Multiply and Divide

This commit is contained in:
yenatch 2013-03-30 01:58:22 -04:00
parent e21fc0fad1
commit 6c3ec2d13d
2 changed files with 249 additions and 24 deletions

View File

@ -26,6 +26,16 @@ hJoyDown EQU $ffa8
hPastLeadingZeroes EQU $ffb3
hDividend EQU $ffb3
hDivisor EQU $ffb7
hQuotient EQU $ffb4
hMultiplicand EQU $ffb4
hMultiplier EQU $ffb7
hProduct EQU $ffb3
hMathBuffer EQU $ffb8
hLCDStatCustom EQU $ffc6
hBGMapMode EQU $ffd4

261
main.asm
View File

@ -2932,34 +2932,49 @@ AddNTimes: ; 0x30fe
ret
; 0x3105
INCBIN "baserom.gbc", $3105, $3119 - $3105
Multiply: ; 0x3119
; function to do multiplication
; all values are big endian
; INPUT
; ffb4-ffb6 = multiplicand
; ffb7 = multiplier
; OUTPUT
; ffb3-ffb6 = product
INCBIN "baserom.gbc", $3119, $3124 - $3119
; 0x3124
Divide: ; 0x3124
; function to do division
; all values are big endian
; INPUT
; ffb3-ffb6 = dividend
; ffb7 = divisor
; b = number of bytes in the dividend (starting from ffb3)
; OUTPUT
; ffb4-ffb6 = quotient
; ffb7 = remainder
INCBIN "baserom.gbc", $3124, $3136 - $3124
; 0x3136
Multiply: ; 3119
; Multiply hMultiplicand (3 bytes) by hMultiplier. Result in hProduct.
; All values are big endian.
push hl
push bc
callab _Multiply
pop bc
pop hl
ret
; 3124
Divide: ; 3124
; Divide hDividend length b (max 4 bytes) by hDivisor. Result in hQuotient.
; All values are big endian.
push hl
push de
push bc
ld a, [hROMBank]
push af
ld a, BANK(_Divide)
rst Bankswitch
call _Divide
pop af
rst Bankswitch
pop bc
pop de
pop hl
ret
; 3136
INCBIN "baserom.gbc", $3136, $313d - $3136
PrintLetterDelay: ; 313d
; wait some frames before printing the next letter
; the text speed setting in Options is actually a frame count
@ -4141,7 +4156,207 @@ CheckNickErrors: ; 669f
db $ff ; end
; 66de
INCBIN "baserom.gbc", $66de, $6eef - $66de
_Multiply: ; 66de
; hMultiplier is one byte.
ld a, 8
ld b, a
xor a
ld [hMultiplicand - 1], a
ld [hMathBuffer + 1], a
ld [hMathBuffer + 2], a
ld [hMathBuffer + 3], a
ld [hMathBuffer + 4], a
.loop
ld a, [hMultiplier]
srl a
ld [hMultiplier], a
jr nc, .next
ld a, [hMathBuffer + 4]
ld c, a
ld a, [hMultiplicand + 2]
add c
ld [hMathBuffer + 4], a
ld a, [hMathBuffer + 3]
ld c, a
ld a, [hMultiplicand + 1]
adc c
ld [hMathBuffer + 3], a
ld a, [hMathBuffer + 2]
ld c, a
ld a, [hMultiplicand + 0]
adc c
ld [hMathBuffer + 2], a
ld a, [hMathBuffer + 1]
ld c, a
ld a, [hMultiplicand - 1]
adc c
ld [hMathBuffer + 1], a
.next
dec b
jr z, .done
; hMultiplicand <<= 1
ld a, [hMultiplicand + 2]
add a
ld [hMultiplicand + 2], a
ld a, [hMultiplicand + 1]
rla
ld [hMultiplicand + 1], a
ld a, [hMultiplicand + 0]
rla
ld [hMultiplicand + 0], a
ld a, [hMultiplicand - 1]
rla
ld [hMultiplicand - 1], a
jr .loop
.done
ld a, [hMathBuffer + 4]
ld [hProduct + 3], a
ld a, [hMathBuffer + 3]
ld [hProduct + 2], a
ld a, [hMathBuffer + 2]
ld [hProduct + 1], a
ld a, [hMathBuffer + 1]
ld [hProduct + 0], a
ret
; 673e
_Divide: ; 673e
xor a
ld [hMathBuffer + 0], a
ld [hMathBuffer + 1], a
ld [hMathBuffer + 2], a
ld [hMathBuffer + 3], a
ld [hMathBuffer + 4], a
ld a, 9
ld e, a
.loop
ld a, [hMathBuffer + 0]
ld c, a
ld a, [hDividend + 1]
sub c
ld d, a
ld a, [hDivisor]
ld c, a
ld a, [hDividend + 0]
sbc c
jr c, .asm_6767
ld [hDividend + 0], a
ld a, d
ld [hDividend + 1], a
ld a, [hMathBuffer + 4]
inc a
ld [hMathBuffer + 4], a
jr .loop
.asm_6767
ld a, b
cp 1
jr z, .done
ld a, [hMathBuffer + 4]
add a
ld [hMathBuffer + 4], a
ld a, [hMathBuffer + 3]
rla
ld [hMathBuffer + 3], a
ld a, [hMathBuffer + 2]
rla
ld [hMathBuffer + 2], a
ld a, [hMathBuffer + 1]
rla
ld [hMathBuffer + 1], a
dec e
jr nz, .asm_6798
ld e, 8
ld a, [hMathBuffer + 0]
ld [hDivisor], a
xor a
ld [hMathBuffer + 0], a
ld a, [hDividend + 1]
ld [hDividend + 0], a
ld a, [hDividend + 2]
ld [hDividend + 1], a
ld a, [hDividend + 3]
ld [hDividend + 2], a
.asm_6798
ld a, e
cp 1
jr nz, .asm_679e
dec b
.asm_679e
ld a, [hDivisor]
srl a
ld [hDivisor], a
ld a, [hMathBuffer + 0]
rr a
ld [hMathBuffer + 0], a
jr .loop
.done
ld a, [hDividend + 1]
ld [hDivisor], a
ld a, [hMathBuffer + 4]
ld [hDividend + 3], a
ld a, [hMathBuffer + 3]
ld [hDividend + 2], a
ld a, [hMathBuffer + 2]
ld [hDividend + 1], a
ld a, [hMathBuffer + 1]
ld [hDividend + 0], a
ret
; 67c1
INCBIN "baserom.gbc", $67c1, $6eef - $67c1
DrawGraphic: ; 6eef
; input: