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<title>read_until (16 of 24 overloads)</title>
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<div class="titlepage"><div><div><h4 class="title">
<a name="asio.reference.read_until.overload16"></a><a class="link" href="overload16.html" title="read_until (16 of 24 overloads)">read_until (16
of 24 overloads)</a>
</h4></div></div></div>
<p>
Read data into a streambuf until a function object indicates a match.
</p>
<pre class="programlisting">template<
typename <a class="link" href="../SyncReadStream.html" title="Buffer-oriented synchronous read stream requirements">SyncReadStream</a>,
typename Allocator,
typename MatchCondition>
std::size_t read_until(
SyncReadStream & s,
asio::basic_streambuf< Allocator > & b,
MatchCondition match_condition,
asio::error_code & ec,
typename enable_if< is_match_condition< MatchCondition >::value >::type * = 0);
</pre>
<p>
This function is used to read data into the specified streambuf until a
user-defined match condition function object, when applied to the data
contained in the streambuf, indicates a successful match. The call will
block until one of the following conditions is true:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
The match condition function object returns a std::pair where the second
element evaluates to true.
</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 match condition function object already indicates
a match, the function returns immediately.
</p>
<h6>
<a name="asio.reference.read_until.overload16.h0"></a>
<span><a name="asio.reference.read_until.overload16.parameters"></a></span><a class="link" href="overload16.html#asio.reference.read_until.overload16.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">b</span></dt>
<dd><p>
A streambuf object into which the data will be read.
</p></dd>
<dt><span class="term">match_condition</span></dt>
<dd>
<p>
The function object to be called to determine whether a match exists.
The signature of the function object must be:
</p>
<pre class="programlisting">pair<iterator, bool> match_condition(iterator begin, iterator end);
</pre>
<p>
where <code class="computeroutput">iterator</code> represents the type:
</p>
<pre class="programlisting">buffers_iterator<basic_streambuf<Allocator>::const_buffers_type>
</pre>
<p>
The iterator parameters <code class="computeroutput">begin</code> and <code class="computeroutput">end</code> define
the range of bytes to be scanned to determine whether there is a
match. The <code class="computeroutput">first</code> member of the return value is an iterator
marking one-past-the-end of the bytes that have been consumed by
the match function. This iterator is used to calculate the <code class="computeroutput">begin</code>
parameter for any subsequent invocation of the match condition. The
<code class="computeroutput">second</code> member of the return value is true if a match
has been found, false otherwise.
</p>
</dd>
<dt><span class="term">ec</span></dt>
<dd><p>
Set to indicate what error occurred, if any.
</p></dd>
</dl>
</div>
<h6>
<a name="asio.reference.read_until.overload16.h1"></a>
<span><a name="asio.reference.read_until.overload16.return_value"></a></span><a class="link" href="overload16.html#asio.reference.read_until.overload16.return_value">Return
Value</a>
</h6>
<p>
The number of bytes in the streambuf's get area that have been fully consumed
by the match function. Returns 0 if an error occurred.
</p>
<h6>
<a name="asio.reference.read_until.overload16.h2"></a>
<span><a name="asio.reference.read_until.overload16.remarks"></a></span><a class="link" href="overload16.html#asio.reference.read_until.overload16.remarks">Remarks</a>
</h6>
<p>
After a successful read_until operation, the streambuf may contain additional
data beyond that which matched the function object. An application will
typically leave that data in the streambuf for a subsequent read_until
operation to examine.
</p>
<p>
The default implementation of the <code class="computeroutput">is_match_condition</code> type
trait evaluates to true for function pointers and function objects with
a <code class="computeroutput">result_type</code> typedef. It must be specialised for other user-defined
function objects.
</p>
</div>
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<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>)
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