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Update fast Z80 decompressor

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emmanuel-marty 2019-04-25 17:19:58 +02:00
parent bd6e31b03c
commit 97dd3ffc1f
1 changed files with 21 additions and 29 deletions
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50
asm/z80/unlzsa_fast_v1.asm
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@ -1,5 +1,5 @@
;
; Speed-optimized LZSA decompressor by spke (v.1 23-24/04/2019, 134 bytes)
; Speed-optimized LZSA decompressor by spke (v.1 03-25/04/2019, 110 bytes)
;
; The data must be comressed using the command line compressor by Emmanuel Marty
; The compression is done as follows:
@ -19,7 +19,6 @@
;
; 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.
@ -35,29 +34,15 @@
; 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
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 m,LongOffset
ld d,#FF : add 3 : cp 15+3 : jp c,CopyMatch
jr LongerMatch
ManyLiterals:
.code1 ld b,a : ld c,(hl) : inc hl : jr nz,CopyLiterals.UseC
.code0 ld b,(hl) : inc hl : jr CopyLiterals.UseC
NoLiterals: xor (hl) : inc hl
push de : ld e,(hl) : inc hl : jp m,LongOffset
ld d,#FF : add 3 : cp 15+3 : jr nc,LongerMatch
; 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
@ -79,12 +64,11 @@ ReadToken: ; first a byte token "O|LLL|MMMM" is read from the stream,
; 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 m,LongOffset
and #8F : jp p,ShortOffset
ShortOffset: ld d,#FF
; short matches have length 0+3..14+3
ReadMatchLen: add 3 : cp 15+3 : jp c,CopyMatch
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
@ -100,10 +84,18 @@ LongerMatch: add (hl) : inc hl : jr nc,CopyMatch
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 : jr nc,CopyMatch
jr LongerMatch.code1
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