(foreign-declare "#include <time.h>")
(define realtime-microsecs (foreign-lambda* double ()
  "uint64_t time = clock_gettime_nsec_np(CLOCK_UPTIME_RAW);
  return( ((double) time) / 1000.0 );"))

#|
(foreign-declare "#include <mach/mach_time.h>")

(define realtime-microsecs)
(let ((%factor (the (or float boolean) #f)))
  ;
  (define %calc-time (foreign-lambda* double ()
    "uint64_t time = mach_absolute_time();
    return( ((double) time) / 1000.0 );"))
  ;
  (define %calc-factor (foreign-lambda* double ()
    "mach_timebase_info_data_t info;
    mach_timebase_info( &info );
    return( ((double) info.numer) / ((double) info.denom) );"))
  ;
  (set! realtime-microsecs (lambda () (* (%calc-time) %factor)))
  ;
  ;we immediatly determine the factor
  ;it should not change as long as the machine runs
  (set! %factor (%calc-factor))
  (when (< %factor 0.0)
    (error 'macosx-realtime-microsecs "cannot determine scale factor") ) )
|#