RNG - mimic Java's Util.Random (#1672)

* initial java Util.Random mimic

* add comment referencing java impl

* fix 64 bit stuff

* copy scf-time definition into math.gc, use for initial seed

* rename java -> knuth

* move knuth-rand to separate file

* move knuth-rand to separate file

* PR comments

decompiler/config/all-types.gc

@@ -6287,7 +6287,6 @@
   :flag-assert         #x900000008
   )
 
-
 ;; ----------------------
 ;; File - capture
 ;; Source Path - engine/gfx/capture.gc

goal_src/jak1/dgos/engine.gd

@@ -51,6 +51,7 @@
   ("connect.o" "connect")
   ("text-h.o" "text-h")
   ("settings-h.o" "settings-h")
+  ("knuth-rand.o" "knuth-rand") ;; added
   ("capture.o" "capture")
   ("memory-usage-h.o" "memory-usage-h")
   ("texture.o" "texture")

goal_src/jak1/dgos/game.gd

@@ -47,6 +47,7 @@
   ("connect.o" "connect")
   ("text-h.o" "text-h")
   ("settings-h.o" "settings-h")
+  ("knuth-rand.o" "knuth-rand") ;; added
   ("capture.o" "capture")
   ("memory-usage-h.o" "memory-usage-h")
   ("texture.o" "texture")

goal_src/jak1/engine/game/settings-h.gc

@@ -233,3 +233,21 @@
   )
 
 (define-extern *setting-control* setting-control)
+
+(defun scf-time-to-uint64 () 
+  (let ((date (new 'stack 'scf-time)))
+    (let ((temp (the uint64 0)))
+      (scf-get-time date)
+      
+      (logior! temp (-> date stat))
+      (logior! temp (shl (-> date second) 8))
+      (logior! temp (shl (-> date minute) 16))
+      (logior! temp (shl (-> date hour) 24))
+      (logior! temp (shl (-> date week) 32))
+      (logior! temp (shl (-> date day) 40))
+      (logior! temp (shl (-> date month) 48))
+      (logior! temp (shl (-> date year) 56))
+      temp
+    )
+  )
+)

goal_src/jak1/engine/math/knuth-rand.gc

@@ -0,0 +1,71 @@
+;;-*-Lisp-*-
+(in-package goal)
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;;; mimicking Java's util.Random https://docs.oracle.com/javase/8/docs/api/java/util/Random.html
+;;;; This is a linear congruential pseudorandom number generator, as defined by D. H. Lehmer 
+;;;;  and described by Donald E. Knuth in The Art of Computer Programming, Volume 3: Seminumerical Algorithms, section 3.2.1.
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+(deftype knuth-rand-state (structure)
+  ((seed uint64))
+  )
+
+(define *knuth-rand-state* (new 'global 'knuth-rand-state))
+
+(defun knuth-rand-init ((newSeed uint))
+  (set! (-> *knuth-rand-state* seed) newSeed)
+)
+(knuth-rand-init (scf-time-to-uint64))
+
+(defun knuth-rand-advance-seed ()
+  ;; seed =  (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)
+  (set! (-> *knuth-rand-state* seed) (the uint64 (logand (+ (imul64 (-> *knuth-rand-state* seed) 25214903917) 11) (- (shl 1 48) 1))))
+)
+
+(defun knuth-rand-next ((bits int))
+  (knuth-rand-advance-seed)
+
+  ;; return (int)(seed >>> (48 - bits))
+  (shr (-> *knuth-rand-state* seed) (- 48 bits))
+)
+
+(defun knuth-rand-nextInt () 
+  (knuth-rand-advance-seed)
+  (-> *knuth-rand-state* seed)
+)
+
+;; returns a pseudorandom int in the range [min, max)
+(defun knuth-rand-nextIntRange ((min int) (max int))
+  (let* ((bound (- max min))
+    ;; int bits, val;
+         (bits (the uint64 0))
+         (val (the uint64 0)))
+
+    ;; if ((bound & -bound) == bound)  // i.e., bound is a power of 2
+    (if (= (logand bound (* -1 bound)) bound)
+      ;; return (int)((bound * (long)next(31)) >> 31);
+      (return (sar (* bound (knuth-rand-next 31)) 31))
+    )
+
+    ;;  do {
+    ;;      bits = next(31);
+    ;;      val = bits % bound;
+    ;;  } while (bits - val + (bound-1) < 0);
+    ;;  return val;
+    (while #t
+      (set! bits (knuth-rand-next 31))
+      (set! val (mod bits bound))
+
+      (if (>= (+ bits (* -1 val) bound -1) 0)
+        (return (+ min val))
+      )
+    )
+  )
+  -1
+)
+
+;; returns a pseudorandom float in the range [0, 1)
+(defun knuth-rand-nextFloat ()
+  ;; return next(24) / ((float)(1 << 24));
+  (/ (the float (knuth-rand-next 24)) (shl 1 24))
+) 

goal_src/jak1/engine/math/math.gc

@@ -315,5 +315,4 @@
 (defmacro rand-float-gen (&key (gen *random-generator*))
   "Generate a float from [0, 1)"
   `(+ -1.0 (the-as float (logior #x3f800000 (/ (rand-uint31-gen ,gen) 256))))
-  )
-
+  )

goal_src/jak1/game.gp

@@ -1696,6 +1696,7 @@
  "engine/connect.gc"
  "ui/text-h.gc"
  "game/settings-h.gc"
+ "math/knuth-rand.gc" ;; added
  "util/capture.gc"
  "debug/memory-usage-h.gc"
  "gfx/texture/texture.gc"