1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>websocket::stream::async_read_some (1 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="../async_read_some.html" title="websocket::stream::async_read_some"> 10<link rel="next" href="overload2.html" title="websocket::stream::async_read_some (2 of 2 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="../async_read_some.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="overload2.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.overload1"></a><a class="link" href="overload1.html" title="websocket::stream::async_read_some (1 of 2 overloads)">websocket::stream::async_read_some 28 (1 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.overload1.h0"></a> 34 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload1.synopsis"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_read_some.overload1.synopsis">Synopsis</a> 35 </h7><pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 36 <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> 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">DynamicBuffer</span><span class="special">&</span> <span class="identifier">buffer</span><span class="special">,</span> 41 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">limit</span><span class="special">,</span> 42 <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> 43</pre> 44<h7><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload1.h1"></a> 45 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload1.description"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_read_some.overload1.description">Description</a> 46 </h7><p> 47 This function is used to asynchronously read some message data. This 48 call always returns immediately. The asynchronous operation will continue 49 until one of the following conditions is true: 50 </p> 51<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 52<li class="listitem"> 53 Some message data is received. 54 </li> 55<li class="listitem"> 56 A close frame is received. In this case the error indicated by the 57 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>. 58 </li> 59<li class="listitem"> 60 An error occurs. 61 </li> 62</ul></div> 63<p> 64 The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>, 65 is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code> 66 and <code class="computeroutput"><span class="identifier">async_write_some</span></code> 67 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 68 until this operation completes. Received message data is appended to 69 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 70 the stream and determine the type of the last received message. Until 71 the operation completes, the implementation will read incoming control 72 frames and handle them automatically as follows: 73 </p> 74<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 75<li class="listitem"> 76 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 77 invoked for each control frame. 78 </li> 79<li class="listitem"> 80 For each received ping frame, a pong frame will be automatically 81 sent. 82 </li> 83<li class="listitem"> 84 If a close frame is received, the WebSocket close procedure is performed. 85 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. 86 </li> 87</ul></div> 88<p> 89 Pong frames and close frames sent by the implementation while the read 90 operation is outstanding do not prevent the application from also writing 91 message data, sending pings, sending pongs, or sending close frames. 92 </p> 93<h7><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload1.h2"></a> 94 <span class="phrase"><a name="beast.ref.boost__beast__websocket__stream.async_read_some.overload1.parameters"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__websocket__stream.async_read_some.overload1.parameters">Parameters</a> 95 </h7><div class="informaltable"><table class="table"> 96<colgroup> 97<col> 98<col> 99</colgroup> 100<thead><tr> 101<th> 102 <p> 103 Name 104 </p> 105 </th> 106<th> 107 <p> 108 Description 109 </p> 110 </th> 111</tr></thead> 112<tbody> 113<tr> 114<td> 115 <p> 116 <code class="computeroutput"><span class="identifier">buffer</span></code> 117 </p> 118 </td> 119<td> 120 <p> 121 A dynamic buffer to append message data to. 122 </p> 123 </td> 124</tr> 125<tr> 126<td> 127 <p> 128 <code class="computeroutput"><span class="identifier">limit</span></code> 129 </p> 130 </td> 131<td> 132 <p> 133 An upper limit on the number of bytes this function will append 134 into the buffer. If this value is zero, then a reasonable size 135 will be chosen automatically. 136 </p> 137 </td> 138</tr> 139<tr> 140<td> 141 <p> 142 <code class="computeroutput"><span class="identifier">handler</span></code> 143 </p> 144 </td> 145<td> 146 <p> 147 The completion handler to invoke when the operation completes. 148 The implementation takes ownership of the handler by performing 149 a decay-copy. The equivalent function signature of the handler 150 must be: 151 </p> 152<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> 153 <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> 154 <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> 155<span class="special">);</span> 156</pre> 157 <p> 158 Regardless of whether the asynchronous operation completes 159 immediately or not, the handler will not be invoked from within 160 this function. Invocation of the handler will be performed 161 in a manner equivalent to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>. 162 </p> 163 </td> 164</tr> 165</tbody> 166</table></div> 167</div> 168<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 169<td align="left"></td> 170<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 171 Falco<p> 172 Distributed under the Boost Software License, Version 1.0. (See accompanying 173 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>) 174 </p> 175</div></td> 176</tr></table> 177<hr> 178<div class="spirit-nav"> 179<a accesskey="p" href="../async_read_some.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="overload2.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 180</div> 181</body> 182</html> 183
