lzsa/asm/z80/unlzsa2_small_v1.asm
2019-06-21 17:39:50 +02:00

97 lines
2.1 KiB
NASM

;
; Size-optimized LZSA2 decompressor by spke (v.1 02-09/06/2019, 145 bytes)
;
; The data must be compressed using the command line compressor by Emmanuel Marty
; The compression is done as follows:
;
; lzsa.exe -f2 -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 DecompressLZSA2
;
; Of course, LZSA2 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
;
@DecompressLZSA2:
xor a : ld b,a : exa : jr ReadToken
CASE0xx ld d,#FF : cp %01000000 : jr c,CASE00x
CASE01x: cp %01100000 : rl d
OffsetReadE: ld e,(hl) : inc hl
SaveOffset: ld iyl,e : ld iyh,d
MatchLen: and %00000111 : add 2 : cp 9 : call z,ExtendedCode
CopyMatch: 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
ReadToken: ld a,(hl) : ld ixl,a : inc hl
and %00011000 : jr z,NoLiterals
rrca : rrca : rrca
call pe,ExtendedCode
ld c,a
ldir
NoLiterals: push de : ld a,ixl
or a : jp p,CASE0xx
CASE1xx cp %11000000 : jr nc,CASE11x
CASE10x: call ReadNibble
ld d,a : ld a,c
cp %10100000 : rl d
dec d : dec d : jr OffsetReadE
CASE00x: call ReadNibble
ld e,a : ld a,c
cp %00100000 : rl e : jr SaveOffset
CASE11x cp %11100000 : jr c,CASE110
CASE111: ld e,iyl : ld d,iyh : jr MatchLen
CASE110: ld d,(hl) : inc hl : jr OffsetReadE
ExtendedCode: call ReadNibble : inc a : jr z,ExtraByte
sub #F0+1 : add c : ret
ExtraByte ld a,15 : add c : add (hl) : inc hl : ret nc
ld a,(hl) : inc hl
ld b,(hl) : inc hl : ret nz
pop de : pop de : ret
ReadNibble: ld c,a : xor a : exa : ret m
UpdateNibble ld a,(hl) : or #F0 : exa
ld a,(hl) : inc hl : or #0F
rrca : rrca : rrca : rrca : ret