1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>read (16 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="overload15.html" title="read (15 of 16 overloads)"> 10<link rel="next" href="../read_at.html" title="read_at"> 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="overload15.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="../read_at.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.overload16"></a><a class="link" href="overload16.html" title="read (16 of 16 overloads)">read (16 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_v2.html" title="Dynamic buffer requirements (version 2)">DynamicBuffer_v2</a>, 36 typename <a class="link" href="../CompletionCondition.html" title="Completion condition requirements">CompletionCondition</a>> 37std::size_t read( 38 SyncReadStream & s, 39 DynamicBuffer_v2 buffers, 40 CompletionCondition completion_condition, 41 boost::system::error_code & ec, 42 typename enable_if< is_dynamic_buffer_v2< DynamicBuffer_v2 >::value >::type * = 0); 43</pre> 44<p> 45 This function is used to read a certain number of bytes of data from a 46 stream. The call will block until one of the following conditions is true: 47 </p> 48<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 49<li class="listitem"> 50 The specified dynamic buffer sequence is full (that is, it has reached 51 maximum size). 52 </li> 53<li class="listitem"> 54 The completion_condition function object returns 0. 55 </li> 56</ul></div> 57<p> 58 This operation is implemented in terms of zero or more calls to the stream's 59 read_some function. 60 </p> 61<h6> 62<a name="boost_asio.reference.read.overload16.h0"></a> 63 <span class="phrase"><a name="boost_asio.reference.read.overload16.parameters"></a></span><a class="link" href="overload16.html#boost_asio.reference.read.overload16.parameters">Parameters</a> 64 </h6> 65<div class="variablelist"> 66<p class="title"><b></b></p> 67<dl class="variablelist"> 68<dt><span class="term">s</span></dt> 69<dd><p> 70 The stream from which the data is to be read. The type must support 71 the SyncReadStream concept. 72 </p></dd> 73<dt><span class="term">buffers</span></dt> 74<dd><p> 75 The dynamic buffer sequence into which the data will be read. 76 </p></dd> 77<dt><span class="term">completion_condition</span></dt> 78<dd> 79<p> 80 The function object to be called to determine whether the read operation 81 is complete. The signature of the function object must be: 82</p> 83<pre class="programlisting">std::size_t completion_condition( 84 // Result of latest read_some operation. 85 const boost::system::error_code& error, 86 87 // Number of bytes transferred so far. 88 std::size_t bytes_transferred 89); 90</pre> 91<p> 92 A return value of 0 indicates that the read operation is complete. 93 A non-zero return value indicates the maximum number of bytes to 94 be read on the next call to the stream's read_some function. 95 </p> 96</dd> 97<dt><span class="term">ec</span></dt> 98<dd><p> 99 Set to indicate what error occurred, if any. 100 </p></dd> 101</dl> 102</div> 103<h6> 104<a name="boost_asio.reference.read.overload16.h1"></a> 105 <span class="phrase"><a name="boost_asio.reference.read.overload16.return_value"></a></span><a class="link" href="overload16.html#boost_asio.reference.read.overload16.return_value">Return 106 Value</a> 107 </h6> 108<p> 109 The number of bytes read. If an error occurs, returns the total number 110 of bytes successfully transferred prior to the error. 111 </p> 112</div> 113<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 114<td align="left"></td> 115<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 116 Kohlhoff<p> 117 Distributed under the Boost Software License, Version 1.0. (See accompanying 118 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>) 119 </p> 120</div></td> 121</tr></table> 122<hr> 123<div class="spirit-nav"> 124<a accesskey="p" href="overload15.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="../read_at.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 125</div> 126</body> 127</html> 128
