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

int main(int argc, char **argv)
{
  time_t tick;
  struct timeval tv[2];
  int prev = 0;
  int fwd = 0;
  int back = 0;
  int max = 0;

  for (;;) {
    gettimeofday(tv, 0);
    if (prev) {
      if (tv[0].tv_sec < tv[1].tv_sec ||
	  (tv[0].tv_sec == tv[1].tv_sec && tv[0].tv_usec < tv[1].tv_usec)) {
	unsigned long long delta = ((tv[1].tv_sec - tv[0].tv_sec) * 1000000 +
				    (tv[1].tv_usec - tv[0].tv_usec));
	if (delta > max) {
	  max = delta;
	}
	++back;
      } else {
	if (tv[0].tv_sec - tv[1].tv_sec > 1) {
	  unsigned long long delta =
	      ((tv[0].tv_sec - tv[1].tv_sec) * 1000000 +
	       (tv[0].tv_usec - tv[1].tv_usec));

	  printf("got a huge step forward, delta=%lldus\n", delta);
	}
	++fwd;
      }
    }
    if (tick != tv[0].tv_sec && tv[0].tv_sec == tv[1].tv_sec + 1) {
      tick = tv[0].tv_sec;
      printf("%.24s: fwd:%d/%d:back max %07u\n",
	     ctime(&tv[0].tv_sec), fwd, back, max);
      fwd = back = 0;
      max = 0;
    }
    prev = 1;
    tv[1] = tv[0];
  }
}