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  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="idm45873472798176"></a>
  31 Read a complete message asynchronously.
  32         </p>
  33 <h6>
  34 <a name="beast.ref.boost__beast__websocket__stream.async_read.h0"></a>
  35           <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>
  36         </h6>
  37 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
  38     <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>
  39     <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>
  40 <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>
  41 <span class="identifier">async_read</span><span class="special">(</span>
  42     <span class="identifier">DynamicBuffer</span><span class="special">&amp;</span> <span class="identifier">buffer</span><span class="special">,</span>
  43     <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>
  44 </pre>
  45 <h6>
  46 <a name="beast.ref.boost__beast__websocket__stream.async_read.h1"></a>
  47           <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>
  48         </h6>
  49 <p>
  50           This function is used to asynchronously read a complete message. This call
  51           always returns immediately. The asynchronous operation will continue until
  52           one of the following conditions is true:
  53         </p>
  54 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  55 <li class="listitem">
  56               A complete message is received.
  57             </li>
  58 <li class="listitem">
  59               A close frame is received. In this case the error indicated by the
  60               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>.
  61             </li>
  62 <li class="listitem">
  63               An error occurs.
  64             </li>
  65 </ul></div>
  66 <p>
  67           The algorithm, known as a <span class="emphasis"><em>composed asynchronous operation</em></span>,
  68           is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code>
  69           and <code class="computeroutput"><span class="identifier">async_write_some</span></code> functions.
  70           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
  71           until this operation completes. Received message data is appended to the
  72           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
  73           the stream and determine the type of the last received message. Until the
  74           operation completes, the implementation will read incoming control frames
  75           and handle them automatically as follows:
  76         </p>
  77 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  78 <li class="listitem">
  79               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 invoked
  80               for each control frame.
  81             </li>
  82 <li class="listitem">
  83               For each received ping frame, a pong frame will be automatically sent.
  84             </li>
  85 <li class="listitem">
  86               If a close frame is received, the WebSocket close procedure is performed.
  87               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.
  88             </li>
  89 </ul></div>
  90 <p>
  91           Pong frames and close frames sent by the implementation while the read
  92           operation is outstanding do not prevent the application from also writing
  93           message data, sending pings, sending pongs, or sending close frames.
  94         </p>
  95 <h6>
  96 <a name="beast.ref.boost__beast__websocket__stream.async_read.h2"></a>
  97           <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>
  98         </h6>
  99 <div class="informaltable"><table class="table">
 100 <colgroup>
 101 <col>
 102 <col>
 103 </colgroup>
 104 <thead><tr>
 105 <th>
 106                   <p>
 107                     Name
 108                   </p>
 109                 </th>
 110 <th>
 111                   <p>
 112                     Description
 113                   </p>
 114                 </th>
 115 </tr></thead>
 116 <tbody>
 117 <tr>
 118 <td>
 119                   <p>
 120                     <code class="computeroutput"><span class="identifier">buffer</span></code>
 121                   </p>
 122                 </td>
 123 <td>
 124                   <p>
 125                     A dynamic buffer to append message data to.
 126                   </p>
 127                 </td>
 128 </tr>
 129 <tr>
 130 <td>
 131                   <p>
 132                     <code class="computeroutput"><span class="identifier">handler</span></code>
 133                   </p>
 134                 </td>
 135 <td>
 136                   <p>
 137                     The completion handler to invoke when the operation completes.
 138                     The implementation takes ownership of the handler by performing
 139                     a decay-copy. The equivalent function signature of the handler
 140                     must be:
 141                   </p>
 142 <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>
 143     <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>
 144     <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>
 145 <span class="special">);</span>
 146 </pre>
 147                   <p>
 148                     Regardless of whether the asynchronous operation completes immediately
 149                     or not, the handler will not be invoked from within this function.
 150                     Invocation of the handler will be performed in a manner equivalent
 151                     to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>.
 152                   </p>
 153                 </td>
 154 </tr>
 155 </tbody>
 156 </table></div>
 157 </div>
 158 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 159 <td align="left"></td>
 160 <td align="right"><div class="copyright-footer">Copyright &#169; 2016-2019 Vinnie
 161       Falco<p>
 162         Distributed under the Boost Software License, Version 1.0. (See accompanying
 163         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>)
 164       </p>
 165 </div></td>
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