/**
* \file lzma/lzma.h
* \brief LZMA1 and LZMA2 filters
*
* \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 LZMA1 Filter ID
*
* LZMA1 is the very same thing as what was called just LZMA in earlier
* LZMA Utils, 7-Zip, and LZMA SDK. It's called LZMA1 here to prevent
* developers from accidentally using LZMA when they actually want LZMA2.
*/
#define LZMA_FILTER_LZMA1 LZMA_VLI_C(0x4000000000000001)
/**
* \brief LZMA2 Filter ID
*
* Usually you want this instead of LZMA1. Compared to LZMA1, LZMA2 adds
* support for LZMA_SYNC_FLUSH, uncompressed chunks (expands uncompressible
* data less), possibility to change lc/lp/pb in the middle of encoding, and
* some other internal improvements.
*/
#define LZMA_FILTER_LZMA2 LZMA_VLI_C(0x21)
/**
* \brief Match finders
*
* Match finder has major effect on both speed and compression ratio.
* Usually hash chains are faster than binary trees.
*
* The memory usage formulas are only rough estimates, which are closest to
* reality when dict_size is a power of two. The formulas are more complex
* in reality, and can also change a little between liblzma versions. Use
* lzma_memusage_encoder() to get more accurate estimate of memory usage.
*/
typedef enum {
LZMA_MF_HC3 = 0x03,
/**<
* \brief Hash Chain with 2- and 3-byte hashing
*
* Minimum nice_len: 3
*
* Memory usage:
* - dict_size <= 16 MiB: dict_size * 7.5
* - dict_size > 16 MiB: dict_size * 5.5 + 64 MiB
*/
LZMA_MF_HC4 = 0x04,
/**<
* \brief Hash Chain with 2-, 3-, and 4-byte hashing
*
* Minimum nice_len: 4
*
* Memory usage: dict_size * 7.5
*/
LZMA_MF_BT2 = 0x12,
/**<
* \brief Binary Tree with 2-byte hashing
*
* Minimum nice_len: 2
*
* Memory usage: dict_size * 9.5
*/
LZMA_MF_BT3 = 0x13,
/**<
* \brief Binary Tree with 2- and 3-byte hashing
*
* Minimum nice_len: 3
*
* Memory usage:
* - dict_size <= 16 MiB: dict_size * 11.5
* - dict_size > 16 MiB: dict_size * 9.5 + 64 MiB
*/
LZMA_MF_BT4 = 0x14
/**<
* \brief Binary Tree with 2-, 3-, and 4-byte hashing
*
* Minimum nice_len: 4
*
* Memory usage: dict_size * 11.5
*/
} lzma_match_finder;
/**
* \brief Test if given match finder is supported
*
* Returns true if the given match finder is supported by this liblzma build.
* Otherwise false is returned. It is safe to call this with a value that
* isn't listed in lzma_match_finder enumeration; the return value will be
* false.
*
* There is no way to list which match finders are available in this
* particular liblzma version and build. It would be useless, because
* a new match finder, which the application developer wasn't aware,
* could require giving additional options to the encoder that the older
* match finders don't need.
*/
extern lzma_bool lzma_mf_is_supported(lzma_match_finder match_finder)
lzma_attr_const;
/**
* \brief LZMA compression modes
*
* This selects the function used to analyze the data produced by the match
* finder.
*/
typedef enum {
LZMA_MODE_FAST = 1,
/**<
* \brief Fast compression
*
* Fast mode is usually at its best when combined with
* a hash chain match finder.
*/
LZMA_MODE_NORMAL = 2
/**<
* \brief Normal compression
*
* 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 Test if given compression mode is supported
*
* Returns true if the given compression mode is supported by this liblzma
* build. Otherwise false is returned. It is safe to call this with a value
* that isn't listed in lzma_mode enumeration; the return value will be false.
*
* There is no way to list which modes are available in this particular
* liblzma version and build. It would be useless, because a new compression
* mode, which the application developer wasn't aware, could require giving
* additional options to the encoder that the older modes don't need.
*/
extern lzma_bool lzma_mode_is_supported(lzma_mode mode) lzma_attr_const;
/**
* \brief Options specific to the LZMA1 and LZMA2 filters
*
* Since LZMA1 and LZMA2 share most of the code, it's simplest to share
* the options structure too. For encoding, all but the reserved variables
* need to be initialized unless specifically mentioned otherwise.
*
* For raw decoding, both LZMA1 and LZMA2 need dict_size, preset_dict, and
* preset_dict_size (if preset_dict != NULL). LZMA1 needs also lc, lp, and pb.
*/
typedef struct {
/**
* \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.
*
* Maximum size of the dictionary depends on multiple things:
* - Memory usage limit
* - Available address space (not a problem on 64-bit systems)
* - Selected match finder (encoder only)
*
* Currently the maximum dictionary size for encoding is 1.5 GiB
* (i.e. (UINT32_C(1) << 30) + (UINT32_C(1) << 29)) even on 64-bit
* systems for certain match finder implementation reasons. In future,
* there may be match finders that support bigger dictionaries (3 GiB
* will probably be the maximum).
*
* Decoder already supports dictionaries up to 4 GiB - 1 B (i.e.
* UINT32_MAX), so increasing the maximum dictionary size of the
* encoder won't cause problems for old decoders.
*
* Because extremely small dictionaries sizes would have unneeded
* overhead in the decoder, the minimum dictionary size is 4096 bytes.
*
* \note When decoding, too big dictionary does no other harm
* than wasting memory.
*/
uint32_t dict_size;
# define LZMA_DICT_SIZE_MIN UINT32_C(4096)
# define LZMA_DICT_SIZE_DEFAULT (UINT32_C(1) << 23)
/**
* \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_dict;
/**
* \brief Size of the preset dictionary
*
* Specifies the size of the preset dictionary. If the size is
* bigger than dict_size, only the last dict_size bytes are processed.
*
* This variable is read only when preset_dict is not NULL.
*/
uint32_t preset_dict_size;
/**
* \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
*
* There is a limit that applies to literal context bits and literal
* position bits together: lc + lp <= 4. Without this limit the
* decoding could become very slow, which could have security related
* results in some cases like email servers doing virus scanning.
* This limit also simplifies the internal implementation in liblzma.
*
* There may be LZMA streams that have lc + lp > 4 (maximum lc
* possible would be 8). It is not possible to decode such streams
* with liblzma.
*/
uint32_t lc;
# define LZMA_LCLP_MIN 0
# define LZMA_LCLP_MAX 4
# define LZMA_LC_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 lp;
# define LZMA_LP_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 pb to 3, because 2**3 == 8.
*/
uint32_t pb;
# define LZMA_PB_MIN 0
# define LZMA_PB_MAX 4
# define LZMA_PB_DEFAULT 2
/**
* \brief Indicate if the options structure is persistent
*
* If this is true, the application must keep this options structure
* available after the LZMA2 encoder has been initialized. With
* persistent structure it is possible to change some encoder options
* in the middle of the encoding process without resetting the encoder.
*
* This option is used only by LZMA2. LZMA1 ignores this and it is
* safe to not initialize this when encoding with LZMA1.
*/
lzma_bool persistent;
/** LZMA compression mode */
lzma_mode mode;
/**
* \brief Nice length of a match
*
* This determines how many bytes the encoder compares from the match
* candidates when looking for the best match. Once a match of at
* least nice_len bytes long is found, the encoder stops looking for
* better condidates and encodes the match. (Naturally, if the found
* match is actually longer than nice_len, the actual length is
* encoded; it's not truncated to nice_len.)
*
* Bigger values usually increase the compression ratio and
* compression time. For most files, 30 to 100 is a good value,
* which gives very good compression ratio at good speed.
*
* The exact minimum value depends on the match finder. The maximum is
* 273, which is the maximum length of a match that LZMA can encode.
*/
uint32_t nice_len;
/** Match finder ID */
lzma_match_finder mf;
/**
* \brief Maximum search depth in the match finder
*
* For every input byte, match finder searches through the hash chain
* or binary tree in a loop, each iteration going one step deeper in
* the chain or tree. The searching stops if
* - a match of at least nice_len bytes long is found;
* - all match candidates from the hash chain or binary tree have
* been checked; or
* - maximum search depth is reached.
*
* Maximum search depth is needed to prevent the match finder from
* wasting too much time in case there are lots of short match
* candidates. On the other hand, stopping the search before all
* candidates have been checked can reduce compression ratio.
*
* Setting depth to zero tells liblzma to use an automatic default
* value, that depends on the selected match finder and nice_len.
* The default is in the range [10, 200] or so (it may vary between
* liblzma versions).
*
* Using a bigger depth value than the default can increase
* compression ratio in some cases. There is no strict maximum value,
* but high values (thousands or millions) should be used with care:
* the encoder could remain fast enough with typical input, but
* malicious input could cause the match finder to slow down
* dramatically, possibly creating a denial of service attack.
*/
uint32_t depth;
/*
* Reserved space to allow possible future extensions without
* breaking the ABI. You should not touch these, because the names
* of these variables may change. These are and will never be used
* with the currently supported options, so it is safe to leave these
* uninitialized.
*/
void *reserved_ptr1;
void *reserved_ptr2;
uint32_t reserved_int1;
uint32_t reserved_int2;
uint32_t reserved_int3;
uint32_t reserved_int4;
uint32_t reserved_int5;
uint32_t reserved_int6;
uint32_t reserved_int7;
uint32_t reserved_int8;
lzma_reserved_enum reserved_enum1;
lzma_reserved_enum reserved_enum2;
lzma_reserved_enum reserved_enum3;
lzma_reserved_enum reserved_enum4;
} lzma_options_lzma;
/**
* \brief Set a compression preset to lzma_options_lzma structure
*
* 0 is the fastest and 9 is the slowest. These match the switches -0 .. -9
* of the xz command line tool. In addition, it is possible to bitwise-or
* flags to the preset. Currently only LZMA_PRESET_EXTREME is supported.
* The flags are defined in container.h, because the flags are used also
* with lzma_easy_encoder().
*
* The preset values are subject to changes between liblzma versions.
*
* This function is available only if LZMA1 or LZMA2 encoder has been enabled
* when building liblzma.
*/
extern lzma_bool lzma_lzma_preset(lzma_options_lzma *options, uint32_t preset);
