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Code: Select all

BLTU:	JSR	REASON		;ASCERTAIN THAT STRING SPACE WON'T
				;BE OVERRUN.
	STWD	STREND
BLTUC:	SEC			;PREPARE TO SUBTRACT.
	LDA	HIGHTR
	SBC	LOWTR		;COMPUTE NUMBER OF THINGS TO MOVE.
	STA	INDEX		;SAVE FOR LATER.
	TAY
	LDA	HIGHTR+1
	SBC	LOWTR+1
	TAX			;PUT IT IN A COUNTER REGISTER.
	INX			;SO THAT COUNTER ALGORITHM WORKS.
	TYA			;SEE IF LOW PART OF COUNT IS ZERO.
	BEQ	DECBLT		;YES, GO START MOVING BLOCKS.
	LDA	HIGHTR		;NO, MUST MODIFY BASE ADDR.
	SEC
	SBC	INDEX		;BORROW IS OFF SINCE [HIGHTR].GT.[LOWTR].
	STA	HIGHTR		;SAVE MODIFIED BASE ADDR.
	BCS	BLT1		;IF NO BORROW, GO SHOVE IT.
	DEC	HIGHTR+1	;BORROW IMPLIES SUB 1 FROM HIGH ORDER.
	SEC
BLT1:	LDA	HIGHDS		;MOD BASE OF DEST ADDR.
	SBC	INDEX
	STA	HIGHDS
	BCS	MOREN1		;NO BORROW.
	DEC	HIGHDS+1	;DECREMENT HIGH ORDER BYTE.
	BCC	MOREN1		;ALWAYS SKIP.
BLTLP:	LDADY	HIGHTR		;FETCH BYTE TO MOVE
	STADY	HIGHDS		;MOVE IT IN, MOVE IT OUT.
MOREN1: DEY
	BNE	BLTLP
	LDADY	HIGHTR		;MOVE LAST OF THE BLOCK.
	STADY	HIGHDS
DECBLT: DEC	HIGHTR+1
	DEC	HIGHDS+1	;START ON NEW BLOCKS.
	DEX
	BNE	MOREN1
	RTS			;RETURN TO CALLER.

Code: Select all

LAB_11CF
	JSR	LAB_121F		; check available memory, "Out of memory" error if no room
					; addr to check is in AY (low/high)
	STA	Earryl		; save new array mem end low byte
	STY	Earryh		; save new array mem end high byte

; open up space in memory
; move (Ostrtl)-(Obendl) to new block ending at (Nbendl)
; don't set array end

LAB_11D6
	SEC				; set carry for subtract
	LDA	Obendl		; get block end low byte
	SBC	Ostrtl		; subtract block start low byte
	TAY				; copy MOD(block length/$100) byte to Y
	LDA	Obendh		; get block end high byte
	SBC	Ostrth		; subtract block start high byte
	TAX				; copy block length high byte to X
	INX				; +1 to allow for count=0 exit
	TYA				; copy block length low byte to A
	BEQ	LAB_120A		; branch if length low byte=0

					; block is (X-1)*256+Y bytes, do the Y bytes first

	SEC				; set carry for add + 1, two's complement
	EOR	#$FF			; invert low byte for subtract
	ADC	Obendl		; add block end low byte

	STA	Obendl		; save corrected old block end low byte
	BCS	LAB_11F3		; branch if no underflow

	DEC	Obendh		; else decrement block end high byte
	SEC				; set carry for add + 1, two's complement
LAB_11F3
	TYA				; get MOD(block length/$100) byte
	EOR	#$FF			; invert low byte for subtract
	ADC	Nbendl		; add destination end low byte
	STA	Nbendl		; save modified new block end low byte
	BCS	LAB_1203		; branch if no underflow

	DEC	Nbendh		; else decrement block end high byte
	BCC	LAB_1203		; branch always

LAB_11FF
	LDA	(Obendl),Y		; get byte from source
	STA	(Nbendl),Y		; copy byte to destination
LAB_1203
	DEY				; decrement index
	BNE	LAB_11FF		; loop until Y=0

					; now do Y=0 indexed byte
	LDA	(Obendl),Y		; get byte from source
	STA	(Nbendl),Y		; save byte to destination
LAB_120A
	DEC	Obendh		; decrement source pointer high byte
	DEC	Nbendh		; decrement destination pointer high byte
	DEX				; decrement block count
	BNE	LAB_1203		; loop until count = $0

	RTS				;