; memrev(void *data, size_t len)
_memrev:
	ld iy, -3
	add iy, sp
	ld bc, (iy + 9)
	ld hl, (iy + 6)
	add hl, bc
	ld de, (iy + 6)
	inc bc
	res 0, c
.loop:
	ld a, (de)
	dec bc
	dec hl
	ldi
	ld (hl), a
	dec hl
	jp po, .loop
	ret