mirror of
https://github.com/emmanuel-marty/lzsa.git
synced 2024-11-22 05:33:58 +00:00
146 lines
4.3 KiB
NASM
146 lines
4.3 KiB
NASM
;
|
|
; Speed-optimized LZSA decompressor by spke (v.1 03-25/04/2019, 110 bytes)
|
|
;
|
|
; The data must be compressed using the command line compressor by Emmanuel Marty
|
|
; The compression is done as follows:
|
|
;
|
|
; lzsa.exe -f1 -r <sourcefile> <outfile>
|
|
;
|
|
; where option -r asks for the generation of raw (frame-less) data.
|
|
;
|
|
; The decompression is done in the standard way:
|
|
;
|
|
; ld hl,FirstByteOfCompressedData
|
|
; ld de,FirstByteOfMemoryForDecompressedData
|
|
; call DecompressLZSA
|
|
;
|
|
; Backward compression is also supported; you can compress files backward using:
|
|
;
|
|
; lzsa.exe -f1 -r -b <sourcefile> <outfile>
|
|
;
|
|
; and decompress the resulting files using:
|
|
;
|
|
; ld hl,LastByteOfCompressedData
|
|
; ld de,LastByteOfMemoryForDecompressedData
|
|
; call DecompressLZSA
|
|
;
|
|
; (do not forget to uncomment the BACKWARD_DECOMPRESS option in the decompressor).
|
|
;
|
|
; Of course, LZSA compression algorithm is (c) 2019 Emmanuel Marty,
|
|
; see https://github.com/emmanuel-marty/lzsa for more information
|
|
;
|
|
; Drop me an email if you have any comments/ideas/suggestions: zxintrospec@gmail.com
|
|
;
|
|
; 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.
|
|
|
|
; DEFINE BACKWARD_DECOMPRESS
|
|
|
|
IFDEF BACKWARD_DECOMPRESS
|
|
|
|
MACRO NEXT_HL
|
|
dec hl
|
|
ENDM
|
|
|
|
MACRO ADD_OFFSET
|
|
or a : sbc hl,de
|
|
ENDM
|
|
|
|
MACRO BLOCKCOPY
|
|
lddr
|
|
ENDM
|
|
|
|
ELSE
|
|
|
|
MACRO NEXT_HL
|
|
inc hl
|
|
ENDM
|
|
|
|
MACRO ADD_OFFSET
|
|
add hl,de
|
|
ENDM
|
|
|
|
MACRO BLOCKCOPY
|
|
ldir
|
|
ENDM
|
|
|
|
ENDIF
|
|
|
|
@DecompressLZSA:
|
|
ld b,0 : jr ReadToken
|
|
|
|
NoLiterals: xor (hl) : NEXT_HL
|
|
push de : ld e,(hl) : NEXT_HL : jp m,LongOffset
|
|
|
|
; short matches have length 0+3..14+3
|
|
ShortOffset: ld d,#FF : add 3 : cp 15+3 : jr nc,LongerMatch
|
|
|
|
; placed here this saves a JP per iteration
|
|
CopyMatch: ld c,a
|
|
.UseC ex (sp),hl : push hl ; BC = len, DE = offset, HL = dest, SP ->[dest,src]
|
|
ADD_OFFSET : pop de ; BC = len, DE = dest, HL = dest-offset, SP->[src]
|
|
BLOCKCOPY : pop hl ; BC = 0, DE = dest, HL = src
|
|
|
|
ReadToken: ; first a byte token "O|LLL|MMMM" is read from the stream,
|
|
; where LLL is the number of literals and MMMM is
|
|
; a length of the match that follows after the literals
|
|
ld a,(hl) : and #70 : jr z,NoLiterals
|
|
|
|
cp #70 : jr z,MoreLiterals ; LLL=7 means 7+ literals...
|
|
rrca : rrca : rrca : rrca ; LLL<7 means 0..6 literals...
|
|
|
|
ld c,a : ld a,(hl) : NEXT_HL
|
|
BLOCKCOPY
|
|
|
|
; next we read the first byte of the offset
|
|
push de : ld e,(hl) : NEXT_HL
|
|
; the top bit of token is set if the offset contains two bytes
|
|
and #8F : jp p,ShortOffset
|
|
|
|
LongOffset: ; read second byte of the offset
|
|
ld d,(hl) : NEXT_HL
|
|
add -128+3 : cp 15+3 : jp c,CopyMatch
|
|
|
|
; MMMM=15 indicates a multi-byte number of literals
|
|
LongerMatch: add (hl) : NEXT_HL : jr nc,CopyMatch
|
|
|
|
; the codes are designed to overflow;
|
|
; the overflow value 1 means read 1 extra byte
|
|
; and overflow value 0 means read 2 extra bytes
|
|
.code1 ld b,a : ld c,(hl) : NEXT_HL : jr nz,CopyMatch.UseC
|
|
.code0 ld b,(hl) : NEXT_HL
|
|
|
|
; the two-byte match length equal to zero
|
|
; designates the end-of-data marker
|
|
ld a,b : or c : jr nz,CopyMatch.UseC
|
|
pop de : ret
|
|
|
|
MoreLiterals: ; there are three possible situations here
|
|
xor (hl) : NEXT_HL : exa
|
|
ld a,7 : add (hl) : NEXT_HL : jr c,ManyLiterals
|
|
|
|
CopyLiterals: ld c,a
|
|
.UseC BLOCKCOPY
|
|
|
|
push de : ld e,(hl) : NEXT_HL
|
|
exa : jp p,ShortOffset : jr LongOffset
|
|
|
|
ManyLiterals:
|
|
.code1 ld b,a : ld c,(hl) : NEXT_HL : jr nz,CopyLiterals.UseC
|
|
.code0 ld b,(hl) : NEXT_HL : jr CopyLiterals.UseC
|
|
|
|
|