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<html>
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<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.basic_streambuf"></a><a class="link" href="basic_streambuf.html" title="basic_streambuf">basic_streambuf</a>
</h3></div></div></div>
<p>
Automatically resizable buffer class based on std::streambuf.
</p>
<pre class="programlisting">template<
typename Allocator = std::allocator<char>>
class basic_streambuf :
noncopyable
</pre>
<h5>
<a name="asio.reference.basic_streambuf.h0"></a>
<span><a name="asio.reference.basic_streambuf.types"></a></span><a class="link" href="basic_streambuf.html#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="asio.reference.basic_streambuf.h1"></a>
<span><a name="asio.reference.basic_streambuf.member_functions"></a></span><a class="link" href="basic_streambuf.html#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> <span class="silver">[constructor]</span>
</p>
</td>
<td>
<p>
Construct a basic_streambuf object.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="basic_streambuf/capacity.html" title="basic_streambuf::capacity"><span class="bold"><strong>capacity</strong></span></a>
</p>
</td>
<td>
<p>
Get the current capacity of the basic_streambuf.
</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="asio.reference.basic_streambuf.h2"></a>
<span><a name="asio.reference.basic_streambuf.protected_member_functions"></a></span><a class="link" href="basic_streambuf.html#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">basic_streambuf</code> class is derived from <code class="computeroutput">std::streambuf</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">basic_streambuf</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">basic_streambuf</code> object are appended to the input
sequence of the same object.
</p>
<p>
The <code class="computeroutput">basic_streambuf</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">basic_streambuf</code></a>
accepts a <code class="computeroutput">size_t</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">basic_streambuf</code> object, the following invariant holds:
</p>
<pre class="programlisting">size() <= max_size()
</pre>
<p>
Any member function that would, if successful, cause the invariant to be
violated shall throw an exception of class <code class="computeroutput">std::length_error</code>.
</p>
<p>
The constructor for <code class="computeroutput">basic_streambuf</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">basic_streambuf</code>
object.
</p>
<h5>
<a name="asio.reference.basic_streambuf.h3"></a>
<span><a name="asio.reference.basic_streambuf.examples"></a></span><a class="link" href="basic_streambuf.html#asio.reference.basic_streambuf.examples">Examples</a>
</h5>
<p>
Writing directly from an streambuf to a socket:
</p>
<pre class="programlisting">asio::streambuf b;
std::ostream os(&b);
os << "Hello, World!\n";
// try sending some data in input sequence
size_t n = sock.send(b.data());
b.consume(n); // sent data is removed from input sequence
</pre>
<p>
Reading from a socket directly into a streambuf:
</p>
<pre class="programlisting">asio::streambuf b;
// reserve 512 bytes in output sequence
asio::streambuf::mutable_buffers_type bufs = b.prepare(512);
size_t n = sock.receive(bufs);
// received data is "committed" from output sequence to input sequence
b.commit(n);
std::istream is(&b);
std::string s;
is >> s;
</pre>
<h5>
<a name="asio.reference.basic_streambuf.h4"></a>
<span><a name="asio.reference.basic_streambuf.requirements"></a></span><a class="link" href="basic_streambuf.html#asio.reference.basic_streambuf.requirements">Requirements</a>
</h5>
<p>
<span class="emphasis"><em>Header: </em></span><code class="literal">asio/basic_streambuf.hpp</code>
</p>
<p>
<span class="emphasis"><em>Convenience header: </em></span><code class="literal">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 © 2003-2020 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>
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