Index: xz/src/liblzma/api/lzma/lzma.h |
=================================================================== |
--- xz/src/liblzma/api/lzma/lzma.h (revision 0) |
+++ xz/src/liblzma/api/lzma/lzma.h (revision 0) |
@@ -0,0 +1,397 @@ |
+/** |
+ * \file lzma/lzma.h |
+ * \brief LZMA1 and LZMA2 filters |
+ */ |
+ |
+/* |
+ * Author: Lasse Collin |
+ * |
+ * This file has been put into the public domain. |
+ * You can do whatever you want with this file. |
+ * |
+ * See ../lzma.h for information about liblzma as a whole. |
+ */ |
+ |
+#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 LZMA Utils, |
+ * 7-Zip, and LZMA SDK. It's called LZMA1 here to prevent developers from |
+ * accidentally using LZMA when they actually want LZMA2. |
+ * |
+ * LZMA1 shouldn't be used for new applications unless you _really_ know |
+ * what you are doing. LZMA2 is almost always a better choice. |
+ */ |
+#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 (smaller expansion |
+ * when trying to compress uncompressible data), 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 |
+ * |
+ * Return 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_API(lzma_bool) lzma_mf_is_supported(lzma_match_finder match_finder) |
+ lzma_nothrow lzma_attr_const; |
+ |
+ |
+/** |
+ * \brief 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 LZMA1 or LZMA2 encoder. |
+ */ |
+} lzma_mode; |
+ |
+ |
+/** |
+ * \brief Test if given compression mode is supported |
+ * |
+ * Return 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_API(lzma_bool) lzma_mode_is_supported(lzma_mode mode) |
+ lzma_nothrow 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 the 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 the |
+ * future, there may be match finders that support bigger |
+ * dictionaries. |
+ * |
+ * 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. It is useful when compressing many |
+ * similar, relatively small chunks of data independently from |
+ * each other. The preset dictionary should contain typical |
+ * strings that occur in the files being compressed. The most |
+ * probable strings should be near the end of the preset dictionary. |
+ * |
+ * This feature should be used only in special situations. For |
+ * now, 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 .xz or .lzma file with preset dictionary, it |
+ * cannot be decoded with the regular decoder functions. In the |
+ * future, the .xz format will likely get support for preset |
+ * dictionary though. |
+ */ |
+ 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. |
+ * If preset_dict is not NULL but preset_dict_size is zero, |
+ * no preset dictionary is used (identical to only setting |
+ * preset_dict to 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 LZMA1 streams that have lc + lp > 4 (maximum possible |
+ * lc 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 |
+ |
+ /** 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 candidates 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, 32 to 128 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 LZMA1 and |
+ * LZMA2 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_API(lzma_bool) lzma_lzma_preset( |
+ lzma_options_lzma *options, uint32_t preset) lzma_nothrow; |
Property changes on: xz/src/liblzma/api/lzma/lzma.h |
___________________________________________________________________ |
Added: svn:eol-style |
+ LF |