set.s

来自「操作系统源代码」· S 代码 · 共 44 行

.define .set
.text

	! #bytes in cx
	! bit # in ax
.set:
	pop     bx              ! return address
	xor     dx,dx
!ifdef create set
	sub	sp,cx
	push	bx
	push	di
	mov     bx,sp
	xor	di,di
	sar	cx,#1
1:
	mov     4(bx)(di),dx
	inc	di
	inc	di
	loop	1b
!endif
	mov     bx,#8
	div     bx
	cmp     ax,di
	jae     2f
	mov	di,dx
	movb	dl,bits(di)
	mov     di,sp
	add     di,ax
	orb     4(di),dl
	pop	di
	ret
2:
ESET = 2
.extern .error
	pop	di
	mov     ax,#ESET
	call	.error
	ret

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