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Diffstat (limited to 'tools/src/minilzlib/lzmadec.h')
| -rw-r--r-- | tools/src/minilzlib/lzmadec.h | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/tools/src/minilzlib/lzmadec.h b/tools/src/minilzlib/lzmadec.h new file mode 100644 index 0000000..652165d --- /dev/null +++ b/tools/src/minilzlib/lzmadec.h @@ -0,0 +1,114 @@ +/*++ + +Copyright (c) Alex Ionescu. All rights reserved. + +Module Name: + + lzmadec.h + +Abstract: + + This header file contains C-style definitions, constants, and enumerations + that map back to the LZMA Standard, specifically the probability model that + is used for encoding probabilities. + +Author: + + Alex Ionescu (@aionescu) 15-Apr-2020 - Initial version + +Environment: + + Windows & Linux, user mode and kernel mode. + +--*/ + +#pragma once + +// +// Literals can be 0-255 and are encoded in 3 different types of slots based on +// the previous literal decoded and the "match byte" used. +// +#define LZMA_LITERALS 256 +#define LZMA_LC_TYPES 3 +#define LZMA_LC_MODEL_SIZE (LZMA_LC_TYPES * LZMA_LITERALS) + +// +// These are the hardcoded LZMA properties we support for position and coders +// +#define LZMA_LC 3 +#define LZMA_PB 2 +#define LZMA_LP 0 +#define LZMA_LITERAL_CODERS (1 << LZMA_LC) +#define LZMA_POSITION_COUNT (1 << LZMA_PB) + +// +// Lengths are described in three different ways using "low", "mid", and "high" +// bit trees. The first two trees encode 3 bits, the last encodes 8. We never +// encode a length less than 2 bytes, since that's wasteful. +// +#define LZMA_MAX_LOW_LENGTH (1 << 3) +#define LZMA_MAX_MID_LENGTH (1 << 3) +#define LZMA_MAX_HIGH_LENGTH (1 << 8) +#define LZMA_MIN_LENGTH 2 + +// +// Distances can be encoded in different ways, based on the distance slot. +// Lengths of 2, 3, 4 bytes are directly encoded with their own slot. Lengths +// over 5 share a slot, which is then further subdivded into 3 different ways +// of encoding them, which are described in the source. +// +#define LZMA_DISTANCE_SLOTS 64 +#define LZMA_FIRST_CONTEXT_DISTANCE_SLOT 4 +#define LZMA_FIRST_FIXED_DISTANCE_SLOT 14 +#define LZMA_DISTANCE_ALIGN_BITS 4 +#define LZMA_DISTANCE_ALIGN_SLOTS (1 << LZMA_DISTANCE_ALIGN_BITS) + +// +// Total number of probabilities that we need to store +// +#define LZMA_BIT_MODEL_SLOTS (1174 + \ + (LZMA_LITERAL_CODERS * \ + LZMA_LC_MODEL_SIZE)) + +// +// The LZMA probability bit model is typically based on the last LZMA sequences +// that were decoded. There are 11 such possibilities that are tracked. +// +typedef enum _LZMA_SEQUENCE_STATE +{ + // + // State where we last saw three literals + // + LzmaLitLitLitState, + // + // States where we last saw two literals preceeded by a non-literal + // + LzmaMatchLitLitState, + LzmaRepLitLitState, + LzmaLitShortrepLitLitState, + // + // States where we last saw one literal preceeded by a non-literal + // + LzmaMatchLitState, + LzmaRepLitState, + LzmaLitShortrepLitState, + // + // Separator between states where we last saw at least one literal + // + LzmaMaxLitState, + // + // States where we last saw a non-literal preceeded by a literal + // + LzmaLitMatchState = 7, + LzmaLitRepState, + LzmaLitShortrepState, + // + // States where we last saw two non-literals + // + LzmaNonlitMatchState, + LzmaNonlitRepState, + // + // Separator for number of total states + // + LzmaMaxState +} LZMA_SEQUENCE_STATE, * PLZMA_SEQUENCE_STATE; |