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; 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
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