clock_gettime reimplementation on OS X

gistfile1.cpp

// posix_public.h
#ifdef __APPLE__
enum clk_id_t { CLOCK_REALTIME, CLOCK_MONOTONIC, CLOCK_MONOTONIC_RAW };
int clock_gettime(clk_id_t clock, struct timespec *tp);
#endif

// posix_main.cpp
#ifdef __APPLE__
// OS X doesn't have clock_gettime()
int clock_gettime(clk_id_t clock, struct timespec *tp)
{
	switch(clock)
	{
		case CLOCK_MONOTONIC_RAW:
		case CLOCK_MONOTONIC:
		{
			clock_serv_t clock_ref;
			mach_timespec_t tm;
			host_name_port_t self = mach_host_self();
			memset(&tm, 0, sizeof(tm));
			if (KERN_SUCCESS != host_get_clock_service(self, SYSTEM_CLOCK, &clock_ref))
			{
				return -1;
			}
			if (KERN_SUCCESS != clock_get_time(clock_ref, &tm))
			{
				mach_port_deallocate(mach_task_self(), self);
				return -1;
			}
			mach_port_deallocate(mach_task_self(), self);
			mach_port_deallocate(mach_task_self(), clock_ref);
			tp->tv_sec = tm.tv_sec;
			tp->tv_nsec = tm.tv_nsec;
			break;
		}

		case CLOCK_REALTIME:
		default:
		{
			struct timeval now;
			if (KERN_SUCCESS != gettimeofday(&now, NULL))
			{
				return -1;
			}
		    tp->tv_sec  = now.tv_sec;
		    tp->tv_nsec = now.tv_usec * 1000;
			break;
		}
	}
	return 0;
}
#endif // __APPLE__