1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>async_write_at (3 of 4 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_at.html" title="async_write_at"> 9<link rel="prev" href="overload2.html" title="async_write_at (2 of 4 overloads)"> 10<link rel="next" href="overload4.html" title="async_write_at (4 of 4 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="overload2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_write_at.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="overload4.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_at.overload3"></a><a class="link" href="overload3.html" title="async_write_at (3 of 4 overloads)">async_write_at 28 (3 of 4 overloads)</a> 29</h4></div></div></div> 30<p> 31 Start an asynchronous operation to write all of the supplied data at the 32 specified offset. 33 </p> 34<pre class="programlisting">template< 35 typename <a class="link" href="../AsyncRandomAccessWriteDevice.html" title="Buffer-oriented asynchronous random-access write device requirements">AsyncRandomAccessWriteDevice</a>, 36 typename Allocator, 37 typename <a class="link" href="../WriteHandler.html" title="Write handler requirements">WriteHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>> 38<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_at( 39 AsyncRandomAccessWriteDevice & d, 40 uint64_t offset, 41 basic_streambuf< Allocator > & b, 42 WriteHandler && handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>); 43</pre> 44<p> 45 This function is used to asynchronously write a certain number of bytes 46 of data to a random access device at a specified offset. The function call 47 always returns immediately. The asynchronous operation will continue until 48 one of the following conditions is true: 49 </p> 50<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 51<li class="listitem"> 52 All of the data in the supplied <a class="link" href="../basic_streambuf.html" title="basic_streambuf"><code class="computeroutput">basic_streambuf</code></a> 53 has been written. 54 </li> 55<li class="listitem"> 56 An error occurred. 57 </li> 58</ul></div> 59<p> 60 This operation is implemented in terms of zero or more calls to the device's 61 async_write_some_at function, and is known as a <span class="emphasis"><em>composed operation</em></span>. 62 The program must ensure that the device performs no <span class="emphasis"><em>overlapping</em></span> 63 write operations (such as async_write_at, the device's async_write_some_at 64 function, or any other composed operations that perform writes) until this 65 operation completes. Operations are overlapping if the regions defined 66 by their offsets, and the numbers of bytes to write, intersect. 67 </p> 68<h6> 69<a name="boost_asio.reference.async_write_at.overload3.h0"></a> 70 <span class="phrase"><a name="boost_asio.reference.async_write_at.overload3.parameters"></a></span><a class="link" href="overload3.html#boost_asio.reference.async_write_at.overload3.parameters">Parameters</a> 71 </h6> 72<div class="variablelist"> 73<p class="title"><b></b></p> 74<dl class="variablelist"> 75<dt><span class="term">d</span></dt> 76<dd><p> 77 The device to which the data is to be written. The type must support 78 the AsyncRandomAccessWriteDevice concept. 79 </p></dd> 80<dt><span class="term">offset</span></dt> 81<dd><p> 82 The offset at which the data will be written. 83 </p></dd> 84<dt><span class="term">b</span></dt> 85<dd><p> 86 A <a class="link" href="../basic_streambuf.html" title="basic_streambuf"><code class="computeroutput">basic_streambuf</code></a> 87 object from which data will be written. Ownership of the streambuf 88 is retained by the caller, which must guarantee that it remains valid 89 until the handler is called. 90 </p></dd> 91<dt><span class="term">handler</span></dt> 92<dd> 93<p> 94 The handler to be called when the write operation completes. Copies 95 will be made of the handler as required. The function signature of 96 the handler must be: 97</p> 98<pre class="programlisting">void handler( 99 // Result of operation. 100 const boost::system::error_code& error, 101 102 // Number of bytes written from the buffers. If an error 103 // occurred, this will be less than the sum of the buffer sizes. 104 std::size_t bytes_transferred 105); 106</pre> 107<p> 108 Regardless of whether the asynchronous operation completes immediately 109 or not, the handler will not be invoked from within this function. 110 On immediate completion, invocation of the handler will be performed 111 in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>. 112 </p> 113</dd> 114</dl> 115</div> 116</div> 117<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 118<td align="left"></td> 119<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 120 Kohlhoff<p> 121 Distributed under the Boost Software License, Version 1.0. (See accompanying 122 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>) 123 </p> 124</div></td> 125</tr></table> 126<hr> 127<div class="spirit-nav"> 128<a accesskey="p" href="overload2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_write_at.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="overload4.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 129</div> 130</body> 131</html> 132
