(foreign-declare "#include <time.h>")
(define get-microsecs (foreign-lambda* double ()
  "uint64_t time = clock_gettime_nsec_np( CLOCK_UPTIME_RAW );"
  "if( 0 == time ) return( -1.0 );"
  "return( ((double) time) / 1e3 );"))

#| ;pre-Sierra 10.12
(foreign-declare "#include <mach/mach_time.h>")
(define get-microsecs)
(let ((%factor (the (or float boolean) #f)))
  ;
  (define %calc-time (foreign-lambda* double ()
    "uint64_t time = mach_absolute_time();"
    "return( ((double) time) / 1e3 );"))
  ;
  (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-microsecs (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-microsecs "cannot determine scale factor" %factor) ) )
|#