ref: d3a01f777d2bbb3bc5ec6822af893d16fda19936
dir: /engine/math/bcd.asm/
DivideBCDPredef:: DivideBCDPredef2:: DivideBCDPredef3:: DivideBCDPredef4:: call GetPredefRegisters DivideBCD:: xor a ldh [hDivideBCDBuffer], a ldh [hDivideBCDBuffer+1], a ldh [hDivideBCDBuffer+2], a ld d, $1 .mulBy10Loop ; multiply the divisor by 10 until the leading digit is nonzero ; to set up the standard long division algorithm ldh a, [hDivideBCDDivisor] and $f0 jr nz, .next inc d ldh a, [hDivideBCDDivisor] swap a and $f0 ld b, a ldh a, [hDivideBCDDivisor+1] swap a ldh [hDivideBCDDivisor+1], a and $f or b ldh [hDivideBCDDivisor], a ldh a, [hDivideBCDDivisor+1] and $f0 ld b, a ldh a, [hDivideBCDDivisor+2] swap a ldh [hDivideBCDDivisor+2], a and $f or b ldh [hDivideBCDDivisor+1], a ldh a, [hDivideBCDDivisor+2] and $f0 ldh [hDivideBCDDivisor+2], a jr .mulBy10Loop .next push de push de call DivideBCD_getNextDigit pop de ld a, b swap a and $f0 ldh [hDivideBCDBuffer], a dec d jr z, .next2 push de call DivideBCD_divDivisorBy10 call DivideBCD_getNextDigit pop de ldh a, [hDivideBCDBuffer] or b ldh [hDivideBCDBuffer], a dec d jr z, .next2 push de call DivideBCD_divDivisorBy10 call DivideBCD_getNextDigit pop de ld a, b swap a and $f0 ldh [hDivideBCDBuffer+1], a dec d jr z, .next2 push de call DivideBCD_divDivisorBy10 call DivideBCD_getNextDigit pop de ldh a, [hDivideBCDBuffer+1] or b ldh [hDivideBCDBuffer+1], a dec d jr z, .next2 push de call DivideBCD_divDivisorBy10 call DivideBCD_getNextDigit pop de ld a, b swap a and $f0 ldh [hDivideBCDBuffer+2], a dec d jr z, .next2 push de call DivideBCD_divDivisorBy10 call DivideBCD_getNextDigit pop de ldh a, [hDivideBCDBuffer+2] or b ldh [hDivideBCDBuffer+2], a .next2 ldh a, [hDivideBCDBuffer] ldh [hDivideBCDQuotient], a ; the same memory location as hDivideBCDDivisor ldh a, [hDivideBCDBuffer+1] ldh [hDivideBCDQuotient+1], a ldh a, [hDivideBCDBuffer+2] ldh [hDivideBCDQuotient+2], a pop de ld a, $6 sub d and a ret z .divResultBy10loop push af call DivideBCD_divDivisorBy10 pop af dec a jr nz, .divResultBy10loop ret DivideBCD_divDivisorBy10: ldh a, [hDivideBCDDivisor+2] swap a and $f ld b, a ldh a, [hDivideBCDDivisor+1] swap a ldh [hDivideBCDDivisor+1], a and $f0 or b ldh [hDivideBCDDivisor+2], a ldh a, [hDivideBCDDivisor+1] and $f ld b, a ldh a, [hDivideBCDDivisor] swap a ldh [hDivideBCDDivisor], a and $f0 or b ldh [hDivideBCDDivisor+1], a ldh a, [hDivideBCDDivisor] and $f ldh [hDivideBCDDivisor], a ret DivideBCD_getNextDigit: ld bc, $3 .loop ld de, hMoney ; the dividend ld hl, hDivideBCDDivisor push bc call StringCmp pop bc ret c inc b ld de, hMoney+2 ; since SubBCD works starting from the least significant digit ld hl, hDivideBCDDivisor+2 push bc call SubBCD pop bc jr .loop 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