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<div class="titlepage"><div><div><h4 class="title">
<a name="asio.reference.read_until.overload21"></a><a class="link" href="overload21.html" title="read_until (21 of 24 overloads)">read_until (21
of 24 overloads)</a>
</h4></div></div></div>
<p>
Read data into a dynamic buffer sequence 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> <a class="link" href="../DynamicBuffer_v2.html" title="Dynamic buffer requirements (version 2)">DynamicBuffer_v2</a><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">DynamicBuffer_v2</span> <span class="identifier">buffers</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>
<span class="keyword">typename</span> <span class="identifier">constraint</span><span class="special"><</span> <span class="identifier">is_dynamic_buffer_v2</span><span class="special"><</span> <span class="identifier">DynamicBuffer_v2</span> <span class="special">>::</span><span class="identifier">value</span> <span class="special">>::</span><span class="identifier">type</span> <span class="special">=</span> <span class="number">0</span><span class="special">);</span>
</pre>
<p>
This function is used to read data into the specified dynamic buffer sequence
until the dynamic buffer sequence'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" type="disc">
<li class="listitem">
A substring of the dynamic buffer sequence'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 dynamic buffer sequence's get area already contains
data that matches the regular expression, the function returns immediately.
</p>
<h6>
<a name="asio.reference.read_until.overload21.h0"></a>
<span><a name="asio.reference.read_until.overload21.parameters"></a></span><a class="link" href="overload21.html#asio.reference.read_until.overload21.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<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">buffers</span></dt>
<dd><p>
A dynamic buffer sequence 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="asio.reference.read_until.overload21.h1"></a>
<span><a name="asio.reference.read_until.overload21.return_value"></a></span><a class="link" href="overload21.html#asio.reference.read_until.overload21.return_value">Return
Value</a>
</h6>
<p>
The number of bytes in the dynamic buffer sequence's get area up to and
including the substring that matches the regular expression.
</p>
<h6>
<a name="asio.reference.read_until.overload21.h2"></a>
<span><a name="asio.reference.read_until.overload21.exceptions"></a></span><a class="link" href="overload21.html#asio.reference.read_until.overload21.exceptions">Exceptions</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">asio::system_error</span></dt>
<dd><p>
Thrown on failure.
</p></dd>
</dl>
</div>
<h6>
<a name="asio.reference.read_until.overload21.h3"></a>
<span><a name="asio.reference.read_until.overload21.remarks"></a></span><a class="link" href="overload21.html#asio.reference.read_until.overload21.remarks">Remarks</a>
</h6>
<p>
After a successful read_until operation, the dynamic buffer sequence may
contain additional data beyond that which matched the regular expression.
An application will typically leave that data in the dynamic buffer sequence
for a subsequent read_until operation to examine.
</p>
<h6>
<a name="asio.reference.read_until.overload21.h4"></a>
<span><a name="asio.reference.read_until.overload21.example"></a></span><a class="link" href="overload21.html#asio.reference.read_until.overload21.example">Example</a>
</h6>
<p>
To read data into a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>
until a CR-LF sequence is encountered:
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">data</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">n</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">asio</span><span class="special">::</span><span class="identifier">dynamic_buffer</span><span class="special">(</span><span class="identifier">data</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">string</span> <span class="identifier">line</span> <span class="special">=</span> <span class="identifier">data</span><span class="special">.</span><span class="identifier">substr</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="identifier">n</span><span class="special">);</span>
<span class="identifier">data</span><span class="special">.</span><span class="identifier">erase</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="identifier">n</span><span class="special">);</span>
</pre>
<p>
After the <code class="computeroutput"><span class="identifier">read_until</span></code> operation
completes successfully, the string <code class="computeroutput"><span class="identifier">data</span></code>
contains the delimiter:
</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">substr</span></code> then
extracts the data up to and including the delimiter, 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>
After the call to <code class="computeroutput"><span class="identifier">erase</span></code>,
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>
</div>
<div class="copyright-footer">Copyright © 2003-2023 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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