Calculate diff of two struct timespec

timespec_diff.c

#include <time.h>

void timespec_diff(struct timespec *start, struct timespec *stop,
                   struct timespec *result)
{
    if ((stop->tv_nsec - start->tv_nsec) < 0) {
        result->tv_sec = stop->tv_sec - start->tv_sec - 1;
        result->tv_nsec = stop->tv_nsec - start->tv_nsec + 1000000000;
    } else {
        result->tv_sec = stop->tv_sec - start->tv_sec;
        result->tv_nsec = stop->tv_nsec - start->tv_nsec;
    }

    return;
}

更多可以参考：
http://blog.csdn.net/liu44235/article/details/37692635
http://www.cnblogs.com/chezxiaoqiang/archive/2012/03/23/2674386.html
http://www.cnblogs.com/spinsoft/p/3767549.html