1 ///////////////////////////////////////////////////////////////////////////////
4 /// \brief LZ in window and match finder API
6 // Authors: Igor Pavlov
9 // This file has been put into the public domain.
10 // You can do whatever you want with this file.
12 ///////////////////////////////////////////////////////////////////////////////
14 #ifndef LZMA_LZ_ENCODER_H
15 #define LZMA_LZ_ENCODER_H
20 /// A table of these is used by the LZ-based encoder to hold
21 /// the length-distance pairs found by the match finder.
28 typedef struct lzma_mf_s lzma_mf;
34 /// Pointer to buffer with data to be compressed
37 /// Total size of the allocated buffer (that is, including all
41 /// Number of bytes that must be kept available in our input history.
42 /// That is, once keep_size_before bytes have been processed,
43 /// buffer[read_pos - keep_size_before] is the oldest byte that
44 /// must be available for reading.
45 uint32_t keep_size_before;
47 /// Number of bytes that must be kept in buffer after read_pos.
48 /// That is, read_pos <= write_pos - keep_size_after as long as
49 /// action is LZMA_RUN; when action != LZMA_RUN, read_pos is allowed
50 /// to reach write_pos so that the last bytes get encoded too.
51 uint32_t keep_size_after;
53 /// Match finders store locations of matches using 32-bit integers.
54 /// To avoid adjusting several megabytes of integers every time the
55 /// input window is moved with move_window, we only adjust the
56 /// offset of the buffer. Thus, buffer[value_in_hash_table - offset]
57 /// is the byte pointed by value_in_hash_table.
60 /// buffer[read_pos] is the next byte to run through the match
61 /// finder. This is incremented in the match finder once the byte
62 /// has been processed.
65 /// Number of bytes that have been ran through the match finder, but
66 /// which haven't been encoded by the LZ-based encoder yet.
69 /// As long as read_pos is less than read_limit, there is enough
70 /// input available in buffer for at least one encoding loop.
72 /// Because of the stateful API, read_limit may and will get greater
73 /// than read_pos quite often. This is taken into account when
74 /// calculating the value for keep_size_after.
77 /// buffer[write_pos] is the first byte that doesn't contain valid
78 /// uncompressed data; that is, the next input byte will be copied
79 /// to buffer[write_pos].
82 /// Number of bytes not hashed before read_pos. This is needed to
83 /// restart the match finder after LZMA_SYNC_FLUSH.
90 /// Find matches. Returns the number of distance-length pairs written
91 /// to the matches array. This is called only via lzma_mf_find().
92 uint32_t (*find)(lzma_mf *mf, lzma_match *matches);
94 /// Skips num bytes. This is like find() but doesn't make the
95 /// distance-length pairs available, thus being a little faster.
96 /// This is called only via mf_skip().
97 void (*skip)(lzma_mf *mf, uint32_t num);
102 uint32_t cyclic_size; // Must be dictionary size + 1.
105 /// Maximum number of loops in the match finder
108 /// Maximum length of a match that the match finder will try to find.
111 /// Maximum length of a match supported by the LZ-based encoder.
112 /// If the longest match found by the match finder is nice_len,
113 /// mf_find() tries to expand it up to match_len_max bytes.
114 uint32_t match_len_max;
116 /// When running out of input, binary tree match finders need to know
117 /// if it is due to flushing or finishing. The action is used also
118 /// by the LZ-based encoders themselves.
121 /// Number of elements in hash[]
124 /// Number of elements in son[]
130 /// Extra amount of data to keep available before the "actual"
134 /// Size of the history buffer
137 /// Extra amount of data to keep available after the "actual"
141 /// Maximum length of a match that the LZ-based encoder can accept.
142 /// This is used to extend matches of length nice_len to the
143 /// maximum possible length.
144 size_t match_len_max;
146 /// Match finder will search matches up to this length.
147 /// This must be less than or equal to match_len_max.
150 /// Type of the match finder to use
151 lzma_match_finder match_finder;
153 /// Maximum search depth
157 const uint8_t *preset_dict;
159 uint32_t preset_dict_size;
164 // The total usable buffer space at any moment outside the match finder:
165 // before_size + dict_size + after_size + match_len_max
167 // In reality, there's some extra space allocated to prevent the number of
168 // memmove() calls reasonable. The bigger the dict_size is, the bigger
169 // this extra buffer will be since with bigger dictionaries memmove() would
172 // A single encoder loop in the LZ-based encoder may call the match finder
173 // (mf_find() or mf_skip()) at most after_size times. In other words,
174 // a single encoder loop may increment lzma_mf.read_pos at most after_size
175 // times. Since matches are looked up to
176 // lzma_mf.buffer[lzma_mf.read_pos + match_len_max - 1], the total
177 // amount of extra buffer needed after dict_size becomes
178 // after_size + match_len_max.
180 // before_size has two uses. The first one is to keep literals available
181 // in cases when the LZ-based encoder has made some read ahead.
182 // TODO: Maybe this could be changed by making the LZ-based encoders to
183 // store the actual literals as they do with length-distance pairs.
185 // Algorithms such as LZMA2 first try to compress a chunk, and then check
186 // if the encoded result is smaller than the uncompressed one. If the chunk
187 // was uncompressible, it is better to store it in uncompressed form in
188 // the output stream. To do this, the whole uncompressed chunk has to be
189 // still available in the history buffer. before_size achieves that.
193 /// Data specific to the LZ-based encoder
196 /// Function to encode from *dict to out[]
197 lzma_ret (*code)(void *coder,
198 lzma_mf *restrict mf, uint8_t *restrict out,
199 size_t *restrict out_pos, size_t out_size);
201 /// Free allocated resources
202 void (*end)(void *coder, const lzma_allocator *allocator);
204 /// Update the options in the middle of the encoding.
205 lzma_ret (*options_update)(void *coder, const lzma_filter *filter);
211 // 1. Input gets copied into the dictionary.
212 // 2. Data in dictionary gets run through the match finder byte by byte.
213 // 3. The literals and matches are encoded using e.g. LZMA.
215 // The bytes that have been ran through the match finder, but not encoded yet,
216 // are called `read ahead'.
219 /// Get pointer to the first byte not ran through the match finder
220 static inline const uint8_t *
221 mf_ptr(const lzma_mf *mf)
223 return mf->buffer + mf->read_pos;
227 /// Get the number of bytes that haven't been ran through the match finder yet.
228 static inline uint32_t
229 mf_avail(const lzma_mf *mf)
231 return mf->write_pos - mf->read_pos;
235 /// Get the number of bytes that haven't been encoded yet (some of these
236 /// bytes may have been ran through the match finder though).
237 static inline uint32_t
238 mf_unencoded(const lzma_mf *mf)
240 return mf->write_pos - mf->read_pos + mf->read_ahead;
244 /// Calculate the absolute offset from the beginning of the most recent
245 /// dictionary reset. Only the lowest four bits are important, so there's no
246 /// problem that we don't know the 64-bit size of the data encoded so far.
248 /// NOTE: When moving the input window, we need to do it so that the lowest
249 /// bits of dict->read_pos are not modified to keep this macro working
251 static inline uint32_t
252 mf_position(const lzma_mf *mf)
254 return mf->read_pos - mf->read_ahead;
258 /// Since everything else begins with mf_, use it also for lzma_mf_find().
259 #define mf_find lzma_mf_find
262 /// Skip the given number of bytes. This is used when a good match was found.
263 /// For example, if mf_find() finds a match of 200 bytes long, the first byte
264 /// of that match was already consumed by mf_find(), and the rest 199 bytes
265 /// have to be skipped with mf_skip(mf, 199).
267 mf_skip(lzma_mf *mf, uint32_t amount)
270 mf->skip(mf, amount);
271 mf->read_ahead += amount;
276 /// Copies at most *left number of bytes from the history buffer
277 /// to out[]. This is needed by LZMA2 to encode uncompressed chunks.
279 mf_read(lzma_mf *mf, uint8_t *out, size_t *out_pos, size_t out_size,
282 const size_t out_avail = out_size - *out_pos;
283 const size_t copy_size = my_min(out_avail, *left);
285 assert(mf->read_ahead == 0);
286 assert(mf->read_pos >= *left);
288 memcpy(out + *out_pos, mf->buffer + mf->read_pos - *left,
291 *out_pos += copy_size;
297 extern lzma_ret lzma_lz_encoder_init(
298 lzma_next_coder *next, const lzma_allocator *allocator,
299 const lzma_filter_info *filters,
300 lzma_ret (*lz_init)(lzma_lz_encoder *lz,
301 const lzma_allocator *allocator, const void *options,
302 lzma_lz_options *lz_options));
305 extern uint64_t lzma_lz_encoder_memusage(const lzma_lz_options *lz_options);
308 // These are only for LZ encoder's internal use.
309 extern uint32_t lzma_mf_find(
310 lzma_mf *mf, uint32_t *count, lzma_match *matches);
312 extern uint32_t lzma_mf_hc3_find(lzma_mf *dict, lzma_match *matches);
313 extern void lzma_mf_hc3_skip(lzma_mf *dict, uint32_t amount);
315 extern uint32_t lzma_mf_hc4_find(lzma_mf *dict, lzma_match *matches);
316 extern void lzma_mf_hc4_skip(lzma_mf *dict, uint32_t amount);
318 extern uint32_t lzma_mf_bt2_find(lzma_mf *dict, lzma_match *matches);
319 extern void lzma_mf_bt2_skip(lzma_mf *dict, uint32_t amount);
321 extern uint32_t lzma_mf_bt3_find(lzma_mf *dict, lzma_match *matches);
322 extern void lzma_mf_bt3_skip(lzma_mf *dict, uint32_t amount);
324 extern uint32_t lzma_mf_bt4_find(lzma_mf *dict, lzma_match *matches);
325 extern void lzma_mf_bt4_skip(lzma_mf *dict, uint32_t amount);