Move more code from home.asm to home/

home/print_bcd.asm

@@ -0,0 +1,77 @@
+; 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