Add original unix v6

source/s3/ttyn.s

@@ -0,0 +1,57 @@
+/ return name of current tty
+
+.globl	ttyn, _ttyn
+
+_ttyn:
+	mov	r5,-(sp)
+	mov	sp,r5
+	mov	4(r5),r0
+	jsr	pc,1f
+	mov	(sp)+,r5
+	rts	pc
+
+ttyn:
+	clr	r0
+1:
+	mov	$'x,name
+	tst	-(sp)
+	sys	fstat; buf
+	bes	er1
+	mov	buf+2,(sp)
+	sys	open; dev; 0
+	bes	er1
+	mov	r0,r1
+1:
+	mov	r1,r0
+	sys	read; buf; 16.
+	bes	er
+	cmp	r0,$16.
+	bne	er
+	mov	$buf,r0
+	cmp	(r0)+,(sp)
+	bne	1b
+	cmp	(r0)+,$"tt
+	bne	1b
+	cmpb	(r0)+,$'y
+	bne	1b
+	tstb	(r0)+
+	beq	1b
+	cmpb	(r0),$'\0
+	bne	1b
+	movb	-(r0),name
+
+er:
+	mov	r1,r0
+	sys	close
+
+er1:
+	tst	(sp)+
+	movb	name,r0
+	rts	pc
+
+.data
+dev:	</dev\0>
+.even
+.bss
+buf:	.=.+40.
+name:	.=.+2