kep-hack/engine/bcd.asm

DivideBCDPredef::
DivideBCDPredef2::
DivideBCDPredef3::
DivideBCDPredef4::
	call GetPredefRegisters

DivideBCD::
	xor a
	ld [$ffa5], a
	ld [$ffa6], a
	ld [$ffa7], a
	ld d, $1
.asm_f72a
	ld a, [$ffa2]
	and $f0
	jr nz, .asm_f75b
	inc d
	ld a, [$ffa2]
	swap a
	and $f0
	ld b, a
	ld a, [$ffa3]
	swap a
	ld [$ffa3], a
	and $f
	or b
	ld [$ffa2], a
	ld a, [$ffa3]
	and $f0
	ld b, a
	ld a, [$ffa4]
	swap a
	ld [$ffa4], a
	and $f
	or b
	ld [$ffa3], a
	ld a, [$ffa4]
	and $f0
	ld [$ffa4], a
	jr .asm_f72a
.asm_f75b
	push de
	push de
	call DivideBCD_f800
	pop de
	ld a, b
	swap a
	and $f0
	ld [$ffa5], a
	dec d
	jr z, .asm_f7bc
	push de
	call DivideBCD_f7d7
	call DivideBCD_f800
	pop de
	ld a, [$ffa5]
	or b
	ld [$ffa5], a
	dec d
	jr z, .asm_f7bc
	push de
	call DivideBCD_f7d7
	call DivideBCD_f800
	pop de
	ld a, b
	swap a
	and $f0
	ld [$ffa6], a
	dec d
	jr z, .asm_f7bc
	push de
	call DivideBCD_f7d7
	call DivideBCD_f800
	pop de
	ld a, [$ffa6]
	or b
	ld [$ffa6], a
	dec d
	jr z, .asm_f7bc
	push de
	call DivideBCD_f7d7
	call DivideBCD_f800
	pop de
	ld a, b
	swap a
	and $f0
	ld [$ffa7], a
	dec d
	jr z, .asm_f7bc
	push de
	call DivideBCD_f7d7
	call DivideBCD_f800
	pop de
	ld a, [$ffa7]
	or b
	ld [$ffa7], a
.asm_f7bc
	ld a, [$ffa5]
	ld [$ffa2], a
	ld a, [$ffa6]
	ld [$ffa3], a
	ld a, [$ffa7]
	ld [$ffa4], a
	pop de
	ld a, $6
	sub d
	and a
	ret z
.asm_f7ce
	push af
	call DivideBCD_f7d7
	pop af
	dec a
	jr nz, .asm_f7ce
	ret

DivideBCD_f7d7:
	ld a, [$ffa4]
	swap a
	and $f
	ld b, a
	ld a, [$ffa3]
	swap a
	ld [$ffa3], a
	and $f0
	or b
	ld [$ffa4], a
	ld a, [$ffa3]
	and $f
	ld b, a
	ld a, [$ffa2]
	swap a
	ld [$ffa2], a
	and $f0
	or b
	ld [$ffa3], a
	ld a, [$ffa2]
	and $f
	ld [$ffa2], a
	ret

DivideBCD_f800:
	ld bc, $3
.asm_f803
	ld de, $ff9f
	ld hl, $ffa2
	push bc
	call StringCmp
	pop bc
	ret c
	inc b
	ld de, $ffa1
	ld hl, $ffa4
	push bc
	call SubBCD
	pop bc
	jr .asm_f803


AddBCDPredef::
	call GetPredefRegisters

AddBCD::
	and a
	ld b, c
.add
	ld a, [de]
	adc [hl]
	daa
	ld [de], a
	dec de
	dec hl
	dec c
	jr nz, .add
	jr nc, .done
	ld a, $99
	inc de
.fill
	ld [de], a
	inc de
	dec b
	jr nz, .fill
.done
	ret


SubBCDPredef::
	call GetPredefRegisters

SubBCD::
	and a
	ld b, c
.sub
	ld a, [de]
	sbc [hl]
	daa
	ld [de], a
	dec de
	dec hl
	dec c
	jr nz, .sub
	jr nc, .done
	ld a, $00
	inc de
.fill
	ld [de], a
	inc de
	dec b
	jr nz, .fill
	scf
.done
	ret