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329 lines
10 KiB
329 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_size_sum;
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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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lzma_coder *coder;
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/// Function to encode from *dict to out[]
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lzma_ret (*code)(lzma_coder *LZMA_RESTRICT coder,
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lzma_mf *LZMA_RESTRICT mf, uint8_t *LZMA_RESTRICT out,
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size_t *LZMA_RESTRICT out_pos, size_t out_size);
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/// Free allocated resources
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void (*end)(lzma_coder *coder, lzma_allocator *allocator);
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/// Update the options in the middle of the encoding.
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lzma_ret (*options_update)(lzma_coder *coder,
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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 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, 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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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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