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  25 <div class="section">
  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="beast.ref.boost__beast__http__async_read_some"></a><a class="link" href="boost__beast__http__async_read_some.html" title="http::async_read_some">http::async_read_some</a>
  28 </h4></div></div></div>
  29 <p>
  30         <a class="indexterm" name="idm45873506803440"></a>
  31 Read part of a message asynchronously from a stream
  32         using a parser.
  33       </p>
  34 <h5>
  35 <a name="beast.ref.boost__beast__http__async_read_some.h0"></a>
  36         <span class="phrase"><a name="beast.ref.boost__beast__http__async_read_some.synopsis"></a></span><a class="link" href="boost__beast__http__async_read_some.html#beast.ref.boost__beast__http__async_read_some.synopsis">Synopsis</a>
  37       </h5>
  38 <p>
  39         Defined in header <code class="literal">&lt;<a href="../../../../../../boost/beast/http/read.hpp" target="_top">boost/beast/http/read.hpp</a>&gt;</code>
  40       </p>
  41 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
  42     <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>
  43     <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>
  44     <span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span>
  45     <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>
  46 <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>
  47 <span class="identifier">async_read_some</span><span class="special">(</span>
  48     <span class="identifier">AsyncReadStream</span><span class="special">&amp;</span> <span class="identifier">stream</span><span class="special">,</span>
  49     <span class="identifier">DynamicBuffer</span><span class="special">&amp;</span> <span class="identifier">buffer</span><span class="special">,</span>
  50     <span class="identifier">basic_parser</span><span class="special">&lt;</span> <span class="identifier">isRequest</span> <span class="special">&gt;&amp;</span> <span class="identifier">parser</span><span class="special">,</span>
  51     <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>
  52 </pre>
  53 <h5>
  54 <a name="beast.ref.boost__beast__http__async_read_some.h1"></a>
  55         <span class="phrase"><a name="beast.ref.boost__beast__http__async_read_some.description"></a></span><a class="link" href="boost__beast__http__async_read_some.html#beast.ref.boost__beast__http__async_read_some.description">Description</a>
  56       </h5>
  57 <p>
  58         This function is used to asynchronously read part of a message from a stream
  59         into an instance of <a class="link" href="boost__beast__http__basic_parser.html" title="http::basic_parser"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">basic_parser</span></code></a>. The function call
  60         always returns immediately. The asynchronous operation will continue until
  61         one of the following conditions is true:
  62       </p>
  63 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  64 <li class="listitem">
  65             A call to <a class="link" href="boost__beast__http__basic_parser/put.html" title="http::basic_parser::put"><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">put</span></code></a> with a non-empty buffer
  66             sequence is successful.
  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> function,
  75         and is known as a <span class="emphasis"><em>composed operation</em></span>. The program must
  76         ensure that the stream performs no other reads until this operation completes.
  77         The implementation may read additional bytes from the stream that lie past
  78         the end of the message being read. These additional bytes are stored in the
  79         dynamic buffer, which must be preserved for subsequent reads. If the end
  80         of file error is received while reading from the stream, then the error returned
  81         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 <h5>
  97 <a name="beast.ref.boost__beast__http__async_read_some.h2"></a>
  98         <span class="phrase"><a name="beast.ref.boost__beast__http__async_read_some.parameters"></a></span><a class="link" href="boost__beast__http__async_read_some.html#beast.ref.boost__beast__http__async_read_some.parameters">Parameters</a>
  99       </h5>
 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 the
 140                   stream. This is both an input and an output parameter; on entry,
 141                   the parser will be presented with any remaining data in the dynamic
 142                   buffer's readable bytes sequence first. The type must meet the
 143                   <span class="emphasis"><em>DynamicBuffer</em></span> requirements. The object must
 144                   remain valid at least until the handler is called; ownership is
 145                   not transferred.
 146                 </p>
 147               </td>
 148 </tr>
 149 <tr>
 150 <td>
 151                 <p>
 152                   <code class="computeroutput"><span class="identifier">parser</span></code>
 153                 </p>
 154               </td>
 155 <td>
 156                 <p>
 157                   The parser to use. The object must remain valid at least until
 158                   the handler is called; ownership is not transferred.
 159                 </p>
 160               </td>
 161 </tr>
 162 <tr>
 163 <td>
 164                 <p>
 165                   <code class="computeroutput"><span class="identifier">handler</span></code>
 166                 </p>
 167               </td>
 168 <td>
 169                 <p>
 170                   The completion handler to invoke when the operation completes.
 171                   The implementation takes ownership of the handler by performing
 172                   a decay-copy. The equivalent function signature of the handler
 173                   must be:
 174                 </p>
 175 <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>
 176     <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>
 177     <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>
 178 <span class="special">);</span>
 179 </pre>
 180                 <p>
 181                   Regardless of whether the asynchronous operation completes immediately
 182                   or not, the handler will not be invoked from within this function.
 183                   Invocation of the handler will be performed in a manner equivalent
 184                   to using <code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code>.
 185                 </p>
 186               </td>
 187 </tr>
 188 </tbody>
 189 </table></div>
 190 <h5>
 191 <a name="beast.ref.boost__beast__http__async_read_some.h3"></a>
 192         <span class="phrase"><a name="beast.ref.boost__beast__http__async_read_some.remarks"></a></span><a class="link" href="boost__beast__http__async_read_some.html#beast.ref.boost__beast__http__async_read_some.remarks">Remarks</a>
 193       </h5>
 194 <p>
 195         The completion handler will receive as a parameter the total number of bytes
 196         transferred from the stream. This may be zero for the case where there is
 197         sufficient pre-existing message data in the dynamic buffer.
 198       </p>
 199 <p>
 200         Convenience header <code class="literal">&lt;<a href="../../../../../../boost/beast/http.hpp" target="_top">boost/beast/http.hpp</a>&gt;</code>
 201       </p>
 202 </div>
 203 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 204 <td align="left"></td>
 205 <td align="right"><div class="copyright-footer">Copyright &#169; 2016-2019 Vinnie
 206       Falco<p>
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 208         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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