1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>read_until (5 of 24 overloads)</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../boost_asio.html" title="Boost.Asio"> 8<link rel="up" href="../read_until.html" title="read_until"> 9<link rel="prev" href="overload4.html" title="read_until (4 of 24 overloads)"> 10<link rel="next" href="overload6.html" title="read_until (6 of 24 overloads)"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="overload4.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../read_until.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="overload6.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="boost_asio.reference.read_until.overload5"></a><a class="link" href="overload5.html" title="read_until (5 of 24 overloads)">read_until 28 (5 of 24 overloads)</a> 29</h4></div></div></div> 30<p> 31 Read data into a dynamic buffer sequence until some part of the data it 32 contains matches a regular expression. 33 </p> 34<pre class="programlisting">template< 35 typename <a class="link" href="../SyncReadStream.html" title="Buffer-oriented synchronous read stream requirements">SyncReadStream</a>, 36 typename <a class="link" href="../DynamicBuffer_v1.html" title="Dynamic buffer requirements (version 1)">DynamicBuffer_v1</a>> 37std::size_t read_until( 38 SyncReadStream & s, 39 DynamicBuffer_v1 && buffers, 40 const boost::regex & expr, 41 typename enable_if< is_dynamic_buffer_v1< typename decay< DynamicBuffer_v1 >::type >::value &&!is_dynamic_buffer_v2< typename decay< DynamicBuffer_v1 >::type >::value >::type * = 0); 42</pre> 43<p> 44 This function is used to read data into the specified dynamic buffer sequence 45 until the dynamic buffer sequence's get area contains some data that matches 46 a regular expression. The call will block until one of the following conditions 47 is true: 48 </p> 49<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 50<li class="listitem"> 51 A substring of the dynamic buffer sequence's get area matches the regular 52 expression. 53 </li> 54<li class="listitem"> 55 An error occurred. 56 </li> 57</ul></div> 58<p> 59 This operation is implemented in terms of zero or more calls to the stream's 60 read_some function. If the dynamic buffer sequence's get area already contains 61 data that matches the regular expression, the function returns immediately. 62 </p> 63<h6> 64<a name="boost_asio.reference.read_until.overload5.h0"></a> 65 <span class="phrase"><a name="boost_asio.reference.read_until.overload5.parameters"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.parameters">Parameters</a> 66 </h6> 67<div class="variablelist"> 68<p class="title"><b></b></p> 69<dl class="variablelist"> 70<dt><span class="term">s</span></dt> 71<dd><p> 72 The stream from which the data is to be read. The type must support 73 the SyncReadStream concept. 74 </p></dd> 75<dt><span class="term">buffers</span></dt> 76<dd><p> 77 A dynamic buffer sequence into which the data will be read. 78 </p></dd> 79<dt><span class="term">expr</span></dt> 80<dd><p> 81 The regular expression. 82 </p></dd> 83</dl> 84</div> 85<h6> 86<a name="boost_asio.reference.read_until.overload5.h1"></a> 87 <span class="phrase"><a name="boost_asio.reference.read_until.overload5.return_value"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.return_value">Return 88 Value</a> 89 </h6> 90<p> 91 The number of bytes in the dynamic buffer sequence's get area up to and 92 including the substring that matches the regular expression. 93 </p> 94<h6> 95<a name="boost_asio.reference.read_until.overload5.h2"></a> 96 <span class="phrase"><a name="boost_asio.reference.read_until.overload5.exceptions"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.exceptions">Exceptions</a> 97 </h6> 98<div class="variablelist"> 99<p class="title"><b></b></p> 100<dl class="variablelist"> 101<dt><span class="term">boost::system::system_error</span></dt> 102<dd><p> 103 Thrown on failure. 104 </p></dd> 105</dl> 106</div> 107<h6> 108<a name="boost_asio.reference.read_until.overload5.h3"></a> 109 <span class="phrase"><a name="boost_asio.reference.read_until.overload5.remarks"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.remarks">Remarks</a> 110 </h6> 111<p> 112 After a successful read_until operation, the dynamic buffer sequence may 113 contain additional data beyond that which matched the regular expression. 114 An application will typically leave that data in the dynamic buffer sequence 115 for a subsequent read_until operation to examine. 116 </p> 117<h6> 118<a name="boost_asio.reference.read_until.overload5.h4"></a> 119 <span class="phrase"><a name="boost_asio.reference.read_until.overload5.example"></a></span><a class="link" href="overload5.html#boost_asio.reference.read_until.overload5.example">Example</a> 120 </h6> 121<p> 122 To read data into a <code class="computeroutput">std::string</code> until a CR-LF sequence is 123 encountered: 124 </p> 125<pre class="programlisting">std::string data; 126std::size_t n = boost::asio::read_until(s, 127 boost::asio::dynamic_buffer(data), boost::regex("\r\n")); 128std::string line = data.substr(0, n); 129data.erase(0, n); 130</pre> 131<p> 132 After the <code class="computeroutput">read_until</code> operation completes successfully, the 133 string <code class="computeroutput">data</code> contains the delimiter: 134 </p> 135<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... } 136</pre> 137<p> 138 The call to <code class="computeroutput">substr</code> then extracts the data up to and including 139 the delimiter, so that the string <code class="computeroutput">line</code> contains: 140 </p> 141<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n' } 142</pre> 143<p> 144 After the call to <code class="computeroutput">erase</code>, the remaining data is left in the 145 buffer <code class="computeroutput">b</code> as follows: 146 </p> 147<pre class="programlisting">{ 'd', 'e', ... } 148</pre> 149<p> 150 This data may be the start of a new line, to be extracted by a subsequent 151 <code class="computeroutput">read_until</code> operation. 152 </p> 153</div> 154<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 155<td align="left"></td> 156<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 157 Kohlhoff<p> 158 Distributed under the Boost Software License, Version 1.0. (See accompanying 159 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>) 160 </p> 161</div></td> 162</tr></table> 163<hr> 164<div class="spirit-nav"> 165<a accesskey="p" href="overload4.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../read_until.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="overload6.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 166</div> 167</body> 168</html> 169
