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lzsa/asm/6502/decompress_fast_v1.asm
Emmanuel Marty a46796b6a9
Fix assembling of 6502 fast v1 depacker
2019-12-24 10:16:01 +01:00

306 lines
9.4 KiB
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; -----------------------------------------------------------------------------
; Decompress raw LZSA1 block. Create one with lzsa -r <original_file> <compressed_file>
;
; in:
; * LZSA_SRC_LO and LZSA_SRC_HI contain the compressed raw block address
; * LZSA_DST_LO and LZSA_DST_HI contain the destination buffer address
;
; out:
; * LZSA_DST_LO and LZSA_DST_HI contain the last decompressed byte address, +1
;
; -----------------------------------------------------------------------------
; Backward decompression is also supported, use lzsa -r -b <original_file> <compressed_file>
; To use it, also define BACKWARD_DECOMPRESS=1 before including this code!
;
; in:
; * LZSA_SRC_LO/LZSA_SRC_HI must contain the address of the last byte of compressed data
; * LZSA_DST_LO/LZSA_DST_HI must contain the address of the last byte of the destination buffer
;
; out:
; * LZSA_DST_LO/LZSA_DST_HI contain the last decompressed byte address, -1
;
; -----------------------------------------------------------------------------
;
; Copyright (C) 2019 Emmanuel Marty, Peter Ferrie
;
; This software is provided 'as-is', without any express or implied
; warranty. In no event will the authors be held liable for any damages
; arising from the use of this software.
;
; Permission is granted to anyone to use this software for any purpose,
; including commercial applications, and to alter it and redistribute it
; freely, subject to the following restrictions:
;
; 1. The origin of this software must not be misrepresented; you must not
; claim that you wrote the original software. If you use this software
; in a product, an acknowledgment in the product documentation would be
; appreciated but is not required.
; 2. Altered source versions must be plainly marked as such, and must not be
; misrepresented as being the original software.
; 3. This notice may not be removed or altered from any source distribution.
; -----------------------------------------------------------------------------
DECOMPRESS_LZSA1_FAST
LDY #$00
DECODE_TOKEN
JSR GETSRC ; read token byte: O|LLL|MMMM
PHA ; preserve token on stack
AND #$70 ; isolate literals count
BEQ NO_LITERALS ; skip if no literals to copy
CMP #$70 ; LITERALS_RUN_LEN?
BNE PREPARE_COPY_LITERALS ; if not, count is directly embedded in token
JSR GETSRC ; get extra byte of variable literals count
; the carry is always set by the CMP above
; GETSRC doesn't change it
SBC #$F9 ; (LITERALS_RUN_LEN)
BCC PREPARE_COPY_LITERALS_DIRECT
BEQ LARGE_VARLEN_LITERALS ; if adding up to zero, go grab 16-bit count
JSR GETSRC ; get single extended byte of variable literals count
INY ; add 256 to literals count
BCS PREPARE_COPY_LITERALS_DIRECT ; (*like JMP PREPARE_COPY_LITERALS_DIRECT but shorter)
LARGE_VARLEN_LITERALS ; handle 16 bits literals count
; literals count = directly these 16 bits
JSR GETLARGESRC ; grab low 8 bits in X, high 8 bits in A
TAY ; put high 8 bits in Y
TXA
JMP PREPARE_COPY_LARGE_LITERALS
PREPARE_COPY_LITERALS
TAX
LDA SHIFT_TABLE-1,X ; shift literals length into place
; -1 because position 00 is reserved
PREPARE_COPY_LITERALS_DIRECT
TAX
PREPARE_COPY_LARGE_LITERALS
BEQ COPY_LITERALS
INY
COPY_LITERALS
JSR GETPUT ; copy one byte of literals
DEX
BNE COPY_LITERALS
DEY
BNE COPY_LITERALS
NO_LITERALS
PLA ; retrieve token from stack
PHA ; preserve token again
BMI GET_LONG_OFFSET ; $80: 16 bit offset
JSR GETSRC ; get 8 bit offset from stream in A
TAX ; save for later
LDA #$FF ; high 8 bits
BNE GOT_OFFSET ; go prepare match
; (*like JMP GOT_OFFSET but shorter)
SHORT_VARLEN_MATCHLEN
JSR GETSRC ; get single extended byte of variable match len
INY ; add 256 to match length
PREPARE_COPY_MATCH
TAX
PREPARE_COPY_MATCH_Y
TXA
BEQ COPY_MATCH_LOOP
INY
COPY_MATCH_LOOP
LDA $AAAA ; get one byte of backreference
JSR PUTDST ; copy to destination
!ifdef BACKWARD_DECOMPRESS {
; Backward decompression -- put backreference bytes backward
LDA COPY_MATCH_LOOP+1
BEQ GETMATCH_ADJ_HI
GETMATCH_DONE
DEC COPY_MATCH_LOOP+1
} else {
; Forward decompression -- put backreference bytes forward
INC COPY_MATCH_LOOP+1
BEQ GETMATCH_ADJ_HI
GETMATCH_DONE
}
DEX
BNE COPY_MATCH_LOOP
DEY
BNE COPY_MATCH_LOOP
BEQ DECODE_TOKEN ; (*like JMP DECODE_TOKEN but shorter)
!ifdef BACKWARD_DECOMPRESS {
GETMATCH_ADJ_HI
DEC COPY_MATCH_LOOP+2
JMP GETMATCH_DONE
} else {
GETMATCH_ADJ_HI
INC COPY_MATCH_LOOP+2
JMP GETMATCH_DONE
}
GET_LONG_OFFSET ; handle 16 bit offset:
JSR GETLARGESRC ; grab low 8 bits in X, high 8 bits in A
GOT_OFFSET
!ifdef BACKWARD_DECOMPRESS {
; Backward decompression - substract match offset
STA OFFSHI ; store high 8 bits of offset
STX OFFSLO
SEC ; substract dest - match offset
LDA PUTDST+1
OFFSLO = *+1
SBC #$AA ; low 8 bits
STA COPY_MATCH_LOOP+1 ; store back reference address
LDA PUTDST+2
OFFSHI = *+1
SBC #$AA ; high 8 bits
STA COPY_MATCH_LOOP+2 ; store high 8 bits of address
SEC
} else {
; Forward decompression - add match offset
STA OFFSHI ; store high 8 bits of offset
TXA
CLC ; add dest + match offset
ADC PUTDST+1 ; low 8 bits
STA COPY_MATCH_LOOP+1 ; store back reference address
OFFSHI = *+1
LDA #$AA ; high 8 bits
ADC PUTDST+2
STA COPY_MATCH_LOOP+2 ; store high 8 bits of address
}
PLA ; retrieve token from stack again
AND #$0F ; isolate match len (MMMM)
ADC #$02 ; plus carry which is always set by the high ADC
CMP #$12 ; MATCH_RUN_LEN?
BCC PREPARE_COPY_MATCH ; if not, count is directly embedded in token
JSR GETSRC ; get extra byte of variable match length
; the carry is always set by the CMP above
; GETSRC doesn't change it
SBC #$EE ; add MATCH_RUN_LEN and MIN_MATCH_SIZE to match length
BCC PREPARE_COPY_MATCH
BNE SHORT_VARLEN_MATCHLEN
; Handle 16 bits match length
JSR GETLARGESRC ; grab low 8 bits in X, high 8 bits in A
TAY ; put high 8 bits in Y
; large match length with zero high byte?
BNE PREPARE_COPY_MATCH_Y ; if not, continue
DECOMPRESSION_DONE
RTS
SHIFT_TABLE
!BYTE $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
!BYTE $01,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01,$01
!BYTE $02,$02,$02,$02,$02,$02,$02,$02,$02,$02,$02,$02,$02,$02,$02,$02
!BYTE $03,$03,$03,$03,$03,$03,$03,$03,$03,$03,$03,$03,$03,$03,$03,$03
!BYTE $04,$04,$04,$04,$04,$04,$04,$04,$04,$04,$04,$04,$04,$04,$04,$04
!BYTE $05,$05,$05,$05,$05,$05,$05,$05,$05,$05,$05,$05,$05,$05,$05,$05
!BYTE $06,$06,$06,$06,$06,$06,$06,$06,$06,$06,$06,$06,$06,$06,$06,$06
!BYTE $07,$07,$07,$07,$07,$07,$07,$07,$07,$07,$07,$07,$07,$07,$07,$07
!ifdef BACKWARD_DECOMPRESS {
; Backward decompression -- get and put bytes backward
GETPUT
JSR GETSRC
PUTDST
LZSA_DST_LO = *+1
LZSA_DST_HI = *+2
STA $AAAA
LDA PUTDST+1
BEQ PUTDST_ADJ_HI
DEC PUTDST+1
RTS
PUTDST_ADJ_HI
DEC PUTDST+2
DEC PUTDST+1
RTS
GETLARGESRC
JSR GETSRC ; grab low 8 bits
TAX ; move to X
; fall through grab high 8 bits
GETSRC
LZSA_SRC_LO = *+1
LZSA_SRC_HI = *+2
LDA $AAAA
PHA
LDA GETSRC+1
BEQ GETSRC_ADJ_HI
DEC GETSRC+1
PLA
RTS
GETSRC_ADJ_HI
DEC GETSRC+2
DEC GETSRC+1
PLA
RTS
} else {
; Forward decompression -- get and put bytes forward
GETPUT
JSR GETSRC
PUTDST
LZSA_DST_LO = *+1
LZSA_DST_HI = *+2
STA $AAAA
INC PUTDST+1
BEQ PUTDST_ADJ_HI
RTS
PUTDST_ADJ_HI
INC PUTDST+2
RTS
GETLARGESRC
JSR GETSRC ; grab low 8 bits
TAX ; move to X
; fall through grab high 8 bits
GETSRC
LZSA_SRC_LO = *+1
LZSA_SRC_HI = *+2
LDA $AAAA
INC GETSRC+1
BEQ GETSRC_ADJ_HI
RTS
GETSRC_ADJ_HI
INC GETSRC+2
RTS
}
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