(foreign-declare "#include <time.h>")
(define get-nanosecs (foreign-lambda* unsigned-integer64 ()
  "uint64_t time = clock_gettime_nsec_np( CLOCK_UPTIME_RAW );"
  "if( 0 == time ) return( 0 );"
  "return( time );"))

#| ;pre-Sierra 10.12
(foreign-declare "#include <mach/mach_time.h>")
(define get-nanosecs)
(let ((%factor 0.0))

  (define %calc-time (foreign-lambda* double ()
    "uint64_t time = mach_absolute_time();"
    "return( ((double) time) );"))

  (define %calc-factor (foreign-lambda* double ()
    "mach_timebase_info_data_t info;"
    "mach_timebase_info( &info );"
    "return( ((double) info.numer) / ((double) info.denom) );"))

  (set! get-nanosecs (lambda () (* (%calc-time) %factor)))

  ;we immediatly determine the factor
  ;it should not change as long as the machine runs
  (set! %factor (%calc-factor))
  (unless (positive? %factor)
    (error 'get-nanosecs "cannot determine scale factor" %factor) ) )
|#