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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="boost_asio.reference.windows__basic_random_access_handle.async_read_some_at"></a><a class="link" href="async_read_some_at.html" title="windows::basic_random_access_handle::async_read_some_at">windows::basic_random_access_handle::async_read_some_at</a>
  28 </h4></div></div></div>
  29 <p>
  30           <a class="indexterm" name="id1612157"></a>
  31 Start an asynchronous
  32           read at the specified offset.
  33         </p>
  34 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
  35     <span class="keyword">typename</span> <a class="link" href="../MutableBufferSequence.html" title="Mutable buffer sequence requirements">MutableBufferSequence</a><span class="special">,</span>
  36     <span class="keyword">typename</span> <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a><span class="special">&gt;</span>
  37 <span class="keyword">void</span> <span class="identifier">async_read_some_at</span><span class="special">(</span>
  38     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">uint64_t</span> <span class="identifier">offset</span><span class="special">,</span>
  39     <span class="keyword">const</span> <span class="identifier">MutableBufferSequence</span> <span class="special">&amp;</span> <span class="identifier">buffers</span><span class="special">,</span>
  40     <span class="identifier">ReadHandler</span> <span class="identifier">handler</span><span class="special">);</span>
  41 </pre>
  42 <p>
  43           This function is used to asynchronously read data from the random-access
  44           handle. The function call always returns immediately.
  45         </p>
  46 <h6>
  47 <a name="boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.h0"></a>
  48           <span><a name="boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.parameters"></a></span><a class="link" href="async_read_some_at.html#boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.parameters">Parameters</a>
  49         </h6>
  50 <div class="variablelist">
  51 <p class="title"><b></b></p>
  52 <dl>
  53 <dt><span class="term">offset</span></dt>
  54 <dd><p>
  55                 The offset at which the data will be read.
  56               </p></dd>
  57 <dt><span class="term">buffers</span></dt>
  58 <dd><p>
  59                 One or more buffers into which the data will be read. Although the
  60                 buffers object may be copied as necessary, ownership of the underlying
  61                 memory blocks is retained by the caller, which must guarantee that
  62                 they remain valid until the handler is called.
  63               </p></dd>
  64 <dt><span class="term">handler</span></dt>
  65 <dd>
  66 <p>
  67                 The handler to be called when the read operation completes. Copies
  68                 will be made of the handler as required. The function signature of
  69                 the handler must be:
  70 </p>
  71 <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span>
  72   <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&amp;</span> <span class="identifier">error</span><span class="special">,</span> <span class="comment">// Result of operation.</span>
  73   <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</span>           <span class="comment">// Number of bytes read.</span>
  74 <span class="special">);</span>
  75 </pre>
  76 <p>
  77                 Regardless of whether the asynchronous operation completes immediately
  78                 or not, the handler will not be invoked from within this function.
  79                 Invocation of the handler will be performed in a manner equivalent
  80                 to using <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">post</span><span class="special">()</span></code>.
  81               </p>
  82 </dd>
  83 </dl>
  84 </div>
  85 <h6>
  86 <a name="boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.h1"></a>
  87           <span><a name="boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.remarks"></a></span><a class="link" href="async_read_some_at.html#boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.remarks">Remarks</a>
  88         </h6>
  89 <p>
  90           The read operation may not read all of the requested number of bytes. Consider
  91           using the <a class="link" href="../async_read_at.html" title="async_read_at"><code class="computeroutput"><span class="identifier">async_read_at</span></code></a> function if you
  92           need to ensure that the requested amount of data is read before the asynchronous
  93           operation completes.
  94         </p>
  95 <h6>
  96 <a name="boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.h2"></a>
  97           <span><a name="boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.example"></a></span><a class="link" href="async_read_some_at.html#boost_asio.reference.windows__basic_random_access_handle.async_read_some_at.example">Example</a>
  98         </h6>
  99 <p>
 100           To read into a single data buffer use the <a class="link" href="../buffer.html" title="buffer"><code class="computeroutput"><span class="identifier">buffer</span></code></a> function as follows:
 101         </p>
 102 <pre class="programlisting"><span class="identifier">handle</span><span class="special">.</span><span class="identifier">async_read_some_at</span><span class="special">(</span><span class="number">42</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">buffer</span><span class="special">(</span><span class="identifier">data</span><span class="special">,</span> <span class="identifier">size</span><span class="special">),</span> <span class="identifier">handler</span><span class="special">);</span>
 103 </pre>
 104 <p>
 105           See the <a class="link" href="../buffer.html" title="buffer"><code class="computeroutput"><span class="identifier">buffer</span></code></a>
 106           documentation for information on reading into multiple buffers in one go,
 107           and how to use it with arrays, boost::array or std::vector.
 108         </p>
 109 </div>
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 114         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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