libs/beast/doc/html/beast/ref/boost__beast__websocket__stream/async_read_some/overload2.html

   1 <html>
   2 <head>
   3 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   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&#160;1.&#160;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="../async_write.html" title="websocket::stream::async_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="../async_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">&lt;</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">&lt;</span>                <span class="identifier">executor_type</span><span class="special">&gt;&gt;</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">&amp;</span> <span class="identifier">buffers</span><span class="special">,</span>
  41     <span class="identifier">ReadHandler</span><span class="special">&amp;&amp;</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">&lt;</span> <span class="identifier">executor_type</span> <span class="special">&gt;{});</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">websocket</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.html" title="websocket::stream::read"><code class="computeroutput"><span class="identifier">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><span class="identifier">read</span></code></a>, <a class="link" href="../read_some.html" title="websocket::stream::read_some"><code class="computeroutput"><span class="identifier">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><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">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><span class="identifier">async_read</span></code></a>, or <a class="link" href="../async_read_some.html" title="websocket::stream::async_read_some"><code class="computeroutput"><span class="identifier">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><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">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><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">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><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.html" title="websocket::stream::control_callback"><code class="computeroutput"><span class="identifier">websocket</span><span class="special">::</span><span class="identifier">stream</span><span class="special">::</span><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">websocket</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">&amp;</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 &#169; 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="../async_write.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
 171 </div>
 172 </body>
 173 </html>