Initial import of the open source release

1 files changed, 118 insertions, 0 deletions

diff --git a/tools/rasm_src/decrunch/lz4_docent.asm b/tools/rasm_src/decrunch/lz4_docent.asm
new file mode 100644
index 0000000..a0b2188
--- /dev/null
+++ b/tools/rasm_src/decrunch/lz4_docent.asm
@@ -0,0 +1,118 @@
+; decompress raw lz4 data packet
+; on entry hl - start of packed buffer, de - destination buffer, bc - size of packed data
+LZ4_decompress_raw:
+	push	de							; store original destination pointer
+	push	hl							; store start of compressed data source
+	add		hl,bc       				; calculate end address of compressed block
+	ld		b,h							; move end address of compressed data to bc
+	ld		c,l	
+	pop		hl							; restore start of compressed data source
+	push	bc							; store end address of compessed data
+; now hl - start of packed buffer, de - destination, bc - end of packed buffer
+	ld		b,0		         			; clear b, c is set later
+
+; get decompression token
+LZ4_GetToken:
+	xor		a 							; reset c flag for sbc later
+	ld		a,(hl)						; read token
+	inc		hl
+	push	af							; store token
+; unpack 4 high bits to get the length of literal
+	rlca
+	rlca
+	rlca
+	rlca
+; copy literals
+	and		#f							; token can be max 15 - mask out unimportant bits
+	jr		z,LZ4_skipcalc   			; there is no literals, skip calculation of literal size
+	ld		c,a							; set the count for calculation
+	cp		#f							; if literal size <15
+	jr		nz, LZ4_copyliterals		; copy literal, else
+; calculate total literal size by adding contents of following bytes
+	push	de							; store destination
+	ex		de,hl
+; a = size of literal to copy, de=pointer to data to be added
+	ld		h,0         				; set hl with size of literal to copy 
+	ld		l,a
+
+LZ4_calcloop:
+	ld		a,(de)						; get additional literal size to add 
+	inc		de
+	ld		c,a							; set bc to the length of literal
+	add		hl,bc						; add it to the total literal length
+	cp		#ff							; if literal=255
+	jr		z,LZ4_calcloop				; continue calculating the total literal size
+	ld		b,h							; store total literal size to copy in bc
+	ld		c,l
+	ex		de,hl						; hl now contains current compressed data pointer  
+	pop		de							; restore destination to de 
+
+LZ4_copyliterals:
+	ldir								; copy literal to destination
+
+LZ4_skipcalc:
+; check for end of compressed data
+	pop		af							; restore token, carry is cleared because of xor a at the beginning of GetToken
+	pop		bc							; restore end address of compressed data 
+	push	hl							; store current compressed data pointer 
+	sbc		hl, bc						; check if we reached the end of compressed data buffer
+	pop		hl							; restore current compressed data pointer
+	jr		z,LZ4_decompress_success	; decompression finished
+	push	bc							; store end address of compressed data
+
+; Copy Matches
+	and		#f							; token can be max 15 - mask out unimportant bits. resets also c flag for sbc later
+; get the offset
+	ld		c,(hl)
+	inc		hl
+	ld		b,(hl)						; bc now contains the offset
+	inc		hl
+	push	hl							; store current compressed data pointer
+	push	de							; store destination pointer
+
+	ex		de,hl
+	sbc		hl,bc   					; calculate from the offset the new decompressed data source to copy from
+; hl contains new copy source, de source ptr
+
+	ld		b,0     					; load bc with the token
+	ld		c,a
+	cp		#f							; if matchlength <15
+	jr nz, LZ4_copymatches				; copy matches. else 
+
+; calculate total matchlength by adding additional bytes
+	push	hl							; store current decompressed data source
+; a = size of match to copy, de= pointer to data to be added
+	ld		h,0     					; set hl with initial matchlength to copy
+	ld		l,a
+LZ4_calcloop2:
+	ld		a,(de)						; get additional matchlength to add
+	inc		de
+	ld		c,a							; set bc to the matchlength
+	add		hl,bc						; add it to the total match length
+	cp		#ff							; if matchlength=255
+	jr		z,LZ4_calcloop2				; continue calculating the total match length		
+	ld		b,h							; store total matchlength to copy in bc
+	ld		c,l			 
+	pop		hl							; restore current decompressed data source
+	pop		af							; set stack to proper position by restoring destination pointer temporarily into af  
+	ex		de,hl
+	ex		(sp),hl						; update current compressed data pointer on the stack to the new value from de
+	ex		de,hl 
+	push	af							; restore stack
+
+LZ4_copymatches:
+	pop		de							; restore destination pointer
+	inc		bc							; add base length of 4 to get the correct size of matchlength 
+	inc		bc
+	inc		bc
+	inc		bc
+	ldir								; copy match
+	pop		hl							; restore current compressed data source
+	jr		LZ4_GetToken				; continue decompression
+LZ4_decompress_success:
+	pop		hl							; store destination pointer 
+	sbc		hl,de						; calculate the number of decompressed bytes 
+	xor		a							; clear exit code
+	ret
+
+