nulbuf.src

        .messg "nulbuf"
        .subttl "nulbuf"
        .page  
;set nul recs in act-buf for exten
;in: nr=last rec in previous buf
;out: nr=last rec for next nulbuf/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