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| author | Christian A. Weber <chris@gna.ch> | 1992-04-16 23:00:42 +0000 |
|---|---|---|
| committer | Christian A. Weber <chris@gna.ch> | 1992-04-16 23:00:42 +0000 |
| commit | 02a2dcac1a41872e1fec6d3b37ddd7ecae57eae4 (patch) | |
| tree | 6c39deb2ce8713b42bad5917b870184ed1d73463 /Rnd.S | |
| parent | ab216e437899d244ad2ad43cdf2ad0b66b06ca42 (diff) | |
| download | gameexec-02a2dcac1a41872e1fec6d3b37ddd7ecae57eae4.tar.gz gameexec-02a2dcac1a41872e1fec6d3b37ddd7ecae57eae4.tar.bz2 gameexec-02a2dcac1a41872e1fec6d3b37ddd7ecae57eae4.zip | |
Initial revision
Diffstat (limited to 'Rnd.S')
| -rw-r--r-- | Rnd.S | 55 |
1 files changed, 55 insertions, 0 deletions
@@ -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 |