1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>read (7 of 16 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.html" title="read"> 9<link rel="prev" href="overload6.html" title="read (6 of 16 overloads)"> 10<link rel="next" href="overload8.html" title="read (8 of 16 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="overload6.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../read.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="overload8.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.overload7"></a><a class="link" href="overload7.html" title="read (7 of 16 overloads)">read (7 of 16 28 overloads)</a> 29</h4></div></div></div> 30<p> 31 Attempt to read a certain amount of data from a stream before returning. 32 </p> 33<pre class="programlisting">template< 34 typename <a class="link" href="../SyncReadStream.html" title="Buffer-oriented synchronous read stream requirements">SyncReadStream</a>, 35 typename <a class="link" href="../DynamicBuffer_v1.html" title="Dynamic buffer requirements (version 1)">DynamicBuffer_v1</a>, 36 typename <a class="link" href="../CompletionCondition.html" title="Completion condition requirements">CompletionCondition</a>> 37std::size_t read( 38 SyncReadStream & s, 39 DynamicBuffer_v1 && buffers, 40 CompletionCondition completion_condition, 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 a certain number of bytes of data from a 45 stream. 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 The specified dynamic buffer sequence is full (that is, it has reached 50 maximum size). 51 </li> 52<li class="listitem"> 53 The completion_condition function object returns 0. 54 </li> 55</ul></div> 56<p> 57 This operation is implemented in terms of zero or more calls to the stream's 58 read_some function. 59 </p> 60<h6> 61<a name="boost_asio.reference.read.overload7.h0"></a> 62 <span class="phrase"><a name="boost_asio.reference.read.overload7.parameters"></a></span><a class="link" href="overload7.html#boost_asio.reference.read.overload7.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">buffers</span></dt> 73<dd><p> 74 The dynamic buffer sequence into which the data will be read. 75 </p></dd> 76<dt><span class="term">completion_condition</span></dt> 77<dd> 78<p> 79 The function object to be called to determine whether the read operation 80 is complete. The signature of the function object must be: 81</p> 82<pre class="programlisting">std::size_t completion_condition( 83 // Result of latest read_some operation. 84 const boost::system::error_code& error, 85 86 // Number of bytes transferred so far. 87 std::size_t bytes_transferred 88); 89</pre> 90<p> 91 A return value of 0 indicates that the read operation is complete. 92 A non-zero return value indicates the maximum number of bytes to 93 be read on the next call to the stream's read_some function. 94 </p> 95</dd> 96</dl> 97</div> 98<h6> 99<a name="boost_asio.reference.read.overload7.h1"></a> 100 <span class="phrase"><a name="boost_asio.reference.read.overload7.return_value"></a></span><a class="link" href="overload7.html#boost_asio.reference.read.overload7.return_value">Return 101 Value</a> 102 </h6> 103<p> 104 The number of bytes transferred. 105 </p> 106<h6> 107<a name="boost_asio.reference.read.overload7.h2"></a> 108 <span class="phrase"><a name="boost_asio.reference.read.overload7.exceptions"></a></span><a class="link" href="overload7.html#boost_asio.reference.read.overload7.exceptions">Exceptions</a> 109 </h6> 110<div class="variablelist"> 111<p class="title"><b></b></p> 112<dl class="variablelist"> 113<dt><span class="term">boost::system::system_error</span></dt> 114<dd><p> 115 Thrown on failure. 116 </p></dd> 117</dl> 118</div> 119</div> 120<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 121<td align="left"></td> 122<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 123 Kohlhoff<p> 124 Distributed under the Boost Software License, Version 1.0. (See accompanying 125 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>) 126 </p> 127</div></td> 128</tr></table> 129<hr> 130<div class="spirit-nav"> 131<a accesskey="p" href="overload6.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../read.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="overload8.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 132</div> 133</body> 134</html> 135
