;;;; entropy-clock.scm
;;;; Kon Lovett, Oct '09

(module entropy-clock

  (;export
    make-entropy-source-system-clock)

  (import
    scheme
    chicken
    foreign)

  (use entropy-source entropy-support)

;;;

#|
#>
#include <time.h>
#include <math.h>

static double
f64init()
{
  return (double) time( NULL );
}

static double
f64rand( double f64seed )
{
  double x = 11.0 + (25214903917.0 * f64seed);
  return fmod( x, 281474976711000.0 ); /* actually remainder */
}
<#

(define f64init (foreign-lambda double "f64init"))
(define f64rand (foreign-lambda double "f64rand" double))
|#

(import extras)

(define (f64init) (randomize))
(define (f64rand n) (random n))

;;; Entropy from system clock

(define (make-entropy-source-system-clock)
  (let* ((f64seed (f64init))
         (_f64rand (lambda () (set! f64seed (f64rand f64seed)) f64seed)) )
    (*make-entropy-source
      ;
      make-entropy-source-system-clock
      ;
      'system-clock
      ;
      "Entropy from system clock"
      ;
      (make-entropic-u8/f64 _f64rand)
      ;
      _f64rand
      ;
      (lambda (u8cnt u8vec) (entropic-u8vector-filled/f64 u8cnt u8vec _f64rand) )
      ;
      (lambda (f64cnt f64vec) (entropic-f64vector-filled f64cnt f64vec _f64rand) ) ) ) )

(register-entropy-source! 'system-clock make-entropy-source-system-clock)

) ;module entropy-clock