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148 lines
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<title>read_until (19 of 24 overloads)</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../../asio.png"></td></tr></table>
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<a accesskey="p" href="overload18.html"><img src="../../../prev.png" alt="Prev"></a><a accesskey="u" href="../read_until.html"><img src="../../../up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../home.png" alt="Home"></a><a accesskey="n" href="overload20.html"><img src="../../../next.png" alt="Next"></a>
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<div class="section">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="asio.reference.read_until.overload19"></a><a class="link" href="overload19.html" title="read_until (19 of 24 overloads)">read_until (19
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of 24 overloads)</a>
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</h4></div></div></div>
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<p>
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Read data into a dynamic buffer sequence until it contains a specified
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delimiter.
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</p>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
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<span class="keyword">typename</span> <a class="link" href="../SyncReadStream.html" title="Buffer-oriented synchronous read stream requirements">SyncReadStream</a><span class="special">,</span>
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<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>
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<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>
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<span class="identifier">SyncReadStream</span> <span class="special">&</span> <span class="identifier">s</span><span class="special">,</span>
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<span class="identifier">DynamicBuffer_v2</span> <span class="identifier">buffers</span><span class="special">,</span>
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<span class="identifier">string_view</span> <span class="identifier">delim</span><span class="special">,</span>
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<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>
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</pre>
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<p>
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This function is used to read data into the specified dynamic buffer sequence
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until the dynamic buffer sequence's get area contains the specified delimiter.
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The call will block until one of the following conditions is true:
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</p>
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<div class="itemizedlist"><ul class="itemizedlist" type="disc">
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<li class="listitem">
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The get area of the dynamic buffer sequence contains the specified
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delimiter.
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</li>
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<li class="listitem">
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An error occurred.
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</li>
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</ul></div>
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<p>
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This operation is implemented in terms of zero or more calls to the stream's
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read_some function. If the dynamic buffer sequence's get area already contains
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the delimiter, the function returns immediately.
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</p>
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<h6>
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<a name="asio.reference.read_until.overload19.h0"></a>
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<span><a name="asio.reference.read_until.overload19.parameters"></a></span><a class="link" href="overload19.html#asio.reference.read_until.overload19.parameters">Parameters</a>
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</h6>
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<div class="variablelist">
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<p class="title"><b></b></p>
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<dl>
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<dt><span class="term">s</span></dt>
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<dd><p>
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The stream from which the data is to be read. The type must support
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the SyncReadStream concept.
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</p></dd>
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<dt><span class="term">buffers</span></dt>
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<dd><p>
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The dynamic buffer sequence into which the data will be read.
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</p></dd>
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<dt><span class="term">delim</span></dt>
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<dd><p>
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The delimiter string.
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</p></dd>
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</dl>
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</div>
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<h6>
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<a name="asio.reference.read_until.overload19.h1"></a>
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<span><a name="asio.reference.read_until.overload19.return_value"></a></span><a class="link" href="overload19.html#asio.reference.read_until.overload19.return_value">Return
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Value</a>
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</h6>
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<p>
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The number of bytes in the dynamic buffer sequence's get area up to and
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including the delimiter.
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</p>
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<h6>
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<a name="asio.reference.read_until.overload19.h2"></a>
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<span><a name="asio.reference.read_until.overload19.remarks"></a></span><a class="link" href="overload19.html#asio.reference.read_until.overload19.remarks">Remarks</a>
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</h6>
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<p>
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After a successful read_until operation, the dynamic buffer sequence may
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contain additional data beyond the delimiter. An application will typically
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leave that data in the dynamic buffer sequence for a subsequent read_until
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operation to examine.
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</p>
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<h6>
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<a name="asio.reference.read_until.overload19.h3"></a>
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<span><a name="asio.reference.read_until.overload19.example"></a></span><a class="link" href="overload19.html#asio.reference.read_until.overload19.example">Example</a>
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</h6>
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<p>
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To read data into a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code>
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until a CR-LF sequence is encountered:
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</p>
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<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>
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<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>
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<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="string">"\r\n"</span><span class="special">);</span>
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<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>
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<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>
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</pre>
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<p>
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After the <code class="computeroutput"><span class="identifier">read_until</span></code> operation
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completes successfully, the string <code class="computeroutput"><span class="identifier">data</span></code>
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contains the delimiter:
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</p>
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<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>
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</pre>
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<p>
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The call to <code class="computeroutput"><span class="identifier">substr</span></code> then
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extracts the data up to and including the delimiter, so that the string
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<code class="computeroutput"><span class="identifier">line</span></code> contains:
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</p>
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<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>
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</pre>
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<p>
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After the call to <code class="computeroutput"><span class="identifier">erase</span></code>,
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the remaining data is left in the buffer <code class="computeroutput"><span class="identifier">b</span></code>
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as follows:
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</p>
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<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>
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</pre>
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<p>
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This data may be the start of a new line, to be extracted by a subsequent
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<code class="computeroutput"><span class="identifier">read_until</span></code> operation.
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</p>
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</div>
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<div class="copyright-footer">Copyright © 2003-2023 Christopher M. Kohlhoff<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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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</p>
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</div>
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<hr>
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