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<title>read_until (3 of 24 overloads)</title>
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<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.read_until.overload3"></a><a class="link" href="overload3.html" title="read_until (3 of 24 overloads)">read_until
(3 of 24 overloads)</a>
</h4></div></div></div>
<p>
Read data into a dynamic buffer sequence until it contains a specified
delimiter.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../SyncReadStream.html" title="Buffer-oriented synchronous read stream requirements">SyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v1.html" title="Dynamic buffer requirements (version 1)">DynamicBuffer_v1</a>&gt;
std::size_t read_until(
SyncReadStream &amp; s,
DynamicBuffer_v1 &amp;&amp; buffers,
string_view delim,
typename constraint&lt; is_dynamic_buffer_v1&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0,
typename constraint&lt; !is_dynamic_buffer_v2&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to read data into the specified dynamic buffer sequence
until the dynamic buffer sequence's get area contains the specified delimiter.
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">
The get area of the dynamic buffer sequence contains the specified
delimiter.
</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
the delimiter, the function returns immediately.
</p>
<h6>
<a name="boost_asio.reference.read_until.overload3.h0"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload3.parameters"></a></span><a class="link" href="overload3.html#boost_asio.reference.read_until.overload3.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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read.
</p></dd>
<dt><span class="term">delim</span></dt>
<dd><p>
The delimiter string.
</p></dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.read_until.overload3.h1"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload3.return_value"></a></span><a class="link" href="overload3.html#boost_asio.reference.read_until.overload3.return_value">Return
Value</a>
</h6>
<p>
The number of bytes in the dynamic buffer sequence's get area up to and
including the delimiter.
</p>
<h6>
<a name="boost_asio.reference.read_until.overload3.h2"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload3.remarks"></a></span><a class="link" href="overload3.html#boost_asio.reference.read_until.overload3.remarks">Remarks</a>
</h6>
<p>
After a successful read_until operation, the dynamic buffer sequence may
contain additional data beyond the delimiter. An application will typically
leave that data in the dynamic buffer sequence for a subsequent read_until
operation to examine.
</p>
<h6>
<a name="boost_asio.reference.read_until.overload3.h3"></a>
<span class="phrase"><a name="boost_asio.reference.read_until.overload3.example"></a></span><a class="link" href="overload3.html#boost_asio.reference.read_until.overload3.example">Example</a>
</h6>
<p>
To read data into a <code class="computeroutput">std::string</code> until a CR-LF sequence is
encountered:
</p>
<pre class="programlisting">std::string data;
std::size_t n = boost::asio::read_until(s,
boost::asio::dynamic_buffer(data), "\r\n");
std::string line = data.substr(0, n);
data.erase(0, n);
</pre>
<p>
After the <code class="computeroutput">read_until</code> operation completes successfully, the
string <code class="computeroutput">data</code> contains the delimiter:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">substr</code> then extracts the data up to and including
the delimiter, so that the string <code class="computeroutput">line</code> contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n' }
</pre>
<p>
After the call to <code class="computeroutput">erase</code>, the remaining data is left in the
buffer <code class="computeroutput">b</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">read_until</code> operation.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2021 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>)
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