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