chiptune: add lz4 decoder

asm_routines/lz4_decode.s

@@ -0,0 +1,174 @@
+; LZ4 data decompressor for Apple II
+; Based heavily on code by Peter Ferrie (peter.ferrie@gmail.com)
+
+; For LZ4 reference see
+; https://github.com/lz4/lz4/wiki/lz4_Frame_format.md
+
+src	EQU $00
+dst	EQU $02
+end	EQU $04
+count	EQU $06
+delta	EQU $08
+A1L	EQU $3c
+A1H	EQU $3d
+A2L	EQU $3e
+A2H	EQU $3f
+A4L	EQU $42
+A4H	EQU $43
+
+size	EQU 794
+orgoff EQU $8000	; offset of first unpacked byte
+paksize	EQU size-$b-8   ; minus 4 for checksum at end
+			; not sure what other 4 is from?
+			; block checksum? though had that disabled?
+
+			; size of packed data
+pakoff EQU $200b	; 11 byte offset to data?
+
+
+lz4_unpack:
+	lda	#<pakoff 		; packed data offset
+	sta	src
+	lda	#<(pakoff+paksize)	; packed data size
+	sta	end
+	lda	#>pakoff
+	sta	src+1
+	lda	#>(pakoff+paksize)
+	sta	end+1
+	lda	#>orgoff		; original unpacked data offset
+	sta	dst+1
+	lda	#<orgoff
+	sta	dst
+
+
+; Should: check for magic number 04 22 4d 18
+;	FLG: 64 in our case (01=version, block.index=1, block.checksum=0
+;		size=0, checksum=1, reserved
+;	MAX Blocksize: 40 (64kB)
+;	HEADER CHECKSUM: a7
+;	BLOCK HEADER: 4 bytes (le)  If highest bit set, uncompressed!
+
+
+unpmain:
+	ldy	#0
+
+parsetoken:
+	jsr	getsrc
+	pha
+	lsr
+	lsr
+	lsr
+	lsr
+	beq	copymatches
+
+	jsr	buildcount
+	tax
+	jsr	docopy
+	lda	src
+	cmp	end
+	lda	src+1
+	sbc	end+1
+	bcs	done
+
+copymatches:
+	jsr	getsrc
+	sta	delta
+	jsr	getsrc
+	sta	delta+1
+	pla
+	and	#$0f
+	jsr	buildcount
+	clc
+	adc	#4
+	tax
+	bcc	copy_skip
+	inc	count+1
+copy_skip:
+	lda	src+1
+	pha
+	lda	src
+	pha
+	sec
+	lda	dst
+	sbc	delta
+	sta	src
+	lda	dst+1
+	sbc	delta+1
+	sta	src+1
+	jsr	docopy
+	pla
+	sta	src
+	pla
+	sta	src+1
+	jmp	parsetoken
+
+done:
+	pla
+	rts
+
+
+
+
+	;=========
+	; getsrc
+	;=========
+getsrc:
+	lda	(src), Y		; get a byte from src
+	inc	src			; increment pointer
+	bne	done_getsrc		; update 16-bit pointer
+	inc	src+1			; on 8-bit overflow
+done_getsrc:
+	rts
+
+	;============
+	; buildcount
+	;============
+buildcount:
+	ldx	#1
+	stx	count+1
+	cmp	#$0f
+	bne	done_buildcount
+minus_buildcount:
+	sta	count
+	jsr	getsrc
+	tax
+	clc
+	adc	count
+	bcc	skip_buildcount
+	inc	count+1
+skip_buildcount:
+	inx
+	beq	minus_buildcount
+done_buildcount:
+	rts
+
+	;============
+	; getput
+	;============
+	; gets a byte, then puts the byte
+getput:
+	jsr	getsrc
+	; fallthrough to putdst
+
+	;=============
+	; putdst
+	;=============
+putdst:
+	sta 	(dst), Y
+	inc	dst
+	bne	putdst_end
+	inc	dst+1
+putdst_end:
+	rts
+
+	;================
+	; docopy
+	;================
+docopy:
+	jsr	getput
+	dex
+	bne	docopy
+	dec	count+1
+	bne	docopy
+	rts
+

chiptune_player/Makefile

@@ -17,6 +17,7 @@ CHIPTUNE_PLAYER:	chiptune_player.o
 chiptune_player.o:	chiptune_player.s \
 	../asm_routines/mockingboard.s \
 	../asm_routines/dos33_routines.s \
+	../asm_routines/lz4_decode.s \
 	rasterbars.s \
 	chip_title.inc zp.inc
 	ca65 -o chiptune_player.o chiptune_player.s -l chiptune_player.lst

chiptune_player/chiptune_player.s

@@ -633,6 +633,7 @@ bloop3:
 .include	"../asm_routines/gr_setpage.s"
 .include	"../asm_routines/dos33_routines.s"
 .include	"../asm_routines/gr_hlin.s"
+.include	"../asm_routines/lz4_decode.s"
 .include	"rasterbars.s"