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<div class="titlepage"><div><div><h3 class="title">
<a name="fiber.integration.embedded_main_loop"></a><a name="embedded_main_loop"></a><a class="link" href="embedded_main_loop.html" title="Embedded Main Loop">Embedded
      Main Loop</a>
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<p>
        More challenging is when the application&#8217;s main loop is embedded in some other
        library or framework. Such an application will typically, after performing
        all necessary setup, pass control to some form of <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code> function from which control does not return
        until application shutdown.
      </p>
<p>
        A <a href="http://www.boost.org/doc/libs/release/libs/asio/index.html" target="_top">Boost.Asio</a>
        program might call <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/io_service/run.html" target="_top"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">run</span><span class="special">()</span></code></a>
        in this way.
      </p>
<p>
        In general, the trick is to arrange to pass control to <a class="link" href="../fiber_mgmt/this_fiber.html#this_fiber_yield"><code class="computeroutput">this_fiber::yield()</code></a> frequently.
        You could use an <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/high_resolution_timer.html" target="_top">Asio
        timer</a> for that purpose. You could instantiate the timer, arranging
        to call a handler function when the timer expires. The handler function could
        call <code class="computeroutput"><span class="identifier">yield</span><span class="special">()</span></code>,
        then reset the timer and arrange to wake up again on its next expiration.
      </p>
<p>
        Since, in this thought experiment, we always pass control to the fiber manager
        via <code class="computeroutput"><span class="identifier">yield</span><span class="special">()</span></code>,
        the calling fiber is never blocked. Therefore there is always at least one
        ready fiber. Therefore the fiber manager never calls <a class="link" href="../scheduling.html#algorithm_suspend_until"><code class="computeroutput">algorithm::suspend_until()</code></a>.
      </p>
<p>
        Using <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/io_service/post.html" target="_top"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">post</span><span class="special">()</span></code></a>
        instead of setting a timer for some nonzero interval would be unfriendly
        to other threads. When all I/O is pending and all fibers are blocked, the
        io_service and the fiber manager would simply spin the CPU, passing control
        back and forth to each other. Using a timer allows tuning the responsiveness
        of this thread relative to others.
      </p>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2013 Oliver Kowalke<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>)
      </p>
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	6	<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
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	24	</div>
	25	<div class="section">
	26	<div class="titlepage"><div><div><h3 class="title">
	27	<a name="fiber.integration.embedded_main_loop"></a><a name="embedded_main_loop"></a><a class="link" href="embedded_main_loop.html" title="Embedded Main Loop">Embedded
	28	Main Loop</a>
	29	</h3></div></div></div>
	30	<p>
	31	More challenging is when the application’s main loop is embedded in some other
	32	library or framework. Such an application will typically, after performing
	33	all necessary setup, pass control to some form of <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code> function from which control does not return
	34	until application shutdown.
	35	</p>
	36	<p>
	37	A <a href="http://www.boost.org/doc/libs/release/libs/asio/index.html" target="_top">Boost.Asio</a>
	38	program might call <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/io_service/run.html" target="_top"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">run</span><span class="special">()</span></code></a>
	39	in this way.
	40	</p>
	41	<p>
	42	In general, the trick is to arrange to pass control to <a class="link" href="../fiber_mgmt/this_fiber.html#this_fiber_yield"><code class="computeroutput">this_fiber::yield()</code></a> frequently.
	43	You could use an <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/high_resolution_timer.html" target="_top">Asio
	44	timer</a> for that purpose. You could instantiate the timer, arranging
	45	to call a handler function when the timer expires. The handler function could
	46	call <code class="computeroutput"><span class="identifier">yield</span><span class="special">()</span></code>,
	47	then reset the timer and arrange to wake up again on its next expiration.
	48	</p>
	49	<p>
	50	Since, in this thought experiment, we always pass control to the fiber manager
	51	via <code class="computeroutput"><span class="identifier">yield</span><span class="special">()</span></code>,
	52	the calling fiber is never blocked. Therefore there is always at least one
	53	ready fiber. Therefore the fiber manager never calls <a class="link" href="../scheduling.html#algorithm_suspend_until"><code class="computeroutput">algorithm::suspend_until()</code></a>.
	54	</p>
	55	<p>
	56	Using <a href="http://www.boost.org/doc/libs/release/doc/html/boost_asio/reference/io_service/post.html" target="_top"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">post</span><span class="special">()</span></code></a>
	57	instead of setting a timer for some nonzero interval would be unfriendly
	58	to other threads. When all I/O is pending and all fibers are blocked, the
	59	io_service and the fiber manager would simply spin the CPU, passing control
	60	back and forth to each other. Using a timer allows tuning the responsiveness
	61	of this thread relative to others.
	62	</p>
	63	</div>
	64	<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
65	<td align="left"></td>
66	<td align="right"><div class="copyright-footer">Copyright © 2013 Oliver Kowalke<p>
67	Distributed under the Boost Software License, Version 1.0. (See accompanying
68	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>)
69	</p>
70	</div></td>
71	</tr></table>
72	<hr>
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74	<a accesskey="p" href="event_driven_program.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../integration.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="deeper_dive_into___boost_asio__.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
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