Fix return value of strcmp and strncmp, optimize strncmp loop

lib/libc/strcmp.src

@@ -1,5 +1,7 @@
 ; (c) Copyright 2007-2008 Zilog, Inc.
 ;   int strcmp(register char *s1, register char *s2)
+; Changed to remove bug of typecasting difference value to signed char - should be difference of unsigned chars
+; Brendan Fletcher 19/03/2024
 
 	assume 	ADL=1
 
@@ -14,22 +16,19 @@ _strcmp:
 	inc	hl
 	ld	hl, (hl)
 
-_loop:
+.loop:
 	ld	a, (de)
 	or	a, a
-	jr	z, _done
+	jr	z, .done
 	cpi
 	inc	de
-	jr	z, _loop
+	jr	z, .loop
 
 	dec	hl
-_done:
+.done:
 	sub	a, (hl)
-
-	ld	b, a
-	rla
 	sbc	hl, hl
-	ld	l, b
+	ld	l, a
 	ret
 
 

lib/libc/strncmp.src

@@ -1,44 +1,39 @@
 ; (c) Copyright 2007-2008 Zilog, Inc.
 ;   int strncmp(char *s1,char *s2,size_t n)
+; Changed to remove bug of typecasting difference value to signed char - should be difference of unsigned chars
+; Brendan Fletcher 19/03/2024
 
 	ASSUME 	ADL=1
 
 	section	.text
 	public	_strncmp
 _strncmp:
-	ld		iy,	0
-	add		iy,	sp
-
-	ld		bc, (iy+9)
-	ld		a,	(iy+11)
-	or		a,	c
-	or		a,	b
-	jr		z,	_done		; n==0 ? return(0)
-
-	ld		hl,	(iy+6)
-	ld		de,	(iy+3)
-
-_cloop:
-	ld		a,	(de)
+	ld	iy, 0
+	add	iy, sp
+
+	ld	bc, (iy+9)
+	ld	a, (iy+11)
+	or	a, c
+	or	a, b
+	jr	z, .done	; n==0 ? return(0)
+
+	ld	hl, (iy+6)
+	ld	de, (iy+3)
+
+.cloop:
+	ld	a, (de)
+	or	a, a
+	jr	z, .diffnul	; return the difference value if *s1=='\0'
 	cpi
-	jr		nz,	_diff		; return the difference value if mismatch occurs
-	jp		po, _done		; if all the chars over then return(0)
-	or		a,	a
-	jr		z,	_done		; if *s1=='\0'	return(0)
-	inc		de
-	jr		_cloop
-
-_diff:
-	dec		hl
-	sub		a, (hl)
-	ld		b,	a
-	rla
-	sbc		hl,	hl
-	ld		l,	b
+	jr	nz, .diff	; return the difference value if mismatch occurs
+	inc	de
+	jp	pe, .cloop	; if all the chars not over then loop
+
+.diff:
+	dec	hl
+.diffnul:
+	sub	a, (hl)
+.done:
+	sbc	hl, hl
+	ld	l, a
 	ret
-
-_done:
-	or		a,	a
-	sbc		hl,	hl
-	ret
-