diff options
Diffstat (limited to 'src/liblzma/lzma/lzma_common.h')
| -rw-r--r-- | src/liblzma/lzma/lzma_common.h | 45 |
1 files changed, 23 insertions, 22 deletions
diff --git a/src/liblzma/lzma/lzma_common.h b/src/liblzma/lzma/lzma_common.h index e31e285f..09efd387 100644 --- a/src/liblzma/lzma/lzma_common.h +++ b/src/liblzma/lzma/lzma_common.h @@ -171,53 +171,54 @@ literal_init(probability (*probs)[LITERAL_CODER_SIZE], // Match distance // //////////////////// -// Different set of probabilities is used for match distances that have very +// 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 LEN_TO_POS_STATES 4 +#define DIST_STATES 4 // Macro to get the index of the appropriate probability array. -#define get_len_to_pos_state(len) \ - ((len) < LEN_TO_POS_STATES + MATCH_LEN_MIN \ +#define get_dist_state(len) \ + ((len) < DIST_STATES + MATCH_LEN_MIN \ ? (len) - MATCH_LEN_MIN \ - : LEN_TO_POS_STATES - 1) + : DIST_STATES - 1) -// The highest two bits of a match distance (pos slot) are encoded using six -// bits. See fastpos.h for more explanation. -#define POS_SLOT_BITS 6 -#define POS_SLOTS (1 << POS_SLOT_BITS) +// The highest two bits of a match distance (distance slot) are encoded +// using six bits. See fastpos.h for more explanation. +#define DIST_SLOT_BITS 6 +#define DIST_SLOTS (1 << DIST_SLOT_BITS) // Match distances up to 127 are fully encoded using probabilities. Since -// the highest two bits (pos slot) are always encoded using six bits, the -// distances 0-3 don't need any additional bits to encode, since the pos -// slot itself is the same as the actual distance. START_POS_MODEL_INDEX -// indicates the first pos slot where at least one additional bit is needed. -#define START_POS_MODEL_INDEX 4 +// 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 4 // Match distances greater than 127 are encoded in three pieces: -// - pos slot: the highest two bits +// - 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 pos slot value of 14 is for distances 128-191 (see the table in +// The distance slot value of 14 is for distances 128-191 (see the table in // fastpos.h to understand why). -#define END_POS_MODEL_INDEX 14 +#define DIST_MODEL_END 14 -// Pos slots that indicate a distance <= 127. -#define FULL_DISTANCES_BITS (END_POS_MODEL_INDEX / 2) +// Distance slots that indicate a distance <= 127. +#define FULL_DISTANCES_BITS (DIST_MODEL_END / 2) #define FULL_DISTANCES (1 << FULL_DISTANCES_BITS) // For match distances greater than 127, only the highest two bits and the // lowest four bits (alignment) is encoded using probabilities. #define ALIGN_BITS 4 -#define ALIGN_TABLE_SIZE (1 << ALIGN_BITS) -#define ALIGN_MASK (ALIGN_TABLE_SIZE - 1) +#define ALIGN_SIZE (1 << ALIGN_BITS) +#define ALIGN_MASK (ALIGN_SIZE - 1) // LZMA remembers the four most recent match distances. Reusing these distances // tends to take less space than re-encoding the actual distance value. -#define REP_DISTANCES 4 +#define REPS 4 #endif |