mirror of
https://github.com/emmanuel-marty/lzsa.git
synced 2024-11-19 16:31:31 +00:00
97 lines
2.1 KiB
NASM
97 lines
2.1 KiB
NASM
;
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; Size-optimized LZSA2 decompressor by spke (v.1 02-09/06/2019, 145 bytes)
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;
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; The data must be compressed using the command line compressor by Emmanuel Marty
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; The compression is done as follows:
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;
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; lzsa.exe -f2 -r <sourcefile> <outfile>
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;
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; where option -r asks for the generation of raw (frame-less) data.
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;
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; The decompression is done in the standard way:
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;
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; ld hl,CompressedData
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; ld de,WhereToDecompress
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; call DecompressLZSA2
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;
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; Of course, LZSA2 compression algorithm is (c) 2019 Emmanuel Marty,
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; see https://github.com/emmanuel-marty/lzsa for more information
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;
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; Drop me an email if you have any comments/ideas/suggestions: zxintrospec@gmail.com
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;
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@DecompressLZSA2:
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xor a : ld b,a : exa : jr ReadToken
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CASE0xx ld d,#FF : cp %01000000 : jr c,CASE00x
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CASE01x: cp %01100000 : rl d
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OffsetReadE: ld e,(hl) : inc hl
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SaveOffset: ld iyl,e : ld iyh,d
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MatchLen: and %00000111 : add 2 : cp 9 : call z,ExtendedCode
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CopyMatch: ld c,a
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ex (sp),hl : push hl ; BC = len, DE = offset, HL = dest, SP ->[dest,src]
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add hl,de : pop de ; BC = len, DE = dest, HL = dest-offset, SP->[src]
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ldir : pop hl
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ReadToken: ld a,(hl) : ld ixl,a : inc hl
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and %00011000 : jr z,NoLiterals
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rrca : rrca : rrca
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call pe,ExtendedCode
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ld c,a
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ldir
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NoLiterals: push de : ld a,ixl
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or a : jp p,CASE0xx
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CASE1xx cp %11000000 : jr nc,CASE11x
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CASE10x: call ReadNibble
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ld d,a : ld a,c
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cp %10100000 : rl d
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dec d : dec d : jr OffsetReadE
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CASE00x: call ReadNibble
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ld e,a : ld a,c
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cp %00100000 : rl e : jr SaveOffset
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CASE11x cp %11100000 : jr c,CASE110
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CASE111: ld e,iyl : ld d,iyh : jr MatchLen
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CASE110: ld d,(hl) : inc hl : jr OffsetReadE
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ExtendedCode: call ReadNibble : inc a : jr z,ExtraByte
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sub #F0+1 : add c : ret
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ExtraByte ld a,15 : add c : add (hl) : inc hl : ret nc
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ld a,(hl) : inc hl
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ld b,(hl) : inc hl : ret nz
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pop de : pop de : ret
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ReadNibble: ld c,a : xor a : exa : ret m
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UpdateNibble ld a,(hl) : or #F0 : exa
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ld a,(hl) : inc hl : or #0F
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rrca : rrca : rrca : rrca : ret
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