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<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.overview.core.coroutine"></a><a class="link" href="coroutine.html" title="Stackless Coroutines">Stackless Coroutines</a>
</h4></div></div></div>
<p>
The <a class="link" href="../../reference/coroutine.html" title="coroutine"><code class="computeroutput">coroutine</code></a>
class provides support for stackless coroutines. Stackless coroutines enable
programs to implement asynchronous logic in a synchronous manner, with
minimal overhead, as shown in the following example:
</p>
<pre class="programlisting">struct session : boost::asio::coroutine
{
boost::shared_ptr<tcp::socket> socket_;
boost::shared_ptr<std::vector<char> > buffer_;
session(boost::shared_ptr<tcp::socket> socket)
: socket_(socket),
buffer_(new std::vector<char>(1024))
{
}
void operator()(boost::system::error_code ec = boost::system::error_code(), std::size_t n = 0)
{
if (!ec) reenter (this)
{
for (;;)
{
yield socket_->async_read_some(boost::asio::buffer(*buffer_), *this);
yield boost::asio::async_write(*socket_, boost::asio::buffer(*buffer_, n), *this);
}
}
}
};
</pre>
<p>
The <code class="computeroutput">coroutine</code> class is used in conjunction with the pseudo-keywords
<code class="computeroutput">reenter</code>, <code class="computeroutput">yield</code> and <code class="computeroutput">fork</code>. These are
preprocessor macros, and are implemented in terms of a <code class="computeroutput">switch</code>
statement using a technique similar to Duff's Device. The <a class="link" href="../../reference/coroutine.html" title="coroutine"><code class="computeroutput">coroutine</code></a>
class's documentation provides a complete description of these pseudo-keywords.
</p>
<h6>
<a name="boost_asio.overview.core.coroutine.h0"></a>
<span class="phrase"><a name="boost_asio.overview.core.coroutine.see_also"></a></span><a class="link" href="coroutine.html#boost_asio.overview.core.coroutine.see_also">See
Also</a>
</h6>
<p>
<a class="link" href="../../reference/coroutine.html" title="coroutine">coroutine</a>, <a class="link" href="../../examples/cpp03_examples.html#boost_asio.examples.cpp03_examples.http_server_4">HTTP Server
4 example</a>, <a class="link" href="spawn.html" title="Stackful Coroutines">Stackful
Coroutines</a>.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2018 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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