mirror of
https://github.com/emmanuel-marty/lzsa.git
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182 lines
4.3 KiB
NASM
182 lines
4.3 KiB
NASM
;
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; Size-optimized LZSA2 decompressor by spke (v.1 02-09/06/2019, 140 bytes);
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; with improvements by uniabis (30/07/2019, -1 byte, +3% speed and support for Hitachi HD64180).
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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,FirstByteOfCompressedData
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; ld de,FirstByteOfMemoryForDecompressedData
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; call DecompressLZSA2
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;
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; Backward compression is also supported; you can compress files backward using:
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;
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; lzsa.exe -f2 -r -b <sourcefile> <outfile>
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;
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; and decompress the resulting files using:
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;
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; ld hl,LastByteOfCompressedData
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; ld de,LastByteOfMemoryForDecompressedData
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; call DecompressLZSA2
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;
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; (do not forget to uncomment the BACKWARD_DECOMPRESS option in the decompressor).
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;
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; Of course, LZSA2 compression algorithms are (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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; This software is provided 'as-is', without any express or implied
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; warranty. In no event will the authors be held liable for any damages
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; arising from the use of this software.
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;
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; Permission is granted to anyone to use this software for any purpose,
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; including commercial applications, and to alter it and redistribute it
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; freely, subject to the following restrictions:
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;
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; 1. The origin of this software must not be misrepresented; you must not
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; claim that you wrote the original software. If you use this software
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; in a product, an acknowledgment in the product documentation would be
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; appreciated but is not required.
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; 2. Altered source versions must be plainly marked as such, and must not be
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; misrepresented as being the original software.
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; 3. This notice may not be removed or altered from any source distribution.
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;
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; DEFINE BACKWARD_DECOMPRESS ; uncomment for data compressed with option -b
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; DEFINE HD64180 ; uncomment for systems using Hitachi HD64180
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IFNDEF BACKWARD_DECOMPRESS
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MACRO NEXT_HL
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inc hl
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ENDM
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MACRO ADD_OFFSET
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ex de,hl : add hl,de
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ENDM
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MACRO BLOCKCOPY
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ldir
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ENDM
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ELSE
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MACRO NEXT_HL
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dec hl
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ENDM
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MACRO ADD_OFFSET
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push hl : or a : sbc hl,de : pop de ; 11+4+15+10 = 40t / 5 bytes
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ENDM
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MACRO BLOCKCOPY
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lddr
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ENDM
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ENDIF
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IFNDEF HD64180
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MACRO LD_IY_DE
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ld iyl,e : ld iyh,d
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ENDM
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MACRO LD_DE_IY
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ld e,iyl : ld d,iyh
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ENDM
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ELSE
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MACRO LD_IY_DE
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push de : pop iy
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ENDM
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MACRO LD_DE_IY
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push iy : pop de
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ENDM
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ENDIF
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@DecompressLZSA2:
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xor a : ld b,a : exa : jr ReadToken
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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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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) : NEXT_HL
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SaveOffset: LD_IY_DE
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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 ; BC = len, DE = -offset, HL = dest, SP -> [src]
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ADD_OFFSET ; BC = len, DE = dest, HL = dest+(-offset), SP -> [src]
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BLOCKCOPY ; BC = 0, DE = dest
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pop hl ; HL = src
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ReadToken: ld a,(hl) : NEXT_HL : push af
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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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BLOCKCOPY
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NoLiterals: pop af : push de
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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 : DB #CA ; jr OffsetReadE ; #CA is JP Z,.. to skip all commands in CASE110 before jr OffsetReadE
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CASE110: ld d,(hl) : NEXT_HL : jr OffsetReadE
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CASE11x cp %11100000 : jr c,CASE110
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CASE111: LD_DE_IY : jr MatchLen
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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) : NEXT_HL : ret nc
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ld a,(hl) : NEXT_HL
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ld b,(hl) : NEXT_HL : ret nz
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pop de : pop de ; RET is not needed, because RET from ReadNibble is sufficient
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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) : NEXT_HL : or #0F
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rrca : rrca : rrca : rrca : ret
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