; Simple libc implementation for the SuB Suite

strtoull:
	phy.w		; Preserve Y.
	and #0		; Reset A.
	tay		; Reset Y.
	pha.q		; Reset the value buffer.
@loop:
	lda (sp+20), y	; Get a character from the string.
	pha		; Preserve the character.
	jsr isdigit	; Is this character, a digit?
	pla		; Get the character back.
	bne @digit	; Yes, so extract the value from it.
	jsr tolower	; No, so convert the character to lowercase.
	pha		; Preserve the character.
	jsr islower	; Is this an alphabetical character?
	pla		; Get the character back.
	beq @end	; No, so we're done.
@alpha:
	sec		; Yes, so prepare for a non borrowing subtract.
	sbc #'a'-10	; Get the numeric value from this digit.
	bra @chkbase	; Check if the value matches the base.
@digit:
	sec		; Prepare for a non borrowing subtract.
	sbc #'0'	; Get the numeric value from this digit.
@chkbase:
	cmp sp+19	; Does the value match the base?
	bcs @end	; No, so we're done.
@addval:
	tab		; Save the digit value.
	lda.q sp+1	; Get the value from the value buffer.
	mul sp+19	; Multiply the value by the base.
	clc		; Prepare for a non carrying add.
	aab		; Add the digit value to the total value.
	sta.q sp+1	; Place the value in the value buffer.
	iny		; Increment the string index.
	and #0		; Reset A.
	bra @loop	; Keep looping.
@end:
	pla.q		; Get the value buffer back.
	ply.w		; Get Y back.
	ldb #0		; Reset B.
	rts		; End of strtoull.


strlen:
	pha.q		; Set the temp variable to the argument.
	ldb #0		; Reset B.
	tba		; Reset A.
	tax		; Reset X.
	phy.w		; Preserve Y.
	txy		; Reset Y.
@loop:
	lda (sp+3), y	; Are we at the end of the string?
	beq @end	; Yes, so we're done.
	iny		; No, so increment the index.
	bra @loop	; Keep looping.
@end:
	tyx		; Return the length in X.
	ply.w		; Get the preserved value back.
	pla.q		; Get the argument back.
	txa		; Get the return value.
	rts		; End of strlen.


strcmp:
	ldb #0		; Reset B.
	tba		; Reset A.
	phy.w		; Preserve Y.
	tay		; Reset Y.
@loop:
	ldb #0		; Set the islong flag to false.
	lda (sp+19), y	; Are we at the end of the first string?
	beq cmpr	; Yes, so check if we're too short, or too long.
	ldb #1		; No, so set the islong flag to true.
	cmp (sp+11), y	; Is the character of both strings, the same?
	bne cmpr	; No, so check if we're too short, or too long.
	iny		; Yes, so increment the index.
	bra @loop	; Keep looping.

strccmp:
strcasecmp:
	ldb #0		; Reset B.
	tba		; Reset A.
	phy.w		; Preserve Y.
	tay		; Reset Y.
@loop:
	ldb #0		; Set the islong flag to false.
	lda (sp+19), y	; Are we at the end of the first string?
	beq cmpr	; Yes, so check if we're too short, or too long.
	ldb #1		; No, so set the islong flag to true.
	jsr tolower	; Convert the character of string 1 to lowercase.
	phb		; Preserve the islong flag.
	pha		; Preserve the converted character.
	lda (sp+13), y	; Get the character of the second string.
	jsr tolower	; Convert the character of string 2 to lowercase.
	tab		; Place it in B.
	pla		; Get the character of string 1 back.
	cab		; Is the character of both strings, the same?
	plb		; Get the islong flag back.
	bne cmpr	; No, so check if we're too short, or too long.
	iny		; Yes, so increment the index.
	bra @loop	; Keep looping.

cmpr:
	lda (sp+11), y	; Are we at the end of the second string?
	beq @islong	; Yes, so check the islong flag.
@isshort:
	lda (sp+19), y	; No, but are we at the end of the first string?
	beq @short	; Yes, so return -1.
@islong:
	cpb #1		; Is the islong flag true?
	bne @equ	; No, so return 0.
@long:
	lda #1		; Yes, so return 1.
	bra @end	; We are done.
@equ:
	lda #0		; Return 0.
	bra @end	; We are done.
@short:
	lda #$FF	; Return -1.
@end:
	ply.w		; Get the preserved value back.
	rts		; End of cmpr.


isdigit:
	sec		; Prepare for a non carrying subtraction.
	sbc #'0'	; Subtract $30 from the passed character.
	and #$FF	; Make sure that we have only one byte.
	cmp #10		; Is the subtracted value, less than 10?
	bcs @false	; No, so return false.
@true:
	lda #1		; Yes, so return true.
	bra @end	; We are done.
@false:
	lda #0		; Return false.
@end:
	rts		; End of isdigit.

isxdigit:
	pha		; Preserve the character.
	jsr isdigit	; Is this character, a decimal digit?
	pla		; Get the character back.
	bne @true	; Yes, so return true.
@alpha:
	sec		; No, so prepare for a non carrying subtract.
	ora #$20	; Convert it to lowercase.
	sbc #'a'	; Subtract $61 from the character.
	and #$FF	; Make sure that we have only one byte.
	cmp #6		; Is the subtracted value, less than 6?
	bcs @false	; No, so return false.
@true:
	lda #1		; Yes, so return true.
	bra @end	; We are done.
@false:
	lda #0		; Return false.
@end:
	rts		; End of isxdigit.


isupper:
	sec		; Prepare for a non carrying subtraction.
	sbc #'A'	; Subtract $41 from the passed character.
	bra isletter	; Check if it's less than 26.
islower:
	sec		; Prepare for a non carrying subtraction.
	sbc #'a'	; Subtract $61 from the passed character.
isletter:
	and #$FF	; Make sure that we have only one byte.
	cmp #26		; Is the subtracted value, less than 26?
	bcs @false	; No, so return false.
@true:
	lda #1		; Yes, so return true.
	bra @end	; We are done.
@false:
	lda #0		; Return false.
@end:
	rts		; End of isletter.


tolower:
	pha		; Preserve the character.
	jsr isupper	; Is this character, an uppercase character?
	pla		; Get the character back.
	beq @end	; No, so we're done.
@lower:
	ora #$20	; Yes, so convert it to lowercase.
@end:
	rts		; End of tolower.


toupper:
	pha		; Preserve the character.
	jsr islower	; Is this character, a lowercase character?
	pla		; Get the character back.
	beq @end	; No, so we're done.
@upper:
	and #$5F	; Yes, so convert it to uppercase.
@end:
	rts		; End of toupper.