1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>websocket::stream::async_read_some (2 of 2 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="../../../../index.html" title="Chapter 1. Boost.Beast"> 8<link rel="up" href="../async_read_some.html" title="websocket::stream::async_read_some"> 9<link rel="prev" href="overload1.html" title="websocket::stream::async_read_some (1 of 2 overloads)"> 10<link rel="next" href="../write.html" title="websocket::stream::write"> 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="overload1.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_read_some.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../write.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h6 class="title"> 27<a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload2"></a><a class="link" href="overload2.html" title="websocket::stream::async_read_some (2 of 2 overloads)">websocket::stream::async_read_some 28 (2 of 2 overloads)</a> 29</h6></div></div></div> 30<p> 31 Read some message data asynchronously. 32 </p> 33<h7><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload2.h0"></a> 34 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload2.synopsis"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__websocket__stream.async_read_some.overload2.synopsis">Synopsis</a> 35 </h7><pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 36 <span class="keyword">class</span> <a href="../../../../../../../../doc/html/boost_asio/reference/MutableBufferSequence.html" target="_top"><span class="emphasis"><em>MutableBufferSequence</em></span></a><span class="special">,</span> 37 <span class="keyword">class</span> <a href="../../../../../../../../doc/html/boost_asio/reference/ReadHandler.html" target="_top"><span class="emphasis"><em>ReadHandler</em></span></a> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special"><</span> <a class="link" href="../executor_type.html" title="websocket::stream::executor_type">executor_type</a><span class="special">>></span> 38<a href="../../../../../../../../doc/html/boost_asio/reference/asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type" target="_top"><span class="emphasis"><em>DEDUCED</em></span></a> 39<span class="identifier">async_read_some</span><span class="special">(</span> 40 <span class="identifier">MutableBufferSequence</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">buffers</span><span class="special">,</span> 41 <span class="identifier">ReadHandler</span><span class="special">&&</span> <span class="identifier">handler</span> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special"><</span> <a class="link" href="../executor_type.html" title="websocket::stream::executor_type">executor_type</a> <span class="special">>{});</span> 42</pre> 43<h7><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload2.h1"></a> 44 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload2.description"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__websocket__stream.async_read_some.overload2.description">Description</a> 45 </h7><p> 46 This function is used to asynchronously read some message data. This 47 call always returns immediately. The asynchronous operation will continue 48 until 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 Some message data is received. 53 </li> 54<li class="listitem"> 55 A close frame is received. In this case the error indicated by the 56 function will be <a class="link" href="../../boost__beast__websocket__error.html" title="websocket::error"><code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">closed</span></code></a>. 57 </li> 58<li class="listitem"> 59 An error occurs. 60 </li> 61</ul></div> 62<p> 63 The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>, 64 is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code> 65 and <code class="computeroutput"><span class="identifier">async_write_some</span></code> 66 functions. The program must ensure that no other calls to <a class="link" href="../read/overload1.html" title="websocket::stream::read (1 of 2 overloads)"><code class="computeroutput"><span class="identifier">read</span></code></a>, <a class="link" href="../read_some/overload1.html" title="websocket::stream::read_some (1 of 4 overloads)"><code class="computeroutput"><span class="identifier">read_some</span></code></a>, <a class="link" href="../async_read.html" title="websocket::stream::async_read"><code class="computeroutput"><span class="identifier">async_read</span></code></a>, or <a class="link" href="overload1.html" title="websocket::stream::async_read_some (1 of 2 overloads)"><code class="computeroutput"><span class="identifier">async_read_some</span></code></a> are performed 67 until this operation completes. Received message data is appended to 68 the buffer. The functions <a class="link" href="../got_binary.html" title="websocket::stream::got_binary"><code class="computeroutput"><span class="identifier">got_binary</span></code></a> and <a class="link" href="../got_text.html" title="websocket::stream::got_text"><code class="computeroutput"><span class="identifier">got_text</span></code></a> may be used to query 69 the stream and determine the type of the last received message. Until 70 the operation completes, the implementation will read incoming control 71 frames and handle them automatically as follows: 72 </p> 73<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 74<li class="listitem"> 75 The <a class="link" href="../control_callback/overload1.html" title="websocket::stream::control_callback (1 of 2 overloads)"><code class="computeroutput"><span class="identifier">control_callback</span></code></a> will be 76 invoked for each control frame. 77 </li> 78<li class="listitem"> 79 For each received ping frame, a pong frame will be automatically 80 sent. 81 </li> 82<li class="listitem"> 83 If a close frame is received, the WebSocket close procedure is performed. 84 In this case, when the function returns, the error <a class="link" href="../../boost__beast__websocket__error.html" title="websocket::error"><code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">closed</span></code></a> will be indicated. 85 </li> 86</ul></div> 87<p> 88 Pong frames and close frames sent by the implementation while the read 89 operation is outstanding do not prevent the application from also writing 90 message data, sending pings, sending pongs, or sending close frames. 91 </p> 92<h7><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload2.h2"></a> 93 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload2.parameters"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__websocket__stream.async_read_some.overload2.parameters">Parameters</a> 94 </h7><div class="informaltable"><table class="table"> 95<colgroup> 96<col> 97<col> 98</colgroup> 99<thead><tr> 100<th> 101 <p> 102 Name 103 </p> 104 </th> 105<th> 106 <p> 107 Description 108 </p> 109 </th> 110</tr></thead> 111<tbody> 112<tr> 113<td> 114 <p> 115 <code class="computeroutput"><span class="identifier">buffers</span></code> 116 </p> 117 </td> 118<td> 119 <p> 120 A buffer sequence to write message data into. The previous 121 contents of the buffers will be overwritten, starting from 122 the beginning. The implementation will make copies of this 123 object as needed, but but ownership of the underlying memory 124 is not transferred. The caller is responsible for ensuring 125 that the memory locations pointed to by the buffer sequence 126 remain valid until the completion handler is called. 127 </p> 128 </td> 129</tr> 130<tr> 131<td> 132 <p> 133 <code class="computeroutput"><span class="identifier">handler</span></code> 134 </p> 135 </td> 136<td> 137 <p> 138 The completion handler to invoke when the operation completes. 139 The implementation takes ownership of the handler by performing 140 a decay-copy. The equivalent function signature of the handler 141 must be: 142 </p> 143<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span> 144 <span class="identifier">error_code</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span> <span class="comment">// Result of operation</span> 145 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_written</span> <span class="comment">// Number of bytes written to the buffers</span> 146<span class="special">);</span> 147</pre> 148 <p> 149 Regardless of whether the asynchronous operation completes 150 immediately or not, the handler will not be invoked from within 151 this function. Invocation of the handler will be performed 152 in a manner equivalent to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>. 153 </p> 154 </td> 155</tr> 156</tbody> 157</table></div> 158</div> 159<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 160<td align="left"></td> 161<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 162 Falco<p> 163 Distributed under the Boost Software License, Version 1.0. (See accompanying 164 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>) 165 </p> 166</div></td> 167</tr></table> 168<hr> 169<div class="spirit-nav"> 170<a accesskey="p" href="overload1.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../async_read_some.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../write.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 171</div> 172</body> 173</html> 174
