Nanosecond resolution timer code for OSX.

nsec_test.c

//clang -pedantic -std=c99 -Wall -o nsec_test nsec_test.c && ./nsec_test
#include <assert.h>
#include <mach/mach.h>
#include <mach/mach_time.h>

#include <pthread.h>

// see https://developer.apple.com/library/mac/qa/qa1398/_index.html
typedef uint64_t nano_time_t;

static mach_timebase_info_data_t mtb_;

static void
init_timebase_conv_(void)
{
    kern_return_t err;

    err = mach_timebase_info(&mtb_);
    assert(err == KERN_SUCCESS);
}

nano_time_t
getCurrentTime(void)
{
     static pthread_once_t once = PTHREAD_ONCE_INIT;
     uint64_t              now;

     pthread_once(&once, init_timebase_conv_);
     now = mach_absolute_time();

     return (now * mtb_.numer) / mtb_.denom;
}

#include <stdio.h>
#include <sys/time.h>
int main()
{
  uint64_t t1, t2;
  struct timeval n1, n2;


  t1 = getCurrentTime();
  t2 = getCurrentTime();

  printf("t1: %llu, t2: %llu [%llu]\n", t1, t2, t2-t1);

  gettimeofday(&n1, NULL);
  gettimeofday(&n2, NULL);

  printf("t1: %d, t2: %d [%d]\n", n1.tv_usec, n2.tv_usec, n2.tv_usec-n2.tv_usec);

  return 0;
}

//output
//t1: 146591969850434, t2: 146591969850519 [85]
//t1: 514592, t2: 514592 [0]