title '//SKIP.MAC Transfer control in Submit file'
;
; by Gary Novasielski.
;
; 2.1	86/10/16 $$$.SUB file always on A0: for CCP+
;
; 2.0	85/10/20 accepts ";" indicating remainder of
; 	line is a comment.  C.B. Falconer
;
version	equ	21;		was 10
;
@msg	set	9
@opn	set	15
@cls	set	16
@del	set	19
@usr	set	32
query	equ	0ffh;		queries to CPM
;
cpmbase	equ	0
boot	set	cpmbase
bdos	set	boot+5
tbuff	equ	boot+80h
tpa	equ	boot+100h
ctrl	equ	' '-1;		Ctrl char mask
cr	set	ctrl and 'M'
lf	set	ctrl and 'J'
;
cpm	macro	func,operand
	if	not nul operand
	 lxi	d,operand
	endif;;		of not nul operand
	if	not nul func
	 mvi	c,@&func
	endif
	call	bdos
	endm
;
fcbs2	equ	14
fcbrc	equ	15
fcbr0	equ	33;	Offsets into File Control Blocks
fcbr1	equ	34
fcbr2	equ	35
;
	org	tpa
;
skipprog:
	jmp	pastc
;
	db	' V', version/10+'0', '.', version mod 10+'0'
	db	' Copyright (c) 1982 Gary P. Novosielski '
	db	ctrl and 'Z'
;
pastc:	lxi	h,0;		Clear HL
	dad	sp;		Get Stack Pointer value
	lxi	sp,lclstak;	Set up local stack
	push	h;		Save old SP on new stack
;	"	"
	mvi	a,query
	call	sgusr
	sta	user;		save entry user
	mvi	e,0
	cpm	usr;		rest is on user 0
	lxi	h,tbuff;	point to Command Buffer
	mov	a,m;		get count
	inr	a;		Point past end of string
	call	hlxa;		Index the pointer
	mvi	m,0;		Insist on null terminator
;	"	"
	lxi	h,tbuff+1;	base of command buffer
	call	scnb;		scan to first non-blank
	ora	a;		An argument present?
	jnz	evalarg;	Yes, evaluate it.
	cpi	';'
	jnz	evalarg;	not terminated by ; for comment
	lxi	h,1;		Else default to one
	jmp	evalexit;	Don't do the loop
;
evalarg:
	xchg;			Scan pointer to DE
	lxi	h,0;		initialize value
evaloop:
	ldax	d;		Get character
	ora	a;		Terminator?
	jz	evalexit;	exit loop
	cpi	';'
	jz	evalexit;	rest of line is comment
;	"	"
	call	isnum;		Test range 0-9 ASCII
	jc	notnum;		argument not numeric
	sui	'0';		Make it binary
;	"	"
;	Multiply current value in HL by 10
	mov	b,h
	mov	c,l
	dad	b;	*2
	dad	h;	*4
	dad	b;	*5
	dad	h;	*10
;	"	"
;	Add in new value from A
	call	hlxa
;	"	"
	inx	d;		bump argument pointer
	jmp	evaloop
;
; Range test.  Must be 1-127
evalexit:
	mov	a,l
	ani	080h
	ora	h
	jnz	rangerr
	ora	l
	jz	exit;		Skip 0 lines = do nothing
;	"	"
; OK so far. Now skip over (L) lines in the .SUB file
	push	h;		Save the value
	cpm	opn,subfile;	Open the $$$.SUB file.
	pop	d;		Restore the value
;	"	"
	inr	a;		Test return code.
	jz	suberr;		Not within a .SUB file??
	lxi	h,subfile+fcbrc; Record counter for the extent
	mov	a,m
;	"	"
	sub	e;		Reduce by number skipped and
	jc	nelerr;		 (Not enough lines remaining)
;	"	"
	mov	m,a;		 put back into the FCB
	xra	a;		And a zero goes into
	sta	subfile+fcbs2;	the S2 byte to mark file altered
	cpm	cls,subfile;	Write change to directory.
	inr	a;		Trouble?
	jz	suberr
;	"	"
; Ok, all finished.
exit:	call	suser;		restore entry user
	pop	h;		Old SP
	sphl;			Restore Stack
	ret;			to Console Command Processor
;
suberr:	call	abend
	db	'Error accessing .SUB file.'
	db	'$'
;
; Argument is not numeric
notnum:	call	abend
	db	'//SKIP argument not numeric.'
	db	'$'
;
rangerr:
nelerr:	call	abend
	db	'//SKIP argument exceeds file size.'
	db	'$'
;
abend:	pop	d;		Message address
	cpm	msg;		Send to console
	cpm	del,subfile;	Abort the jobstream
	cpm	msg,cancel
	call	suser;		restore entry user
	jmp	boot
;
cancel:	db	'...CANCELED'
	db	'$'
;
;
; Utility subroutines
;
; set user #
suser:	lda	user
;	"	"
; set/get user #
sgusr:	mov	e,a
	cpm	usr
	ret
;
; Index HL by the value of A. Returned flags not defined
; a,f,h,l
hlxa:	add	l
	mov	l,a
	adc	h
	sub	l
	mov	h,a
	ret
;
; Scan over leading blanks. Return char in A
; a,f,h,l
scnb:	mov	a,m
	cpi	' '
	rnz
	inx	h
	jmp	scnb
;
; Return carry set if not ASCII decimal char 0-9.
; f
isnum:	cpi	'0'
	rc
	cpi	'9'+1
	cmc
	ret
;
user:	db	0;		User # at entry
;
subfile:	
	db	1;		Drive A:
	db	'$$$     SUB'
	db	0,0,0,0
	ds	subfile-$+36
;
	ds	48
lclstak	equ	$
;
	end	skipprog