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<title>PTypes: multithreading: message</title>
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<p><a href="../index.html"><img src="title-21.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.1" border="0"></a>
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<p class="hpath"><a href="index.html">Top</a>: <a href="async.html">Multithreading</a>:
message</p>
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<pre class="lang">#include <pasync.h>
struct message {
int id;
pintptr param;
pintptr result;
message(int id, pintptr param = 0);
}</pre>
</blockquote>
<p>A <span class="lang">message</span> object or an object of a derived class
can be used to post data to message queues (<a href="async.msgqueue.html">msgqueue</a>)
or job queues (<a href="async.jobqueue.html">jobqueue</a>). Messages are distinguished
by a ID that are defined in your application. The user message IDs can be in the
range <span class="lang">0</span> through <span class="lang">INT_MAX</span>. Negative
values are reserved for internal use by the library.</p>
<p>A simple message can also contain an additional parameter of type <span class="lang">pintptr</span>,
which is an integer with a size equal to the size of a pointer on the given platform.
For more complex message structures you can define classes derived from <span class="lang">message
</span> - the message queue manager can work with any descendant class as well.</p>
<p><span class="def">message::message(int id, pintptr param = 0)</span> constructs
a message object and assigns <span class="lang">id</span> and <span class="lang">param</span>
fields. <span class="lang">param</span> is an additional field that can be used
in your application at your own discretion.</p>
<p><span class="def">int message::id</span> -- this field contains a message ID
assigned through the constructor.</p>
<p><span class="def">pintptr message::param</span> contains the optional parameter.</p>
<p><span class="def">pintptr message::result</span> -- through this field a message
handler can return some simple answer to the sender of this message.</p>
<p class="seealso">See also: <a href="async.msgqueue.html">msgqueue</a>, <a href="async.jobqueue.html">jobqueue</a>,
<a href="async.examples.html">Examples</a></p>
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