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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_asio.reference.SyncRandomAccessReadDevice"></a><a class="link" href="SyncRandomAccessReadDevice.html" title="Buffer-oriented synchronous random-access read device requirements">Buffer-oriented
  28       synchronous random-access read device requirements</a>
  29 </h3></div></div></div>
  30 <p>
  31         In the table below, <code class="computeroutput"><span class="identifier">a</span></code> denotes
  32         a synchronous random-access read device object, <code class="computeroutput"><span class="identifier">o</span></code>
  33         denotes an offset of type <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">uint64_t</span></code>,
  34         <code class="computeroutput"><span class="identifier">mb</span></code> denotes an object satisfying
  35         <a class="link" href="MutableBufferSequence.html" title="Mutable buffer sequence requirements">mutable buffer
  36         sequence</a> requirements, and <code class="computeroutput"><span class="identifier">ec</span></code>
  37         denotes an object of type <code class="computeroutput"><span class="identifier">error_code</span></code>.
  38       </p>
  39 <div class="table">
  40 <a name="boost_asio.reference.SyncRandomAccessReadDevice.t0"></a><p class="title"><b>Table&#160;34.&#160;Buffer-oriented synchronous random-access read device requirements</b></p>
  41 <div class="table-contents"><table class="table" summary="Buffer-oriented synchronous random-access read device requirements">
  42 <colgroup>
  43 <col>
  44 <col>
  45 <col>
  46 </colgroup>
  47 <thead><tr>
  48 <th>
  49                 <p>
  50                   operation
  51                 </p>
  52               </th>
  53 <th>
  54                 <p>
  55                   type
  56                 </p>
  57               </th>
  58 <th>
  59                 <p>
  60                   semantics, pre/post-conditions
  61                 </p>
  62               </th>
  63 </tr></thead>
  64 <tbody>
  65 <tr>
  66 <td>
  67                 <p>
  68                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">read_some_at</span><span class="special">(</span><span class="identifier">o</span><span class="special">,</span>
  69                   <span class="identifier">mb</span><span class="special">);</span></code>
  70                 </p>
  71               </td>
  72 <td>
  73                 <p>
  74                   <code class="computeroutput"><span class="identifier">size_t</span></code>
  75                 </p>
  76               </td>
  77 <td>
  78                 <p>
  79                   Equivalent to:
  80 </p>
  81 <pre class="programlisting"><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">;</span>
  82 <span class="identifier">size_t</span> <span class="identifier">s</span> <span class="special">=</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">read_some_at</span><span class="special">(</span><span class="identifier">o</span><span class="special">,</span> <span class="identifier">mb</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
  83 <span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span><span class="special">)</span> <span class="keyword">throw</span> <span class="identifier">system_error</span><span class="special">(</span><span class="identifier">ec</span><span class="special">);</span>
  84 <span class="keyword">return</span> <span class="identifier">s</span><span class="special">;</span>
  85 </pre>
  86 <p>
  87                 </p>
  88               </td>
  89 </tr>
  90 <tr>
  91 <td>
  92                 <p>
  93                   <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">read_some_at</span><span class="special">(</span><span class="identifier">o</span><span class="special">,</span>
  94                   <span class="identifier">mb</span><span class="special">,</span>
  95                   <span class="identifier">ec</span><span class="special">);</span></code>
  96                 </p>
  97               </td>
  98 <td>
  99                 <p>
 100                   <code class="computeroutput"><span class="identifier">size_t</span></code>
 101                 </p>
 102               </td>
 103 <td>
 104                 <p>
 105                   Reads one or more bytes of data from the device <code class="computeroutput"><span class="identifier">a</span></code>
 106                   at offset <code class="computeroutput"><span class="identifier">o</span></code>.<br>
 107                   <br> The mutable buffer sequence <code class="computeroutput"><span class="identifier">mb</span></code>
 108                   specifies memory where the data should be placed. The <code class="computeroutput"><span class="identifier">read_some_at</span></code> operation shall
 109                   always fill a buffer in the sequence completely before proceeding
 110                   to the next.<br> <br> If successful, returns the number of
 111                   bytes read and sets <code class="computeroutput"><span class="identifier">ec</span></code>
 112                   such that <code class="computeroutput"><span class="special">!</span><span class="identifier">ec</span></code>
 113                   is true. If an error occurred, returns <code class="computeroutput"><span class="number">0</span></code>
 114                   and sets <code class="computeroutput"><span class="identifier">ec</span></code> such
 115                   that <code class="computeroutput"><span class="special">!!</span><span class="identifier">ec</span></code>
 116                   is true.<br> <br> If the total size of all buffers in the sequence
 117                   <code class="computeroutput"><span class="identifier">mb</span></code> is <code class="computeroutput"><span class="number">0</span></code>, the function shall return <code class="computeroutput"><span class="number">0</span></code> immediately.
 118                 </p>
 119               </td>
 120 </tr>
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