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<html>
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<div class="section" title="streambuf">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.streambuf"></a><a class="link" href="streambuf.html" title="streambuf"> streambuf</a>
</h3></div></div></div>
<p>
<a class="indexterm" name="id1132334"></a>
Typedef for the typical usage of <a class="link" href="basic_streambuf.html" title="basic_streambuf"><code class="computeroutput"><span class="identifier">basic_streambuf</span></code></a>.
</p>
<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">basic_streambuf</span> <span class="identifier">streambuf</span><span class="special">;</span>
</pre>
<a name="boost_asio.reference.streambuf.types"></a><h5>
<a name="id1132393"></a>
<a class="link" href="streambuf.html#boost_asio.reference.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>
<a name="boost_asio.reference.streambuf.member_functions"></a><h5>
<a name="id1132503"></a>
<a class="link" href="streambuf.html#boost_asio.reference.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>
<a name="boost_asio.reference.streambuf.protected_member_functions"></a><h5>
<a name="id1132749"></a>
<a class="link" href="streambuf.html#boost_asio.reference.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>
<p>
</p>
</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" 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>
<a name="boost_asio.reference.streambuf.examples"></a><h5>
<a name="id1133113"></a>
<a class="link" href="streambuf.html#boost_asio.reference.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>
<a name="boost_asio.reference.streambuf.requirements"></a><h5>
<a name="id1133592"></a>
<a class="link" href="streambuf.html#boost_asio.reference.streambuf.requirements">Requirements</a>
</h5>
<p>
<span class="bold"><strong>Header: </strong></span><code class="literal">boost/asio/streambuf.hpp</code>
</p>
<p>
<span class="bold"><strong>Convenience header: </strong></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 - 2010 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>
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