/*
   Set of utilities for writing systems-experimentation programs
*/

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

/* you may need to recalibrate the following constant, used in busywait: */
#define SECONDTIME 25000000

void busywait(double sec) // cpu loops for sec seconds
{
  long i, limit;
  limit = (long)(sec*SECONDTIME);
  for (i=0;i<limit;i++) { }
}

void sleepwait(double sec)  // suspends thread for approximately sec seconds
{
  struct timeval tv;
  tv.tv_sec = (long) sec;
  tv.tv_usec = (long)((sec - (double)(tv.tv_sec))*1000000.0);
  select(0,NULL,NULL,NULL,&tv);
} // sleepwait


struct timer   /* real time timer */
{
   struct timeval start;
   struct timeval end;
};

void starttimer(struct timer * tm)
{
    gettimeofday(&(tm->start),NULL);
}

void stoptimer(struct timer * tm)
{
    gettimeofday(&(tm->end),NULL);
}

long elapsed(struct timer *tm)
{
    long e1, e2;  // ms times
    stoptimer(tm);
    e1 = (tm->start.tv_sec * 1000) + (tm->start.tv_usec / 1000);
    e2 = (tm->end.tv_sec * 1000) + (tm->end.tv_usec / 1000);
    starttimer(tm);
    return e2-e1;
}


void realwait(double sec)
{  int i = 4;
   struct timer tm;
   starttimer(&tm);
   while (elapsed(&tm) < (sec * 1000.0))
     { i++; i--; }
}


void clockwait(double sec)
{
   double elapsed;
   clock_t start, total;
  
   total = (clock_t)(sec*CLOCKS_PER_SEC);
   start = clock();
   while ((clock()-start) < total) {}
}