mirror of
https://github.com/emmanuel-marty/lzsa.git
synced 2024-07-01 22:29:44 +00:00
63 lines
1.9 KiB
NASM
Executable File
63 lines
1.9 KiB
NASM
Executable File
;
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; Size-optimized LZSA decompressor by spke (v.1 19/04/2019, 81 bytes)
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;
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; The data must be comressed 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 -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 DecompressLZSA
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;
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; Of course, LZSA 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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@DecompressLZSA:
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ld b,0
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ReadToken: ; first a byte token "O|LLL|MMMM" is read from the stream,
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; where LLL is the number of literals and MMMM is
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; a length of the match that follows after the literals
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ld a,(hl) : exa : ld a,(hl) : inc hl
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and #70 : jr z,NoLiterals
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rrca : rrca : rrca : rrca ; LLL<7 means 0..6 literals...
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cp #07 : call z,ReadLongBA ; LLL=7 means 7+ literals...
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ld c,a : ldir
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; next we read the first byte of the offset
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NoLiterals: push de : ld e,(hl) : inc hl : ld d,b
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; the top bit of token is set if the offset contains two bytes
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exa : or a : jp p,ShortOffset
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LongOffset: ld d,(hl) : inc hl
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ShortOffset: and #0F : add 3 : cp 15+3 : call z,ReadLongBA
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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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scf : sbc hl,de : pop de ; BC = len, DE = dest, HL = dest-offset, SP->[src]
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ldir : pop hl ; BC = 0, DE = dest, HL = src
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jr ReadToken
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ReadLongBA: ld c,(hl) : inc hl
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add c : jr nc,$+3 : inc b
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inc c : jr z,.Code255
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inc c : ret nz
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.Code254 add (hl) : inc hl : ret nc : inc b : ret
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.Code255 ld c,(hl) : inc hl : ld b,(hl) : inc hl
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ld a,b : or c : ld a,c : ret nz
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pop de : pop de : ret
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