From 02a2dcac1a41872e1fec6d3b37ddd7ecae57eae4 Mon Sep 17 00:00:00 2001
From: "Christian A. Weber" <chris@gna.ch>
Date: Thu, 16 Apr 1992 23:00:42 +0000
Subject: Initial revision

---
 Rnd.S | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 Rnd.S

(limited to 'Rnd.S')

diff --git a/Rnd.S b/Rnd.S
new file mode 100644
index 0000000..8aeea74
--- /dev/null
+++ b/Rnd.S
@@ -0,0 +1,55 @@
+
+		SECTION	text,CODE
+
+		INCLUDE	"MyExec.i"
+
+		XDEF	RandomizeFunc,RandomFunc
+
+
+	*** Random initialisieren, D0/D1 :  Zufallswerte
+
+RandomizeFunc:	movem.l	d0-d3,-(SP)
+		add.l	d0,d1			; user seed in d0 (d1 too)
+		move.l	d0,meb_LastRnd1(a6)	; save for next time through
+		move.l	d1,meb_LastRnd2(a6)
+		bsr.s	LongRnd
+		movem.l	(SP)+,d0-d3
+		rts
+
+
+	*** Zufallszahl [0..D0.W] berechnen
+
+RandomFunc:	movem.l	d1-d4,-(SP)
+		move.w	d0,d4		; save upper limit
+		beq.s	1$		; range of 0 returns 0 always
+		bsr.s	LongRnd		; get a longword random number
+		clr.w	d0		; use upper word (it's most random)
+		swap	d0
+		divu.w	d4,d0		; divide by range...
+		clr.w	d0		; ...and use remainder for the value
+		swap	d0		; result in D0.W
+1$:		movem.l	(SP)+,d1-d4
+		rts
+
+
+LongRnd:	movem.l	meb_LastRnd1(a6),d0/d1 ; D0=LSB's, D1=MSB's of random number
+		andi.b	#$0e,d0		; ensure upper 59 bits are an...
+		ori.b	#$20,d0		; ...odd binary number
+		move.l	d0,d2
+		move.l	d1,d3
+		add.l	d2,d2		; accounts for 1 of 17 left shifts
+		addx.l	d3,d3		; [D2/D3] = RND*2
+		add.l	d2,d0
+		addx.l	d3,d1		; [D0/D1] = RND*3
+		swap	d3		; shift [D2/D3] additional 16 times
+		swap	d2
+		move.w	d2,d3
+		clr.w	d2
+		add.l	d2,d0		; add to [D0/D1]
+		addx.l	d3,d1
+		movem.l	d0/d1,meb_LastRnd1(a6)	; save for next time through
+		move.l	d1,d0		; most random part to D0
+		rts
+
+
+		END
-- 
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