72 lines
674 B
ArmAsm
72 lines
674 B
ArmAsm
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.segment "ZEROPAGE"
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RAND_SEED: .res 2
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.segment "CODE"
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.export _rand8,_rand16,_set_rand
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.exportzp RAND_SEED
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;unsigned char __fastcall__ rand8(void);
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;Galois random generator, found somewhere
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;out: A random number 0..255
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rand1:
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lda <RAND_SEED
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beq @z1
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asl a
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bcc @1
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@z1: eor #$cf
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@1:
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sta <RAND_SEED
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rts
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rand2:
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lda <RAND_SEED+1
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beq @z2
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asl a
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bcc @1
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@z2: eor #$d7
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@1:
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sta <RAND_SEED+1
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rts
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_rand8:
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jsr rand1
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jsr rand2
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adc <RAND_SEED
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ldx #$00
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rts
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;unsigned int __fastcall__ rand16(void);
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_rand16:
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jsr rand1
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tax
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jsr rand2
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rts
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;void __fastcall__ set_rand(unsigned char seed);
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_set_rand:
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ora #1
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sta <RAND_SEED
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stx <RAND_SEED+1
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rts
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