From 30bf0f51335e87812ffeb54e9437f0b6a1514d67 Mon Sep 17 00:00:00 2001 From: "Juan J. Martinez" Date: Tue, 6 Sep 2022 07:37:20 +0100 Subject: Updated rasm to 1.7 --- tools/rasm/decrunch/dzx0_fast.asm | 237 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 237 insertions(+) create mode 100644 tools/rasm/decrunch/dzx0_fast.asm (limited to 'tools/rasm/decrunch/dzx0_fast.asm') diff --git a/tools/rasm/decrunch/dzx0_fast.asm b/tools/rasm/decrunch/dzx0_fast.asm new file mode 100644 index 0000000..55f4388 --- /dev/null +++ b/tools/rasm/decrunch/dzx0_fast.asm @@ -0,0 +1,237 @@ +; +; Speed-optimized ZX0 decompressor by spke (187 bytes) +; +; ver.00 by spke (27/01-23/03/2021, 191 bytes) +; ver.01 by spke (24/03/2021, 193(+2) bytes - fixed a bug in the initialization) +; ver.01patch2 by uniabis (25/03/2021, 191(-2) bytes - fixed a bug with elias over 8bits) +; ver.01patch9 by uniabis (10/09/2021, 187(-4) bytes - support for new v2 format) +; +; Original ZX0 decompressors were written by Einar Saukas +; +; This decompressor was written on the basis of "Standard" decompressor by +; Einar Saukas and optimized for speed by spke. This decompressor is +; about 5% faster than the "Turbo" decompressor, which is 128 bytes long. +; It has about the same speed as the 412 bytes version of the "Mega" decompressor. +; +; The decompressor uses AF, BC, DE, HL and IX and relies upon self-modified code. +; +; The decompression is done in the standard way: +; +; ld hl,FirstByteOfCompressedData +; ld de,FirstByteOfMemoryForDecompressedData +; call DecompressZX0 +; +; Of course, ZX0 compression algorithms are (c) 2021 Einar Saukas, +; see https://github.com/einar-saukas/ZX0 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. + +macro DecompressZX0 + + ld ix, @CopyMatch1 + ld bc, $ffff + ld (@PrevOffset+1), bc ; default offset is -1 + inc bc + ld a, $80 + jr @RunOfLiterals ; BC is assumed to contains 0 most of the time + +@ShorterOffsets: + ld b, $ff ; the top byte of the offset is always $FF + ld c, (hl) + inc hl + rr c + ld (@PrevOffset+1), bc + jr nc, @LongerMatch + +@CopyMatch2: ; the case of matches with len=2 + ld bc, 2 + + ; the faster match copying code +@CopyMatch1: + push hl ; preserve source + +@PrevOffset: + ld hl, $ffff ; restore offset (default offset is -1) + add hl, de ; HL = dest - offset + ldir + pop hl ; restore source + + ; after a match you can have either + ; 0 + = run of literals, or + ; 1 + + [7-bits of offset lsb + 1-bit of length] + = another match +@AfterMatch1: + add a, a + jr nc, @RunOfLiterals + +@UsualMatch: ; this is the case of usual match+offset + add a, a + jr nc, @LongerOffets + jr nz, @ShorterOffsets ; NZ after NC == "confirmed C" + + ld a, (hl) ; reload bits + inc hl + rla + + jr c, @ShorterOffsets + +@LongerOffets: + ld c, $fe + + add a, a ; inline read gamma + rl c + add a, a + jr nc, $-4 + + call z, @ReloadReadGamma + +@ProcessOffset: + + inc c + ret z ; end-of-data marker (only checked for longer offsets) + rr c + ld b, c + ld c, (hl) + inc hl + rr c + ld (@PrevOffset+1), bc + + ; lowest bit is the first bit of the gamma code for length + jr c, @CopyMatch2 + +@LongerMatch: + ld bc, 1 + + add a, a ; inline read gamma + rl c + add a, a + jr nc, $-4 + + call z,@ReloadReadGamma + +@CopyMatch3: + push hl ; preserve source + ld hl, (@PrevOffset+1) ; restore offset + add hl, de ; HL = dest - offset + + ; because BC>=3-1, we can do 2 x LDI safely + ldi + ldir + inc c + ldi + pop hl ; restore source + + ; after a match you can have either + ; 0 + = run of literals, or + ; 1 + + [7-bits of offset lsb + 1-bit of length] + = another match +@AfterMatch3: + add a, a + jr c, @UsualMatch + +@RunOfLiterals: + inc c + add a, a + jr nc, @LongerRun + jr nz, @CopyLiteral ; NZ after NC == "confirmed C" + + ld a, (hl) ; reload bits + inc hl + rla + + jr c, @CopyLiteral + +@LongerRun: + add a, a ; inline read gamma + rl c + add a, a + jr nc, $-4 + + jr nz, @CopyLiterals + + ld a, (hl) ; reload bits + inc hl + rla + + call nc, @ReadGammaAligned + +@CopyLiterals: + ldi + +@CopyLiteral: + ldir + + ; after a literal run you can have either + ; 0 + = match using a repeated offset, or + ; 1 + + [7-bits of offset lsb + 1-bit of length] + = another match + add a, a + jr c, @UsualMatch + +@RepMatch: + inc c + add a, a + jr nc, @LongerRepMatch + jr nz, @CopyMatch1 ; NZ after NC == "confirmed C" + + ld a, (hl) ; reload bits + inc hl + rla + + jr c, @CopyMatch1 + +@LongerRepMatch: + add a, a ; inline read gamma + rl c + add a, a + jr nc, $-4 + + jp nz, @CopyMatch1 + + ; this is a crafty equivalent of CALL ReloadReadGamma : JP CopyMatch1 + push ix + + ; the subroutine for reading the remainder of the partly read Elias gamma code. + ; it has two entry points: ReloadReadGamma first refills the bit reservoir in A, + ; while ReadGammaAligned assumes that the bit reservoir has just been refilled. +@ReloadReadGamma: + ld a, (hl) ; reload bits + inc hl + rla + + ret c +@ReadGammaAligned: + add a, a + rl c + add a, a + ret c + add a, a + rl c + add a, a +@ReadingLongGamma: ; this loop does not need unrolling, as it does not get much use anyway + ret c + add a, a + rl c + rl b + add a, a + jr nz, @ReadingLongGamma + + ld a, (hl) ; reload bits + inc hl + rla + jr @ReadingLongGamma +mend + -- cgit v1.2.3