src/time.c

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#include <pelib/time.h>

#ifdef __cplusplus
extern "C" {
#endif

const long long int pelib_nsec_in_sec = 1000000000;

int
pelib_timespec_subtract(struct timespec *result, struct timespec *x, struct timespec *y)
{
        /* Perform the carry for the later subtraction by updating y. */
        if (x->tv_nsec < y->tv_nsec)
        {
                int nsec = (y->tv_nsec - x->tv_nsec) / pelib_nsec_in_sec + 1;
                y->tv_nsec -= pelib_nsec_in_sec * nsec;
                y->tv_sec += nsec;
        }
        if (x->tv_nsec - y->tv_nsec > pelib_nsec_in_sec)
        {
                int nsec = (x->tv_nsec - y->tv_nsec) / pelib_nsec_in_sec;
                y->tv_nsec += pelib_nsec_in_sec * nsec;
                y->tv_sec -= nsec;
        }
     
        /* Compute the time remaining to wait. tv_nsec is certainly positive. */
        result->tv_sec = x->tv_sec - y->tv_sec;
        result->tv_nsec = x->tv_nsec - y->tv_nsec;
     
        /* Return 1 if result is negative. */
        return x->tv_sec < y->tv_sec;
}

#ifdef __cplusplus
}
#endif