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<div class="titlepage"><div><div><h4 class="title">
<a name="asio.reference.basic_serial_port.async_read_some"></a><a class="link" href="async_read_some.html" title="basic_serial_port::async_read_some">basic_serial_port::async_read_some</a>
</h4></div></div></div>
<p>
<a class="indexterm" name="id823224"></a>
Start an asynchronous read.
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
<span class="keyword">typename</span> <a class="link" href="../MutableBufferSequence.html" title="Mutable buffer sequence requirements">MutableBufferSequence</a><span class="special">,</span>
<span class="keyword">typename</span> <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a><span class="special">></span>
<span class="keyword">void</span> <span class="identifier">async_read_some</span><span class="special">(</span>
<span class="keyword">const</span> <span class="identifier">MutableBufferSequence</span> <span class="special">&</span> <span class="identifier">buffers</span><span class="special">,</span>
<span class="identifier">ReadHandler</span> <span class="identifier">handler</span><span class="special">);</span>
</pre>
<p>
This function is used to asynchronously read data from the serial port.
The function call always returns immediately.
</p>
<a name="asio.reference.basic_serial_port.async_read_some.parameters"></a><h6>
<a name="id823356"></a>
<a class="link" href="async_read_some.html#asio.reference.basic_serial_port.async_read_some.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">buffers</span></dt>
<dd><p>
One or more buffers into which the data will be read. Although the
buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain valid until the handler is called.
</p></dd>
<dt><span class="term">handler</span></dt>
<dd>
<p>
The handler to be called when the read operation completes. Copies
will be made of the handler as required. The function signature of
the handler must be:
</p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span>
<span class="keyword">const</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">error</span><span class="special">,</span> <span class="comment">// Result of operation.
</span> <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><span class="special">);</span>
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
Invocation of the handler will be performed in a manner equivalent
to using <code class="computeroutput"><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>.
</p>
</dd>
</dl>
</div>
<a name="asio.reference.basic_serial_port.async_read_some.remarks"></a><h6>
<a name="id823541"></a>
<a class="link" href="async_read_some.html#asio.reference.basic_serial_port.async_read_some.remarks">Remarks</a>
</h6>
<p>
The read operation may not read all of the requested number of bytes. Consider
using the <a class="link" href="../async_read.html" title="async_read"><code class="computeroutput"><span class="identifier">async_read</span></code></a>
function if you need to ensure that the requested amount of data is read
before the asynchronous operation completes.
</p>
<a name="asio.reference.basic_serial_port.async_read_some.example"></a><h6>
<a name="id823582"></a>
<a class="link" href="async_read_some.html#asio.reference.basic_serial_port.async_read_some.example">Example</a>
</h6>
<p>
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:
</p>
<pre class="programlisting"><span class="identifier">serial_port</span><span class="special">.</span><span class="identifier">async_read_some</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>
</pre>
<p>
See the <a class="link" href="../buffer.html" title="buffer"><code class="computeroutput"><span class="identifier">buffer</span></code></a>
documentation for information on reading into multiple buffers in one go,
and how to use it with arrays, boost::array or std::vector.
</p>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="right"><div class="copyright-footer">Copyright © 2003 - 2010 Christopher M. Kohlhoff<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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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