Length of 0-terminate str

; Length of 0-terminate string
; IN:
; Stack par - Addr of string
; RETURN:
; Al - length
Length:
        ; In bx - Addr in stack
        push    bx
        mov     bx, sp
        add     bx, 4
        mov     bx, [ss:bx]
        ; Find pos of 0
        push    di
        mov     di, bx
        mov     al, 0
        repne   scasb
        sub     di, bx
        mov     ax, di
        dec     ax
        pop     di
        pop     bx
        ret     2