diffset.asm

来自「汇编编程艺术」· 汇编 代码 · 共 52 行

StdGrp		group	stdlib,stddata
stddata		segment	para public 'sldata'
stddata		ends
;
stdlib		segment	para public 'slcode'
		assume	cs:stdgrp
;
;
; difference-	Computes the difference of one set with another.
;
; inputs:
;
;	ES:DI-  Points at the destination set (at its mask byte).
;	DX:SI-	Points at the mask byte of the source set.
;
;
;
		public	sl_difference
;
sl_difference	proc	far
		push	ds
		push	ax
		push	cx
		push	si
		push	di
		mov	ds, dx
;
		mov	al, es:[di]		;Get mask bytes
		not	al
		mov	ah, [si]
		add	si, 8			;Skip to start of set
                add	di, 8
		mov	cx, 256
DifLp:		test	ah, [si]
		jz	Next
		and	es:[di], al
Next:		inc	si
		inc	di
		loop	DifLp
;
		pop	di
		pop	si
		pop	cx
		pop	ax
		pop	ds
		ret
sl_difference	endp
;
;
stdlib		ends
		end