erkyrath.infocom-zcode-terps/acorn/machine.asm

	PAGE
	SBTTL 'MACHINE DEPENDENT I/O'

GETKEY:	TXA			;SAVE X AND Y
	PHA
	TYA
	PHA

GKEY0:	JSR OSRDCH		;GET A CHAR

	;CHECK TO MAKE SURE KEY IS VALID, ONLY ACCEPT IT IF IT IS

GKEY3:	AND #$7F		;SCREEN OUT SHIFTS

	CMP #EOL		;CHECK FOR GOOD (BAD) CHAR
	BEQ OK
	CMP #BACKSP
	BEQ OK
	CMP #SPACE
	BCC BADKEY		;IF < SPACE, BAD
	CMP #$40		;@
	BEQ BADKEY

	CMP #$25		;%
	BCC OK			;BELOW RANGE
	CMP #$27		;'
	BEQ OK			;GOOD CHAR
	CMP #$2C			;+ +1
	BCS MASK0		;NOT IN THIS GROUP, TRY OTHER

	ORA #$10		;SET BIT 4, CHANGE %&()*+ TO 5689:;
				;(FROM BAD TO GOOD CHAR AS SAME KEY LOCATION)
	JMP OK			;GOOD, DONE NOW

MASK0:	CMP #$3C		;<
	BCC OK			;LESS
	CMP #$3F		;> +1
	BCS MASK1		;OK, GO DO LETTERS

	AND #$2F		;CLEAR BIT 4, CHANGE <=> TO ,-.
	BNE OK			;BRANCH ALWAYS, DONE

MASK1:	CMP #'z'+1
	BCS BADKEY		;IF > BAD
	CMP #'a'	
	BCS OK			;IF > OK
	CMP #'Z'+1
	BCC OK			;IF < OK

BADKEY:	JSR BOOP		;BAD KEY, GIVE WARNING NOISE
	JMP GKEY0		;TRY AGAIN

OK:	STA IOCHAR		;HOLD ON TO IT

	ADC RAND1
	STA RAND2
	LSR A
	STA RAND1

	PLA
	TAY
	PLA
	TAX
	LDA IOCHAR		;RETRIEVE IT
	RTS

BOOP:	LDA #BELL		;(DOES NOT WORK, STOLE SOUND GENERATION MEMORY)
	JSR OSWRCH
	RTS


	;PUT A CHAR TO SCREEN (PHYSICALLY), HANDLE EOL, SCROLLING IF NECESSARY

CHAR:	STA IOCHAR		;PRESERVE X,Y SAVE A TO USE
	TXA
	PHA
	TYA
	PHA

	LDA #RDCPOS		;READ TEXT CURSOR POS.
	JSR OSBYTE		;GIVES X,Y

	LDA IOCHAR
	CMP #EOL
	BEQ OUTEOL		;EOL = SPECIAL HANDLING

	CMP #BACKSP		;IF DEL CHAR DON'T SCROLL
	BEQ NOSCRL

	CPY #YSIZE-1		;ON LAST SCREEN LINE?
	BCC NOSCRL		;NO, NO SCROLL NEEDED
	CPX #XSIZE		;LAST CHAR ON LINE?
	BCC NOSCRL		;NO, NO SCROLL YET

DOSCRL:	LDA #11			;MOVE CURSOR UP 1 LINE
	JSR VDU			;FOR ALIGNMENT AFTER SCROLL

	LDX #1			;START TRANSFERING FROM LINE 1
SRL0:	CPX #YSIZE
	BEQ SRL2

	LDA LOLINE,X		;GET ADDR OF DEST LINE
	STA LTO+LO		;INTO [LTO]
	LDA HILINE,X
	STA LTO+HI

	INX			;NEXT LINE
	LDA LOLINE,X		;GET ADDR OF SOURCE LINE
	STA LFROM+LO		;INTO [LFROM]
	LDA HILINE,X
	STA LFROM+HI

	LDY #XSIZE
SRL1:	LDA (LFROM),Y		;MOVE SOURCE LINE
	STA (LTO),Y		;TO DEST LINE
	DEY
	BPL SRL1

	BMI SRL0		;LOOP TILL X = YSIZE

SRL2:	LDX #XSIZE		;CLEAR LAST LINE 
	LDA #SPACE		;OF SCREEN RAM
SRL3:	STA SCREEN+960,X
	DEX
	BPL SRL3

	;DROP THRU TO SEND CHAR OUT NOW

NOSCRL:	LDA IOCHAR
	JSR OSWRCH		;SEND CHAR TO SCREEN
	CMP #EOL		;IF CR
	BNE NS1
	LDA #$0A		;SEND LF
	JSR OSWRCH
NS1:	PLA
	TAY
	PLA
	TAX
	LDA IOCHAR
	RTS

OUTEOL:	CPY #YSIZE-1		;LAST LINE ON SCREEN?
	BCC NOSCRL		;NO
	BCS DOSCRL		;YES, SO SCROLL

;*******

INPUT:  ;FETCH A LINE OF INPUT FOR READ RTN

	;ENTRY: ABS ADDR OF READ BUFFR IN ARG1
	;EXIT: # CHARS READ IN A

	JSR LINOUT		;FLUSH LBUFF
	LDY #0
	STY LINCNT		;RESET LINE COUNT

INLOOP:	JSR GETKEY		;GET ASCII INTO A
	CMP #EOL		;<RET>?
	BEQ ENDLIN		;LINE DONE IF SO
	CMP #BACKSP		;BACKSPACE?
	BEQ BACKUP		;SPECIAL HANDLING

	STA LBUFF,Y		;ELSE ADD CHAR TO INPUT BUFFR
	INY			;NEXT POSITION IN LINE

SHOWIT:	JSR CHAR		;DISPLAY CHAR
	CPY #77			;2 SCREEN LINES FULL?
	BCC INLOOP		;NO, KEEP GOING

	;HANDLE LINE OVERFLOW
NOMORE:	JSR GETKEY
	CMP #EOL		;IF EOL, WRAP UP THE LINE
	BEQ ENDLIN
	CMP #BACKSP		;BACKSPACE OK TOO
	BEQ BACKUP
	JSR BOOP		;ELSE COMPLAIN
	JMP NOMORE		;AND INSIST

	;HANDLE BACKSPACE
BACKUP:	DEY			;BACKUP THE POINTER
	BPL SHOWIT		;SEND BS IF NOT START OF LINE
	JSR BOOP		;ELSE SAY BAD
	LDY #0			;RESET POINTER
	BEQ INLOOP		;AND TRY AGAIN

	;END OF LINE
ENDLIN:	STA LBUFF,Y		;PLACE IN BUFFER
	INY			;UPDATE INDEX
	STY LINLEN		;SAVE FOR "READ"
	STY PRLEN		;AND "PRINT"
	JSR CHAR		;SEND EOL TO SCREEN

	;MOVE LBUFF TO ARG1 W/LOWER CASE CONVERSION
LEX1:	LDA LBUFF-1,Y		;GET A CHAR FROM LBUFF
	CMP #'A'		;IF CHAR IS ALPHA
	BCC LEX2		;CONVERT TO LOWER CASE
	CMP #'Z'+1
	BCS LEX2
	ADC #$20
LEX2:	STA (ARG1),Y		;MOVE CHAR TO INPUT BUFF AT ARG1
	DEY			;LOOP TILL ALL CHARS MOVED
	BPL LEX1

	JSR PPRINT		;SCRIPT LBUFF IF ENABLED

	LDA LINLEN		;RESTORE # CHARS
	RTS			;INTO A

DLINE:  ;DISPLAY A STRING
	;ENTRY:  STRING ADDR  X=LSB A=MSB
	;        STRING LENGTH IN Y

	STX STRNG+LO		;DROP STRING ADDRESS
	STA STRNG+HI		;INTO DUMMY BYTES
	LDX #0			;INIT INDEX

DOUT:	DB $BD			;6502 "LDA nnnn,X" OPCODE
STRNG:	DW $0000		;DUMMY OPERAND BYTES
	JSR CHAR
	INX			;NEXT CHAR
	DEY			;DECREMENT CHAR COUNT
	BNE DOUT		;LOOP TILL OUT OF CHARS
	RTS


	;CLEAR SCREEN

CLS:	LDA	#HIGH SCREEN
	STA	I+HI
	LDA	#0
	STA	I+LO
	TAY
	LDX	#$04
CLS0:	STA	(I),Y
	INY
	BNE	CLS0
	INC	I+HI
	DEX
	BNE	CLS0

	LDA #MVTXC		;ALIGN CURSOR AT 
	JSR VDU			;TOP OF SCREEN
	LDA #0			;COL 0
	JSR VDU
	LDA #1			;TOP LINE
	JMP VDU

	;*****
	;PRINT ON PRINTER
	;*****

PPRINT:	LDA SCRIPT		;SCRIPTING INTERNALLY ENABLED?
	BEQ PEX			;NO, LEAVE
	LDA ZBEGIN+ZSCRIP+1	;CHECK SCRIPT FLAG
	AND #%00000001		;SCRIPTING ON?
	BEQ PEX			;NO, LEAVE

	LDA #OUTSTR		;SET OUTPUT STREAM
	LDX #2			;TO PRINTER
	JSR OSBYTE
	LDA #IGNORE		;SET TO PRINT
	LDX #0			;LINE FEEDS
	JSR OSBYTE

	LDY #0			;PRINT OUT LINE
POUT:	LDA LBUFF,Y
	JSR OSWRCH
	INY
	DEC PRLEN
	BNE POUT		;DO WHOLE LINE

	LDA #OUTSTR		;RESET OUTPUT STREAM
	LDA #4			;TO VIDEO
	JSR OSBYTE
PEX:	RTS			;AND LEAVE


	;   ************
	;NO SPLIT SCREEN OPTION IS BEING INCLUDED SO I AM INSERTING 
	;   ************  RETURNS FOR THE ROUTINES

ZSPLIT:	RTS

ZSCRN:	RTS

	;*******************
	;LINE ADDRESS TABLES
	;*******************

LOLINE:	DB	$00,$28,$50,$78,$A0,$C8,$F0,$18
	DB	$40,$68,$90,$B8,$E0,$08,$30,$58
	DB	$80,$A8,$D0,$F8,$20,$48,$70,$98
	DB	$C0

HILINE:	DB	$7C,$7C,$7C,$7C,$7C,$7C,$7C,$7D
	DB	$7D,$7D,$7D,$7D,$7D,$7E,$7E,$7E
	DB	$7E,$7E,$7E,$7E,$7F,$7F,$7F,$7F
	DB	$7F

	END