1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>async_write (6 of 8 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="../async_write.html" title="async_write"> 9<link rel="prev" href="overload5.html" title="async_write (5 of 8 overloads)"> 10<link rel="next" href="overload7.html" title="async_write (7 of 8 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="overload5.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_write.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="overload7.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.async_write.overload6"></a><a class="link" href="overload6.html" title="async_write (6 of 8 overloads)">async_write 28 (6 of 8 overloads)</a> 29</h4></div></div></div> 30<p> 31 Start an asynchronous operation to write a certain amount of data to a 32 stream. 33 </p> 34<pre class="programlisting">template< 35 typename <a class="link" href="../AsyncWriteStream.html" title="Buffer-oriented asynchronous write stream requirements">AsyncWriteStream</a>, 36 typename Allocator, 37 typename <a class="link" href="../CompletionCondition.html" title="Completion condition requirements">CompletionCondition</a>, 38 typename <a class="link" href="../WriteHandler.html" title="Write handler requirements">WriteHandler</a>> 39<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_write( 40 AsyncWriteStream & s, 41 basic_streambuf< Allocator > & b, 42 CompletionCondition completion_condition, 43 WriteHandler && handler); 44</pre> 45<p> 46 This function is used to asynchronously write a certain number of bytes 47 of data to a stream. The function call always returns immediately. The 48 asynchronous operation will continue until one of the following conditions 49 is true: 50 </p> 51<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 52<li class="listitem"> 53 All of the data in the supplied <a class="link" href="../basic_streambuf.html" title="basic_streambuf"><code class="computeroutput">basic_streambuf</code></a> 54 has been written. 55 </li> 56<li class="listitem"> 57 The completion_condition function object returns 0. 58 </li> 59</ul></div> 60<p> 61 This operation is implemented in terms of zero or more calls to the stream's 62 async_write_some function, and is known as a <span class="emphasis"><em>composed operation</em></span>. 63 The program must ensure that the stream performs no other write operations 64 (such as async_write, the stream's async_write_some function, or any other 65 composed operations that perform writes) until this operation completes. 66 </p> 67<h6> 68<a name="boost_asio.reference.async_write.overload6.h0"></a> 69 <span class="phrase"><a name="boost_asio.reference.async_write.overload6.parameters"></a></span><a class="link" href="overload6.html#boost_asio.reference.async_write.overload6.parameters">Parameters</a> 70 </h6> 71<div class="variablelist"> 72<p class="title"><b></b></p> 73<dl class="variablelist"> 74<dt><span class="term">s</span></dt> 75<dd><p> 76 The stream to which the data is to be written. The type must support 77 the AsyncWriteStream concept. 78 </p></dd> 79<dt><span class="term">b</span></dt> 80<dd><p> 81 A <a class="link" href="../basic_streambuf.html" title="basic_streambuf"><code class="computeroutput">basic_streambuf</code></a> 82 object from which data will be written. Ownership of the streambuf 83 is retained by the caller, which must guarantee that it remains valid 84 until the handler is called. 85 </p></dd> 86<dt><span class="term">completion_condition</span></dt> 87<dd> 88<p> 89 The function object to be called to determine whether the write operation 90 is complete. The signature of the function object must be: 91</p> 92<pre class="programlisting">std::size_t completion_condition( 93 // Result of latest async_write_some operation. 94 const boost::system::error_code& error, 95 96 // Number of bytes transferred so far. 97 std::size_t bytes_transferred 98); 99</pre> 100<p> 101 A return value of 0 indicates that the write operation is complete. 102 A non-zero return value indicates the maximum number of bytes to 103 be written on the next call to the stream's async_write_some function. 104 </p> 105</dd> 106<dt><span class="term">handler</span></dt> 107<dd> 108<p> 109 The handler to be called when the write operation completes. Copies 110 will be made of the handler as required. The function signature of 111 the handler must be: 112</p> 113<pre class="programlisting">void handler( 114 const boost::system::error_code& error, // Result of operation. 115 116 std::size_t bytes_transferred // Number of bytes written from the 117 // buffers. If an error occurred, 118 // this will be less than the sum 119 // of the buffer sizes. 120); 121</pre> 122<p> 123 Regardless of whether the asynchronous operation completes immediately 124 or not, the handler will not be invoked from within this function. 125 On immediate completion, invocation of the handler will be performed 126 in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>. 127 </p> 128</dd> 129</dl> 130</div> 131</div> 132<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 133<td align="left"></td> 134<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 135 Kohlhoff<p> 136 Distributed under the Boost Software License, Version 1.0. (See accompanying 137 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>) 138 </p> 139</div></td> 140</tr></table> 141<hr> 142<div class="spirit-nav"> 143<a accesskey="p" href="overload5.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_write.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="overload7.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 144</div> 145</body> 146</html> 147
