;
;   swap.a
;
;   swap (s1, s2, len)
;	  A0  A1  D0
;	  4   8   12
;
;   swap two regions of memory
;
;   this routine looks a bit like CMPMEM.A from DICE, because I took it
;   from there :-)
;

		section text,code

		xdef	_swapmem
		xdef	@swapmem

_swapmem:	move.l	4(sp),A0
		move.l	8(sp),A1
		move.l	12(sp),D0

@swapmem:	cmp.l	A0,A1
		bne	w2

		rts

w2:		movem.l D2/D3,-(sp)

		move.l	D0,D1
		move.w	A0,D0
		lsr.l	#1,D0
		bcs	swapbyte
		move.w	A1,D0
		lsr.l	#1,D0
		bcs	swapbyte

		move.l	D1,D0
		lsr.l	#2,D0

		subq.l	#1,D1
		bcs	w1

loop:		move.l	(A0),D2
		move.l	(A1),D3
		move.l	D2,(A0)+
		move.l	D3,(A1)+
		dbf	D1,loop
		sub.l	#$10000,D1
		bcc	loop

w1:		move.l	D0,D1
		and.l	#3,D1

swapbyte:	subq.l	#1,D1
		bcs	end

loop2:		move.b	(A0),D2
		move.b	(A1),D3
		move.b	D2,(A0)+
		move.b	D3,(A1)+
		dbf	D1,loop2
		sub.l	#$10000,D1
		bcc	loop2

end:		movem.l (sp)+,D2/D3
		rts

		END