_file_source_params_open'>open</A>(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);
void <A CLASS='documented' HREF='#mapped_file_source_basic_open'>open</A>( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );
<SPAN CLASS='keyword'>bool</SPAN> <A CLASS='documented' HREF='#mapped_file_source_is_open'>is_open</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#mapped_file_source_close'>close</A>();
size_type <A CLASS='documented' HREF='#mapped_file_source_size'>size</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>const</SPAN> <SPAN CLASS='keyword'>char</SPAN>* <A CLASS='documented' HREF='#mapped_file_source_data'>data</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>static</SPAN> <SPAN CLASS='keyword'>int</SPAN> <A CLASS='documented' HREF='#mapped_file_source_alignment'>alignment</A>();
};
} } // End namespace boost::io</PRE>
<A NAME="mapped_file_source_default_ctor"></A>
<H4><CODE>mapped_file_source::mapped_file_source</CODE></H4>
<PRE CLASS="broken_ie"> mapped_file_source();</PRE>
<P>Constructs a <CODE>mapped_file_source</CODE> which must be opened before it can be used to perform i/o.</P>
<A NAME="mapped_file_source_params_ctor"></A>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>explicit</SPAN> mapped_file_source(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);</PRE>
<P>Constructs a <CODE>mapped_file_source</CODE> from the given parameters.</P>
<A NAME="mapped_file_source_basic_ctor"></A>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>explicit</SPAN> mapped_file_source( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );</PRE>
<P>Constructs a <CODE>mapped_file_source</CODE> to access a specified file. The parameters have the following interpretation:</P>
<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
<TR>
<TR>
<TD VALIGN="top"><I>path</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The pathname of the file to map.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>length</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The number of bytes to map. If this parameter is not specified, the entire file is mapped.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>offset</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The offset where the mapping is to begin. This value must be a multiple of the operating system's virtual memory allocation granularity, which can be obtained using the static member function <A HREF='#mapped_file_source_alignment'><CODE>alignment</CODE></A>.</TD>
</TR>
</TABLE>
<A NAME="mapped_file_source_params_open"></A>
<H4><CODE>mapped_file_source::open</CODE></H4>
<PRE CLASS="broken_ie"> void open(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);</PRE>
<P>Connects this <CODE>mapped_file_source</CODE> to a memory-mapped file obtained as described by the given parameters.</P>
<A NAME="mapped_file_source_basic_open"></A>
<PRE CLASS="broken_ie"> void open( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );</PRE>
<P>Connects this <CODE>mapped_file_source</CODE> to a memory-mapped file obtained as described by the given parameters, which have the following interpretation:</P>
<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
<TR>
<TR>
<TD VALIGN="top"><I>path</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The pathname of the file to map.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>length</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The number of bytes to map. If this parameter is not specified, the entire file is mapped.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>offset</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The offset where the mapping is to begin. This value must be a multiple of the operating system's virtual memory allocation granularity, which can be obtained using the static member function <A HREF='#mapped_file_source_alignment'><CODE>alignment</CODE></A>.</TD>
</TR>
</TABLE>
<A NAME="mapped_file_source_is_open"></A>
<H4><CODE>mapped_file_source::is_open</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>bool</SPAN> is_open() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns <CODE>true</CODE> if this <CODE>mapped_file_source</CODE> has been successfully opened without subsequently having been closed.</P>
<A NAME="mapped_file_source_close"></A>
<H4><CODE>mapped_file_source::close</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>void</SPAN> close();</PRE>
<P>Frees the mapping associated with this <CODE>mapped_file_source</CODE>.</P>
<A NAME="mapped_file_source_size"></A>
<H4><CODE>mapped_file_source::size</CODE></H4>
<PRE CLASS="broken_ie"> size_type size() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns the size in bytes of the mapping associated with this <CODE>mapped_file_source</CODE>.</P>
<A NAME="mapped_file_source_data"></A>
<H4><CODE>mapped_file_source::data</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>const</SPAN> <SPAN CLASS='keyword'>char</SPAN>* data() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns a pointer to the first byte of data in the mapping associated with this <CODE>mapped_file_source</CODE>.</P>
<A NAME="mapped_file_source_alignment"></A>
<H4><CODE>mapped_file_source::alignment</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>static</SPAN> <SPAN CLASS='keyword'>int</SPAN> alignment();</PRE>
<P>Returns the operating system's virtual memory allocation granularity.</P>
<A NAME="mapped_file_sink">
<H3>3. Class <CODE>mapped_file_sink</CODE></H3>
<H4>Description</H4>
<P>Model of <A HREF="../concepts/sink.html">Sink</A> providing write-only access to memory-mapped files on Windows and POSIX systems.</P>
<H4>Synopsis</H4>
<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
<SPAN CLASS="keyword">class</SPAN> <SPAN CLASS="defined">mapped_file_sink</SPAN> {
<SPAN CLASS="keyword">public</SPAN>:
<SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='keyword'>char</SPAN> char_type;
<SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN> category;
<A CLASS='documented' HREF='#mapped_file_sink_default_ctor'>mapped_file_sink</A>();
<SPAN CLASS='keyword'>explicit</SPAN> <A CLASS='documented' HREF='#mapped_file_sink_params_ctor'>mapped_file_sink</A>(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);
<SPAN CLASS='keyword'>explicit</SPAN> <A CLASS='documented' HREF='#mapped_file_sink_basic_ctor'>mapped_file_sink</A>( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );
void <A CLASS='documented' HREF='#mapped_file_sink_params_open'>open</A>(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);
void <A CLASS='documented' HREF='#mapped_file_sink_basic_open'>open</A>( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );
<SPAN CLASS='keyword'>bool</SPAN> <A CLASS='documented' HREF='#mapped_file_sink_is_open'>is_open</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#mapped_file_sink_close'>close</A>();
size_type <A CLASS='documented' HREF='#mapped_file_sink_size'>size</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>char</SPAN>* <A CLASS='documented' HREF='#mapped_file_sink_data'>data</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>static</SPAN> <SPAN CLASS='keyword'>int</SPAN> <A CLASS='documented' HREF='#mapped_file_sink_alignment'>alignment</A>();
};
} } // End namespace boost::io</PRE>
<A NAME="mapped_file_sink_default_ctor"></A>
<H4><CODE>mapped_file_sink::mapped_file_sink</CODE></H4>
<PRE CLASS="broken_ie"> mapped_file_sink();</PRE>
<P>Constructs a <CODE>mapped_file_sink</CODE> which must be opened before it can be used to perform i/o.</P>
<A NAME="mapped_file_sink_params_ctor"></A>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>explicit</SPAN> mapped_file_sink(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);</PRE>
<P>Constructs a <CODE>mapped_file_sink</CODE> from the given parameters.</P>
<A NAME="mapped_file_sink_basic_ctor"></A>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>explicit</SPAN> mapped_file_sink( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );</PRE>
<P>Constructs a <CODE>mapped_file_sink</CODE> to access a specified file. The parameters have the following interpretation:</P>
<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
<TR>
<TR>
<TD VALIGN="top"><I>path</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The pathname of the file to map.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>length</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The number of bytes to map. If this parameter is not specified, the entire file is mapped.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>offset</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The offset where the mapping is to begin. This value must be a multiple of the operating system's virtual memory allocation granularity, which can be obtained using the static member function <A HREF='#mapped_file_sink_alignment'><CODE>alignment</CODE></A>.</TD>
</TR>
</TABLE>
<A NAME="mapped_file_sink_params_open"></A>
<H4><CODE>mapped_file_sink::open</CODE></H4>
<PRE CLASS="broken_ie"> void open(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);</PRE>
<P>Connects this <CODE>mapped_file_sink</CODE> to a memory-mapped file obtained as described by the given parameters.</P>
<A NAME="mapped_file_sink_basic_open"></A>
<PRE CLASS="broken_ie"> void open( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );</PRE>
<P>Connects this <CODE>mapped_file_sink</CODE> to a memory-mapped file obtained as described by the given parameters, which have the following interpretation:</P>
<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
<TR>
<TR>
<TD VALIGN="top"><I>path</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The pathname of the file to map.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>length</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The number of bytes to map. If this parameter is not specified, the entire file is mapped.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>offset</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The offset where the mapping is to begin. This value must be a multiple of the operating system's virtual memory allocation granularity, which can be obtained using the static member function <A HREF='#mapped_file_sink_alignment'><CODE>alignment</CODE></A>.</TD>
</TR>
</TABLE>
<A NAME="mapped_file_sink_is_open"></A>
<H4><CODE>mapped_file_sink::is_open</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>bool</SPAN> is_open() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns <CODE>true</CODE> if this <CODE>mapped_file_sink</CODE> has been successfully opened without subsequently having been closed.</P>
<A NAME="mapped_file_sink_close"></A>
<H4><CODE>mapped_file_sink::close</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>void</SPAN> close();</PRE>
<P>Frees the mapping associated with this <CODE>mapped_file_sink</CODE>.</P>
<A NAME="mapped_file_sink_size"></A>
<H4><CODE>mapped_file_sink::size</CODE></H4>
<PRE CLASS="broken_ie"> size_type size() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns the size in bytes of the mapping associated with this <CODE>mapped_file_sink</CODE>.</P>
<A NAME="mapped_file_sink_data"></A>
<H4><CODE>mapped_file_sink::data</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>char</SPAN>* data() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns a pointer to the first byte of data in the mapping associated with this <CODE>mapped_file_sink</CODE>.</P>
<A NAME="mapped_file_sink_alignment"></A>
<H4><CODE>mapped_file_sink::alignment</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>static</SPAN> <SPAN CLASS='keyword'>int</SPAN> alignment();</PRE>
<P>Returns the operating system's virtual memory allocation granularity.</P>
<A NAME="mapped_file">
<H3>4. Class <CODE>mapped_file</CODE></H3>
<H4>Description</H4>
<P>Model of <A HREF="../concepts/seekable_device.html">SeekableDevice</A> providing read-write access to memory-mapped files on Windows and POSIX systems.</P>
<H4>Synopsis</H4>
<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
<SPAN CLASS="keyword">class</SPAN> <SPAN CLASS="defined">mapped_file</SPAN> {
<SPAN CLASS="keyword">public</SPAN>:
<SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='keyword'>char</SPAN> char_type;
<SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN> category;
<A CLASS='documented' HREF='#mapped_file_default_ctor'>mapped_file</A>();
<SPAN CLASS='keyword'>explicit</SPAN> <A CLASS='documented' HREF='#mapped_file_params_ctor'>mapped_file</A>(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);
<SPAN CLASS='keyword'>explicit</SPAN> <A CLASS='documented' HREF='#mapped_file_basic_ctor'>mapped_file</A>( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
std::ios_base::openmode mode =
std::ios_base | std::ios_base,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );
void <A CLASS='documented' HREF='#mapped_file_params_open'>open</A>(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);
void <A CLASS='documented' HREF='#mapped_file_basic_open'>open</A>( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
std::ios_base::openmode mode =
std::ios_base | std::ios_base,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );
<SPAN CLASS='keyword'>bool</SPAN> <A CLASS='documented' HREF='#mapped_file_is_open'>is_open</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#mapped_file_close'>close</A>();
size_type <A CLASS='documented' HREF='#mapped_file_size'>size</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>char</SPAN>* <A CLASS='documented' HREF='#mapped_file_data'>data</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>const</SPAN> <SPAN CLASS='keyword'>char</SPAN>* <A CLASS='documented' HREF='#mapped_file_const_data'>const_data</A>() <SPAN CLASS='keyword'>const</SPAN>;
<SPAN CLASS='keyword'>static</SPAN> <SPAN CLASS='keyword'>int</SPAN> <A CLASS='documented' HREF='#mapped_file_alignment'>alignment</A>();
};
} } // End namespace boost::io</PRE>
<A NAME="mapped_file_default_ctor"></A>
<H4><CODE>mapped_file::mapped_file</CODE></H4>
<PRE CLASS="broken_ie"> mapped_file();</PRE>
<P>Constructs a <CODE>mapped_file</CODE> which must be opened before it can be used to perform i/o.</P>
<A NAME="mapped_file_params_ctor"></A>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>explicit</SPAN> mapped_file(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);</PRE>
<P>Constructs a <CODE>mapped_file</CODE> from the given parameters.</P>
<A NAME="mapped_file_basic_ctor"></A>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>explicit</SPAN> mapped_file( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
std::ios_base::openmode mode =
std::ios_base | std::ios_base,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );</PRE>
<P>Constructs a <CODE>mapped_file</CODE> to access a specified file. The parameters have the following interpretation:</P>
<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
<TR>
<TR>
<TD VALIGN="top"><I>path</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The pathname of the file to map.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>mode</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>Indicates whether the file should be opened with read-access, write-access or both.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>length</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The number of bytes to map. If this parameter is not specified, the entire file is mapped.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>offset</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The offset where the mapping is to begin. This value must be a multiple of the operating system's virtual memory allocation granularity, which can be obtained using the static member function <A HREF='#mapped_file_alignment'><CODE>alignment</CODE></A>.</TD>
</TR>
</TABLE>
<A NAME="mapped_file_params_open"></A>
<H4><CODE>mapped_file::open</CODE></H4>
<PRE CLASS="broken_ie"> void open(<A CLASS='documented' HREF='#mapped_file_params'>mapped_file_params</A> params);</PRE>
<P>Connects this <CODE>mapped_file</CODE> to a memory-mapped file obtained as described by the given parameters.</P>
<A NAME="mapped_file_basic_open"></A>
<PRE CLASS="broken_ie"> void open( <SPAN CLASS='keyword'>const</SPAN> std::string& path,
std::ios_base::openmode mode =
std::ios_base | std::ios_base,
size_type length = max_length,
boost::intmax_t offset = <SPAN CLASS='numeric_literal'>0</SPAN> );</PRE>
<P>Connects this <CODE>mapped_file</CODE> to a memory-mapped file obtained as described by the given parameters, which have the following interpretation:</P>
<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
<TR>
<TR>
<TD VALIGN="top"><I>path</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The pathname of the file to map.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>mode</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>Indicates whether the file should be opened with read-access, write-access or both.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>length</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The number of bytes to map. If this parameter is not specified, the entire file is mapped.</TD>
</TR>
<TR>
<TD VALIGN="top"><I>offset</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The offset where the mapping is to begin. This value must be a multiple of the operating system's virtual memory allocation granularity, which can be obtained using the static member function <A HREF='#mapped_file_alignment'><CODE>alignment</CODE></A>.</TD>
</TR>
</TABLE>
<A NAME="mapped_file_is_open"></A>
<H4><CODE>mapped_file::is_open</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>bool</SPAN> is_open() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns <CODE>true</CODE> if this <CODE>mapped_file</CODE> has been successfully opened without subsequently having been closed.</P>
<A NAME="mapped_file_close"></A>
<H4><CODE>mapped_file::close</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>void</SPAN> close();</PRE>
<P>Frees the mapping associated with this <CODE>mapped_file</CODE>.</P>
<A NAME="mapped_file_size"></A>
<H4><CODE>mapped_file::size</CODE></H4>
<PRE CLASS="broken_ie"> size_type size() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns the size in bytes of the mapping associated with this <CODE>mapped_file</CODE>.</P>
<A NAME="mapped_file_data"></A>
<H4><CODE>mapped_file::data</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>char</SPAN>* data() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns a pointer to the first byte of data in the mapping associated with this <CODE>mapped_file</CODE>, if it was opened with write-access, and a null pointer otherwise.</P>
<A NAME="mapped_file_data"></A>
<H4><CODE>mapped_file::data</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>const</SPAN> <SPAN CLASS='keyword'>char</SPAN>* const_data() <SPAN CLASS='keyword'>const</SPAN>;</PRE>
<P>Returns a pointer to the first byte of data in the mapping associated with this <CODE>mapped_file</CODE>.</P>
<A NAME="mapped_file_alignment"></A>
<H4><CODE>mapped_file::alignment</CODE></H4>
<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>static</SPAN> <SPAN CLASS='keyword'>int</SPAN> alignment();</PRE>
<P>Returns the operating system's virtual memory allocation granularity.</P>
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<P CLASS="copyright">Revised
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
20 May, 2004
<!--webbot bot="Timestamp" endspan i-checksum="38504" -->
</P>
<P CLASS="copyright">&copy; Copyright Jonathan Turkanis, 2004</P>
<P CLASS="copyright">
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>)
</P>
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