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<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.overview.core.reactor"></a><a class="link" href="reactor.html" title="Reactor-Style Operations">Reactor-Style Operations</a>
</h4></div></div></div>
<p>
Sometimes a program must be integrated with a third-party library that
wants to perform the I/O operations itself. To facilitate this, Boost.Asio
includes a <code class="computeroutput"><span class="identifier">null_buffers</span></code>
type that can be used with both read and write operations. A <code class="computeroutput"><span class="identifier">null_buffers</span></code> operation doesn't return
until the I/O object is "ready" to perform the operation.
</p>
<p>
As an example, to perform a non-blocking read something like the following
may be used:
</p>
<pre class="programlisting"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span> <span class="identifier">socket</span><span class="special">(</span><span class="identifier">my_io_service</span><span class="special">);</span>
<span class="special">...</span>
<span class="identifier">socket</span><span class="special">.</span><span class="identifier">non_blocking</span><span class="special">(</span><span class="keyword">true</span><span class="special">);</span>
<span class="special">...</span>
<span class="identifier">socket</span><span class="special">.</span><span class="identifier">async_read_some</span><span class="special">(</span><span class="identifier">null_buffers</span><span class="special">(),</span> <span class="identifier">read_handler</span><span class="special">);</span>
<span class="special">...</span>
<span class="keyword">void</span> <span class="identifier">read_handler</span><span class="special">(</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="identifier">ec</span><span class="special">)</span>
<span class="special">{</span>
<span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">char</span><span class="special">></span> <span class="identifier">buf</span><span class="special">(</span><span class="identifier">socket</span><span class="special">.</span><span class="identifier">available</span><span class="special">());</span>
<span class="identifier">socket</span><span class="special">.</span><span class="identifier">read_some</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">(</span><span class="identifier">buf</span><span class="special">));</span>
<span class="special">}</span>
<span class="special">}</span>
</pre>
<p>
These operations are supported for sockets on all platforms, and for the
POSIX stream-oriented descriptor classes.
</p>
<h6>
<a name="boost_asio.overview.core.reactor.h0"></a>
<span class="phrase"><a name="boost_asio.overview.core.reactor.see_also"></a></span><a class="link" href="reactor.html#boost_asio.overview.core.reactor.see_also">See
Also</a>
</h6>
<p>
<a class="link" href="../../reference/null_buffers.html" title="null_buffers">null_buffers</a>,
<a class="link" href="../../reference/basic_socket/non_blocking.html" title="basic_socket::non_blocking">basic_socket::non_blocking()</a>,
<a class="link" href="../../reference/basic_socket/native_non_blocking.html" title="basic_socket::native_non_blocking">basic_socket::native_non_blocking()</a>,
<a class="link" href="../../examples/cpp03_examples.html#boost_asio.examples.cpp03_examples.nonblocking">nonblocking
example</a>.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2015 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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