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  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="beast.ref.boost__beast__http__async_read.overload2"></a><a class="link" href="overload2.html" title="http::async_read (2 of 2 overloads)">http::async_read
  28         (2 of 2 overloads)</a>
  29 </h5></div></div></div>
  30 <p>
  31           Read a complete message asynchronously from a stream.
  32         </p>
  33 <h6>
  34 <a name="beast.ref.boost__beast__http__async_read.overload2.h0"></a>
  35           <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload2.synopsis"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__http__async_read.overload2.synopsis">Synopsis</a>
  36         </h6>
  37 <p>
  38           Defined in header <code class="literal">&lt;<a href="../../../../../../../boost/beast/http/read.hpp" target="_top">boost/beast/http/read.hpp</a>&gt;</code>
  39         </p>
  40 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
  41     <span class="keyword">class</span> <a href="../../../../../../../doc/html/boost_asio/reference/AsyncReadStream.html" target="_top"><span class="emphasis"><em>AsyncReadStream</em></span></a><span class="special">,</span>
  42     <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>
  43     <span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span>
  44     <span class="keyword">class</span> <a class="link" href="../../concepts/Body.html" title="Body"><span class="emphasis"><em>Body</em></span></a><span class="special">,</span>
  45     <span class="keyword">class</span> <a href="https://en.cppreference.com/w/cpp/named_req/Allocator" target="_top"><span class="emphasis"><em>Allocator</em></span></a><span class="special">,</span>
  46     <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">&lt;</span><span class="identifier">AsyncReadStream</span><span class="special">&gt;&gt;&gt;</span>
  47 <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>
  48 <span class="identifier">async_read</span><span class="special">(</span>
  49     <span class="identifier">AsyncReadStream</span><span class="special">&amp;</span> <span class="identifier">stream</span><span class="special">,</span>
  50     <span class="identifier">DynamicBuffer</span><span class="special">&amp;</span> <span class="identifier">buffer</span><span class="special">,</span>
  51     <span class="identifier">message</span><span class="special">&lt;</span> <span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">basic_fields</span><span class="special">&lt;</span> <span class="identifier">Allocator</span> <span class="special">&gt;&gt;&amp;</span> <span class="identifier">msg</span><span class="special">,</span>
  52     <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">&lt;</span> <span class="identifier">AsyncReadStream</span> <span class="special">&gt;&gt;{});</span>
  53 </pre>
  54 <h6>
  55 <a name="beast.ref.boost__beast__http__async_read.overload2.h1"></a>
  56           <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload2.description"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__http__async_read.overload2.description">Description</a>
  57         </h6>
  58 <p>
  59           This function is used to asynchronously read a complete message from a
  60           stream into an instance of <a class="link" href="../boost__beast__http__message.html" title="http::message"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">message</span></code></a>. The function call always
  61           returns immediately. The asynchronous operation will continue until one
  62           of the following conditions is true:
  63         </p>
  64 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  65 <li class="listitem">
  66               The entire message is read in.
  67             </li>
  68 <li class="listitem">
  69               An error occurs.
  70             </li>
  71 </ul></div>
  72 <p>
  73           This operation is implemented in terms of zero or more calls to the next
  74           layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code>
  75           function, and is known as a <span class="emphasis"><em>composed operation</em></span>. The
  76           program must ensure that the stream performs no other reads until this
  77           operation completes. The implementation may read additional bytes from
  78           the stream that lie past the end of the message being read. These additional
  79           bytes are stored in the dynamic buffer, which must be preserved for subsequent
  80           reads. If the end of file error is received while reading from the stream,
  81           then the error returned from this function will be:
  82         </p>
  83 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  84 <li class="listitem">
  85               <a class="link" href="../boost__beast__http__error.html" title="http::error"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">end_of_stream</span></code></a>
  86               if no bytes were parsed, or
  87             </li>
  88 <li class="listitem">
  89               <a class="link" href="../boost__beast__http__error.html" title="http::error"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">partial_message</span></code></a>
  90               if any bytes were parsed but the message was incomplete, otherwise:
  91             </li>
  92 <li class="listitem">
  93               A successful result. The next attempt to read will return <a class="link" href="../boost__beast__http__error.html" title="http::error"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">end_of_stream</span></code></a>
  94             </li>
  95 </ul></div>
  96 <h6>
  97 <a name="beast.ref.boost__beast__http__async_read.overload2.h2"></a>
  98           <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload2.parameters"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__http__async_read.overload2.parameters">Parameters</a>
  99         </h6>
 100 <div class="informaltable"><table class="table">
 101 <colgroup>
 102 <col>
 103 <col>
 104 </colgroup>
 105 <thead><tr>
 106 <th>
 107                   <p>
 108                     Name
 109                   </p>
 110                 </th>
 111 <th>
 112                   <p>
 113                     Description
 114                   </p>
 115                 </th>
 116 </tr></thead>
 117 <tbody>
 118 <tr>
 119 <td>
 120                   <p>
 121                     <code class="computeroutput"><span class="identifier">stream</span></code>
 122                   </p>
 123                 </td>
 124 <td>
 125                   <p>
 126                     The stream from which the data is to be read. The type must meet
 127                     the <span class="emphasis"><em>AsyncReadStream</em></span> requirements.
 128                   </p>
 129                 </td>
 130 </tr>
 131 <tr>
 132 <td>
 133                   <p>
 134                     <code class="computeroutput"><span class="identifier">buffer</span></code>
 135                   </p>
 136                 </td>
 137 <td>
 138                   <p>
 139                     Storage for additional bytes read by the implementation from
 140                     the stream. This is both an input and an output parameter; on
 141                     entry, the parser will be presented with any remaining data in
 142                     the dynamic buffer's readable bytes sequence first. The type
 143                     must meet the <span class="emphasis"><em>DynamicBuffer</em></span> requirements.
 144                     The object must remain valid at least until the handler is called;
 145                     ownership is not transferred.
 146                   </p>
 147                 </td>
 148 </tr>
 149 <tr>
 150 <td>
 151                   <p>
 152                     <code class="computeroutput"><span class="identifier">msg</span></code>
 153                   </p>
 154                 </td>
 155 <td>
 156                   <p>
 157                     The container in which to store the message contents. This message
 158                     container should not have previous contents, otherwise the behavior
 159                     is undefined. The type must be meet the <span class="emphasis"><em>MoveAssignable</em></span>
 160                     and <span class="emphasis"><em>MoveConstructible</em></span> requirements. The
 161                     object must remain valid at least until the handler is called;
 162                     ownership is not transferred.
 163                   </p>
 164                 </td>
 165 </tr>
 166 <tr>
 167 <td>
 168                   <p>
 169                     <code class="computeroutput"><span class="identifier">handler</span></code>
 170                   </p>
 171                 </td>
 172 <td>
 173                   <p>
 174                     The completion handler to invoke when the operation completes.
 175                     The implementation takes ownership of the handler by performing
 176                     a decay-copy. The equivalent function signature of the handler
 177                     must be:
 178                   </p>
 179 <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>
 180     <span class="identifier">error_code</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">error</span><span class="special">,</span>        <span class="comment">// result of operation</span>
 181     <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</span>   <span class="comment">// the total number of bytes transferred from the stream</span>
 182 <span class="special">);</span>
 183 </pre>
 184                   <p>
 185                     Regardless of whether the asynchronous operation completes immediately
 186                     or not, the handler will not be invoked from within this function.
 187                     Invocation of the handler will be performed in a manner equivalent
 188                     to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>.
 189                   </p>
 190                 </td>
 191 </tr>
 192 </tbody>
 193 </table></div>
 194 <h6>
 195 <a name="beast.ref.boost__beast__http__async_read.overload2.h3"></a>
 196           <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload2.remarks"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__http__async_read.overload2.remarks">Remarks</a>
 197         </h6>
 198 <p>
 199           The completion handler will receive as a parameter the total number of
 200           bytes transferred from the stream. This may be zero for the case where
 201           there is sufficient pre-existing message data in the dynamic buffer. The
 202           implementation will call <a class="link" href="../boost__beast__http__basic_parser/eager.html" title="http::basic_parser::eager"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">basic_parser</span><span class="special">::</span><span class="identifier">eager</span></code></a> with the value <code class="computeroutput"><span class="keyword">true</span></code> on the parser passed in.
 203         </p>
 204 <p>
 205           Convenience header <code class="literal">&lt;<a href="../../../../../../../boost/beast/http.hpp" target="_top">boost/beast/http.hpp</a>&gt;</code>
 206         </p>
 207 </div>
 208 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 209 <td align="left"></td>
 210 <td align="right"><div class="copyright-footer">Copyright &#169; 2016-2019 Vinnie
 211       Falco<p>
 212         Distributed under the Boost Software License, Version 1.0. (See accompanying
 213         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>)
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