/* * LZMA2 definitions * * Authors: Lasse Collin <[email protected]> * Igor Pavlov <https://7-zip.org/> * * This file has been put into the public domain. * You can do whatever you want with this file. */ #ifndef XZ_LZMA2_H #define XZ_LZMA2_H /* Range coder constants */ #define RC_SHIFT_BITS … #define RC_TOP_BITS … #define RC_TOP_VALUE … #define RC_BIT_MODEL_TOTAL_BITS … #define RC_BIT_MODEL_TOTAL … #define RC_MOVE_BITS … /* * Maximum number of position states. A position state is the lowest pb * number of bits of the current uncompressed offset. In some places there * are different sets of probabilities for different position states. */ #define POS_STATES_MAX … /* * This enum is used to track which LZMA symbols have occurred most recently * and in which order. This information is used to predict the next symbol. * * Symbols: * - Literal: One 8-bit byte * - Match: Repeat a chunk of data at some distance * - Long repeat: Multi-byte match at a recently seen distance * - Short repeat: One-byte repeat at a recently seen distance * * The symbol names are in from STATE_oldest_older_previous. REP means * either short or long repeated match, and NONLIT means any non-literal. */ enum lzma_state { … }; /* Total number of states */ #define STATES … /* The lowest 7 states indicate that the previous state was a literal. */ #define LIT_STATES … /* Indicate that the latest symbol was a literal. */ static inline void lzma_state_literal(enum lzma_state *state) { … } /* Indicate that the latest symbol was a match. */ static inline void lzma_state_match(enum lzma_state *state) { … } /* Indicate that the latest state was a long repeated match. */ static inline void lzma_state_long_rep(enum lzma_state *state) { … } /* Indicate that the latest symbol was a short match. */ static inline void lzma_state_short_rep(enum lzma_state *state) { … } /* Test if the previous symbol was a literal. */ static inline bool lzma_state_is_literal(enum lzma_state state) { … } /* Each literal coder is divided in three sections: * - 0x001-0x0FF: Without match byte * - 0x101-0x1FF: With match byte; match bit is 0 * - 0x201-0x2FF: With match byte; match bit is 1 * * Match byte is used when the previous LZMA symbol was something else than * a literal (that is, it was some kind of match). */ #define LITERAL_CODER_SIZE … /* Maximum number of literal coders */ #define LITERAL_CODERS_MAX … /* Minimum length of a match is two bytes. */ #define MATCH_LEN_MIN … /* Match length is encoded with 4, 5, or 10 bits. * * Length Bits * 2-9 4 = Choice=0 + 3 bits * 10-17 5 = Choice=1 + Choice2=0 + 3 bits * 18-273 10 = Choice=1 + Choice2=1 + 8 bits */ #define LEN_LOW_BITS … #define LEN_LOW_SYMBOLS … #define LEN_MID_BITS … #define LEN_MID_SYMBOLS … #define LEN_HIGH_BITS … #define LEN_HIGH_SYMBOLS … #define LEN_SYMBOLS … /* * Maximum length of a match is 273 which is a result of the encoding * described above. */ #define MATCH_LEN_MAX … /* * Different sets of probabilities are used for match distances that have * very short match length: Lengths of 2, 3, and 4 bytes have a separate * set of probabilities for each length. The matches with longer length * use a shared set of probabilities. */ #define DIST_STATES … /* * Get the index of the appropriate probability array for decoding * the distance slot. */ static inline uint32_t lzma_get_dist_state(uint32_t len) { … } /* * The highest two bits of a 32-bit match distance are encoded using six bits. * This six-bit value is called a distance slot. This way encoding a 32-bit * value takes 6-36 bits, larger values taking more bits. */ #define DIST_SLOT_BITS … #define DIST_SLOTS … /* Match distances up to 127 are fully encoded using probabilities. Since * the highest two bits (distance slot) are always encoded using six bits, * the distances 0-3 don't need any additional bits to encode, since the * distance slot itself is the same as the actual distance. DIST_MODEL_START * indicates the first distance slot where at least one additional bit is * needed. */ #define DIST_MODEL_START … /* * Match distances greater than 127 are encoded in three pieces: * - distance slot: the highest two bits * - direct bits: 2-26 bits below the highest two bits * - alignment bits: four lowest bits * * Direct bits don't use any probabilities. * * The distance slot value of 14 is for distances 128-191. */ #define DIST_MODEL_END … /* Distance slots that indicate a distance <= 127. */ #define FULL_DISTANCES_BITS … #define FULL_DISTANCES … /* * For match distances greater than 127, only the highest two bits and the * lowest four bits (alignment) is encoded using probabilities. */ #define ALIGN_BITS … #define ALIGN_SIZE … #define ALIGN_MASK … /* Total number of all probability variables */ #define PROBS_TOTAL … /* * LZMA remembers the four most recent match distances. Reusing these * distances tends to take less space than re-encoding the actual * distance value. */ #define REPS … #endif
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