Intel® oneAPI DPC++/C++ Compiler Developer Guide and Reference

ID 767253
Date 9/08/2022
Public

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Example for aio_cancel Function

The following example illustrates how aio_cancel() function can be used.

int aio_ex_4(HANDLE fd)
{
  static struct aiocb   aio;
  static struct aiocb  *aio_list[] = {&aio};
  int    ret;
  char  *dat = "Hello from Ex-4\n";
 
 printf("AIO_CANCELED=%d AIO_NOTCANCELED=%d\n", 
 AIO_CANCELED,   AIO_NOTCANCELED);
     
/* Data initialization and asynchronously writing */
     
 IC_AIO_DATA_INIT(aio, fd, dat, strlen(dat), 0);
 if (aio_write(&aio) == -1) return errno;
     
 ret = aio_cancel(fd, &aio);
 if ( ret == AIO_NOTCANCELED ) {
 fprintf(stderr, "ERRNO=%d STR=%s\n", ret, strerror(ret));
 ret = aio_suspend(aio_list, 1, NULL);
 if (ret == -1) return errno;}
 
 ret = aio_cancel(fd, &aio);
 if ( ret == AIO_CANCELED )
 fprintf(stderr, "ERRNO=%d STR=%s\n", ret, strerror(ret));
 else if (ret) return ret;
 
 return 0;
}/* aio_ex_4 */

Result upon execution:

-bash-3.00$ ./a.out
AIO_CANCELED=0 AIO_NOTCANCELED=1
ERRNO=1 STR=Operation not permitted
-bash-3.00$ cat dat
Hello from Ex-4
-bash-3.00$

Remarks:

  1. In the example, the IC_AIO_DATA_INIT is defined as follows:

    #define IC_AIO_DATA_INIT(_aio, _fd, _dat, _len, _off)\
     {memset(&_aio, 0, sizeof(_aio)); \
     _aio.aio_fildes = _fd;          \
     _aio.aio_buf    = _dat;         \
     _aio.aio_nbytes = _len;         \
     _aio.aio_offset = _off;}

  2. The file descriptor fd is obtained as:

    HANDLE fd = CreateFile("dat",
      GENERIC_READ | GENERIC_WRITE,
      FILE_SHARE_READ,
      NULL,
      OPEN_ALWAYS,
      FILE_ATTRIBUTE_NORMAL/*|FILE_FLAG_OVERLAPPED*/,
      NULL);

See Also