c-iosys6.html

this about vxworks operations systems

 
<b><a name="84283">#define BUFFER_SIZE 200</a></b><dd>
 
<b><a name="84285">/************************************************************************ 
* aioExample - use AIO library 
* 
* This example shows the basic functions of the AIO library. 
* 
* RETURNS: OK if successful, otherwise ERROR. 
*/</a></b><dd>
 
<b><a name="84287">STATUS aioExample (void) 
  { 
  int       fd; 
  static char   exFile [] = "/pipe/1stPipe"; 
  struct aiocb  aiocb_read; /* read aiocb */ 
  struct aiocb  aiocb_write; /* write aiocb */ 
  static char *  test_string = "testing 1 2 3"; 
  char      buffer [BUFFER_SIZE]; /* buffer for read aiocb */</a></b><dd>
 
<b><a name="84289">pipeDevCreate (exFile, 50, 100);</a></b><dd>
 
<b><a name="84291">if ((fd = open (exFile, O_CREAT | O_TRUNC | O_RDWR, 0666)) == 
    ERROR) 
  { 
  printf ("aioExample: cannot open %s errno 0x%x\n", exFile, errno); 
  return (ERROR); 
  }</a></b><dd>
 
<b><a name="84293">printf ("aioExample: Example file = %s\tFile descriptor = %d\n", 
      exFile, fd); </a></b><dd>
 
<b><a name="84295">/* initialize read and write aiocbs */ 
  bzero ((char *) &amp;aiocb_read, sizeof (struct aiocb)); 
  bzero ((char *) buffer, sizeof (buffer)); 
  aiocb_read.aio_fildes = fd; 
  aiocb_read.aio_buf = buffer; 
  aiocb_read.aio_nbytes = BUFFER_SIZE; 
  aiocb_read.aio_reqprio = 0;</a></b><dd>
 
<b><a name="84297">bzero ((char *) &amp;aiocb_write, sizeof (struct aiocb)); 
  aiocb_write.aio_fildes = fd; 
  aiocb_write.aio_buf = test_string; 
  aiocb_write.aio_nbytes = strlen (test_string); 
  aiocb_write.aio_reqprio = 0;</a></b><dd>
 
<b><a name="84299">/* initiate the read */ 
  if (aio_read (&amp;aiocb_read) == -1) 
    printf ("aioExample: aio_read failed\n");</a></b><dd>
 
<b><a name="84301">/* verify that it is in progress */ 
  if (aio_error (&amp;aiocb_read) == EINPROGRESS) 
    printf ("aioExample: read is still in progress\n");</a></b><dd>
 
<b><a name="84303">/* write to pipe - the read should be able to complete */ 
  printf ("aioExample: getting ready to initiate the write\n"); 
  if (aio_write (&amp;aiocb_write) == -1) 
    printf ("aioExample: aio_write failed\n"); </a></b><dd>
 
<b><a name="84305">/* wait til both read and write are complete */ 
  while ((aio_error (&amp;aiocb_read) == EINPROGRESS) ||  
      (aio_error (&amp;aiocb_write) == EINPROGRESS)) 
    taskDelay (1);</a></b><dd>
 
<b><a name="84307">/* print out what was read */ 
  printf ("aioExample: message = %s\n", buffer);</a></b><dd>
 
<b><a name="84309">/* clean up */ 
  if (aio_return (&amp;aiocb_read) == -1) 
    printf ("aioExample: aio_return for aiocb_read failed\n"); 
  if (aio_return (&amp;aiocb_write) == -1) 
    printf ("aioExample: aio_return for aiocb_write failed\n");</a></b><dd>
 
<b><a name="84311">close (fd); 
  return (OK); 
  }</a></b></pre>
</dl>

</dl>

<font face="Helvetica, sans-serif" class="sans">
<h4 class="H4"><i><a name="84312">Alternatives for Testing AIO Completion</a></i></h4>
</font>
<dl class="margin">

<dl class="margin">

<dd><p class="Body"><a name="84314"> </a>A task can determine whether an AIO request is complete in any of the following ways: </p>
</dl>

<dl class="margin">

<p class="listspace">
<ul class="Bullet" type="disc"><li><a name="84315"> </a>Check the result of <b class="routine"><i class="routine">aio_error</i></b><b>(&nbsp;)</b> periodically, as in the previous example, until the status of an AIO request is no longer <b class="symbol_UC">EINPROGRESS</b>.</li></ul>
</p>
<p class="listspace">
<ul class="Bullet" type="disc"><li><a name="84317"> </a>Use <b class="routine"><i class="routine">aio_suspend</i></b><b>(&nbsp;)</b> to suspend the task until the AIO request is complete.</li></ul>
</p>
<p class="listspace">
<ul class="Bullet" type="disc"><li><a name="84318"> </a>Use signals to be informed when the AIO request is complete. </li></ul>
</p>
</dl>

<dl class="margin">

<dd><p class="Body"><a name="84319"> </a>The following example is similar to the preceding <b class="routine"><i class="routine">aioExample</i></b><b>(&nbsp;)</b>, except that it uses signals to be notified when the write is complete. If you test this from the shell, spawn the routine to run at a lower priority than the AIO system tasks to assure that the test routine does not block completion of the AIO request. (For details on the shell, see the <i class="title">Tornado User's Guide: Shell</i>.)</p>
</dl>

</dl>

<h4 class="EntityTitle"><a name="84320"><font face="Helvetica, sans-serif" size="-1" class="sans">Example 3-3:&nbsp;&nbsp;Asynchronous I/O with Signals</font></a></h4>
<dl class="margin">

<dl class="margin">

<dd><pre class="Code"><b><a name="84321">/* aioExSig.c - example code for using signals with asynchronous I/O */</a></b><dd>
 
<b><a name="84323">/* includes */</a></b><dd>
 
<b><a name="84324">#include "vxWorks.h" 
#include "aio.h" 
#include "errno.h"</a></b><dd>
 
<b><a name="84326">/* defines */</a></b><dd>
 
<b><a name="84327">#define BUFFER_SIZE   200 
#define LIST_SIZE    1 
#define EXAMPLE_SIG_NO  25 /* signal number */</a></b><dd>
 
<b><a name="84329">/* forward declarations */</a></b><dd>
 
<b><a name="84330">void mySigHandler (int sig, struct siginfo * info, void * pContext);</a></b><dd>
 
<b><a name="84332">/************************************************************************ 
* aioExampleSig - use AIO library. 
* 
* This example shows the basic functions of the AIO library. 
* Note if this is run from the shell it must be spawned. Use: 
*  -&gt; sp aioExampleSig 
* 
* RETURNS: OK if successful, otherwise ERROR. 
*/</a></b><dd>
 
<b><a name="84334">STATUS aioExampleSig (void) 
  { 
  int           fd; 
  static char       exFile [] = "/pipe/1stPipe"; 
  struct aiocb      aiocb_read;      /* read aiocb */ 
  static struct aiocb   aiocb_write;      /* write aiocb */ 
  struct sigaction    action;        /* signal info */ 
  static char *      test_string = "testing 1 2 3"; 
  char          buffer [BUFFER_SIZE]; /* aiocb read buffer */</a></b><dd>
 
<b><a name="84336">pipeDevCreate (exFile, 50, 100);</a></b><dd>
 
<b><a name="84338">if ((fd = open (exFile, O_CREAT | O_TRUNC| O_RDWR, 0666)) == ERROR) 
    { 
    printf ("aioExample: cannot open %s errno 0x%x\n", exFile, errno); 
    return (ERROR); 
    }</a></b><dd>
 
<b><a name="93621">printf ("aioExampleSig: Example file = %s\tFile descriptor = %d\n",  
      exFile, fd); </a></b><dd>
 
<b><a name="84344">/* set up signal handler for EXAMPLE_SIG_NO */ 
 
  action.sa_sigaction = mySigHandler; 
  action.sa_flags = SA_SIGINFO; 
  sigemptyset (&amp;action.sa_mask); 
  sigaction (EXAMPLE_SIG_NO, &amp;action, NULL);</a></b><dd>
 
<b><a name="84346">/* initialize read and write aiocbs */ 
 
  bzero ((char *) &amp;aiocb_read, sizeof (struct aiocb)); 
  bzero ((char *) buffer, sizeof (buffer)); 
  aiocb_read.aio_fildes = fd; 
  aiocb_read.aio_buf = buffer; 
  aiocb_read.aio_nbytes = BUFFER_SIZE; 
  aiocb_read.aio_reqprio = 0;</a></b><dd>
 
<b><a name="84348">bzero ((char *) &amp;aiocb_write, sizeof (struct aiocb)); 
  aiocb_write.aio_fildes = fd; 
  aiocb_write.aio_buf = test_string; 
  aiocb_write.aio_nbytes = strlen (test_string); 
  aiocb_write.aio_reqprio = 0;</a></b><dd>
 
<b><a name="84350">/* set up signal info */ 
 
  aiocb_write.aio_sigevent.sigev_signo = EXAMPLE_SIG_NO; 
  aiocb_write.aio_sigevent.sigev_notify = SIGEV_SIGNAL; 
  aiocb_write.aio_sigevent.sigev_value.sival_ptr =  
                        (void *) &amp;aiocb_write;</a></b><dd>
 
<b><a name="84352">/* initiate the read */ 
 
  if (aio_read (&amp;aiocb_read) == -1) 
    printf ("aioExampleSig: aio_read failed\n");</a></b><dd>
 
<b><a name="84354">/* verify that it is in progress */ 
 
  if (aio_error (&amp;aiocb_read) == EINPROGRESS) 
    printf ("aioExampleSig: read is still in progress\n");</a></b><dd>
 
<b><a name="84356">/* write to pipe - the read should be able to complete */ 
 
  printf ("aioExampleSig: getting ready to initiate the write\n"); 
  if (aio_write (&amp;aiocb_write) == -1) 
    printf ("aioExampleSig: aio_write failed\n");</a></b><dd>
 
<b><a name="84358">/* clean up */ 
 
  if (aio_return (&amp;aiocb_read) == -1) 
    printf ("aioExampleSig: aio_return for aiocb_read failed\n"); 
  else 
    printf ("aioExampleSig: aio read message = %s\n", 
         aiocb_read.aio_buf);</a></b><dd>
 
<b><a name="84360">close (fd); 
  return (OK); 
  }</a></b><dd>
 
<b><a name="84362">void mySigHandler  
  ( 
  int        sig, 
  struct siginfo * info, 
  void *      pContext 
  )</a></b><dd>
 
<b><a name="84363">  { 
  /* print out what was read */ 
 
  printf ("mySigHandler: Got signal for aio write\n");</a></b><dd>
 
<b><a name="95759">  /* write is complete so let's do cleanup for it here */ 
 
  if (aio_return (info-&gt;si_value.sival_ptr) == -1) 
    { 
    printf ("mySigHandler: aio_return for aiocb_write failed\n"); 
    printErrno (0); 
    } 
  }</a></b></pre>
</dl>

</dl>


<a name="foot"><hr></a>


<p class="navbar" align="right"><a href="index.html"><img border="0" alt="[Contents]" src="icons/contents.gif"></a><a href="GuideIX.html"><img border="0" alt="[Index]" src="icons/index.gif"></a><a href="c-iosys.html"><img border="0" alt="[Top]" src="icons/top.gif"></a><a href="c-iosys5.html"><img border="0" alt="[Prev]" src="icons/prev.gif"></a><a href="c-iosys7.html"><img border="0" alt="[Next]" src="icons/next.gif"></a></p>

</body>

</html>
<!---
by WRS Documentation (), Wind River Systems, Inc.
    conversion tool:  Quadralay WebWorks Publisher 4.0.11
    template:         CSS Template, Jan 1998 - Jefro --->