mirror of
https://github.com/emmanuel-marty/lzsa.git
synced 2024-11-16 11:04:49 +00:00
86 lines
3.1 KiB
NASM
Executable File
86 lines
3.1 KiB
NASM
Executable File
;
|
|
; Size-optimized LZSA decompressor by spke (v.1 23/04/2019, 69 bytes)
|
|
;
|
|
; The data must be compressed using the command line compressor by Emmanuel Marty
|
|
; The compression is done as follows:
|
|
;
|
|
; lzsa.exe -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,CompressedData
|
|
; ld de,WhereToDecompress
|
|
; call DecompressLZSA
|
|
;
|
|
; 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.
|
|
;
|
|
|
|
@DecompressLZSA:
|
|
ld b,0
|
|
|
|
; 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
|
|
ReadToken: ld a,(hl) : exa : ld a,(hl) : inc hl
|
|
and #70 : jr z,NoLiterals
|
|
|
|
rrca : rrca : rrca : rrca ; LLL<7 means 0..6 literals...
|
|
cp #07 : call z,ReadLongBA ; LLL=7 means 7+ literals...
|
|
|
|
ld c,a : ldir
|
|
|
|
; next we read the low byte of the -offset
|
|
NoLiterals: push de : ld e,(hl) : inc hl : ld d,#FF
|
|
; the top bit of token is set if
|
|
; the offset contains the high byte as well
|
|
exa : or a : jp p,ShortOffset
|
|
|
|
LongOffset: ld d,(hl) : inc hl
|
|
|
|
; last but not least, the match length is read
|
|
ShortOffset: and #0F : add 3 ; MMMM<15 means match lengths 0+3..14+3
|
|
cp 15+3 : call z,ReadLongBA ; MMMM=15 means lengths 14+3+
|
|
ld c,a
|
|
|
|
ex (sp),hl : push hl ; BC = len, DE = -offset, HL = dest, SP ->[dest,src]
|
|
add hl,de : pop de ; BC = len, DE = dest, HL = dest+(-offset), SP->[src]
|
|
ldir : pop hl ; BC = 0, DE = dest, HL = src
|
|
jr ReadToken
|
|
|
|
; a standard routine to read extended codes
|
|
; into registers B (higher byte) and A (lower byte).
|
|
ReadLongBA: add (hl) : inc hl : ret nc
|
|
|
|
; 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 a,(hl) : inc hl : ret nz
|
|
.code0: ld c,a : ld b,(hl) : inc hl
|
|
|
|
; the two-byte match length equal to zero
|
|
; designates the end-of-data marker
|
|
or b : ld a,c : ret nz
|
|
pop de : pop de : ret
|
|
|