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<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.asio_handler_invoke"></a><a class="link" href="asio_handler_invoke.html" title="asio_handler_invoke"> asio_handler_invoke</a>
</h3></div></div></div>
<p>
<a class="indexterm" name="id578223"></a>
Default invoke function for handlers.
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
<span class="keyword">typename</span> <span class="identifier">Function</span><span class="special">></span>
<span class="keyword">void</span> <span class="identifier">asio_handler_invoke</span><span class="special">(</span>
<span class="identifier">Function</span> <span class="identifier">function</span><span class="special">,</span>
<span class="special">...</span> <span class="special">);</span>
</pre>
<p>
Completion handlers for asynchronous operations are invoked by the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>
associated with the corresponding object (e.g. a socket or deadline_timer).
Certain guarantees are made on when the handler may be invoked, in particular
that a handler can only be invoked from a thread that is currently calling
<code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>
on the corresponding <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> object. Handlers may
subsequently be invoked through other objects (such as <a class="link" href="io_service__strand.html" title="io_service::strand"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">strand</span></code></a> objects) that provide additional
guarantees.
</p>
<p>
When asynchronous operations are composed from other asynchronous operations,
all intermediate handlers should be invoked using the same method as the
final handler. This is required to ensure that user-defined objects are not
accessed in a way that may violate the guarantees. This hooking function
ensures that the invoked method used for the final handler is accessible
at each intermediate step.
</p>
<p>
Implement asio_handler_invoke for your own handlers to specify a custom invocation
strategy.
</p>
<p>
This default implementation is simply:
</p>
<pre class="programlisting"><span class="identifier">function</span><span class="special">();</span>
</pre>
<a name="asio.reference.asio_handler_invoke.example"></a><h5>
<a name="id578420"></a>
<a class="link" href="asio_handler_invoke.html#asio.reference.asio_handler_invoke.example">Example</a>
</h5>
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">my_handler</span><span class="special">;</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Function</span><span class="special">></span>
<span class="keyword">void</span> <span class="identifier">asio_handler_invoke</span><span class="special">(</span><span class="identifier">Function</span> <span class="identifier">function</span><span class="special">,</span> <span class="identifier">my_handler</span><span class="special">*</span> <span class="identifier">context</span><span class="special">)</span>
<span class="special">{</span>
<span class="identifier">context</span><span class="special">-></span><span class="identifier">strand_</span><span class="special">.</span><span class="identifier">dispatch</span><span class="special">(</span><span class="identifier">function</span><span class="special">);</span>
<span class="special">}</span>
</pre>
<a name="asio.reference.asio_handler_invoke.requirements"></a><h5>
<a name="id578586"></a>
<a class="link" href="asio_handler_invoke.html#asio.reference.asio_handler_invoke.requirements">Requirements</a>
</h5>
<p>
<span class="bold"><strong>Header: </strong></span><code class="literal">asio/handler_invoke_hook.hpp</code>
</p>
<p>
<span class="bold"><strong>Convenience header: </strong></span><code class="literal">asio.hpp</code>
</p>
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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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