.title	scopy
;
; call scopy( a, b, [len], [ierr] )
; reverse assemled RT-11 scopy
;
	.psect	user$i
scopy::
	mov	r1,-(sp)
	mov	r2,-(sp)
	mov	r3,-(sp)

	mov	(r5)+,r3		; r3 = nargs
	mov	(r5)+,r1		; r1 = 1st address
	mov	(r5)+,r2		; r2 = 2nd address

	cmpb	#2,r3			; 2 args ??
	beq	40$			; br, if yes, copy until null
	cmp	#-1,(r5)		; default argument ??
	beq	40$			; br, if yes

	mov	@(r5)+,r4		; r4 = len
	beq	20$			; br, if 0
10$:	movb	(r1)+,(r2)+		; copy byte
	beq	30$			; br, if null
	dec	r4			; otherwise keep on going
	bgt	10$

20$:	clrb	(r2)+			; null terminate o/p string
	cmpb	#4,r3			; 4 args ??
	bhi	30$			; if more than 4, exit
	cmp	#-1,(r5)		; default argument ??
	beq	30$			; br, if yes
	tstb	(r1)			; null ??
	beq	30$			; br, if yes
	movb	#-1,@(r5)+		; return -1, truncated flag

30$:	mov	(sp)+,r3
	mov	(sp)+,r2
	mov	(sp)+,r1
	return

40$:	movb	(r1)+,(r2)+		; copy, including null
	bne	40$
	br	30$

	.end