ref: 6fa8a553cbb53a9abe59bee8d0cc176d19cde47f
dir: /home/print_bcd.asm/
; function to print a BCD (Binary-coded decimal) number ; de = address of BCD number ; hl = destination address ; c = flags and length ; bit 7: if set, do not print leading zeroes ; if unset, print leading zeroes ; bit 6: if set, left-align the string (do not pad empty digits with spaces) ; if unset, right-align the string ; bit 5: if set, print currency symbol at the beginning of the string ; if unset, do not print the currency symbol ; bits 0-4: length of BCD number in bytes ; Note that bits 5 and 7 are modified during execution. The above reflects ; their meaning at the beginning of the functions's execution. PrintBCDNumber:: ld b, c ; save flags in b res 7, c res 6, c res 5, c ; c now holds the length bit 5, b jr z, .loop bit 7, b jr nz, .loop ld [hl], "¥" inc hl .loop ld a, [de] swap a call PrintBCDDigit ; print upper digit ld a, [de] call PrintBCDDigit ; print lower digit inc de dec c jr nz, .loop bit 7, b ; were any non-zero digits printed? jr z, .done ; if so, we are done .numberEqualsZero ; if every digit of the BCD number is zero bit 6, b ; left or right alignment? jr nz, .skipRightAlignmentAdjustment dec hl ; if the string is right-aligned, it needs to be moved back one space .skipRightAlignmentAdjustment bit 5, b jr z, .skipCurrencySymbol ld [hl], "¥" inc hl .skipCurrencySymbol ld [hl], "0" call PrintLetterDelay inc hl .done ret PrintBCDDigit:: and $f and a jr z, .zeroDigit .nonzeroDigit bit 7, b ; have any non-space characters been printed? jr z, .outputDigit ; if bit 7 is set, then no numbers have been printed yet bit 5, b ; print the currency symbol? jr z, .skipCurrencySymbol ld [hl], "¥" inc hl res 5, b .skipCurrencySymbol res 7, b ; unset 7 to indicate that a nonzero digit has been reached .outputDigit add "0" ld [hli], a jp PrintLetterDelay .zeroDigit bit 7, b ; either printing leading zeroes or already reached a nonzero digit? jr z, .outputDigit ; if so, print a zero digit bit 6, b ; left or right alignment? ret nz inc hl ; if right-aligned, "print" a space by advancing the pointer ret