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24 lines
421 B
NASM
24 lines
421 B
NASM
; function to count how many bits are set in a string of bytes
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; INPUT:
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; hl = address of string of bytes
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; b = length of string of bytes
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; OUTPUT:
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; [wNumSetBits] = number of set bits
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CountSetBits::
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ld c, 0
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.loop
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ld a, [hli]
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ld e, a
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ld d, 8
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.innerLoop ; count how many bits are set in the current byte
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srl e
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ld a, 0
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adc c
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ld c, a
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dec d
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jr nz, .innerLoop
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dec b
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jr nz, .loop
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ld a, c
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ld [wNumSetBits], a
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ret
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