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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> | |
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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>) | |
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