New small decompressor for LZSA2 (-5 bytes, +1% speed)
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specke
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@ -1,5 +1,5 @@
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;
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; Size-optimized LZSA2 decompressor by spke & uniabis (139 bytes)
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; Size-optimized LZSA2 decompressor by spke & uniabis (134 bytes)
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;
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; ver.00 by spke for LZSA 1.0.0 (02-09/06/2019, 145 bytes);
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; ver.01 by spke for LZSA 1.0.5 (24/07/2019, added support for backward decompression);
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@ -7,6 +7,8 @@
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; ver.03 by spke for LZSA 1.0.7 (01/08/2019, 140(-4) bytes, -1.4% speed and small re-organization of macros);
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; ver.04 by spke for LZSA 1.1.0 (26/09/2019, removed usage of IY, added full revision history)
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; ver.05 by spke for LZSA 1.1.1 (11/10/2019, 139(-1) bytes, +0.1% speed)
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; ver.06 by spke (11-12/04/2021, added some comments)
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; ver.07 by spke (04-05/04/2022, 134(-5) bytes, +1% speed, using self-modifying code by default)
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;
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; The data must be compressed using the command line compressor by Emmanuel Marty
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; The compression is done as follows:
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@ -55,8 +57,8 @@
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; 3. This notice may not be removed or altered from any source distribution.
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;
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; DEFINE BACKWARD_DECOMPRESS ; uncomment for data compressed with option -b
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; DEFINE HD64180 ; uncomment for systems using Hitachi HD64180
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; DEFINE BACKWARD_DECOMPRESS ; uncomment for data compressed with option -b (+5 bytes, -3% speed)
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; DEFINE AVOID_SELFMODIFYING_CODE ; uncomment to disallow self-modifying code (-1 byte, -4% speed)
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IFNDEF BACKWARD_DECOMPRESS
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@ -65,7 +67,7 @@
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ENDM
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MACRO ADD_OFFSET
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ex de,hl : add hl,de
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add hl,de
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ENDM
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MACRO BLOCKCOPY
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@ -79,7 +81,10 @@
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ENDM
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MACRO ADD_OFFSET
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push hl : or a : sbc hl,de : pop de ; 11+4+15+10 = 40t / 5 bytes
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;push hl : or a : sbc hl,de : pop de ; 11+4+15+10 = 40t / 5 bytes
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; HL = DE - HL
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ld a,e : sub l : ld l,a
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ld a,d : sbc h : ld h,a ; 6*4 = 24t / 6 bytes
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ENDM
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MACRO BLOCKCOPY
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@ -88,85 +93,90 @@
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ENDIF
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IFNDEF HD64180
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@DecompressLZSA2:
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; in many places we assume that B = 0
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; flag P in A' signals the need to re-load the nibble store
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xor a : ld b,a : exa : jr .ReadToken
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MACRO LD_IX_DE
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ld ixl,e : ld ixh,d
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ENDM
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.CASE00x: ; token "00Z" stands for 5-bit offsets
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; (read a nibble for offset bits 1-4 and use the inverted bit Z
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; of the token as bit 0 of the offset; set bits 5-15 of the offset to 1)
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push af
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call ReadNibble.skipLDCA : ld c,a
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pop af
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cp %00100000 : rl c : jr .SaveOffset
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MACRO LD_DE_IX
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ld e,ixl : ld d,ixh
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ENDM
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.CASE0xx dec b : cp %01000000 : jr c,.CASE00x
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.CASE01x: ; token "01Z" stands for 9-bit offsets
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; (read a byte for offset bits 0-7 and use the inverted bit Z
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; for bit 8 of the offset; set bits 9-15 of the offset to 1)
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cp %01100000
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.doRLB rl b
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.OffsetReadC: ld c,(hl) : NEXT_HL
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IFNDEF AVOID_SELFMODIFYING_CODE
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.SaveOffset: ld (.PrevOffset),bc : ld b,0
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ELSE
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MACRO LD_IX_DE
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push de : pop ix
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ENDM
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MACRO LD_DE_IX
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push ix : pop de
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ENDM
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.SaveOffset: push bc : pop ix : ld b,0
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ENDIF
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@DecompressLZSA2:
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xor a : ld b,a : exa : jr ReadToken
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.MatchLen: and %00000111 : add 2 : cp 9
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call z,ExtendedCode
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CASE00x: call ReadNibble
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ld e,a : ld a,c
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cp %00100000 : rl e : jr SaveOffset
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.CopyMatch: ld c,a
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push hl ; BC = len, DE = dest, HL = -offset, SP -> [src]
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CASE0xx ld d,#FF : cp %01000000 : jr c,CASE00x
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IFNDEF AVOID_SELFMODIFYING_CODE
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.PrevOffset EQU $+1 : ld hl,0
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ELSE
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push ix : pop hl
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ENDIF
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ADD_OFFSET
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BLOCKCOPY ; BC = 0, DE = dest
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pop hl ; HL = src
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CASE01x: cp %01100000 : rl d
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.ReadToken: ld a,(hl) : NEXT_HL : push af
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and %00011000 : jr z,.NoLiterals
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OffsetReadE: ld e,(hl) : NEXT_HL
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SaveOffset: LD_IX_DE
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rrca : rrca : rrca
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call pe,ExtendedCode
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MatchLen: and %00000111 : add 2 : cp 9 : call z,ExtendedCode
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ld c,a
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BLOCKCOPY
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CopyMatch: ld c,a
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ex (sp),hl ; BC = len, DE = -offset, HL = dest, SP -> [src]
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ADD_OFFSET ; BC = len, DE = dest, HL = dest+(-offset), SP -> [src]
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BLOCKCOPY ; BC = 0, DE = dest
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pop hl ; HL = src
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.NoLiterals: pop af : or a : jp p,.CASE0xx
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ReadToken: ld a,(hl) : NEXT_HL : push af
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and %00011000 : jr z,NoLiterals
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.CASE1xx cp %11000000 : jr c,.CASE10x
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; token "111" stands for repeat offsets
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; (reuse the offset value of the previous match command)
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cp %11100000 : jr nc,.MatchLen
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rrca : rrca : rrca
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call pe,ExtendedCode
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.CASE110: ; token "110" stands for 16-bit offset
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; (read a byte for offset bits 8-15, then another byte for offset bits 0-7)
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ld b,(hl) : NEXT_HL : jr .OffsetReadC
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ld c,a
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BLOCKCOPY
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.CASE10x: ; token "10Z" stands for 13-bit offsets
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; (read a nibble for offset bits 9-12 and use the inverted bit Z
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; for bit 8 of the offset, then read a byte for offset bits 0-7.
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; set bits 13-15 of the offset to 1. substract 512 from the offset to get the final value)
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call ReadNibble : ld b,a
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ld a,c : cp %10100000
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dec b : jr .doRLB
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NoLiterals: pop af : push de
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or a : jp p,CASE0xx
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CASE1xx cp %11000000 : jr nc,CASE11x
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CASE10x: call ReadNibble
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ld d,a : ld a,c
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cp %10100000 ;: rl d
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dec d : rl d : DB #CA ; jr OffsetReadE ; #CA is JP Z,.. to skip all commands in CASE110 before jr OffsetReadE
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CASE110: ld d,(hl) : NEXT_HL : jr OffsetReadE
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CASE11x cp %11100000 : jr c,CASE110
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CASE111: LD_DE_IX : jr MatchLen
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ExtendedCode: call ReadNibble : inc a : jr z,ExtraByte
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sub #F0+1 : add c : ret
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ExtraByte ld a,15 : add c : add (hl) : NEXT_HL : ret nc
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ld a,(hl) : NEXT_HL
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ld b,(hl) : NEXT_HL : ret nz
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pop de : pop de ; RET is not needed, because RET from ReadNibble is sufficient
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pop bc ; RET is not needed, because RET from ReadNibble is sufficient
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ReadNibble: ld c,a : xor a : exa : ret m
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UpdateNibble ld a,(hl) : or #F0 : exa
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ReadNibble: ld c,a
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.skipLDCA xor a : exa : ret m
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ld a,(hl) : or #F0 : exa
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ld a,(hl) : NEXT_HL : or #0F
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rrca : rrca : rrca : rrca : ret
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