1 ///////////////////////////////////////////////////////////////////////////////
4 /// \brief LZ in window
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 #include "lz_encoder.h"
15 #include "lz_encoder_hash.h"
17 // See lz_encoder_hash.h. This is a bit hackish but avoids making
18 // endianness a conditional in makefiles.
19 #if defined(WORDS_BIGENDIAN) && !defined(HAVE_SMALL)
20 # include "lz_encoder_hash_table.h"
23 #include "memcmplen.h"
27 /// LZ-based encoder e.g. LZMA
30 /// History buffer and match finder
33 /// Next coder in the chain
38 /// \brief Moves the data in the input window to free space for new data
40 /// mf->buffer is a sliding input window, which keeps mf->keep_size_before
41 /// bytes of input history available all the time. Now and then we need to
42 /// "slide" the buffer to make space for the new data to the end of the
43 /// buffer. At the same time, data older than keep_size_before is dropped.
46 move_window(lzma_mf *mf)
48 // Align the move to a multiple of 16 bytes. Some LZ-based encoders
49 // like LZMA use the lowest bits of mf->read_pos to know the
50 // alignment of the uncompressed data. We also get better speed
51 // for memmove() with aligned buffers.
52 assert(mf->read_pos > mf->keep_size_before);
53 const uint32_t move_offset
54 = (mf->read_pos - mf->keep_size_before) & ~UINT32_C(15);
56 assert(mf->write_pos > move_offset);
57 const size_t move_size = mf->write_pos - move_offset;
59 assert(move_offset + move_size <= mf->size);
61 memmove(mf->buffer, mf->buffer + move_offset, move_size);
63 mf->offset += move_offset;
64 mf->read_pos -= move_offset;
65 mf->read_limit -= move_offset;
66 mf->write_pos -= move_offset;
72 /// \brief Tries to fill the input window (mf->buffer)
74 /// If we are the last encoder in the chain, our input data is in in[].
75 /// Otherwise we call the next filter in the chain to process in[] and
76 /// write its output to mf->buffer.
78 /// This function must not be called once it has returned LZMA_STREAM_END.
81 fill_window(lzma_coder *coder, const lzma_allocator *allocator,
82 const uint8_t *in, size_t *in_pos, size_t in_size,
85 assert(coder->mf.read_pos <= coder->mf.write_pos);
87 // Move the sliding window if needed.
88 if (coder->mf.read_pos >= coder->mf.size - coder->mf.keep_size_after)
89 move_window(&coder->mf);
91 // Maybe this is ugly, but lzma_mf uses uint32_t for most things
92 // (which I find cleanest), but we need size_t here when filling
93 // the history window.
94 size_t write_pos = coder->mf.write_pos;
96 if (coder->next.code == NULL) {
97 // Not using a filter, simply memcpy() as much as possible.
98 lzma_bufcpy(in, in_pos, in_size, coder->mf.buffer,
99 &write_pos, coder->mf.size);
101 ret = action != LZMA_RUN && *in_pos == in_size
102 ? LZMA_STREAM_END : LZMA_OK;
105 ret = coder->next.code(coder->next.coder, allocator,
107 coder->mf.buffer, &write_pos,
108 coder->mf.size, action);
111 coder->mf.write_pos = write_pos;
113 // Silence Valgrind. lzma_memcmplen() can read extra bytes
114 // and Valgrind will give warnings if those bytes are uninitialized
115 // because Valgrind cannot see that the values of the uninitialized
116 // bytes are eventually ignored.
117 memzero(coder->mf.buffer + write_pos, LZMA_MEMCMPLEN_EXTRA);
119 // If end of stream has been reached or flushing completed, we allow
120 // the encoder to process all the input (that is, read_pos is allowed
121 // to reach write_pos). Otherwise we keep keep_size_after bytes
122 // available as prebuffer.
123 if (ret == LZMA_STREAM_END) {
124 assert(*in_pos == in_size);
126 coder->mf.action = action;
127 coder->mf.read_limit = coder->mf.write_pos;
129 } else if (coder->mf.write_pos > coder->mf.keep_size_after) {
130 // This needs to be done conditionally, because if we got
131 // only little new input, there may be too little input
132 // to do any encoding yet.
133 coder->mf.read_limit = coder->mf.write_pos
134 - coder->mf.keep_size_after;
137 // Restart the match finder after finished LZMA_SYNC_FLUSH.
138 if (coder->mf.pending > 0
139 && coder->mf.read_pos < coder->mf.read_limit) {
140 // Match finder may update coder->pending and expects it to
141 // start from zero, so use a temporary variable.
142 const uint32_t pending = coder->mf.pending;
143 coder->mf.pending = 0;
145 // Rewind read_pos so that the match finder can hash
146 // the pending bytes.
147 assert(coder->mf.read_pos >= pending);
148 coder->mf.read_pos -= pending;
150 // Call the skip function directly instead of using
151 // mf_skip(), since we don't want to touch mf->read_ahead.
152 coder->mf.skip(&coder->mf, pending);
160 lz_encode(lzma_coder *coder, const lzma_allocator *allocator,
161 const uint8_t *restrict in, size_t *restrict in_pos,
163 uint8_t *restrict out, size_t *restrict out_pos,
164 size_t out_size, lzma_action action)
166 while (*out_pos < out_size
167 && (*in_pos < in_size || action != LZMA_RUN)) {
168 // Read more data to coder->mf.buffer if needed.
169 if (coder->mf.action == LZMA_RUN && coder->mf.read_pos
170 >= coder->mf.read_limit)
171 return_if_error(fill_window(coder, allocator,
172 in, in_pos, in_size, action));
175 const lzma_ret ret = coder->lz.code(coder->lz.coder,
176 &coder->mf, out, out_pos, out_size);
177 if (ret != LZMA_OK) {
178 // Setting this to LZMA_RUN for cases when we are
179 // flushing. It doesn't matter when finishing or if
180 // an error occurred.
181 coder->mf.action = LZMA_RUN;
191 lz_encoder_prepare(lzma_mf *mf, const lzma_allocator *allocator,
192 const lzma_lz_options *lz_options)
194 // For now, the dictionary size is limited to 1.5 GiB. This may grow
195 // in the future if needed, but it needs a little more work than just
196 // changing this check.
197 if (lz_options->dict_size < LZMA_DICT_SIZE_MIN
198 || lz_options->dict_size
199 > (UINT32_C(1) << 30) + (UINT32_C(1) << 29)
200 || lz_options->nice_len > lz_options->match_len_max)
203 mf->keep_size_before = lz_options->before_size + lz_options->dict_size;
205 mf->keep_size_after = lz_options->after_size
206 + lz_options->match_len_max;
208 // To avoid constant memmove()s, allocate some extra space. Since
209 // memmove()s become more expensive when the size of the buffer
210 // increases, we reserve more space when a large dictionary is
211 // used to make the memmove() calls rarer.
213 // This works with dictionaries up to about 3 GiB. If bigger
214 // dictionary is wanted, some extra work is needed:
215 // - Several variables in lzma_mf have to be changed from uint32_t
217 // - Memory usage calculation needs something too, e.g. use uint64_t
219 uint32_t reserve = lz_options->dict_size / 2;
220 if (reserve > (UINT32_C(1) << 30))
223 reserve += (lz_options->before_size + lz_options->match_len_max
224 + lz_options->after_size) / 2 + (UINT32_C(1) << 19);
226 const uint32_t old_size = mf->size;
227 mf->size = mf->keep_size_before + reserve + mf->keep_size_after;
229 // Deallocate the old history buffer if it exists but has different
230 // size than what is needed now.
231 if (mf->buffer != NULL && old_size != mf->size) {
232 lzma_free(mf->buffer, allocator);
236 // Match finder options
237 mf->match_len_max = lz_options->match_len_max;
238 mf->nice_len = lz_options->nice_len;
240 // cyclic_size has to stay smaller than 2 Gi. Note that this doesn't
241 // mean limiting dictionary size to less than 2 GiB. With a match
242 // finder that uses multibyte resolution (hashes start at e.g. every
243 // fourth byte), cyclic_size would stay below 2 Gi even when
244 // dictionary size is greater than 2 GiB.
246 // It would be possible to allow cyclic_size >= 2 Gi, but then we
247 // would need to be careful to use 64-bit types in various places
248 // (size_t could do since we would need bigger than 32-bit address
249 // space anyway). It would also require either zeroing a multigigabyte
250 // buffer at initialization (waste of time and RAM) or allow
251 // normalization in lz_encoder_mf.c to access uninitialized
252 // memory to keep the code simpler. The current way is simple and
253 // still allows pretty big dictionaries, so I don't expect these
255 mf->cyclic_size = lz_options->dict_size + 1;
257 // Validate the match finder ID and setup the function pointers.
258 switch (lz_options->match_finder) {
261 mf->find = &lzma_mf_hc3_find;
262 mf->skip = &lzma_mf_hc3_skip;
267 mf->find = &lzma_mf_hc4_find;
268 mf->skip = &lzma_mf_hc4_skip;
273 mf->find = &lzma_mf_bt2_find;
274 mf->skip = &lzma_mf_bt2_skip;
279 mf->find = &lzma_mf_bt3_find;
280 mf->skip = &lzma_mf_bt3_skip;
285 mf->find = &lzma_mf_bt4_find;
286 mf->skip = &lzma_mf_bt4_skip;
294 // Calculate the sizes of mf->hash and mf->son and check that
295 // nice_len is big enough for the selected match finder.
296 const uint32_t hash_bytes = lz_options->match_finder & 0x0F;
297 if (hash_bytes > mf->nice_len)
300 const bool is_bt = (lz_options->match_finder & 0x10) != 0;
303 if (hash_bytes == 2) {
306 // Round dictionary size up to the next 2^n - 1 so it can
307 // be used as a hash mask.
308 hs = lz_options->dict_size - 1;
316 if (hs > (UINT32_C(1) << 24)) {
318 hs = (UINT32_C(1) << 24) - 1;
332 No match finder uses this at the moment.
333 if (mf->hash_bytes > 4)
337 const uint32_t old_hash_count = mf->hash_count;
338 const uint32_t old_sons_count = mf->sons_count;
340 mf->sons_count = mf->cyclic_size;
344 // Deallocate the old hash array if it exists and has different size
345 // than what is needed now.
346 if (old_hash_count != mf->hash_count
347 || old_sons_count != mf->sons_count) {
348 lzma_free(mf->hash, allocator);
351 lzma_free(mf->son, allocator);
355 // Maximum number of match finder cycles
356 mf->depth = lz_options->depth;
357 if (mf->depth == 0) {
359 mf->depth = 16 + mf->nice_len / 2;
361 mf->depth = 4 + mf->nice_len / 4;
369 lz_encoder_init(lzma_mf *mf, const lzma_allocator *allocator,
370 const lzma_lz_options *lz_options)
372 // Allocate the history buffer.
373 if (mf->buffer == NULL) {
374 // lzma_memcmplen() is used for the dictionary buffer
375 // so we need to allocate a few extra bytes to prevent
376 // it from reading past the end of the buffer.
377 mf->buffer = lzma_alloc(mf->size + LZMA_MEMCMPLEN_EXTRA,
379 if (mf->buffer == NULL)
382 // Keep Valgrind happy with lzma_memcmplen() and initialize
383 // the extra bytes whose value may get read but which will
384 // effectively get ignored.
385 memzero(mf->buffer + mf->size, LZMA_MEMCMPLEN_EXTRA);
388 // Use cyclic_size as initial mf->offset. This allows
389 // avoiding a few branches in the match finders. The downside is
390 // that match finder needs to be normalized more often, which may
391 // hurt performance with huge dictionaries.
392 mf->offset = mf->cyclic_size;
399 #if UINT32_MAX >= SIZE_MAX / 4
400 // Check for integer overflow. (Huge dictionaries are not
401 // possible on 32-bit CPU.)
402 if (mf->hash_count > SIZE_MAX / sizeof(uint32_t)
403 || mf->sons_count > SIZE_MAX / sizeof(uint32_t))
407 // Allocate and initialize the hash table. Since EMPTY_HASH_VALUE
408 // is zero, we can use lzma_alloc_zero() or memzero() for mf->hash.
410 // We don't need to initialize mf->son, but not doing that may
411 // make Valgrind complain in normalization (see normalize() in
412 // lz_encoder_mf.c). Skipping the initialization is *very* good
413 // when big dictionary is used but only small amount of data gets
414 // actually compressed: most of the mf->son won't get actually
415 // allocated by the kernel, so we avoid wasting RAM and improve
416 // initialization speed a lot.
417 if (mf->hash == NULL) {
418 mf->hash = lzma_alloc_zero(mf->hash_count * sizeof(uint32_t),
420 mf->son = lzma_alloc(mf->sons_count * sizeof(uint32_t),
423 if (mf->hash == NULL || mf->son == NULL) {
424 lzma_free(mf->hash, allocator);
427 lzma_free(mf->son, allocator);
434 for (uint32_t i = 0; i < mf->hash_count; ++i)
435 mf->hash[i] = EMPTY_HASH_VALUE;
437 memzero(mf->hash, mf->hash_count * sizeof(uint32_t));
442 // Handle preset dictionary.
443 if (lz_options->preset_dict != NULL
444 && lz_options->preset_dict_size > 0) {
445 // If the preset dictionary is bigger than the actual
446 // dictionary, use only the tail.
447 mf->write_pos = my_min(lz_options->preset_dict_size, mf->size);
448 memcpy(mf->buffer, lz_options->preset_dict
449 + lz_options->preset_dict_size - mf->write_pos,
451 mf->action = LZMA_SYNC_FLUSH;
452 mf->skip(mf, mf->write_pos);
455 mf->action = LZMA_RUN;
462 lzma_lz_encoder_memusage(const lzma_lz_options *lz_options)
464 // Old buffers must not exist when calling lz_encoder_prepare().
473 // Setup the size information into mf.
474 if (lz_encoder_prepare(&mf, NULL, lz_options))
477 // Calculate the memory usage.
478 return ((uint64_t)(mf.hash_count) + mf.sons_count) * sizeof(uint32_t)
479 + mf.size + sizeof(lzma_coder);
484 lz_encoder_end(lzma_coder *coder, const lzma_allocator *allocator)
486 lzma_next_end(&coder->next, allocator);
488 lzma_free(coder->mf.son, allocator);
489 lzma_free(coder->mf.hash, allocator);
490 lzma_free(coder->mf.buffer, allocator);
492 if (coder->lz.end != NULL)
493 coder->lz.end(coder->lz.coder, allocator);
495 lzma_free(coder->lz.coder, allocator);
497 lzma_free(coder, allocator);
503 lz_encoder_update(lzma_coder *coder, const lzma_allocator *allocator,
504 const lzma_filter *filters_null lzma_attribute((__unused__)),
505 const lzma_filter *reversed_filters)
507 if (coder->lz.options_update == NULL)
508 return LZMA_PROG_ERROR;
510 return_if_error(coder->lz.options_update(
511 coder->lz.coder, reversed_filters));
513 return lzma_next_filter_update(
514 &coder->next, allocator, reversed_filters + 1);
519 lzma_lz_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
520 const lzma_filter_info *filters,
521 lzma_ret (*lz_init)(lzma_lz_encoder *lz,
522 const lzma_allocator *allocator, const void *options,
523 lzma_lz_options *lz_options))
526 // We need that the CRC32 table has been initialized.
530 // Allocate and initialize the base data structure.
531 if (next->coder == NULL) {
532 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
533 if (next->coder == NULL)
534 return LZMA_MEM_ERROR;
536 next->code = &lz_encode;
537 next->end = &lz_encoder_end;
538 next->update = &lz_encoder_update;
540 next->coder->lz.coder = NULL;
541 next->coder->lz.code = NULL;
542 next->coder->lz.end = NULL;
544 // mf.size is initialized to silence Valgrind
545 // when used on optimized binaries (GCC may reorder
546 // code in a way that Valgrind gets unhappy).
547 next->coder->mf.buffer = NULL;
548 next->coder->mf.size = 0;
549 next->coder->mf.hash = NULL;
550 next->coder->mf.son = NULL;
551 next->coder->mf.hash_count = 0;
552 next->coder->mf.sons_count = 0;
554 next->coder->next = LZMA_NEXT_CODER_INIT;
557 // Initialize the LZ-based encoder.
558 lzma_lz_options lz_options;
559 return_if_error(lz_init(&next->coder->lz, allocator,
560 filters[0].options, &lz_options));
562 // Setup the size information into next->coder->mf and deallocate
563 // old buffers if they have wrong size.
564 if (lz_encoder_prepare(&next->coder->mf, allocator, &lz_options))
565 return LZMA_OPTIONS_ERROR;
567 // Allocate new buffers if needed, and do the rest of
568 // the initialization.
569 if (lz_encoder_init(&next->coder->mf, allocator, &lz_options))
570 return LZMA_MEM_ERROR;
572 // Initialize the next filter in the chain, if any.
573 return lzma_next_filter_init(&next->coder->next, allocator,
578 extern LZMA_API(lzma_bool)
579 lzma_mf_is_supported(lzma_match_finder mf)
584 if (mf == LZMA_MF_HC3)
589 if (mf == LZMA_MF_HC4)
594 if (mf == LZMA_MF_BT2)
599 if (mf == LZMA_MF_BT3)
604 if (mf == LZMA_MF_BT4)