1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>websocket::stream::async_read</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="../boost__beast__websocket__stream.html" title="websocket::stream"> 9<link rel="prev" href="read/overload2.html" title="websocket::stream::read (2 of 2 overloads)"> 10<link rel="next" href="read_some.html" title="websocket::stream::read_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="read/overload2.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost__beast__websocket__stream.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="read_some.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="beast.ref.boost__beast__websocket__stream.async_read"></a><a class="link" href="async_read.html" title="websocket::stream::async_read">websocket::stream::async_read</a> 28</h5></div></div></div> 29<p> 30 <a class="indexterm" name="idm46057518306688"></a> 31 </p> 32<p> 33 Read a complete message asynchronously. 34 </p> 35<h6> 36<a name="beast.ref.boost__beast__websocket__stream.async_read.h0"></a> 37 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read.synopsis"></a></span><a class="link" href="async_read.html#beast.ref.boost__beast__websocket__stream.async_read.synopsis">Synopsis</a> 38 </h6> 39<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 40 <span class="keyword">class</span> <a class="link" href="../../concepts/DynamicBuffer.html" title="DynamicBuffer"><span class="emphasis"><em>DynamicBuffer</em></span></a><span class="special">,</span> 41 <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> 42<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> 43<span class="identifier">async_read</span><span class="special">(</span> 44 <span class="identifier">DynamicBuffer</span><span class="special">&</span> <span class="identifier">buffer</span><span class="special">,</span> 45 <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> 46</pre> 47<h6> 48<a name="beast.ref.boost__beast__websocket__stream.async_read.h1"></a> 49 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read.description"></a></span><a class="link" href="async_read.html#beast.ref.boost__beast__websocket__stream.async_read.description">Description</a> 50 </h6> 51<p> 52 This function is used to asynchronously read a complete message. This call 53 always returns immediately. The asynchronous operation will continue until 54 one of the following conditions is true: 55 </p> 56<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 57<li class="listitem"> 58 A complete message is received. 59 </li> 60<li class="listitem"> 61 A close frame is received. In this case the error indicated by the 62 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>. 63 </li> 64<li class="listitem"> 65 An error occurs. 66 </li> 67</ul></div> 68<p> 69 The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>, 70 is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code> 71 and <code class="computeroutput"><span class="identifier">async_write_some</span></code> functions. 72 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="async_read_some/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 73 until this operation completes. Received message data is appended to the 74 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 75 the stream and determine the type of the last received message. Until the 76 operation completes, the implementation will read incoming control frames 77 and handle them automatically as follows: 78 </p> 79<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 80<li class="listitem"> 81 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 invoked 82 for each control frame. 83 </li> 84<li class="listitem"> 85 For each received ping frame, a pong frame will be automatically sent. 86 </li> 87<li class="listitem"> 88 If a close frame is received, the WebSocket close procedure is performed. 89 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. 90 </li> 91</ul></div> 92<p> 93 Pong frames and close frames sent by the implementation while the read 94 operation is outstanding do not prevent the application from also writing 95 message data, sending pings, sending pongs, or sending close frames. 96 </p> 97<h6> 98<a name="beast.ref.boost__beast__websocket__stream.async_read.h2"></a> 99 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read.parameters"></a></span><a class="link" href="async_read.html#beast.ref.boost__beast__websocket__stream.async_read.parameters">Parameters</a> 100 </h6> 101<div class="informaltable"><table class="table"> 102<colgroup> 103<col> 104<col> 105</colgroup> 106<thead><tr> 107<th> 108 <p> 109 Name 110 </p> 111 </th> 112<th> 113 <p> 114 Description 115 </p> 116 </th> 117</tr></thead> 118<tbody> 119<tr> 120<td> 121 <p> 122 <code class="computeroutput"><span class="identifier">buffer</span></code> 123 </p> 124 </td> 125<td> 126 <p> 127 A dynamic buffer to append message data to. 128 </p> 129 </td> 130</tr> 131<tr> 132<td> 133 <p> 134 <code class="computeroutput"><span class="identifier">handler</span></code> 135 </p> 136 </td> 137<td> 138 <p> 139 The completion handler to invoke when the operation completes. 140 The implementation takes ownership of the handler by performing 141 a decay-copy. The equivalent function signature of the handler 142 must be: 143 </p> 144<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> 145 <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> 146 <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 appended to buffer</span> 147<span class="special">);</span> 148</pre> 149 <p> 150 Regardless of whether the asynchronous operation completes immediately 151 or not, the handler will not be invoked from within this function. 152 Invocation of the handler will be performed in a manner equivalent 153 to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>. 154 </p> 155 </td> 156</tr> 157</tbody> 158</table></div> 159</div> 160<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 161<td align="left"></td> 162<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 163 Falco<p> 164 Distributed under the Boost Software License, Version 1.0. (See accompanying 165 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>) 166 </p> 167</div></td> 168</tr></table> 169<hr> 170<div class="spirit-nav"> 171<a accesskey="p" href="read/overload2.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost__beast__websocket__stream.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="read_some.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 172</div> 173</body> 174</html> 175
