timing ?

[Ken Dunn <luser@xtra.co.nz>]

Can anyone see anything wrong with doing this for a simple
delay between up dates, outside of non-portability ? 


/* for a least 1/20 pause */
#define USEC_DELAY 50000 

void tick(void)
{
struct timeval nt;
static int64_t old;
static int64_t new;
long long t_delta;
for(;;) {
        gettimeofday(&nt, NULL);
        new=(int64_t) nt.tv_usec + (int64_t)\
                (1000000 * (int64_t) nt.tv_sec);
        t_delta = new - old;
        if(t_delta > (int64_t) USEC_DELAY)
                { old = new;
                  return;
                }
        /* has system time gone backwards ?*/
        if(t_delta < 0)
                { old = new;
                  continue;
                }
        usleep(1); /* works very nicely on my machine. Where HZ = 1024 */
        }
}