1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>read_until (13 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="overload12.html" title="read_until (12 of 24 overloads)"> 10<link rel="next" href="overload14.html" title="read_until (14 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="overload12.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="overload14.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.overload13"></a><a class="link" href="overload13.html" title="read_until (13 of 24 overloads)">read_until 28 (13 of 24 overloads)</a> 29</h4></div></div></div> 30<p> 31 Read data into a streambuf until some part of the data it contains matches 32 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 Allocator> 37std::size_t read_until( 38 SyncReadStream & s, 39 boost::asio::basic_streambuf< Allocator > & b, 40 const boost::regex & expr); 41</pre> 42<p> 43 This function is used to read data into the specified streambuf until the 44 streambuf's get area contains some data that matches a regular expression. 45 The call will block until one of the following conditions is true: 46 </p> 47<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 48<li class="listitem"> 49 A substring of the streambuf's get area matches the regular expression. 50 </li> 51<li class="listitem"> 52 An error occurred. 53 </li> 54</ul></div> 55<p> 56 This operation is implemented in terms of zero or more calls to the stream's 57 read_some function. If the streambuf's get area already contains data that 58 matches the regular expression, the function returns immediately. 59 </p> 60<h6> 61<a name="boost_asio.reference.read_until.overload13.h0"></a> 62 <span class="phrase"><a name="boost_asio.reference.read_until.overload13.parameters"></a></span><a class="link" href="overload13.html#boost_asio.reference.read_until.overload13.parameters">Parameters</a> 63 </h6> 64<div class="variablelist"> 65<p class="title"><b></b></p> 66<dl class="variablelist"> 67<dt><span class="term">s</span></dt> 68<dd><p> 69 The stream from which the data is to be read. The type must support 70 the SyncReadStream concept. 71 </p></dd> 72<dt><span class="term">b</span></dt> 73<dd><p> 74 A streambuf object into which the data will be read. 75 </p></dd> 76<dt><span class="term">expr</span></dt> 77<dd><p> 78 The regular expression. 79 </p></dd> 80</dl> 81</div> 82<h6> 83<a name="boost_asio.reference.read_until.overload13.h1"></a> 84 <span class="phrase"><a name="boost_asio.reference.read_until.overload13.return_value"></a></span><a class="link" href="overload13.html#boost_asio.reference.read_until.overload13.return_value">Return 85 Value</a> 86 </h6> 87<p> 88 The number of bytes in the streambuf's get area up to and including the 89 substring that matches the regular expression. 90 </p> 91<h6> 92<a name="boost_asio.reference.read_until.overload13.h2"></a> 93 <span class="phrase"><a name="boost_asio.reference.read_until.overload13.exceptions"></a></span><a class="link" href="overload13.html#boost_asio.reference.read_until.overload13.exceptions">Exceptions</a> 94 </h6> 95<div class="variablelist"> 96<p class="title"><b></b></p> 97<dl class="variablelist"> 98<dt><span class="term">boost::system::system_error</span></dt> 99<dd><p> 100 Thrown on failure. 101 </p></dd> 102</dl> 103</div> 104<h6> 105<a name="boost_asio.reference.read_until.overload13.h3"></a> 106 <span class="phrase"><a name="boost_asio.reference.read_until.overload13.remarks"></a></span><a class="link" href="overload13.html#boost_asio.reference.read_until.overload13.remarks">Remarks</a> 107 </h6> 108<p> 109 After a successful read_until operation, the streambuf may contain additional 110 data beyond that which matched the regular expression. An application will 111 typically leave that data in the streambuf for a subsequent read_until 112 operation to examine. 113 </p> 114<h6> 115<a name="boost_asio.reference.read_until.overload13.h4"></a> 116 <span class="phrase"><a name="boost_asio.reference.read_until.overload13.example"></a></span><a class="link" href="overload13.html#boost_asio.reference.read_until.overload13.example">Example</a> 117 </h6> 118<p> 119 To read data into a streambuf until a CR-LF sequence is encountered: 120 </p> 121<pre class="programlisting">boost::asio::streambuf b; 122boost::asio::read_until(s, b, boost::regex("\r\n")); 123std::istream is(&b); 124std::string line; 125std::getline(is, line); 126</pre> 127<p> 128 After the <code class="computeroutput">read_until</code> operation completes successfully, the 129 buffer <code class="computeroutput">b</code> contains the data which matched the regular expression: 130 </p> 131<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... } 132</pre> 133<p> 134 The call to <code class="computeroutput">std::getline</code> then extracts the data up to and 135 including the newline (which is discarded), so that the string <code class="computeroutput">line</code> 136 contains: 137 </p> 138<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r' } 139</pre> 140<p> 141 The remaining data is left in the buffer <code class="computeroutput">b</code> as follows: 142 </p> 143<pre class="programlisting">{ 'd', 'e', ... } 144</pre> 145<p> 146 This data may be the start of a new line, to be extracted by a subsequent 147 <code class="computeroutput">read_until</code> operation. 148 </p> 149</div> 150<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 151<td align="left"></td> 152<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 153 Kohlhoff<p> 154 Distributed under the Boost Software License, Version 1.0. (See accompanying 155 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>) 156 </p> 157</div></td> 158</tr></table> 159<hr> 160<div class="spirit-nav"> 161<a accesskey="p" href="overload12.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="overload14.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 162</div> 163</body> 164</html> 165
