strlen.s

linux 的引导程序源码The Microsoft&reg Windows&reg Software Development Kit (SDK) provides the documentation

; strlen.S
;
; Copyright 2000 John Coffman.
; All rights reserved.
;
;
; strlen:  find length of a string
;	enter with:
;		DS:BX = pointer to string
;
;	return with:
;		AX = length of string
;
strlen:
	mov	ax,bx
strlen1:
	test	byte (bx),#0xFF
	jz	strlen2
	inc	bx
	jmp	strlen1
strlen2:
	sub	bx,ax
	xchg	ax,bx
	ret

; end strlen.S