/*
 *  NAME:
 *      usleep     -- This is the precision timer for Test Set
 *                    Automation. It uses the select(2) system
 *                    call to delay for the desired number of
 *                    micro-seconds. This call returns ZERO
 *                    (which is usually ignored) on successful
 *                    completion, -1 otherwise.
 *
 *  ALGORITHM:
 *      1) We range check the passed in microseconds and log a
 *         warning message if appropriate. We then return without
 *         delay, flagging an error.
 *      2) Load the Seconds and micro-seconds portion of the
 *         interval timer structure.
 *      3) Call select(2) with no file descriptors set, just the
 *         timer, this results in either delaying the proper
 *         ammount of time or being interupted early by a signal.
 *
 *  HISTORY:
 *      Added when the need for a subsecond timer was evident.
 *
 *  AUTHOR:
 *      Michael J. Dyer   <mike@sherlock.med.ge.com>
 */

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <time.h>
#include <sys/time.h>
#include <sys/param.h>
#include <sys/types.h>

int
usleep (unsigned long microSeconds)
{
  unsigned int     Seconds, uSec;
  int              nfds = 0;
  fd_set           readfds, writefds, exceptfds;
  struct  timeval  Timer;

  if( (microSeconds == (unsigned long) 0) ||
      microSeconds  >  (unsigned long) 4000000 )
    {
      errno = ERANGE;         /* value out of range */
      perror( "usleep time out of range ( 0 -> 4000000 ) " );
      return -1;
    }

  Seconds = microSeconds / (unsigned long) 1000000;
  uSec    = microSeconds % (unsigned long) 1000000;

  Timer.tv_sec  = Seconds;
  Timer.tv_usec = uSec;

  if( select( nfds, &readfds, &writefds, &exceptfds, &Timer ) < 0 )
    {
      perror( "usleep (select) failed" );
      return -1;
    }

  return 0;
}