/* getitimerV.c
 *
 * Neal Nelson  2009.11.04
 *
 * Set and read the virtual timer.
 * It doesn't appear to work properly on my laptop.
 *
 */

#include <stdio.h>
#include <sys/time.h>

/* prototypes */
unsigned long fib(unsigned int n);

main()
{ struct itimerval itval;
  unsigned long thefib;

  /* Initialize the virtual itimer to ten seconds */

  itval.it_interval.tv_sec = 9;
  itval.it_interval.tv_usec = 999999;
  itval.it_value.tv_sec = 9;                /* why do I need to set value? */
  itval.it_value.tv_usec = 999999;          /* works only if I do */
  setitimer(ITIMER_VIRTUAL, &itval, NULL);


  /* read and display the virtual timer before sleep */

  if (getitimer(ITIMER_VIRTUAL, &itval) == 0 )
  {
    printf("Virtual Timer interval: %ld seconds, %ld microseconds\n",
            itval.it_interval.tv_sec, itval.it_interval.tv_usec);
    printf("   Virtual Timer value: %ld seconds, %ld microseconds\n",
            itval.it_value.tv_sec, itval.it_value.tv_usec);
  }
  
/*--------------------------------------------------------------------------*/
  printf("\nBusy computuing fib(40)\n");
  thefib = fib(40);
/*--------------------------------------------------------------------------*/
  

  /* read and display the virtual timer after busy loop */

  printf("thefib %ld\n", thefib);
  if (getitimer(ITIMER_VIRTUAL, &itval) == 0 )
  {
    printf("Virtual Timer interval: %ld seconds, %ld microseconds\n",
            itval.it_interval.tv_sec, itval.it_interval.tv_usec);
    printf("   Virtual Timer value: %ld seconds, %ld microseconds\n",
            itval.it_value.tv_sec, itval.it_value.tv_usec);
  }
  
}

unsigned long fib(unsigned int n)
{ if (n == 0) return 0;
  else if (n == 1 || n == 2) return 1;
  else return (fib(n-1) + fib(n-2));
}