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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"><span class="identifier">coroutine</span></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"><span class="keyword">struct</span> <span class="identifier">session</span> <span class="special">:</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">coroutine</span> |
| <span class="special">{</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_ptr</span><span class="special"><</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">></span> <span class="identifier">socket_</span><span class="special">;</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_ptr</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="special">></span> <span class="identifier">buffer_</span><span class="special">;</span> |
| |
| <span class="identifier">session</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_ptr</span><span class="special"><</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span class="special">></span> <span class="identifier">socket</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">socket_</span><span class="special">(</span><span class="identifier">socket</span><span class="special">),</span> |
| <span class="identifier">buffer_</span><span class="special">(</span><span class="keyword">new</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="number">1024</span><span class="special">))</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">void</span> <span class="keyword">operator</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="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">(),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">n</span> <span class="special">=</span> <span class="number">0</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="identifier">reenter</span> <span class="special">(</span><span class="keyword">this</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">for</span> <span class="special">(;;)</span> |
| <span class="special">{</span> |
| <span class="identifier">yield</span> <span class="identifier">socket_</span><span class="special">-></span><span class="identifier">async_read_some</span><span class="special">(</span><span class="identifier">boost</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">buffer_</span><span class="special">),</span> <span class="special">*</span><span class="keyword">this</span><span class="special">);</span> |
| <span class="identifier">yield</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">async_write</span><span class="special">(*</span><span class="identifier">socket_</span><span class="special">,</span> <span class="identifier">boost</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">buffer_</span><span class="special">,</span> <span class="identifier">n</span><span class="special">),</span> <span class="special">*</span><span class="keyword">this</span><span class="special">);</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| The <code class="computeroutput"><span class="identifier">coroutine</span></code> class is |
| used in conjunction with the pseudo-keywords <code class="computeroutput"><span class="identifier">reenter</span></code>, |
| <code class="computeroutput"><span class="identifier">yield</span></code> and <code class="computeroutput"><span class="identifier">fork</span></code>. These are preprocessor macros, |
| and are implemented in terms of a <code class="computeroutput"><span class="keyword">switch</span></code> |
| statement using a technique similar to Duff's Device. The <a class="link" href="../../reference/coroutine.html" title="coroutine"><code class="computeroutput"><span class="identifier">coroutine</span></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> |
| </div> |
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| <td align="left"></td> |
| <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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