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lzsa/asm/65816/decompress_v2.asm
Peter Ferrie 2442d6e489 not-fast 65816 version
2020-09-10 13:12:17 -07:00

339 lines
11 KiB
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; -----------------------------------------------------------------------------
; Decompress raw LZSA2 block.
; Create one with lzsa -r -f2 <original_file> <compressed_file>
;
; in:
; * LZSA_SRC_LO/LZSA_SRC_HI/LZSA_SRC_BANK contain the compressed raw block address
; * LZSA_DST_LO/LZSA_DST_HI/LZSA_DST_BANK contain the destination buffer address
;
; out:
; * LZSA_DST_LO/LZSA_DST_HI/LZSA_DST_BANK contain the last decompressed byte address, +1
;
; -----------------------------------------------------------------------------
; Backward decompression is also supported, use lzsa -r -b -f2 <original_file> <compressed_file>
; To use it, also define BACKWARD_DECOMPRESS=1 before including this code!
;
; in:
; * LZSA_SRC_LO/LZSA_SRC_HI/LZSA_SRC_BANK must contain the address of the last byte of compressed data
; * LZSA_DST_LO/LZSA_DST_HI/LZSA_DST_BANK must contain the address of the last byte of the destination buffer
;
; out:
; * LZSA_DST_LO/LZSA_DST_HI/BANK contain the last decompressed byte address, -1
;
; -----------------------------------------------------------------------------
;
; Copyright (C) 2019-2020 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.
; -----------------------------------------------------------------------------
!cpu 65816
NIBCOUNT = $FC ; zero-page location for temp offset
DECOMPRESS_LZSA2
SEP #$30
!as
!rs
LDY #$00
STY NIBCOUNT
DECODE_TOKEN
JSR GETSRC ; read token byte: XYZ|LL|MMM
PHA ; preserve token on stack
AND #$18 ; isolate literals count (LL)
BEQ NO_LITERALS ; skip if no literals to copy
CMP #$18 ; LITERALS_RUN_LEN_V2?
BCC PREPARE_COPY_LITERALS ; if less, count is directly embedded in token
JSR GETNIBBLE ; get extra literals length nibble
; add nibble to len from token
ADC #$02 ; (LITERALS_RUN_LEN_V2) minus carry
CMP #$12 ; LITERALS_RUN_LEN_V2 + 15 ?
BCC PREPARE_COPY_LITERALS_DIRECT ; if less, literals count is complete
JSR GETSRC ; get extra byte of variable literals count
; the carry is always set by the CMP above
; GETSRC doesn't change it
SBC #$EE ; overflow?
BRA PREPARE_COPY_LITERALS_DIRECT
PREPARE_COPY_LITERALS_LARGE
; 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
BCS PREPARE_COPY_LITERALS_HIGH ; (*same as JMP PREPARE_COPY_LITERALS_HIGH but shorter)
PREPARE_COPY_LITERALS
LSR ; shift literals count into place
LSR
LSR
PREPARE_COPY_LITERALS_DIRECT
TAX
BCS PREPARE_COPY_LITERALS_LARGE ; if so, literals count is large
PREPARE_COPY_LITERALS_HIGH
TXA
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
ASL
BCS REPMATCH_OR_LARGE_OFFSET ; 1YZ: rep-match or 13/16 bit offset
ASL ; 0YZ: 5 or 9 bit offset
BCS OFFSET_9_BIT
; 00Z: 5 bit offset
LDX #$FF ; set offset bits 15-8 to 1
JSR GETCOMBINEDBITS ; rotate Z bit into bit 0, read nibble for bits 4-1
ORA #$E0 ; set bits 7-5 to 1
BNE GOT_OFFSET_LO ; go store low byte of match offset and prepare match
OFFSET_9_BIT ; 01Z: 9 bit offset
;;ASL ; shift Z (offset bit 8) in place
ROL
ROL
AND #$01
EOR #$FF ; set offset bits 15-9 to 1
BNE GOT_OFFSET_HI ; go store high byte, read low byte of match offset and prepare match
; (*same as JMP GOT_OFFSET_HI but shorter)
REPMATCH_OR_LARGE_OFFSET
ASL ; 13 bit offset?
BCS REPMATCH_OR_16_BIT ; handle rep-match or 16-bit offset if not
; 10Z: 13 bit offset
JSR GETCOMBINEDBITS ; rotate Z bit into bit 8, read nibble for bits 12-9
ADC #$DE ; set bits 15-13 to 1 and substract 2 (to substract 512)
BNE GOT_OFFSET_HI ; go store high byte, read low byte of match offset and prepare match
; (*same as JMP GOT_OFFSET_HI but shorter)
REPMATCH_OR_16_BIT ; rep-match or 16 bit offset
;;ASL ; XYZ=111?
BMI REP_MATCH ; reuse previous offset if so (rep-match)
; 110: handle 16 bit offset
JSR GETSRC ; grab high 8 bits
GOT_OFFSET_HI
TAX
JSR GETSRC ; grab low 8 bits
GOT_OFFSET_LO
STA OFFSLO ; store low byte of match offset
STX OFFSHI ; store high byte of match offset
REP_MATCH
!ifdef BACKWARD_DECOMPRESS {
; Backward decompression - substract match offset
SEC ; add dest + match offset
REP #$20
!al
LDA PUTDST+1 ; 16 bits
OFFSLO = *+1
OFFSHI = *+2
SBC #$AAAA
STA COPY_MATCH_LOOP+1 ; store back reference address
SEP #$20
!as
SEC
} else {
; Forward decompression - add match offset
CLC ; add dest + match offset
REP #$20
!al
LDA PUTDST+1 ; 16 bits
OFFSLO = *+1
OFFSHI = *+2
ADC #$AAAA
STA COPY_MATCH_LOOP+1 ; store back reference address
SEP #$20
!as
}
LDA PUTDST+3 ; bank
STA COPY_MATCH_LOOP+3 ; store back reference address
PLA ; retrieve token from stack again
AND #$07 ; isolate match len (MMM)
ADC #$01 ; add MIN_MATCH_SIZE_V2 and carry
CMP #$09 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2?
BCC PREPARE_COPY_MATCH ; if less, length is directly embedded in token
JSR GETNIBBLE ; get extra match length nibble
; add nibble to len from token
ADC #$08 ; (MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2) minus carry
CMP #$18 ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2 + 15?
BCC PREPARE_COPY_MATCH ; if less, match length is complete
JSR GETSRC ; get extra byte of variable match length
; the carry is always set by the CMP above
; GETSRC doesn't change it
SBC #$E8 ; overflow?
PREPARE_COPY_MATCH
TAX
BCC PREPARE_COPY_MATCH_Y ; if not, the match length is complete
BEQ DECOMPRESSION_DONE ; if EOD code, bail
; 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
PREPARE_COPY_MATCH_Y
TXA
BEQ COPY_MATCH_LOOP
INY
COPY_MATCH_LOOP
LDA $AAAAAA ; get one byte of backreference
JSR PUTDST ; copy to destination
REP #$20
!ifdef BACKWARD_DECOMPRESS {
; Backward decompression -- put backreference bytes backward
DEC COPY_MATCH_LOOP+1
} else {
; Forward decompression -- put backreference bytes forward
INC COPY_MATCH_LOOP+1
}
SEP #$20
DEX
BNE COPY_MATCH_LOOP
DEY
BNE COPY_MATCH_LOOP
JMP DECODE_TOKEN
GETCOMBINEDBITS
EOR #$80
ASL
PHP
JSR GETNIBBLE ; get nibble into bits 0-3 (for offset bits 1-4)
PLP ; merge Z bit as the carry bit (for offset bit 0)
COMBINEDBITZ
ROL ; nibble -> bits 1-4; carry(!Z bit) -> bit 0 ; carry cleared
DECOMPRESSION_DONE
RTS
GETNIBBLE
NIBBLES = *+1
LDA #$AA
LSR NIBCOUNT
BCC NEED_NIBBLES
AND #$0F ; isolate low 4 bits of nibble
RTS
NEED_NIBBLES
INC NIBCOUNT
JSR GETSRC ; get 2 nibbles
STA NIBBLES
LSR
LSR
LSR
LSR
SEC
RTS
!ifdef BACKWARD_DECOMPRESS {
; Backward decompression -- get and put bytes backward
GETPUT
JSR GETSRC
PUTDST
LZSA_DST_LO = *+1
LZSA_DST_HI = *+2
LZSA_DST_BANK = *+3
STA $AAAAAA
REP #$20
DEC PUTDST+1
SEP #$20
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
LZSA_SRC_BANK = *+3
LDA $AAAAAA
REP #$20
DEC GETSRC+1
SEP #$20
RTS
} else {
; Forward decompression -- get and put bytes forward
GETPUT
JSR GETSRC
PUTDST
LZSA_DST_LO = *+1
LZSA_DST_HI = *+2
LZSA_DST_BANK = *+3
STA $AAAAAA
REP #$20
INC PUTDST+1
SEP #$20
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
LZSA_SRC_BANK = *+3
LDA $AAAAAA
REP #$20
INC GETSRC+1
SEP #$20
RTS
}
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