nulbuf.src

	.page
	.subttl  nulbuf
;*********************************
;* nulbuf: set null records in   *
;*         act-buf for extention *
;*    vars:  nr,rs,lx,act-buf    *
;*      in: nr= last record      *
;*          position in previous *
;*          buffer.              *
;*     out: nr= last record      *
;*          position in buffer   *
;*          for next nulbuf or   *
;*          to set lstchr.       *
;*********************************

nulbuf	jsr  set00      ;set indirect ptr
	ldy  #2
	lda  #0

nb10	sta  (dirbuf),y	;clear buffer
	iny
	bne  nb10

	jsr  addnr      ;advance nr

nb20	sta  nr,x
	tay
	lda  #$ff
	sta  (dirbuf),y	;init record w/ cr
	jsr  addnr
	bcc  nb20       ;not done

	bne  nb30
	lda  #0
	sta  nr,x
nb30	rts


; add rs & nr, leave in accum
; c=1: cross buffer boundary

addnr	ldx  lindx
	lda  nr,x
	sec
	beq  an05

	clc
	adc  rs,x
	bcc  an10
	bne  an05
	lda  #2
	bit  er00
	rts

an05	adc  #1		;adjust for link
	sec
an10	rts


;	.end