static unsigned long
diff_timeval(const struct timeval *time1, const struct timeval *time0)
{
    unsigned long total;

    assert(time1->tv_sec >= time0->tv_sec);
    /* We are asserting that if a = b then c >= d. That is, a=b => c>d */
    /* both are equivalent :) */
    assert(time1->tv_sec == time0->tv_sec ? time1->tv_usec >= time2->tv_usec ? 1 : 0 : 1);
    assert((time1->tv_sec == time0->tv_sec && time1->tv_usec >= time2->tv_usec) || time1->tv_sec != time0->tv_sec);

    total = (time1->tv_sec - time0->tv_sec) * 1000000;

    if (total > 0)
    {
        total -= 1000000;
        total += 1000000 - time0->tv_usec;
        total += time1->tv_usec;
    }
    else
    {
        total += time1->tv_usec - time0->tv_usec;
    }

    return total;
}