41 lines
659 B
NASM
41 lines
659 B
NASM
; random number generation routines
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; by lua :3 - 2022 https://foxgirl.dev/
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const RANDOM_STATE: 0x0228218E ; 4 bytes
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; generate a random number
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; inputs:
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; none
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; outputs:
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; r0: random number
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random:
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push r1
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mov r0, [RANDOM_STATE]
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mov r1, r0
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sla r1, 13
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xor r0, r1
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mov r1, r0
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srl r1, 17
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xor r0, r1
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mov r1, r0
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sla r1, 5
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xor r0, r1
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mov [RANDOM_STATE], r0
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pop r1
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ret
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; generate a random number in the range [r1, r2)
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; inputs:
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; r1: minimum value, inclusive
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; r2: maximum value, exclusive
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; outputs:
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; r0: random number
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random_range:
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call random
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sub r2, r1
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rem r0, r2
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add r0, r1
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ret
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