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<h1>pipe.c</h1><div class="fragment"><pre class="fragment"><span class="preprocessor">#include <sys/types.h></span>
<span class="preprocessor">#include <fcntl.h></span>
<span class="preprocessor">#include <string.h></span>
<span class="preprocessor">#include <stdio.h></span>
<span class="preprocessor">#include <<a class="code" href="native_2pipe_8h.html" title="This file is part of the Xenomai project.">native/pipe.h</a>></span>
<span class="preprocessor">#define PIPE_MINOR 0</span>
<span class="preprocessor"></span>
<span class="comment">/* User-space side */</span>
<span class="keywordtype">int</span> pipe_fd;
<span class="keywordtype">int</span> main(<span class="keywordtype">int</span> argc, <span class="keywordtype">char</span> *argv[])
{
<span class="keywordtype">char</span> devname[32], buf[16];
<span class="comment">/* ... */</span>
sprintf(devname, <span class="stringliteral">"/dev/rtp%d"</span>, PIPE_MINOR);
pipe_fd = open(devname, O_RDWR);
<span class="keywordflow">if</span> (pipe_fd < 0)
fail();
<span class="comment">/* Wait for the prompt string "Hello"... */</span>
read(pipe_fd, buf, <span class="keyword">sizeof</span>(buf));
<span class="comment">/* Then send the reply string "World": */</span>
write(pipe_fd, <span class="stringliteral">"World"</span>, <span class="keyword">sizeof</span>(<span class="stringliteral">"World"</span>));
<span class="comment">/* ... */</span>
}
<span class="keywordtype">void</span> cleanup(<span class="keywordtype">void</span>)
{
<a name="a0"></a><a class="code" href="group__posix__shm.html#gafbcde67669a1b96577e735ddebd8634" title="Close a file descriptor.">close</a>(pipe_fd);
}
<span class="comment">/* Kernel-side */</span>
<span class="preprocessor">#define TASK_PRIO 0 </span><span class="comment">/* Highest RT priority */</span>
<span class="preprocessor">#define TASK_MODE T_FPU|T_CPU(0) </span><span class="comment">/* Uses FPU, bound to CPU #0 */</span>
<span class="preprocessor">#define TASK_STKSZ 4096 </span><span class="comment">/* Stack size (in bytes) */</span>
RT_TASK task_desc;
RT_PIPE pipe_desc;
<span class="keywordtype">void</span> task_body(<span class="keywordtype">void</span>)
{
RT_PIPE_MSG *msgout, *msgin;
<span class="keywordtype">int</span> err, len, n;
<span class="keywordflow">for</span> (;;) {
<span class="comment">/* ... */</span>
len = <span class="keyword">sizeof</span>(<span class="stringliteral">"Hello"</span>);
<span class="comment">/* Get a message block of the right size in order to</span>
<span class="comment"> initiate the message-oriented dialog with the</span>
<span class="comment"> user-space process. Sending a continuous stream of</span>
<span class="comment"> bytes is also possible using rt_pipe_stream(), in</span>
<span class="comment"> which case no message buffer needs to be</span>
<span class="comment"> preallocated. */</span>
msgout = <a name="a1"></a><a class="code" href="group__pipe.html#g40f294bf6254d2e1b66b8b6b400fc2e5" title="Allocate a message pipe buffer.">rt_pipe_alloc</a>(len);
<span class="keywordflow">if</span> (!msgout)
fail();
<span class="comment">/* Send prompt message "Hello" (the output buffer will be freed</span>
<span class="comment"> automatically)... */</span>
strcpy(RT_PIPE_MSGPTR(msgout), <span class="stringliteral">"Hello"</span>);
<a name="a2"></a><a class="code" href="group__pipe.html#gf40b20cad1dcd7bedcda72beaa16c057" title="Send a message through a pipe.">rt_pipe_send</a>(&pipe_desc, msgout, len, P_NORMAL);
<span class="comment">/* Then wait for the reply string "World": */</span>
n = <a name="a3"></a><a class="code" href="group__pipe.html#g731e5ef18007dcd58a9346bea66abbc6" title="Receive a message from a pipe.">rt_pipe_receive</a>(&pipe_desc, &msgin, TM_INFINITE);
<span class="keywordflow">if</span> (n < 0) {
printf(<span class="stringliteral">"receive error> errno=%d\n"</span>, n);
<span class="keywordflow">continue</span>;
}
<span class="keywordflow">if</span> (n == 0) {
<span class="keywordflow">if</span> (msg == NULL) {
printf(<span class="stringliteral">"pipe closed by peer while reading\n"</span>);
<span class="keywordflow">continue</span>;
}
printf(<span class="stringliteral">"empty message received\n"</span>);
} <span class="keywordflow">else</span>
printf(<span class="stringliteral">"received msg> %s, size=%d\n"</span>, P_MSGPTR(msg),
P_MSGSIZE(msg));
<span class="comment">/* Free the received message buffer. */</span>
<a name="a4"></a><a class="code" href="group__pipe.html#g8face1c57df99cf43b029b3e3b6a05c6" title="Free a message pipe buffer.">rt_pipe_free</a>(&pipe_desc, msgin);
<span class="comment">/* ... */</span>
}
}
init init_module(<span class="keywordtype">void</span>)
{
<span class="keywordtype">int</span> err;
err = <a name="a5"></a><a class="code" href="group__pipe.html#g29521cc898afa0069963964955167aa5" title="Create a message pipe.">rt_pipe_create</a>(&pipe_desc, NULL, PIPE_MINOR);
<span class="keywordflow">if</span> (err)
fail();
<span class="comment">/* ... */</span>
err = <a name="a6"></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="a7"></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="keywordtype">void</span> cleanup_module(<span class="keywordtype">void</span>)
{
<a name="a8"></a><a class="code" href="group__pipe.html#g1d84976a1b9b668366261ca9b836b677" title="Delete a message pipe.">rt_pipe_delete</a>(&pipe_desc);
<a name="a9"></a><a class="code" href="group__task.html#gb6e0d411830710e8cc82d77b9df19510" title="Delete a real-time task.">rt_task_delete</a>(&task_desc);
}
</pre></div> </div>
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