;
; Christian Groessler, 10.02.2009
; derived from strncmp.s and stricmp.s
;
; int __fastcall__ strnicmp (const char* s1, const char* s2, size_t count);
; int __fastcall__ strncasecmp (const char* s1, const char* s2, size_t count);
;

	.export		_strnicmp, _strncasecmp
	.import		popax, __ctype
	.importzp	ptr1, ptr2, ptr3, tmp1

        .include        "ctype.inc"

_strnicmp:
_strncasecmp:

; Convert the given counter value in a/x from a downward counter into an
; upward counter, so we can increment the counter in the loop below instead
; of decrementing it. This adds some overhead now, but is cheaper than
; executing a more complex test in each iteration of the loop. We do also
; correct the value by one, so we can do the test on top of the loop.

	eor	#$FF
	sta	ptr3
	txa
	eor	#$FF
	sta	ptr3+1

; Get the remaining arguments

       	jsr	popax 	     	; get s2
     	sta	ptr2
     	stx	ptr2+1
     	jsr	popax 	     	; get s1
     	sta	ptr1
     	stx	ptr1+1

; Loop setup

     	ldy	#0

; Start of compare loop. Check the counter.

Loop:  	inc	ptr3
	beq	IncHi		; Increment high byte

; Compare a byte from the strings

Comp:	lda   	(ptr2),y
	tax
	lda	__ctype,x      	; get character classification
       	and    	#CT_LOWER      	; lower case char?
	beq	L1	       	; jump if no
	txa		       	; get character back
	sec
	sbc	#<('a'-'A')     ; make upper case char
	tax		 	;
L1:	stx    	tmp1   	       	; remember upper case equivalent

	lda	(ptr1),y 	; get character from first string
	tax
	lda	__ctype,x	; get character classification
	and	#CT_LOWER       ; lower case char?
       	beq    	L2	 	; jump if no
	txa	  	 	; get character back
	sec
       	sbc    	#<('a'-'A')     ; make upper case char
	tax

L2:	cpx	tmp1	 	; compare characters
       	bne    	NotEqual 	; Jump if strings different
	txa   	  	 	; End of strings?
       	beq    	Equal1 	       	; Jump if EOS reached, a/x == 0

; Increment the pointers

      	iny
      	bne   	Loop
      	inc   	ptr1+1
      	inc   	ptr2+1
      	bne   	Loop  	      	; Branch always

; Increment hi byte

IncHi:	inc	ptr3+1
       	bne    	Comp  		; Jump if counter not zero

; Exit code if strings are equal. a/x not set

Equal:	lda	#$00
      	tax
Equal1:	rts

; Exit code if strings not equal

NotEqual:
      	bcs	L3
      	ldx	#$FF		; Make result negative
      	rts

L3:   	ldx	#$01		; Make result positive
      	rts