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<title>read_until (5 of 8 overloads)</title>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.read_until.overload5"></a><a class="link" href="overload5.html" title="read_until (5 of 8 overloads)">read_until
(5 of 8 overloads)</a>
</h4></div></div></div>
<p>
Read data into a streambuf until some part of the data it contains matches
a regular expression.
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
<span class="keyword">typename</span> <a class="link" href="../SyncReadStream.html" title="Buffer-oriented synchronous read stream requirements">SyncReadStream</a><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">size_t</span> <span class="identifier">read_until</span><span class="special">(</span>
<span class="identifier">SyncReadStream</span> <span class="special">&</span> <span class="identifier">s</span><span class="special">,</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">basic_streambuf</span><span class="special"><</span> <span class="identifier">Allocator</span> <span class="special">></span> <span class="special">&</span> <span class="identifier">b</span><span class="special">,</span>
<span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="special">&</span> <span class="identifier">expr</span><span class="special">);</span>
</pre>
<p>
This function is used to read data into the specified streambuf until the
streambuf's get area contains some data that matches a regular expression.
The call will block until one of the following conditions is true:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
A substring of the streambuf's get area matches the regular expression.
</li>
<li class="listitem">
An error occurred.
</li>
</ul></div>
<p>
This operation is implemented in terms of zero or more calls to the stream's
read_some function. If the streambuf's get area already contains data that
matches the regular expression, the function returns immediately.
</p>
<h6>
<a name="boost_asio.reference.read_until.overload5.h0"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload5.parameters"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">s</span></dt>
<dd><p>
The stream from which the data is to be read. The type must support
the SyncReadStream concept.
</p></dd>
<dt><span class="term">b</span></dt>
<dd><p>
A streambuf object into which the data will be read.
</p></dd>
<dt><span class="term">expr</span></dt>
<dd><p>
The regular expression.
</p></dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.read_until.overload5.h1"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload5.return_value"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.return_value">Return
Value</a>
</h6>
<p>
The number of bytes in the streambuf's get area up to and including the
substring that matches the regular expression.
</p>
<h6>
<a name="boost_asio.reference.read_until.overload5.h2"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload5.exceptions"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.exceptions">Exceptions</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">boost::system::system_error</span></dt>
<dd><p>
Thrown on failure.
</p></dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.read_until.overload5.h3"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload5.remarks"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.remarks">Remarks</a>
</h6>
<p>
After a successful read_until operation, the streambuf may contain additional
data beyond that which matched the regular expression. An application will
typically leave that data in the streambuf for a subsequent read_until
operation to examine.
</p>
<h6>
<a name="boost_asio.reference.read_until.overload5.h4"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload5.example"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.example">Example</a>
</h6>
<p>
To read data into a streambuf until a CR-LF sequence is encountered:
</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">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">read_until</span><span class="special">(</span><span class="identifier">s</span><span class="special">,</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">(</span><span class="string">"\r\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">line</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">getline</span><span class="special">(</span><span class="identifier">is</span><span class="special">,</span> <span class="identifier">line</span><span class="special">);</span>
</pre>
<p>
After the <code class="computeroutput"><span class="identifier">read_until</span></code> operation
completes successfully, the buffer <code class="computeroutput"><span class="identifier">b</span></code>
contains the data which matched the regular expression:
</p>
<pre class="programlisting"><span class="special">{</span> <span class="char">'a'</span><span class="special">,</span> <span class="char">'b'</span><span class="special">,</span> <span class="special">...,</span> <span class="char">'c'</span><span class="special">,</span> <span class="char">'\r'</span><span class="special">,</span> <span class="char">'\n'</span><span class="special">,</span> <span class="char">'d'</span><span class="special">,</span> <span class="char">'e'</span><span class="special">,</span> <span class="special">...</span> <span class="special">}</span>
</pre>
<p>
The call to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">getline</span></code> then extracts the data up to
and including the match, so that the string <code class="computeroutput"><span class="identifier">line</span></code>
contains:
</p>
<pre class="programlisting"><span class="special">{</span> <span class="char">'a'</span><span class="special">,</span> <span class="char">'b'</span><span class="special">,</span> <span class="special">...,</span> <span class="char">'c'</span><span class="special">,</span> <span class="char">'\r'</span><span class="special">,</span> <span class="char">'\n'</span> <span class="special">}</span>
</pre>
<p>
The remaining data is left in the buffer <code class="computeroutput"><span class="identifier">b</span></code>
as follows:
</p>
<pre class="programlisting"><span class="special">{</span> <span class="char">'d'</span><span class="special">,</span> <span class="char">'e'</span><span class="special">,</span> <span class="special">...</span> <span class="special">}</span>
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput"><span class="identifier">read_until</span></code> operation.
</p>
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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" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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