1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>windows::basic_stream_handle::async_read_some</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="../windows__basic_stream_handle.html" title="windows::basic_stream_handle"> 9<link rel="prev" href="assign/overload2.html" title="windows::basic_stream_handle::assign (2 of 2 overloads)"> 10<link rel="next" href="async_write_some.html" title="windows::basic_stream_handle::async_write_some"> 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="assign/overload2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../windows__basic_stream_handle.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="async_write_some.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.windows__basic_stream_handle.async_read_some"></a><a class="link" href="async_read_some.html" title="windows::basic_stream_handle::async_read_some">windows::basic_stream_handle::async_read_some</a> 28</h4></div></div></div> 29<p> 30 <a class="indexterm" name="boost_asio.indexterm.windows__basic_stream_handle.async_read_some"></a> 31Start 32 an asynchronous read. 33 </p> 34<pre class="programlisting">template< 35 typename <a class="link" href="../MutableBufferSequence.html" title="Mutable buffer sequence requirements">MutableBufferSequence</a>, 36 typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>> 37<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_read_some( 38 const MutableBufferSequence & buffers, 39 ReadHandler && handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>); 40</pre> 41<p> 42 This function is used to asynchronously read data from the stream handle. 43 The function call always returns immediately. 44 </p> 45<h6> 46<a name="boost_asio.reference.windows__basic_stream_handle.async_read_some.h0"></a> 47 <span class="phrase"><a name="boost_asio.reference.windows__basic_stream_handle.async_read_some.parameters"></a></span><a class="link" href="async_read_some.html#boost_asio.reference.windows__basic_stream_handle.async_read_some.parameters">Parameters</a> 48 </h6> 49<div class="variablelist"> 50<p class="title"><b></b></p> 51<dl class="variablelist"> 52<dt><span class="term">buffers</span></dt> 53<dd><p> 54 One or more buffers into which the data will be read. Although the 55 buffers object may be copied as necessary, ownership of the underlying 56 memory blocks is retained by the caller, which must guarantee that 57 they remain valid until the handler is called. 58 </p></dd> 59<dt><span class="term">handler</span></dt> 60<dd> 61<p> 62 The handler to be called when the read operation completes. Copies 63 will be made of the handler as required. The function signature of 64 the handler must be: 65</p> 66<pre class="programlisting">void handler( 67 const boost::system::error_code& error, // Result of operation. 68 std::size_t bytes_transferred // Number of bytes read. 69); 70</pre> 71<p> 72 Regardless of whether the asynchronous operation completes immediately 73 or not, the handler will not be invoked from within this function. 74 On immediate completion, invocation of the handler will be performed 75 in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>. 76 </p> 77</dd> 78</dl> 79</div> 80<h6> 81<a name="boost_asio.reference.windows__basic_stream_handle.async_read_some.h1"></a> 82 <span class="phrase"><a name="boost_asio.reference.windows__basic_stream_handle.async_read_some.remarks"></a></span><a class="link" href="async_read_some.html#boost_asio.reference.windows__basic_stream_handle.async_read_some.remarks">Remarks</a> 83 </h6> 84<p> 85 The read operation may not read all of the requested number of bytes. Consider 86 using the <a class="link" href="../async_read.html" title="async_read"><code class="computeroutput">async_read</code></a> 87 function if you need to ensure that the requested amount of data is read 88 before the asynchronous operation completes. 89 </p> 90<h6> 91<a name="boost_asio.reference.windows__basic_stream_handle.async_read_some.h2"></a> 92 <span class="phrase"><a name="boost_asio.reference.windows__basic_stream_handle.async_read_some.example"></a></span><a class="link" href="async_read_some.html#boost_asio.reference.windows__basic_stream_handle.async_read_some.example">Example</a> 93 </h6> 94<p> 95 To read into a single data buffer use the <a class="link" href="../buffer.html" title="buffer"><code class="computeroutput">buffer</code></a> 96 function as follows: 97 </p> 98<pre class="programlisting">handle.async_read_some(boost::asio::buffer(data, size), handler); 99</pre> 100<p> 101 See the <a class="link" href="../buffer.html" title="buffer"><code class="computeroutput">buffer</code></a> 102 documentation for information on reading into multiple buffers in one go, 103 and how to use it with arrays, boost::array or std::vector. 104 </p> 105</div> 106<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 107<td align="left"></td> 108<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 109 Kohlhoff<p> 110 Distributed under the Boost Software License, Version 1.0. (See accompanying 111 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>) 112 </p> 113</div></td> 114</tr></table> 115<hr> 116<div class="spirit-nav"> 117<a accesskey="p" href="assign/overload2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../windows__basic_stream_handle.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="async_write_some.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 118</div> 119</body> 120</html> 121
