clock_gettime.c

#include <mach/mach.h>
#include <mach/mach_time.h>
#include <sys/time.h>
#include <time.h>

static mach_timebase_info_data_t timebase_info;

int
clock_gettime_monotonic(struct timespec *tp) {
	uint64_t mticks = mach_absolute_time();

	if (timebase_info.denom == 0)
		mach_timebase_info(&timebase_info);

	uint64_t nsecs = mticks * timebase_info.numer / timebase_info.denom;
	tp->tv_sec = nsecs / 1000000000;
	tp->tv_nsec = nsecs % 1000000000;
	return 0;
}