From fa3f23105ddcf07c5900de47f19af43d1db1b597 Mon Sep 17 00:00:00 2001
From: Bryan Newbold <bnewbold@robocracy.org>
Date: Mon, 20 Feb 2017 00:05:27 -0800
Subject: Import Upstream version 2c3

---
 random.scm | 117 +++++++++++++++++++++++++++++--------------------------------
 1 file changed, 56 insertions(+), 61 deletions(-)

(limited to 'random.scm')

diff --git a/random.scm b/random.scm
index 4f5a11d..d22388e 100644
--- a/random.scm
+++ b/random.scm
@@ -17,85 +17,80 @@
 ;promotional, or sales literature without prior written consent in
 ;each case.
 
+(require 'byte)
 (require 'logical)
 
-(define random:tap 24)
-(define random:size 55)
+(define (make-rng seed)
+  (define mutex #f)
+  (define idx 0)
+  (define idy 0)
+  (define sta (make-bytes 256))
+					; initialize state
+  (do ((idx #xff (+ -1 idx)))
+      ((negative? idx))
+    (byte-set! sta idx idx))
 
-(define (random:size-int l)
-  (let ((trial (string->number (make-string l #\f) 16)))
-  (if (and (exact? trial) (>= most-positive-fixnum trial))
-      l
-      (random:size-int (- l 1)))))
-(define random:chunk-size (* 4 (random:size-int 8)))
+  (if (number? seed)
+      (set! seed (number->string seed)))
 
-(define random:MASK
-  (string->number (make-string (quotient random:chunk-size 4) #\f) 16))
+					; merge seed into state
+  (do ((idx 0 (+ 1 idx))
+       (kdx 0 (modulo (+ 1 kdx) seed-len))
+       (seed-len (bytes-length seed)))
+      ((>= idx 256) (set! idy 0))
+    (let ((swp (byte-ref sta idx)))
+      (set! idy (logand #xff (+ idy (byte-ref seed kdx) swp)))
+      (byte-set! sta idx (byte-ref sta idy))
+      (byte-set! sta idy swp)))
+					; spew
+  (lambda ()
+    (if mutex (slib:error "random state called reentrantly"))
+    (set! mutex #t)
+    (set! idx (logand #xff (+ 1 idx)))
+    (let ((xtm (byte-ref sta idx)))
+      (set! idy (logand #xff (+ idy xtm)))
+      (let ((ytm (byte-ref sta idy)))
+	(byte-set! sta idy xtm)
+	(byte-set! sta idx ytm)
+	(let ((ans (byte-ref sta (logand #xff (+ ytm xtm)))))
+	  (set! mutex #f)
+	  ans)))))
 
 (define *random-state*
-  '#(
- "d909ef3e" "fd330ab3" "e33f7843" "76783fbd" "f3675fb3"
- "b54ef879" "0be45590" "a6794679" "0bcd56d3" "fabcdef8"
- "9cbd3efd" "3fd3efcd" "e064ef27" "dddecc08" "34444292"
- "85444454" "4c519210" "c0366273" "54734567" "70abcddc"
- "1bbdac53" "616c5a86" "a982efa9" "105996a0" "5f0cccba"
- "1ea055e1" "fe2acd8d" "1891c1d4" "e6690270" "6912bccc"
- "2678e141" "61222224" "907abcbb" "4ad6829b" "9cdd1404"
- "57798841" "5b892496" "871c9cd1" "d1e67bda" "8b0a3233"
- "578ef23f" "28274ef6" "823ef5ef" "845678c5" "e67890a5"
- "5890abcb" "851fa9ab" "13efa13a" "b12278d6" "daf805ab"
- "a0befc36" "0068a7b5" "e024fd90" "a7b690e2" "27f3571a"
- 0))
+  (make-rng "http://swissnet.ai.mit.edu/~jaffer/SLIB.html"))
 
-(let ((random-strings *random-state*))
-  (set! *random-state* (make-vector (+ random:size 1) 0))
-  (let ((nibbles (quotient random:chunk-size 4)))
-    (do ((i 0 (+ i 1)))
-	((= i random:size))
-      (vector-set!
-       *random-state* i
-       (string->number (substring (vector-ref random-strings i)
-				  0 nibbles)
-		       16)))))
-
-;;; random:chunk returns an integer in the range of
-;;; 0 to (- (expt 2 random:chunk-size) 1)
-(define (random:chunk v)
-  (let* ((p (vector-ref v random:size))
-	 (ans (logical:logxor
-	       (vector-ref v (modulo (- p random:tap) random:size))
-	       (vector-ref v p))))
-    (vector-set! v p ans)
-    (vector-set! v random:size (modulo (- p 1) random:size))
-    ans))
+;;; random:chunk returns an integer in the range of 0 to 255.
+(define (random:chunk v) (v))
 
 (define (random:random modu . args)
   (let ((state (if (null? args) *random-state* (car args))))
     (if (exact? modu)
-	(do ((ilen 0 (+ 1 ilen))
-	     (s random:MASK
-		(+ random:MASK (* (+ 1 random:MASK) s))))
-	    ((>= s (- modu 1))
-	     (let ((slop (modulo (+ s (- 1 modu)) modu)))
-	       (let loop ((n ilen)
-			  (r (random:chunk state)))
-		 (cond ((not (zero? n))
-			(loop (+ -1 n)
-			      (+ (* r (+ 1 random:MASK))
-				 (random:chunk state))))
-		       ((>= r slop) (modulo r modu))
-		       (else (loop ilen (random:chunk state))))))))
+	(let ((bitlen (integer-length (+ -1 modu))))
+	  (do ((bln bitlen (+ -8 bln))
+	       (rbs 0 (+ (ash rbs 8) (random:chunk state))))
+	      ((<= bln 7)
+	       (modulo
+		(if (zero? bln) rbs
+		    (+ (ash rbs bln)
+		       (logand (bit-field (random:chunk state) 0 bln))))
+		modu))))
 
 	(* (random:uniform state) modu))))
 ;;;random:uniform is in randinex.scm.  It is needed only if inexact is
 ;;;supported.
 
-(define (random:make-random-state . args)
-  (let ((state (if (null? args) *random-state* (car args))))
-    (list->vector (vector->list state))))
+(define (make-random-state . args)
+  (let ((seed (if (null? args)
+		  (do ((bts (make-bytes 10))
+		       (idx 0 (+ 1 idx)))
+		      ((>= idx 10) bts)
+		    (byte-set! bts idx (random:random 256)))
+		  (let ()
+		    (require 'object->string)
+		    (object->limited-string (car args) 20)))))
+    (make-rng seed)))
 
 (define random random:random)
-(define make-random-state random:make-random-state)
 
 (provide 'random)			;to prevent loops
 (if (provided? 'inexact) (require 'random-inexact))
-- 
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