lzsa/asm/z80/unlzsa2_fast_v1.asm

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;
; Speed-optimized LZSA2 decompressor by spke (v.1 02-07/06/2019, 218 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,FirstByteOfCompressedData
; ld de,FirstByteOfMemoryForDecompressedData
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; call DecompressLZSA2
;
; Backward compression is also supported; you can compress files backward using:
;
; lzsa.exe -f2 -r -b <sourcefile> <outfile>
;
; and decompress the resulting files using:
;
; ld hl,LastByteOfCompressedData
; ld de,LastByteOfMemoryForDecompressedData
; call DecompressLZSA2
;
; (do not forget to uncomment the BACKWARD_DECOMPRESS option in the decompressor).
;
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; 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
;
; 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
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@DecompressLZSA2:
; A' stores next nibble as %1111.... or assumed to contain trash
; B is assumed to be 0
xor a : ld b,a : exa : jr ReadToken
LongerMatch: exa : jp m,.noUpdate
ld a,(hl) : or #F0 : exa
ld a,(hl) : NEXT_HL : or #0F
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rrca : rrca : rrca : rrca
.noUpdate sub #F0-9 : cp 15+9 : jr c,CopyMatch
;inc a : jr z,LongMatch : sub #F0-9+1 : jp CopyMatch
LongMatch: ;ld a,24 :
add (hl) : NEXT_HL : jr nc,CopyMatch
ld c,(hl) : NEXT_HL
ld b,(hl) : NEXT_HL
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jr nz,CopyMatch.useC
pop de : ret
ManyLiterals: ld a,18 :
add (hl) : NEXT_HL : jr nc,CopyLiterals
ld c,(hl) : NEXT_HL
ld a,b : ld b,(hl) : NEXT_HL
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jr CopyLiterals.useBC
MoreLiterals: ld b,(hl) : NEXT_HL
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exa : jp m,.noUpdate
ld a,(hl) : or #F0 : exa
ld a,(hl) : NEXT_HL : or #0F
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rrca : rrca : rrca : rrca
.noUpdate ;sub #F0-3 : cp 15+3 : jr z,ManyLiterals
inc a : jr z,ManyLiterals : sub #F0-3+1
CopyLiterals: ld c,a
.useC ld a,b : ld b,0
.useBC BLOCKCOPY
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push de : or a : jp p,CASE0xx : jr CASE1xx
; if "LL" of the byte token is equal to 0,
; there are no literals to copy
NoLiterals: xor (hl) : NEXT_HL
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push de : jp m,CASE1xx
; short (5 or 9 bit long) offsets
CASE0xx ld d,#FF : cp %01000000 : jr c,CASE00x
; "01x": the case of the 9-bit offset
CASE01x: cp %01100000 : rl d
ReadOffsetE: ld e,(hl) : NEXT_HL
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SaveOffset: ld ixl,e : ld ixh,d
MatchLen: inc a : and %00000111 : jr z,LongerMatch : inc a
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
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; compressed data stream contains records
; each record begins with the byte token "XYZ|LL|MMM"
ReadToken: ld a,(hl) : and %00011000 : jr z,NoLiterals
jp pe,MoreLiterals ; 00 has already been processed; this identifies the case of 11
rrca : rrca : rrca
ld c,a : ld a,(hl) : NEXT_HL ; token is re-read for further processing
BLOCKCOPY
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; the token and literals are followed by the offset
push de : or a : jp p,CASE0xx
CASE1xx cp %11000000 : jr nc,CASE11x
; "10x": the case of the 5-bit offset
CASE10x: ld c,a : xor a
exa : jp m,.noUpdate
ld a,(hl) : or #F0 : exa
ld a,(hl) : NEXT_HL : or #0F
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rrca : rrca : rrca : rrca
.noUpdate ld d,a : ld a,c
cp %10100000 : rl d
dec d : dec d : jr ReadOffsetE
; "00x": the case of the 5-bit offset
CASE00x: ld c,a : xor a
exa : jp m,.noUpdate
ld a,(hl) : or #F0 : exa
ld a,(hl) : NEXT_HL : or #0F
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rrca : rrca : rrca : rrca
.noUpdate ld e,a : ld a,c
cp %00100000 : rl e : jp SaveOffset
; two remaining cases
CASE11x cp %11100000 : jr c,CASE110
; "111": repeated offset
CASE111: ld e,ixl : ld d,ixh : jr MatchLen
; "110": 16-bit offset
CASE110: ld d,(hl) : NEXT_HL : jr ReadOffsetE
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