Add original unix v6

source/s2/rew.s

@@ -0,0 +1,47 @@
+/ rew -- rewind dec/mag tape
+
+	cmp	(sp)+,$2
+	blt	1f
+	tst	(sp)+
+	mov	(sp)+,r0
+	movb	(r0)+,r1
+	cmp	r1,$'m
+	beq	rewm
+	movb	r1,tapx+8
+	tstb	(r0)
+	bne	error
+1:
+	sys	open; tapx; 0
+	br	rew
+
+rewm:
+	movb	(r0)+,r1
+	beq	1f
+	movb	r1,mtx+7
+	tstb	(r0)
+	bne	error
+1:
+	sys	open; mtx; 0
+
+rew:
+	bes	error
+	sys	read; word; 2
+	bes	error
+	sys	exit
+
+error:
+	mov	$1,r0
+	sys	write; 0f; 2
+	sys	exit
+0:
+	<?\n>
+
+tapx:
+	</dev/tap0\0>
+mtx:
+	</dev/mt0\0>
+	.even
+
+.bss
+word:	.=.+2
+