; -- strlen(s) returns the length of null terminated string s
;    version 2, using pointer incrementing to advance through string

STRLEN:	; expects R3 = s, a pointer to a string
	; returns R3 = i, the length of s
	; uses    R5 = s[i], successive values
	;         R6 = i, during the code

	LIS	R6,0		; i = 0
STRLLP:				; loop {
	LOADS	R5,R3		;   -- get word holding *s
	EXTB	R5,R5,R3	;   -- get *s
	BZS	STRLQT		;   if (*s == 0) break

	ADDSI	R6,1		;   i = i + 1
	ADDSI	R3,1		;   s++

	BR	STRLLP
STRLQT:				; }
	MOVE	R3,R6		; -- move return value into place
	JUMPS	R1		; return i