mirror of https://github.com/pret/pokecrystal.git
197 lines
2.4 KiB
NASM
197 lines
2.4 KiB
NASM
_Multiply:: ; 66de
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; hMultiplier is one byte.
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ld a, 8
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ld b, a
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xor a
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ld [hProduct], a
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ld [hMathBuffer + 1], a
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ld [hMathBuffer + 2], a
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ld [hMathBuffer + 3], a
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ld [hMathBuffer + 4], a
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.loop
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ld a, [hMultiplier]
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srl a
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ld [hMultiplier], a
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jr nc, .next
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ld a, [hMathBuffer + 4]
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ld c, a
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ld a, [hMultiplicand + 2]
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add c
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ld [hMathBuffer + 4], a
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ld a, [hMathBuffer + 3]
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ld c, a
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ld a, [hMultiplicand + 1]
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adc c
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ld [hMathBuffer + 3], a
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ld a, [hMathBuffer + 2]
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ld c, a
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ld a, [hMultiplicand + 0]
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adc c
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ld [hMathBuffer + 2], a
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ld a, [hMathBuffer + 1]
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ld c, a
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ld a, [hProduct]
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adc c
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ld [hMathBuffer + 1], a
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.next
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dec b
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jr z, .done
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; hMultiplicand <<= 1
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ld a, [hMultiplicand + 2]
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add a
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ld [hMultiplicand + 2], a
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ld a, [hMultiplicand + 1]
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rla
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ld [hMultiplicand + 1], a
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ld a, [hMultiplicand + 0]
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rla
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ld [hMultiplicand + 0], a
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ld a, [hProduct]
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rla
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ld [hProduct], a
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jr .loop
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.done
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ld a, [hMathBuffer + 4]
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ld [hProduct + 3], a
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ld a, [hMathBuffer + 3]
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ld [hProduct + 2], a
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ld a, [hMathBuffer + 2]
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ld [hProduct + 1], a
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ld a, [hMathBuffer + 1]
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ld [hProduct + 0], a
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ret
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; 673e
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_Divide:: ; 673e
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xor a
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ld [hMathBuffer + 0], a
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ld [hMathBuffer + 1], a
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ld [hMathBuffer + 2], a
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ld [hMathBuffer + 3], a
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ld [hMathBuffer + 4], a
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ld a, 9
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ld e, a
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.loop
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ld a, [hMathBuffer + 0]
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ld c, a
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ld a, [hDividend + 1]
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sub c
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ld d, a
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ld a, [hDivisor]
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ld c, a
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ld a, [hDividend + 0]
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sbc c
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jr c, .next
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ld [hDividend + 0], a
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ld a, d
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ld [hDividend + 1], a
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ld a, [hMathBuffer + 4]
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inc a
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ld [hMathBuffer + 4], a
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jr .loop
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.next
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ld a, b
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cp 1
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jr z, .done
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ld a, [hMathBuffer + 4]
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add a
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ld [hMathBuffer + 4], a
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ld a, [hMathBuffer + 3]
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rla
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ld [hMathBuffer + 3], a
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ld a, [hMathBuffer + 2]
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rla
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ld [hMathBuffer + 2], a
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ld a, [hMathBuffer + 1]
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rla
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ld [hMathBuffer + 1], a
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dec e
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jr nz, .next2
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ld e, 8
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ld a, [hMathBuffer + 0]
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ld [hDivisor], a
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xor a
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ld [hMathBuffer + 0], a
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ld a, [hDividend + 1]
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ld [hDividend + 0], a
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ld a, [hDividend + 2]
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ld [hDividend + 1], a
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ld a, [hDividend + 3]
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ld [hDividend + 2], a
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.next2
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ld a, e
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cp 1
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jr nz, .okay
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dec b
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.okay
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ld a, [hDivisor]
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srl a
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ld [hDivisor], a
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ld a, [hMathBuffer + 0]
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rr a
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ld [hMathBuffer + 0], a
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jr .loop
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.done
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ld a, [hDividend + 1]
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ld [hDivisor], a
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ld a, [hMathBuffer + 4]
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ld [hDividend + 3], a
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ld a, [hMathBuffer + 3]
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ld [hDividend + 2], a
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ld a, [hMathBuffer + 2]
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ld [hDividend + 1], a
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ld a, [hMathBuffer + 1]
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ld [hDividend + 0], a
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ret
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; 67c1
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