<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>basic_streambuf</title> <link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../../boost_asio.html" title="Boost.Asio"> <link rel="up" href="../reference.html" title="Reference"> <link rel="prev" href="basic_stream_socket/write_some/overload2.html" title="basic_stream_socket::write_some (2 of 2 overloads)"> <link rel="next" href="basic_streambuf/basic_streambuf.html" title="basic_streambuf::basic_streambuf"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> <td align="center"><a href="../../../../index.html">Home</a></td> <td align="center"><a 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title="basic_streambuf">basic_streambuf</a> </h3></div></div></div> <p> Automatically resizable buffer class based on std::streambuf. </p> <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">Allocator</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">allocator</span><span class="special"><</span><span class="keyword">char</span><span class="special">>></span> <span class="keyword">class</span> <span class="identifier">basic_streambuf</span> <span class="special">:</span> <span class="identifier">noncopyable</span> </pre> <h5> <a name="boost_asio.reference.basic_streambuf.h0"></a> <span class="phrase"><a name="boost_asio.reference.basic_streambuf.types"></a></span><a class="link" href="basic_streambuf.html#boost_asio.reference.basic_streambuf.types">Types</a> </h5> <div class="informaltable"><table class="table"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Name </p> </th> <th> <p> Description </p> </th> </tr></thead> <tbody> <tr> <td> <p> <a class="link" href="basic_streambuf/const_buffers_type.html" title="basic_streambuf::const_buffers_type"><span class="bold"><strong>const_buffers_type</strong></span></a> </p> </td> <td> <p> The type used to represent the input sequence as a list of buffers. </p> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/mutable_buffers_type.html" title="basic_streambuf::mutable_buffers_type"><span class="bold"><strong>mutable_buffers_type</strong></span></a> </p> </td> <td> <p> The type used to represent the output sequence as a list of buffers. </p> </td> </tr> </tbody> </table></div> <h5> <a name="boost_asio.reference.basic_streambuf.h1"></a> <span class="phrase"><a name="boost_asio.reference.basic_streambuf.member_functions"></a></span><a class="link" href="basic_streambuf.html#boost_asio.reference.basic_streambuf.member_functions">Member Functions</a> </h5> <div class="informaltable"><table class="table"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Name </p> </th> <th> <p> Description </p> </th> </tr></thead> <tbody> <tr> <td> <p> <a class="link" href="basic_streambuf/basic_streambuf.html" title="basic_streambuf::basic_streambuf"><span class="bold"><strong>basic_streambuf</strong></span></a> </p> </td> <td> <p> Construct a basic_streambuf object. </p> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/commit.html" title="basic_streambuf::commit"><span class="bold"><strong>commit</strong></span></a> </p> </td> <td> <p> Move characters from the output sequence to the input sequence. </p> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/consume.html" title="basic_streambuf::consume"><span class="bold"><strong>consume</strong></span></a> </p> </td> <td> <p> Remove characters from the input sequence. </p> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/data.html" title="basic_streambuf::data"><span class="bold"><strong>data</strong></span></a> </p> </td> <td> <p> Get a list of buffers that represents the input sequence. </p> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/max_size.html" title="basic_streambuf::max_size"><span class="bold"><strong>max_size</strong></span></a> </p> </td> <td> <p> Get the maximum size of the basic_streambuf. </p> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/prepare.html" title="basic_streambuf::prepare"><span class="bold"><strong>prepare</strong></span></a> </p> </td> <td> <p> Get a list of buffers that represents the output sequence, with the given size. </p> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/size.html" title="basic_streambuf::size"><span class="bold"><strong>size</strong></span></a> </p> </td> <td> <p> Get the size of the input sequence. </p> </td> </tr> </tbody> </table></div> <h5> <a name="boost_asio.reference.basic_streambuf.h2"></a> <span class="phrase"><a name="boost_asio.reference.basic_streambuf.protected_member_functions"></a></span><a class="link" href="basic_streambuf.html#boost_asio.reference.basic_streambuf.protected_member_functions">Protected Member Functions</a> </h5> <div class="informaltable"><table class="table"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Name </p> </th> <th> <p> Description </p> </th> </tr></thead> <tbody> <tr> <td> <p> <a class="link" href="basic_streambuf/overflow.html" title="basic_streambuf::overflow"><span class="bold"><strong>overflow</strong></span></a> </p> </td> <td> <p> Override std::streambuf behaviour. </p> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/reserve.html" title="basic_streambuf::reserve"><span class="bold"><strong>reserve</strong></span></a> </p> </td> <td> </td> </tr> <tr> <td> <p> <a class="link" href="basic_streambuf/underflow.html" title="basic_streambuf::underflow"><span class="bold"><strong>underflow</strong></span></a> </p> </td> <td> <p> Override std::streambuf behaviour. </p> </td> </tr> </tbody> </table></div> <p> The <code class="computeroutput"><span class="identifier">basic_streambuf</span></code> class is derived from <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">streambuf</span></code> to associate the streambuf's input and output sequences with one or more character arrays. These character arrays are internal to the <code class="computeroutput"><span class="identifier">basic_streambuf</span></code> object, but direct access to the array elements is provided to permit them to be used efficiently with I/O operations. Characters written to the output sequence of a <code class="computeroutput"><span class="identifier">basic_streambuf</span></code> object are appended to the input sequence of the same object. </p> <p> The <code class="computeroutput"><span class="identifier">basic_streambuf</span></code> class's public interface is intended to permit the following implementation strategies: </p> <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> A single contiguous character array, which is reallocated as necessary to accommodate changes in the size of the character sequence. This is the implementation approach currently used in Asio. </li> <li class="listitem"> A sequence of one or more character arrays, where each array is of the same size. Additional character array objects are appended to the sequence to accommodate changes in the size of the character sequence. </li> <li class="listitem"> A sequence of one or more character arrays of varying sizes. Additional character array objects are appended to the sequence to accommodate changes in the size of the character sequence. </li> </ul></div> <p> The constructor for <a class="link" href="basic_streambuf.html" title="basic_streambuf"><code class="computeroutput"><span class="identifier">basic_streambuf</span></code></a> accepts a <code class="computeroutput"><span class="identifier">size_t</span></code> argument specifying the maximum of the sum of the sizes of the input sequence and output sequence. During the lifetime of the <code class="computeroutput"><span class="identifier">basic_streambuf</span></code> object, the following invariant holds: </p> <pre class="programlisting"><span class="identifier">size</span><span class="special">()</span> <span class="special"><=</span> <span class="identifier">max_size</span><span class="special">()</span> </pre> <p> Any member function that would, if successful, cause the invariant to be violated shall throw an exception of class <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">length_error</span></code>. </p> <p> The constructor for <code class="computeroutput"><span class="identifier">basic_streambuf</span></code> takes an Allocator argument. A copy of this argument is used for any memory allocation performed, by the constructor and by all member functions, during the lifetime of each <code class="computeroutput"><span class="identifier">basic_streambuf</span></code> object. </p> <h5> <a name="boost_asio.reference.basic_streambuf.h3"></a> <span class="phrase"><a name="boost_asio.reference.basic_streambuf.examples"></a></span><a class="link" href="basic_streambuf.html#boost_asio.reference.basic_streambuf.examples">Examples</a> </h5> <p> Writing directly from an streambuf to a socket: </p> <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">streambuf</span> <span class="identifier">b</span><span class="special">;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span> <span class="identifier">os</span><span class="special">(&</span><span class="identifier">b</span><span class="special">);</span> <span class="identifier">os</span> <span class="special"><<</span> <span class="string">"Hello, World!\n"</span><span class="special">;</span> <span class="comment">// try sending some data in input sequence</span> <span class="identifier">size_t</span> <span class="identifier">n</span> <span class="special">=</span> <span class="identifier">sock</span><span class="special">.</span><span class="identifier">send</span><span class="special">(</span><span class="identifier">b</span><span class="special">.</span><span class="identifier">data</span><span class="special">());</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">consume</span><span class="special">(</span><span class="identifier">n</span><span class="special">);</span> <span class="comment">// sent data is removed from input sequence</span> </pre> <p> Reading from a socket directly into a streambuf: </p> <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">streambuf</span> <span class="identifier">b</span><span class="special">;</span> <span class="comment">// reserve 512 bytes in output sequence</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">streambuf</span><span class="special">::</span><span class="identifier">mutable_buffers_type</span> <span class="identifier">bufs</span> <span class="special">=</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">prepare</span><span class="special">(</span><span class="number">512</span><span class="special">);</span> <span class="identifier">size_t</span> <span class="identifier">n</span> <span class="special">=</span> <span class="identifier">sock</span><span class="special">.</span><span class="identifier">receive</span><span class="special">(</span><span class="identifier">bufs</span><span class="special">);</span> <span class="comment">// received data is "committed" from output sequence to input sequence</span> <span class="identifier">b</span><span class="special">.</span><span class="identifier">commit</span><span class="special">(</span><span class="identifier">n</span><span class="special">);</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">istream</span> <span class="identifier">is</span><span class="special">(&</span><span class="identifier">b</span><span class="special">);</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">s</span><span class="special">;</span> <span class="identifier">is</span> <span class="special">>></span> <span class="identifier">s</span><span class="special">;</span> </pre> <h5> <a name="boost_asio.reference.basic_streambuf.h4"></a> <span class="phrase"><a name="boost_asio.reference.basic_streambuf.requirements"></a></span><a class="link" href="basic_streambuf.html#boost_asio.reference.basic_streambuf.requirements">Requirements</a> </h5> <p> <span class="emphasis"><em>Header: </em></span><code class="literal">boost/asio/basic_streambuf.hpp</code> </p> <p> <span class="emphasis"><em>Convenience header: </em></span><code class="literal">boost/asio.hpp</code> </p> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2003-2015 Christopher M. Kohlhoff<p> 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" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) </p> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="basic_stream_socket/write_some/overload2.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../boost_asio.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="basic_streambuf/basic_streambuf.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>