Check in optimized-for-speed Z80 decompressor contributed by spke

This commit is contained in:
emmanuel-marty 2019-04-07 00:01:42 +02:00
parent 6aa2dae4b3
commit be54a4f889

103
asm/z80/unlzsa_fast_v1.asm Executable file
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;
; Speed-optimized LZSA decompressor by spke (v.1 03-05/04/2019, 122 bytes)
;
; The data must be comressed 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
MoreLiterals: ; there are three possible situations here
; 1) a byte 0..253 is added to LLL and that is it or
; 2) a byte 254 is followed by another byte to add or
; 3) a byte 255 is followed by a word to be used
ld a,7 : add (hl) : inc hl : jp nc,CopyLiterals
.Overflow ; we get here if the literals length byte plus 7 is greater than 255
inc b : cp 5 : jr c,CopyLiterals : jr nz,.Code255 ; 5 is 7+254 modulo 256
.Code254 add (hl) : inc hl : jr nc,CopyLiterals : inc b : jr CopyLiterals
.Code255 ld c,(hl) : inc hl : ld b,(hl) : inc hl : jr CopyLiterals.UseC
; placed here this saves a JP per iteration
CopyMatchNC scf ; flag C for SBC HL,DE below must be set!!!
CopyMatch: ld c,a
.UseC ex (sp),hl : push hl ; BC = len, DE = offset, HL = dest, SP ->[dest,src]
sbc 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) : exa : ld a,(hl) : inc hl ; token is read twice to be re-used later
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...
CopyLiterals: ld c,a
.UseC ldir
NoLiterals: ; 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
exa : and #8F : jp m,LongOffset
ShortOffset: ld d,b ; we keep B=0 for situations like this
; short matches have length 0+3..14+3
ReadMatchLen: add 3 : cp 15+3 : jp c,CopyMatch
; MMMM=15 indicates a multi-byte number of literals
; there are three possible situations here
; 1) a byte 0..253 is added to MMMM and that is it or
; 2) a byte 254 is followed by another byte to add or
; 3) a byte 255 is followed by a word to be used
LongerMatch: add (hl) : inc hl : jp nc,CopyMatchNC
.Overflow ; we get here if the match length byte plus 15+3 is greater than 255
inc b : cp 16 : jr c,CopyMatch : jr nz,.Code255 ; 16 is 15+3+254 modulo 256
.Code254 add (hl) : inc hl : jr nc,CopyMatchNC : inc b : jr CopyMatch
.Code255 ld c,(hl) : inc hl : ld b,(hl) : inc hl
; two-byte match length that is equal to zero is the marker for End-of-Data (EOD)
.CheckEOD ld a,b : or c : jr nz,CopyMatch.UseC
pop de : ret
LongOffset: ; read second byte of the offset
ld d,(hl) : inc hl
add -128+3 : cp 15+3 : jp c,CopyMatch
add (hl) : inc hl : jp nc,CopyMatchNC
jr LongerMatch.Overflow