pokecrystal/engine/math/math.asm

190 lines
2.5 KiB
NASM

_Multiply::
; hMultiplier is one byte.
ld a, 8
ld b, a
xor a
ldh [hProduct], a
ldh [hMathBuffer + 1], a
ldh [hMathBuffer + 2], a
ldh [hMathBuffer + 3], a
ldh [hMathBuffer + 4], a
.loop
ldh a, [hMultiplier]
srl a
ldh [hMultiplier], a
jr nc, .next
ldh a, [hMathBuffer + 4]
ld c, a
ldh a, [hMultiplicand + 2]
add c
ldh [hMathBuffer + 4], a
ldh a, [hMathBuffer + 3]
ld c, a
ldh a, [hMultiplicand + 1]
adc c
ldh [hMathBuffer + 3], a
ldh a, [hMathBuffer + 2]
ld c, a
ldh a, [hMultiplicand + 0]
adc c
ldh [hMathBuffer + 2], a
ldh a, [hMathBuffer + 1]
ld c, a
ldh a, [hProduct]
adc c
ldh [hMathBuffer + 1], a
.next
dec b
jr z, .done
; hMultiplicand <<= 1
ldh a, [hMultiplicand + 2]
add a
ldh [hMultiplicand + 2], a
ldh a, [hMultiplicand + 1]
rla
ldh [hMultiplicand + 1], a
ldh a, [hMultiplicand + 0]
rla
ldh [hMultiplicand + 0], a
ldh a, [hProduct]
rla
ldh [hProduct], a
jr .loop
.done
ldh a, [hMathBuffer + 4]
ldh [hProduct + 3], a
ldh a, [hMathBuffer + 3]
ldh [hProduct + 2], a
ldh a, [hMathBuffer + 2]
ldh [hProduct + 1], a
ldh a, [hMathBuffer + 1]
ldh [hProduct + 0], a
ret
_Divide::
xor a
ldh [hMathBuffer + 0], a
ldh [hMathBuffer + 1], a
ldh [hMathBuffer + 2], a
ldh [hMathBuffer + 3], a
ldh [hMathBuffer + 4], a
ld a, 9
ld e, a
.loop
ldh a, [hMathBuffer + 0]
ld c, a
ldh a, [hDividend + 1]
sub c
ld d, a
ldh a, [hDivisor]
ld c, a
ldh a, [hDividend + 0]
sbc c
jr c, .next
ldh [hDividend + 0], a
ld a, d
ldh [hDividend + 1], a
ldh a, [hMathBuffer + 4]
inc a
ldh [hMathBuffer + 4], a
jr .loop
.next
ld a, b
cp 1
jr z, .done
ldh a, [hMathBuffer + 4]
add a
ldh [hMathBuffer + 4], a
ldh a, [hMathBuffer + 3]
rla
ldh [hMathBuffer + 3], a
ldh a, [hMathBuffer + 2]
rla
ldh [hMathBuffer + 2], a
ldh a, [hMathBuffer + 1]
rla
ldh [hMathBuffer + 1], a
dec e
jr nz, .next2
ld e, 8
ldh a, [hMathBuffer + 0]
ldh [hDivisor], a
xor a
ldh [hMathBuffer + 0], a
ldh a, [hDividend + 1]
ldh [hDividend + 0], a
ldh a, [hDividend + 2]
ldh [hDividend + 1], a
ldh a, [hDividend + 3]
ldh [hDividend + 2], a
.next2
ld a, e
cp 1
jr nz, .okay
dec b
.okay
ldh a, [hDivisor]
srl a
ldh [hDivisor], a
ldh a, [hMathBuffer + 0]
rr a
ldh [hMathBuffer + 0], a
jr .loop
.done
ldh a, [hDividend + 1]
ldh [hDivisor], a
ldh a, [hMathBuffer + 4]
ldh [hDividend + 3], a
ldh a, [hMathBuffer + 3]
ldh [hDividend + 2], a
ldh a, [hMathBuffer + 2]
ldh [hDividend + 1], a
ldh a, [hMathBuffer + 1]
ldh [hDividend + 0], a
ret