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