/**
* \file lzma/lzma.h
* \brief LZMA filter
*
* \author Copyright (C) 1999-2006 Igor Pavlov
* \author Copyright (C) 2007 Lasse Collin
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
#ifndef LZMA_H_INTERNAL
# error Never include this file directly. Use <lzma.h> instead.
#endif
/**
* \brief Filter ID
*
* Filter ID of the LZMA filter. This is used as lzma_options_filter.id.
*/
#define LZMA_FILTER_LZMA LZMA_VLI_C(0x40)
/**
* \brief LZMA compression modes
*
* Currently there are only two modes. Earlier LZMA SDKs had also third
* mode between fast and best.
*/
typedef enum {
LZMA_MODE_INVALID = -1,
/**<
* \brief Invalid mode
*
* Used as array terminator in lzma_available_modes.
*/
LZMA_MODE_FAST = 0,
/**<
* \brief Fast compression
*
* Fast mode is usually at its best when combined with
* a hash chain match finder.
*/
LZMA_MODE_BEST = 2
/**<
* \brief Best compression ratio
*
* This is usually notably slower than fast mode. Use this
* together with binary tree match finders to expose the
* full potential of the LZMA encoder.
*/
} lzma_mode;
/**
* \brief Match finders
*
* Match finder has major effect on both speed and compression ratio.
* Usually hash chains are faster than binary trees.
*/
typedef enum {
LZMA_MF_INVALID = -1,
/**<
* \brief Invalid match finder ID
*
* Used as array terminator in lzma_available_match_finders.
*/
LZMA_MF_HC3 = 0x03,
/**<
* \brief Hash Chain with 3 bytes hashing
*
* \todo Memory requirements
*
* \note It's possible that this match finder gets
* removed in future. The definition will stay
* in this header, but liblzma may return
* LZMA_HEADER_ERROR if it is specified (just
* like it would if the match finder had been
* disabled at compile time).
*/
LZMA_MF_HC4 = 0x04,
/**<
* \brief Hash Chain with 4 bytes hashing
*
* Memory requirements: 7.5 * dictionary_size + 4 MiB
*
* \note It's possible that this match finder gets
* removed in future. The definition will stay
* in this header, but liblzma may return
* LZMA_HEADER_ERROR if it is specified (just
* like it would if the match finder had been
* disabled at compile time).
*/
LZMA_MF_BT2 = 0x12,
/**<
* \brief Binary Tree with 2 bytes hashing
*
* Memory requirements: 9.5 * dictionary_size + 4 MiB
*/
LZMA_MF_BT3 = 0x13,
/**<
* \brief Binary Tree with 3 bytes hashing
*
* Memory requirements: 11.5 * dictionary_size + 4 MiB
*/
LZMA_MF_BT4 = 0x14
/**<
* \brief Binary Tree with 4 bytes hashing
*
* Memory requirements: 11.5 * dictionary_size + 4 MiB
*/
} lzma_match_finder;
/**
* \brief Options specific to the LZMA method handler
*/
typedef struct {
/**********************************
* LZMA encoding/decoding options *
**********************************/
/* These options are required in encoder and also with raw decoding. */
/**
* \brief Dictionary size in bytes
*
* Dictionary size indicates how many bytes of the recently processed
* uncompressed data is kept in memory. One method to reduce size of
* the uncompressed data is to store distance-length pairs, which
* indicate what data to repeat from the dictionary buffer. Thus,
* the bigger the dictionary, the better compression ratio usually is.
*
* Raw decoding: Too big dictionary does no other harm than
* wasting memory. This value is ignored by lzma_raw_decode_buffer(),
* because it uses the target buffer as the dictionary.
*/
uint32_t dictionary_size;
# define LZMA_DICTIONARY_SIZE_MIN (UINT32_C(1) << 12)
# define LZMA_DICTIONARY_SIZE_MAX (UINT32_C(1) << 30)
# define LZMA_DICTIONARY_SIZE_DEFAULT (UINT32_C(1) << 23)
/**
* \brief Number of literal context bits
*
* How many of the highest bits of the previous uncompressed
* eight-bit byte (also known as `literal') are taken into
* account when predicting the bits of the next literal.
*
* \todo Example
*/
uint32_t literal_context_bits;
# define LZMA_LITERAL_CONTEXT_BITS_MIN 0
# define LZMA_LITERAL_CONTEXT_BITS_MAX 8
# define LZMA_LITERAL_CONTEXT_BITS_DEFAULT 3
/**
* \brief Number of literal position bits
*
* How many of the lowest bits of the current position (number
* of bytes from the beginning of the uncompressed data) in the
* uncompressed data is taken into account when predicting the
* bits of the next literal (a single eight-bit byte).
*
* \todo Example
*/
uint32_t literal_pos_bits;
# define LZMA_LITERAL_POS_BITS_MIN 0
# define LZMA_LITERAL_POS_BITS_MAX 4
# define LZMA_LITERAL_POS_BITS_DEFAULT 0
/**
* \brief Number of position bits
*
* How many of the lowest bits of the current position in the
* uncompressed data is taken into account when estimating
* probabilities of matches. A match is a sequence of bytes for
* which a matching sequence is found from the dictionary and
* thus can be stored as distance-length pair.
*
* Example: If most of the matches occur at byte positions
* of 8 * n + 3, that is, 3, 11, 19, ... set pos_bits to 3,
* because 2**3 == 8.
*/
uint32_t pos_bits;
# define LZMA_POS_BITS_MIN 0
# define LZMA_POS_BITS_MAX 4
# define LZMA_POS_BITS_DEFAULT 2
/**
* \brief Pointer to an initial dictionary
*
* It is possible to initialize the LZ77 history window using
* a preset dictionary. Here is a good quote from zlib's
* documentation; this applies to LZMA as is:
*
* "The dictionary should consist of strings (byte sequences) that
* are likely to be encountered later in the data to be compressed,
* with the most commonly used strings preferably put towards the
* end of the dictionary. Using a dictionary is most useful when
* the data to be compressed is short and can be predicted with
* good accuracy; the data can then be compressed better than
* with the default empty dictionary."
* (From deflateSetDictionary() in zlib.h of zlib version 1.2.3)
*
* This feature should be used only in special situations.
* It works correctly only with raw encoding and decoding.
* Currently none of the container formats supported by
* liblzma allow preset dictionary when decoding, thus if
* you create a .lzma file with preset dictionary, it cannot
* be decoded with the regular .lzma decoder functions.
*
* \todo This feature is not implemented yet.
*/
const uint8_t *preset_dictionary;
/**
* \brief Size of the preset dictionary
*
* Specifies the size of the preset dictionary. If the size is
* bigger than dictionary_size, only the last dictionary_size
* bytes are processed.
*
* This variable is read only when preset_dictionary is not NULL.
*/
uint32_t preset_dictionary_size;
/******************************************
* LZMA options needed only when encoding *
******************************************/
/** LZMA compression mode */
lzma_mode mode;
/**
* \brief Number of fast bytes
*
* Number of fast bytes determines how many bytes the encoder
* compares from the match candidates when looking for the best
* match. Bigger fast bytes value usually increase both compression
* ratio and time.
*/
uint32_t fast_bytes;
# define LZMA_FAST_BYTES_MIN 5
# define LZMA_FAST_BYTES_MAX 273
# define LZMA_FAST_BYTES_DEFAULT 128
/** Match finder ID */
lzma_match_finder match_finder;
/**
* \brief Match finder cycles
*
* Higher values give slightly better compression ratio but
* decrease speed. Use special value 0 to let liblzma use
* match-finder-dependent default value.
*
* \todo Write much better description.
*/
uint32_t match_finder_cycles;
} lzma_options_lzma;
/**
* \brief Available LZMA encoding modes
*
* Pointer to an array containing the list of available encoding modes.
*
* This variable is available only if LZMA encoder has been enabled.
*/
extern const lzma_mode *const lzma_available_modes;
/**
* \brief Available match finders
*
* Pointer to an array containing the list of available match finders.
* The last element is LZMA_MF_INVALID.
*
* This variable is available only if LZMA encoder has been enabled.
*/
extern const lzma_match_finder *const lzma_available_match_finders;
/**
* \brief Table of presets for the LZMA filter
*
* lzma_preset_lzma[0] is the fastest and lzma_preset_lzma[8] is the slowest.
* These presets match the switches -1 .. -9 of the lzma command line tool
*
* The preset values are subject to changes between liblzma versions.
*
* This variable is available only if LZMA encoder has been enabled.
*/
extern const lzma_options_lzma lzma_preset_lzma[9];
