谷歌时间给
this first result.从那个页面:
通常需要减去struct timeval或struct timespec的两个值.这是最好的方法.即使在某些特殊的操作系统中,tv_sec成员具有无符号类型,它也可以工作.
/* 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 (result,x,y)
struct timeval *result,*x,*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 = (x->tv_usec - y->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;
}