.sect .text; .sect .rom; .sect .data; .sect .bss
.sect .text
.define .inn

	! #bytes in cx
	! bit # in ax
.inn:
	xor     dx,dx
	mov     bx,8
	div     bx
	mov     bx,sp
	add	bx,2
	add     bx,ax
	cmp     ax,cx
	jae     1f
	movb	al,(bx)
	mov	bx,dx
	testb   al,bits(bx)
	jz      1f
	mov	ax,1
	jmp	2f
1:
	xor	ax,ax
2:
	pop	bx
	add     sp,cx
	! ax is result
	jmp     bx

	.sect .data
bits:
	.data1 1,2,4,8,16,32,64,128
