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327 lines
10 KiB
327 lines
10 KiB
/////////////////////////////////////////////////////////////////////////////// |
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// |
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/// \file lz_encoder.h |
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/// \brief LZ in window and match finder API |
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/// |
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// Authors: Igor Pavlov |
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// Lasse Collin |
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// |
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// This file has been put into the public domain. |
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// You can do whatever you want with this file. |
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// |
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/////////////////////////////////////////////////////////////////////////////// |
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#ifndef LZMA_LZ_ENCODER_H |
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#define LZMA_LZ_ENCODER_H |
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#include "common.h" |
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/// A table of these is used by the LZ-based encoder to hold |
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/// the length-distance pairs found by the match finder. |
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typedef struct { |
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uint32_t len; |
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uint32_t dist; |
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} lzma_match; |
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typedef struct lzma_mf_s lzma_mf; |
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struct lzma_mf_s { |
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/////////////// |
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// In Window // |
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/////////////// |
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/// Pointer to buffer with data to be compressed |
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uint8_t *buffer; |
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/// Total size of the allocated buffer (that is, including all |
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/// the extra space) |
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uint32_t size; |
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/// Number of bytes that must be kept available in our input history. |
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/// That is, once keep_size_before bytes have been processed, |
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/// buffer[read_pos - keep_size_before] is the oldest byte that |
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/// must be available for reading. |
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uint32_t keep_size_before; |
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/// Number of bytes that must be kept in buffer after read_pos. |
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/// That is, read_pos <= write_pos - keep_size_after as long as |
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/// action is LZMA_RUN; when action != LZMA_RUN, read_pos is allowed |
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/// to reach write_pos so that the last bytes get encoded too. |
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uint32_t keep_size_after; |
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/// Match finders store locations of matches using 32-bit integers. |
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/// To avoid adjusting several megabytes of integers every time the |
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/// input window is moved with move_window, we only adjust the |
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/// offset of the buffer. Thus, buffer[value_in_hash_table - offset] |
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/// is the byte pointed by value_in_hash_table. |
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uint32_t offset; |
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/// buffer[read_pos] is the next byte to run through the match |
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/// finder. This is incremented in the match finder once the byte |
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/// has been processed. |
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uint32_t read_pos; |
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/// Number of bytes that have been ran through the match finder, but |
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/// which haven't been encoded by the LZ-based encoder yet. |
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uint32_t read_ahead; |
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/// As long as read_pos is less than read_limit, there is enough |
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/// input available in buffer for at least one encoding loop. |
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/// |
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/// Because of the stateful API, read_limit may and will get greater |
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/// than read_pos quite often. This is taken into account when |
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/// calculating the value for keep_size_after. |
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uint32_t read_limit; |
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/// buffer[write_pos] is the first byte that doesn't contain valid |
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/// uncompressed data; that is, the next input byte will be copied |
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/// to buffer[write_pos]. |
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uint32_t write_pos; |
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/// Number of bytes not hashed before read_pos. This is needed to |
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/// restart the match finder after LZMA_SYNC_FLUSH. |
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uint32_t pending; |
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////////////////// |
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// Match Finder // |
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////////////////// |
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/// Find matches. Returns the number of distance-length pairs written |
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/// to the matches array. This is called only via lzma_mf_find(). |
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uint32_t (*find)(lzma_mf *mf, lzma_match *matches); |
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/// Skips num bytes. This is like find() but doesn't make the |
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/// distance-length pairs available, thus being a little faster. |
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/// This is called only via mf_skip(). |
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void (*skip)(lzma_mf *mf, uint32_t num); |
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uint32_t *hash; |
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uint32_t *son; |
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uint32_t cyclic_pos; |
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uint32_t cyclic_size; // Must be dictionary size + 1. |
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uint32_t hash_mask; |
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/// Maximum number of loops in the match finder |
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uint32_t depth; |
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/// Maximum length of a match that the match finder will try to find. |
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uint32_t nice_len; |
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/// Maximum length of a match supported by the LZ-based encoder. |
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/// If the longest match found by the match finder is nice_len, |
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/// mf_find() tries to expand it up to match_len_max bytes. |
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uint32_t match_len_max; |
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/// When running out of input, binary tree match finders need to know |
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/// if it is due to flushing or finishing. The action is used also |
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/// by the LZ-based encoders themselves. |
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lzma_action action; |
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/// Number of elements in hash[] |
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uint32_t hash_count; |
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/// Number of elements in son[] |
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uint32_t sons_count; |
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}; |
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typedef struct { |
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/// Extra amount of data to keep available before the "actual" |
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/// dictionary. |
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size_t before_size; |
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/// Size of the history buffer |
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size_t dict_size; |
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/// Extra amount of data to keep available after the "actual" |
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/// dictionary. |
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size_t after_size; |
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/// Maximum length of a match that the LZ-based encoder can accept. |
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/// This is used to extend matches of length nice_len to the |
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/// maximum possible length. |
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size_t match_len_max; |
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/// Match finder will search matches up to this length. |
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/// This must be less than or equal to match_len_max. |
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size_t nice_len; |
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/// Type of the match finder to use |
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lzma_match_finder match_finder; |
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/// Maximum search depth |
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uint32_t depth; |
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/// TODO: Comment |
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const uint8_t *preset_dict; |
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uint32_t preset_dict_size; |
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} lzma_lz_options; |
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// The total usable buffer space at any moment outside the match finder: |
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// before_size + dict_size + after_size + match_len_max |
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// |
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// In reality, there's some extra space allocated to prevent the number of |
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// memmove() calls reasonable. The bigger the dict_size is, the bigger |
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// this extra buffer will be since with bigger dictionaries memmove() would |
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// also take longer. |
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// |
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// A single encoder loop in the LZ-based encoder may call the match finder |
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// (mf_find() or mf_skip()) at most after_size times. In other words, |
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// a single encoder loop may increment lzma_mf.read_pos at most after_size |
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// times. Since matches are looked up to |
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// lzma_mf.buffer[lzma_mf.read_pos + match_len_max - 1], the total |
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// amount of extra buffer needed after dict_size becomes |
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// after_size + match_len_max. |
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// |
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// before_size has two uses. The first one is to keep literals available |
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// in cases when the LZ-based encoder has made some read ahead. |
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// TODO: Maybe this could be changed by making the LZ-based encoders to |
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// store the actual literals as they do with length-distance pairs. |
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// |
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// Algorithms such as LZMA2 first try to compress a chunk, and then check |
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// if the encoded result is smaller than the uncompressed one. If the chunk |
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// was uncompressible, it is better to store it in uncompressed form in |
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// the output stream. To do this, the whole uncompressed chunk has to be |
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// still available in the history buffer. before_size achieves that. |
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typedef struct { |
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/// Data specific to the LZ-based encoder |
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void *coder; |
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/// Function to encode from *dict to out[] |
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lzma_ret (*code)(void *coder, |
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lzma_mf *restrict mf, uint8_t *restrict out, |
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size_t *restrict out_pos, size_t out_size); |
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/// Free allocated resources |
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void (*end)(void *coder, const lzma_allocator *allocator); |
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/// Update the options in the middle of the encoding. |
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lzma_ret (*options_update)(void *coder, const lzma_filter *filter); |
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} lzma_lz_encoder; |
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// Basic steps: |
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// 1. Input gets copied into the dictionary. |
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// 2. Data in dictionary gets run through the match finder byte by byte. |
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// 3. The literals and matches are encoded using e.g. LZMA. |
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// |
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// The bytes that have been ran through the match finder, but not encoded yet, |
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// are called `read ahead'. |
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/// Get pointer to the first byte not ran through the match finder |
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static inline const uint8_t * |
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mf_ptr(const lzma_mf *mf) |
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{ |
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return mf->buffer + mf->read_pos; |
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} |
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/// Get the number of bytes that haven't been ran through the match finder yet. |
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static inline uint32_t |
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mf_avail(const lzma_mf *mf) |
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{ |
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return mf->write_pos - mf->read_pos; |
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} |
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/// Get the number of bytes that haven't been encoded yet (some of these |
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/// bytes may have been ran through the match finder though). |
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static inline uint32_t |
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mf_unencoded(const lzma_mf *mf) |
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{ |
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return mf->write_pos - mf->read_pos + mf->read_ahead; |
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} |
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/// Calculate the absolute offset from the beginning of the most recent |
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/// dictionary reset. Only the lowest four bits are important, so there's no |
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/// problem that we don't know the 64-bit size of the data encoded so far. |
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/// |
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/// NOTE: When moving the input window, we need to do it so that the lowest |
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/// bits of dict->read_pos are not modified to keep this macro working |
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/// as intended. |
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static inline uint32_t |
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mf_position(const lzma_mf *mf) |
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{ |
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return mf->read_pos - mf->read_ahead; |
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} |
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/// Since everything else begins with mf_, use it also for lzma_mf_find(). |
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#define mf_find lzma_mf_find |
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/// Skip the given number of bytes. This is used when a good match was found. |
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/// For example, if mf_find() finds a match of 200 bytes long, the first byte |
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/// of that match was already consumed by mf_find(), and the rest 199 bytes |
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/// have to be skipped with mf_skip(mf, 199). |
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static inline void |
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mf_skip(lzma_mf *mf, uint32_t amount) |
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{ |
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if (amount != 0) { |
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mf->skip(mf, amount); |
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mf->read_ahead += amount; |
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} |
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} |
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/// Copies at most *left number of bytes from the history buffer |
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/// to out[]. This is needed by LZMA2 to encode uncompressed chunks. |
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static inline void |
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mf_read(lzma_mf *mf, uint8_t *out, size_t *out_pos, size_t out_size, |
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size_t *left) |
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{ |
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const size_t out_avail = out_size - *out_pos; |
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const size_t copy_size = my_min(out_avail, *left); |
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assert(mf->read_ahead == 0); |
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assert(mf->read_pos >= *left); |
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memcpy(out + *out_pos, mf->buffer + mf->read_pos - *left, |
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copy_size); |
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*out_pos += copy_size; |
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*left -= copy_size; |
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return; |
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} |
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extern lzma_ret lzma_lz_encoder_init( |
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lzma_next_coder *next, const lzma_allocator *allocator, |
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const lzma_filter_info *filters, |
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lzma_ret (*lz_init)(lzma_lz_encoder *lz, |
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const lzma_allocator *allocator, const void *options, |
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lzma_lz_options *lz_options)); |
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extern uint64_t lzma_lz_encoder_memusage(const lzma_lz_options *lz_options); |
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// These are only for LZ encoder's internal use. |
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extern uint32_t lzma_mf_find( |
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lzma_mf *mf, uint32_t *count, lzma_match *matches); |
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extern uint32_t lzma_mf_hc3_find(lzma_mf *dict, lzma_match *matches); |
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extern void lzma_mf_hc3_skip(lzma_mf *dict, uint32_t amount); |
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extern uint32_t lzma_mf_hc4_find(lzma_mf *dict, lzma_match *matches); |
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extern void lzma_mf_hc4_skip(lzma_mf *dict, uint32_t amount); |
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extern uint32_t lzma_mf_bt2_find(lzma_mf *dict, lzma_match *matches); |
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extern void lzma_mf_bt2_skip(lzma_mf *dict, uint32_t amount); |
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extern uint32_t lzma_mf_bt3_find(lzma_mf *dict, lzma_match *matches); |
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extern void lzma_mf_bt3_skip(lzma_mf *dict, uint32_t amount); |
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extern uint32_t lzma_mf_bt4_find(lzma_mf *dict, lzma_match *matches); |
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extern void lzma_mf_bt4_skip(lzma_mf *dict, uint32_t amount); |
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#endif
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