93 lines
6.9 KiB
HTML
93 lines
6.9 KiB
HTML
<html>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<title>Channels</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../asio.png"></td></tr></table>
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<a accesskey="p" href="signals.html"><img src="../../prev.png" alt="Prev"></a><a accesskey="u" href="../overview.html"><img src="../../up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../home.png" alt="Home"></a><a accesskey="n" href="posix.html"><img src="../../next.png" alt="Next"></a>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="asio.overview.channels"></a><a class="link" href="channels.html" title="Channels">Channels</a>
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</h3></div></div></div>
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<div class="note"><table border="0" summary="Note">
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<tr>
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<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../note.png"></td>
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<th align="left">Note</th>
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</tr>
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<tr><td align="left" valign="top"><p>
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This is an experimental feature.
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</p></td></tr>
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</table></div>
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<p>
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The templates <a class="link" href="../reference/experimental__basic_channel.html" title="experimental::basic_channel">experimental::basic_channel</a>
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and <a class="link" href="../reference/experimental__basic_concurrent_channel.html" title="experimental::basic_concurrent_channel">experimental::basic_concurrent_channel</a>,
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with aliases <code class="computeroutput"><span class="identifier">experimental</span><span class="special">::</span><span class="identifier">channel</span></code>
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and <code class="computeroutput"><span class="identifier">experimental</span><span class="special">::</span><span class="identifier">concurrent_channel</span></code>, may be used to send
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messages between different parts of the same application. A <span class="emphasis"><em>message</em></span>
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is defined as a collection of arguments to be passed to a completion handler,
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and the set of messages supported by a channel is specified by its template
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parameters. Messages may be sent and received using asynchronous or non-blocking
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synchronous operations.
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</p>
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<p>
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For example:
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</p>
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<pre class="programlisting"><span class="comment">// Create a channel with no buffer space.</span>
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<span class="identifier">channel</span><span class="special"><</span><span class="keyword">void</span><span class="special">(</span><span class="identifier">error_code</span><span class="special">,</span> <span class="identifier">size_t</span><span class="special">)></span> <span class="identifier">ch</span><span class="special">(</span><span class="identifier">ctx</span><span class="special">);</span>
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<span class="comment">// The call to try_send fails as there is no buffer</span>
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<span class="comment">// space and no waiting receive operations.</span>
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<span class="keyword">bool</span> <span class="identifier">ok</span> <span class="special">=</span> <span class="identifier">ch</span><span class="special">.</span><span class="identifier">try_send</span><span class="special">(</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">eof</span><span class="special">,</span> <span class="number">123</span><span class="special">);</span>
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<span class="identifier">assert</span><span class="special">(!</span><span class="identifier">ok</span><span class="special">);</span>
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<span class="comment">// The async_send operation is outstanding until</span>
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<span class="comment">// a receive operation consumes the message.</span>
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<span class="identifier">ch</span><span class="special">.</span><span class="identifier">async_send</span><span class="special">(</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span class="special">::</span><span class="identifier">eof</span><span class="special">,</span> <span class="number">123</span><span class="special">,</span>
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<span class="special">[](</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="comment">// ...</span>
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<span class="special">});</span>
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<span class="comment">// The async_receive consumes the message. Both the</span>
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<span class="comment">// async_send and async_receive operations complete</span>
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<span class="comment">// immediately.</span>
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<span class="identifier">ch</span><span class="special">.</span><span class="identifier">async_receive</span><span class="special">(</span>
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<span class="special">[](</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">,</span> <span class="identifier">size_t</span> <span class="identifier">n</span><span class="special">)</span>
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<span class="special">{</span>
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<span class="comment">// ...</span>
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<span class="special">});</span>
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</pre>
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<h5>
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<a name="asio.overview.channels.h0"></a>
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<span><a name="asio.overview.channels.see_also"></a></span><a class="link" href="channels.html#asio.overview.channels.see_also">See
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Also</a>
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</h5>
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<p>
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<a class="link" href="../reference/experimental__basic_channel.html" title="experimental::basic_channel">experimental::basic_channel</a>,
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<a class="link" href="../reference/experimental__basic_concurrent_channel.html" title="experimental::basic_concurrent_channel">experimental::basic_concurrent_channel</a>,
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<a class="link" href="../examples/cpp20_examples.html#asio.examples.cpp20_examples.channels">Channels examples (C++20)</a>.
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</p>
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</div>
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<div class="copyright-footer">Copyright © 2003-2023 Christopher M. Kohlhoff<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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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</p>
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</div>
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<hr>
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