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<title>Xenomai API: msg_queue.c</title>
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<h1>msg_queue.c</h1><div class="fragment"><pre class="fragment"><span class="preprocessor">#include <sys/mman.h></span>
<span class="preprocessor">#include <stdio.h></span>
<span class="preprocessor">#include <string.h></span>
<span class="preprocessor">#include <<a class="code" href="task_8h.html" title="This file is part of the Xenomai project.">native/task.h</a>></span>
<span class="preprocessor">#include <<a class="code" href="native_2queue_8h.html" title="This file is part of the Xenomai project.">native/queue.h</a>></span>
<span class="preprocessor">#define TASK_PRIO 99 </span><span class="comment">/* Highest RT priority */</span>
<span class="preprocessor">#define TASK_MODE 0 </span><span class="comment">/* No flags */</span>
<span class="preprocessor">#define TASK_STKSZ 0 </span><span class="comment">/* Stack size (use default one) */</span>
RT_QUEUE q_desc;
RT_TASK task_desc;
<span class="keywordtype">void</span> consumer (<span class="keywordtype">void</span> *cookie)
{
ssize_t len;
<span class="keywordtype">void</span> *msg;
<span class="keywordtype">int</span> err;
<span class="comment">/* Bind to a queue which has been created elsewhere, either in</span>
<span class="comment"> kernel or user-space. The call will block us until such queue</span>
<span class="comment"> is created with the expected name. The queue should have been</span>
<span class="comment"> created with the Q_SHARED mode set, which is implicit when</span>
<span class="comment"> creation takes place in user-space. */</span>
err = <a name="a0"></a><a class="code" href="group__native__queue.html#g162bb372c5c3616666e8e1fbdcc79343" title="Bind to a shared message queue.">rt_queue_bind</a>(&q_desc,<span class="stringliteral">"SomeQueueName"</span>,TM_INFINITE);
<span class="keywordflow">if</span> (err)
fail();
<span class="comment">/* Collect each message sent to the queue by the queuer() routine,</span>
<span class="comment"> until the queue is eventually removed from the system by a call</span>
<span class="comment"> to rt_queue_delete(). */</span>
<span class="keywordflow">while</span> ((len = <a name="a1"></a><a class="code" href="group__native__queue.html#g44759168a589ddbb2b60c1c1b183f448" title="Receive a message from a queue.">rt_queue_receive</a>(&q_desc,&msg,TM_INFINITE)) > 0)
{
printf(<span class="stringliteral">"received message> len=%d bytes, ptr=%p, s=%s\n"</span>,
len,msg,(<span class="keyword">const</span> <span class="keywordtype">char</span> *)msg);
<a name="a2"></a><a class="code" href="group__native__queue.html#g40d16a5ab14ea033889bb839967204e4" title="Free a message queue buffer.">rt_queue_free</a>(&q_desc,msg);
}
<span class="comment">/* We need to unbind explicitly from the queue in order to</span>
<span class="comment"> properly release the underlying memory mapping. Exiting the</span>
<span class="comment"> process unbinds all mappings automatically. */</span>
<a name="a3"></a><a class="code" href="group__native__queue.html#g1f190858ca18d906db339e086bfa8ced" title="Unbind from a shared message queue.">rt_queue_unbind</a>(&q_desc);
<span class="keywordflow">if</span> (len != -EIDRM)
<span class="comment">/* We received some unexpected error notification. */</span>
fail();
<span class="comment">/* ... */</span>
}
<span class="keywordtype">int</span> main (<span class="keywordtype">int</span> argc, <span class="keywordtype">char</span> *argv[])
{
<span class="keyword">static</span> <span class="keywordtype">char</span> *messages[] = { <span class="stringliteral">"hello"</span>, <span class="stringliteral">"world"</span>, NULL };
<span class="keywordtype">int</span> n, len;
<span class="keywordtype">void</span> *msg;
mlockall(MCL_CURRENT|MCL_FUTURE);
err = <a name="a4"></a><a class="code" href="group__task.html#g03387550693c21d0223f739570ccd992" title="Create a new real-time task.">rt_task_create</a>(&task_desc,
<span class="stringliteral">"MyTaskName"</span>,
TASK_STKSZ,
TASK_PRIO,
TASK_MODE);
<span class="keywordflow">if</span> (!err)
<a name="a5"></a><a class="code" href="group__task.html#gc9638918b8310a430088f5c9a04d2bb7" title="Start a real-time task.">rt_task_start</a>(&task_desc,&task_body,NULL);
<span class="comment">/* ... */</span>
<span class="keywordflow">for</span> (n = 0; messages[n] != NULL; n++)
{
len = strlen(messages[n]) + 1;
<span class="comment">/* Get a message block of the right size. */</span>
msg = <a name="a6"></a><a class="code" href="group__native__queue.html#g8eaee8ca7d0c3af801c4df6f0adae421" title="Allocate a message queue buffer.">rt_queue_alloc</a>(&q_desc,len);
<span class="keywordflow">if</span> (!msg)
<span class="comment">/* No memory available. */</span>
fail();
strcpy(msg,messages[n]);
<a name="a7"></a><a class="code" href="group__native__queue.html#g8b1dcb15753bdfce02f25f166e18948d" title="Send a message to a queue.">rt_queue_send</a>(&q_desc,msg,len,Q_NORMAL);
}
<a name="a8"></a><a class="code" href="group__task.html#gb6e0d411830710e8cc82d77b9df19510" title="Delete a real-time task.">rt_task_delete</a>(&task_desc);
}
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