Asynchronous I/O Function Errors

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

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ID 767253

Date 3/22/2024

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Asynchronous I/O Function Errors

This topic only applies to Windows* OS.

The errno macro is used to obtain the errors that occur during asynchronous request functions such as aio_read(), aio_write(), aio_fsync(), and lio_listio() or asynchronous control functions, such as aio_cancel(), aio_error(), aio_return(), and aio_suspend().

The following example illustrates how errno can be used.

#include <stdio.h>
#include <stdlib.h>
#include <aio.h>
 
struct aiocb    my_aio;
struct aiocb   *my_aio_list[1] = {&my_aio};
 
int main()
{
  int   res;
  double  arr[123456];
 timespec_t   my_t = {1, 0};
     
/* Data initialization */
 my_aio.aio_fildes = CreateFile("dat",
   GENERIC_READ | GENERIC_WRITE,
   FILE_SHARE_READ,
   NULL,
   OPEN_ALWAYS,
   FILE_ATTRIBUTE_NORMAL,
   NULL);
 my_aio.aio_buf    = (volatile char *)arr;
 my_aio.aio_nbytes = sizeof(arr);
 
/* Do asynchronous writing with computation overlapping */
 aio_write(&my_aio);
 do_compute(arr, 123456);
 
/* Suspend the asynchronous writing for 1 sec */
 res = aio_suspend(my_aio_list, 1, &my_t);
 if ( res ) {
 
/* The call was ended by timeout, before the indicated operations had completed. */
  if ( errno == EAGAIN ) {
  res = aio_suspend(my_aio_list, 1, 0);
  if ( res ) {
  printf("aio_suspend returned non-0\n"); return errno;}
  }
  else
  if ( res ) {
  printf("aio_suspend returned neither 0 nor EAGAIN\n");
  return errno;
  }
 }
 
 CloseHandle(my_aio.aio_fildes);
 printf("\nPass\n");
 
 return 0;
}

In the example, the program executes an asynchronous write operation, using aio_write(), overlapping with some computation, the do_compute() function execution. The pending write operation is suspended for one second using aio_suspend().

On successful execution of the asynchronous write operation, zero is returned. EAGAIN or any other error value is returned when the call is ended by timeout before the indicated operation has completed.

You can check EAGAIN using the errno macro.

Parent topic: Intel's C++ Asynchronous I/O Library for Windows

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Asynchronous I/O Function Errors