1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>write_at (4 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="../write_at.html" title="write_at"> 9<link rel="prev" href="overload3.html" title="write_at (3 of 8 overloads)"> 10<link rel="next" href="overload5.html" title="write_at (5 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="overload3.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../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="overload5.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.write_at.overload4"></a><a class="link" href="overload4.html" title="write_at (4 of 8 overloads)">write_at (4 28 of 8 overloads)</a> 29</h4></div></div></div> 30<p> 31 Write a certain amount of data at a specified offset before returning. 32 </p> 33<pre class="programlisting">template< 34 typename <a class="link" href="../SyncRandomAccessWriteDevice.html" title="Buffer-oriented synchronous random-access write device requirements">SyncRandomAccessWriteDevice</a>, 35 typename <a class="link" href="../ConstBufferSequence.html" title="Constant buffer sequence requirements">ConstBufferSequence</a>, 36 typename <a class="link" href="../CompletionCondition.html" title="Completion condition requirements">CompletionCondition</a>> 37std::size_t write_at( 38 SyncRandomAccessWriteDevice & d, 39 uint64_t offset, 40 const ConstBufferSequence & buffers, 41 CompletionCondition completion_condition, 42 boost::system::error_code & ec); 43</pre> 44<p> 45 This function is used to write a certain number of bytes of data to a random 46 access device at a specified offset. The call will block until one of the 47 following conditions is true: 48 </p> 49<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 50<li class="listitem"> 51 All of the data in the supplied buffers has been written. That is, 52 the bytes transferred is equal to the sum of the buffer sizes. 53 </li> 54<li class="listitem"> 55 The completion_condition function object returns 0. 56 </li> 57</ul></div> 58<p> 59 This operation is implemented in terms of zero or more calls to the device's 60 write_some_at function. 61 </p> 62<h6> 63<a name="boost_asio.reference.write_at.overload4.h0"></a> 64 <span class="phrase"><a name="boost_asio.reference.write_at.overload4.parameters"></a></span><a class="link" href="overload4.html#boost_asio.reference.write_at.overload4.parameters">Parameters</a> 65 </h6> 66<div class="variablelist"> 67<p class="title"><b></b></p> 68<dl class="variablelist"> 69<dt><span class="term">d</span></dt> 70<dd><p> 71 The device to which the data is to be written. The type must support 72 the SyncRandomAccessWriteDevice concept. 73 </p></dd> 74<dt><span class="term">offset</span></dt> 75<dd><p> 76 The offset at which the data will be written. 77 </p></dd> 78<dt><span class="term">buffers</span></dt> 79<dd><p> 80 One or more buffers containing the data to be written. The sum of 81 the buffer sizes indicates the maximum number of bytes to write to 82 the device. 83 </p></dd> 84<dt><span class="term">completion_condition</span></dt> 85<dd> 86<p> 87 The function object to be called to determine whether the write operation 88 is complete. The signature of the function object must be: 89</p> 90<pre class="programlisting">std::size_t completion_condition( 91 // Result of latest write_some_at operation. 92 const boost::system::error_code& error, 93 94 // Number of bytes transferred so far. 95 std::size_t bytes_transferred 96); 97</pre> 98<p> 99 A return value of 0 indicates that the write operation is complete. 100 A non-zero return value indicates the maximum number of bytes to 101 be written on the next call to the device's write_some_at function. 102 </p> 103</dd> 104<dt><span class="term">ec</span></dt> 105<dd><p> 106 Set to indicate what error occurred, if any. 107 </p></dd> 108</dl> 109</div> 110<h6> 111<a name="boost_asio.reference.write_at.overload4.h1"></a> 112 <span class="phrase"><a name="boost_asio.reference.write_at.overload4.return_value"></a></span><a class="link" href="overload4.html#boost_asio.reference.write_at.overload4.return_value">Return Value</a> 113 </h6> 114<p> 115 The number of bytes written. If an error occurs, returns the total number 116 of bytes successfully transferred prior to the error. 117 </p> 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="overload3.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../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="overload5.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 131</div> 132</body> 133</html> 134
