<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>read_until (21 of 24 overloads)</title> <link rel="stylesheet" href="../../../boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> <link rel="home" href="../../../index.html" title="Asio"> <link rel="up" href="../read_until.html" title="read_until"> <link rel="prev" href="overload20.html" title="read_until (20 of 24 overloads)"> <link rel="next" href="overload22.html" title="read_until (22 of 24 overloads)"> <meta name="viewport" content="width=device-width, initial-scale=1"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../../asio.png"></td></tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="overload20.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="overload22.html"><img src="../../../next.png" alt="Next"></a> </div> <div class="section"> <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> </div> <hr> <div class="spirit-nav"> <a accesskey="p" href="overload20.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="overload22.html"><img src="../../../next.png" alt="Next"></a> </div> </body> </html>