lzsa/asm/z80/unlzsa_fast_v1.asm
2019-06-21 17:39:50 +02:00

102 lines
3.5 KiB
NASM
Executable File

;
; 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 -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 : jr ReadToken
NoLiterals: xor (hl) : inc hl
push de : ld e,(hl) : inc 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 hl,de : pop de ; BC = len, DE = dest, HL = dest-offset, SP->[src]
ldir : 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) : inc hl
ldir
; next we read the first byte of the offset
push de : ld e,(hl) : inc 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) : inc hl
add -128+3 : cp 15+3 : jp c,CopyMatch
; MMMM=15 indicates a multi-byte number of literals
LongerMatch: add (hl) : inc 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) : inc hl : jr nz,CopyMatch.UseC
.code0 ld b,(hl) : inc 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) : inc hl : exa
ld a,7 : add (hl) : inc hl : jr c,ManyLiterals
CopyLiterals: ld c,a
.UseC ldir
push de : ld e,(hl) : inc hl
exa : jp p,ShortOffset : jr LongOffset
ManyLiterals:
.code1 ld b,a : ld c,(hl) : inc hl : jr nz,CopyLiterals.UseC
.code0 ld b,(hl) : inc hl : jr CopyLiterals.UseC