nflog_utils.c

#include <sys/time.h>

/* Subtract the `struct timeval' values X and Y,
   storing the result in RESULT.
   Return 1 if the difference is negative, otherwise 0.  */

int timeval_subtract (struct timeval *result, struct timeval *x, struct timeval *y)
{
        /* Perform the carry for the later subtraction by updating y. */
        if (x->tv_usec < y->tv_usec) {
                int nsec = (y->tv_usec - x->tv_usec) / 1000000 + 1;
                y->tv_usec -= 1000000 * nsec;
                y->tv_sec += nsec;
        }
        if (x->tv_usec - y->tv_usec > 1000000) {
                int nsec = (y->tv_usec - x->tv_usec) / 1000000;
                y->tv_usec += 1000000 * nsec;
                y->tv_sec -= nsec;
        }

        /* Compute the time remaining to wait.
           tv_usec  is certainly positive. */
        result->tv_sec = x->tv_sec - y->tv_sec;
        result->tv_usec = x->tv_usec - y->tv_usec;

        /* Return 1 if result is negative. */
        return x->tv_sec < y->tv_sec;
}