1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>read (11 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="overload10.html" title="read (10 of 16 overloads)"> 10<link rel="next" href="overload12.html" title="read (12 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="overload10.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="overload12.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.overload11"></a><a class="link" href="overload11.html" title="read (11 of 16 overloads)">read (11 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 Allocator, 36 typename <a class="link" href="../CompletionCondition.html" title="Completion condition requirements">CompletionCondition</a>> 37std::size_t read( 38 SyncReadStream & s, 39 basic_streambuf< Allocator > & b, 40 CompletionCondition completion_condition); 41</pre> 42<p> 43 This function is used to read a certain number of bytes of data from a 44 stream. The call will block until one of the following conditions is true: 45 </p> 46<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 47<li class="listitem"> 48 The supplied buffer is full (that is, it has reached maximum size). 49 </li> 50<li class="listitem"> 51 The completion_condition function object returns 0. 52 </li> 53</ul></div> 54<p> 55 This operation is implemented in terms of zero or more calls to the stream's 56 read_some function. 57 </p> 58<h6> 59<a name="boost_asio.reference.read.overload11.h0"></a> 60 <span class="phrase"><a name="boost_asio.reference.read.overload11.parameters"></a></span><a class="link" href="overload11.html#boost_asio.reference.read.overload11.parameters">Parameters</a> 61 </h6> 62<div class="variablelist"> 63<p class="title"><b></b></p> 64<dl class="variablelist"> 65<dt><span class="term">s</span></dt> 66<dd><p> 67 The stream from which the data is to be read. The type must support 68 the SyncReadStream concept. 69 </p></dd> 70<dt><span class="term">b</span></dt> 71<dd><p> 72 The <a class="link" href="../basic_streambuf.html" title="basic_streambuf"><code class="computeroutput">basic_streambuf</code></a> 73 object into which the data will be read. 74 </p></dd> 75<dt><span class="term">completion_condition</span></dt> 76<dd> 77<p> 78 The function object to be called to determine whether the read operation 79 is complete. The signature of the function object must be: 80</p> 81<pre class="programlisting">std::size_t completion_condition( 82 // Result of latest read_some operation. 83 const boost::system::error_code& error, 84 85 // Number of bytes transferred so far. 86 std::size_t bytes_transferred 87); 88</pre> 89<p> 90 A return value of 0 indicates that the read operation is complete. 91 A non-zero return value indicates the maximum number of bytes to 92 be read on the next call to the stream's read_some function. 93 </p> 94</dd> 95</dl> 96</div> 97<h6> 98<a name="boost_asio.reference.read.overload11.h1"></a> 99 <span class="phrase"><a name="boost_asio.reference.read.overload11.return_value"></a></span><a class="link" href="overload11.html#boost_asio.reference.read.overload11.return_value">Return 100 Value</a> 101 </h6> 102<p> 103 The number of bytes transferred. 104 </p> 105<h6> 106<a name="boost_asio.reference.read.overload11.h2"></a> 107 <span class="phrase"><a name="boost_asio.reference.read.overload11.exceptions"></a></span><a class="link" href="overload11.html#boost_asio.reference.read.overload11.exceptions">Exceptions</a> 108 </h6> 109<div class="variablelist"> 110<p class="title"><b></b></p> 111<dl class="variablelist"> 112<dt><span class="term">boost::system::system_error</span></dt> 113<dd><p> 114 Thrown on failure. 115 </p></dd> 116</dl> 117</div> 118</div> 119<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 120<td align="left"></td> 121<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 122 Kohlhoff<p> 123 Distributed under the Boost Software License, Version 1.0. (See accompanying 124 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>) 125 </p> 126</div></td> 127</tr></table> 128<hr> 129<div class="spirit-nav"> 130<a accesskey="p" href="overload10.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="overload12.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 131</div> 132</body> 133</html> 134
