aboutsummaryrefslogtreecommitdiff
path: root/src/liblzma/lz/lz_encoder.c
blob: 9e980a2c71dc08ecf7d27efaba3fefdcd6c29f4b (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
///////////////////////////////////////////////////////////////////////////////
//
/// \file       lz_encoder.c
/// \brief      LZ in window
///
//  Authors:    Igor Pavlov
//              Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "lz_encoder.h"
#include "lz_encoder_hash.h"

// See lz_encoder_hash.h. This is a bit hackish but avoids making
// endianness a conditional in makefiles.
#if defined(WORDS_BIGENDIAN) && !defined(HAVE_SMALL)
#	include "lz_encoder_hash_table.h"
#endif


struct lzma_coder_s {
	/// LZ-based encoder e.g. LZMA
	lzma_lz_encoder lz;

	/// History buffer and match finder
	lzma_mf mf;

	/// Next coder in the chain
	lzma_next_coder next;
};


/// \brief      Moves the data in the input window to free space for new data
///
/// mf->buffer is a sliding input window, which keeps mf->keep_size_before
/// bytes of input history available all the time. Now and then we need to
/// "slide" the buffer to make space for the new data to the end of the
/// buffer. At the same time, data older than keep_size_before is dropped.
///
static void
move_window(lzma_mf *mf)
{
	// Align the move to a multiple of 16 bytes. Some LZ-based encoders
	// like LZMA use the lowest bits of mf->read_pos to know the
	// alignment of the uncompressed data. We also get better speed
	// for memmove() with aligned buffers.
	assert(mf->read_pos > mf->keep_size_before);
	const uint32_t move_offset
		= (mf->read_pos - mf->keep_size_before) & ~UINT32_C(15);

	assert(mf->write_pos > move_offset);
	const size_t move_size = mf->write_pos - move_offset;

	assert(move_offset + move_size <= mf->size);

	memmove(mf->buffer, mf->buffer + move_offset, move_size);

	mf->offset += move_offset;
	mf->read_pos -= move_offset;
	mf->read_limit -= move_offset;
	mf->write_pos -= move_offset;

	return;
}


/// \brief      Tries to fill the input window (mf->buffer)
///
/// If we are the last encoder in the chain, our input data is in in[].
/// Otherwise we call the next filter in the chain to process in[] and
/// write its output to mf->buffer.
///
/// This function must not be called once it has returned LZMA_STREAM_END.
///
static lzma_ret
fill_window(lzma_coder *coder, lzma_allocator *allocator, const uint8_t *in,
		size_t *in_pos, size_t in_size, lzma_action action)
{
	assert(coder->mf.read_pos <= coder->mf.write_pos);

	// Move the sliding window if needed.
	if (coder->mf.read_pos >= coder->mf.size - coder->mf.keep_size_after)
		move_window(&coder->mf);

	// Maybe this is ugly, but lzma_mf uses uint32_t for most things
	// (which I find cleanest), but we need size_t here when filling
	// the history window.
	size_t write_pos = coder->mf.write_pos;
	lzma_ret ret;
	if (coder->next.code == NULL) {
		// Not using a filter, simply memcpy() as much as possible.
		lzma_bufcpy(in, in_pos, in_size, coder->mf.buffer,
				&write_pos, coder->mf.size);

		ret = action != LZMA_RUN && *in_pos == in_size
				? LZMA_STREAM_END : LZMA_OK;

	} else {
		ret = coder->next.code(coder->next.coder, allocator,
				in, in_pos, in_size,
				coder->mf.buffer, &write_pos,
				coder->mf.size, action);
	}

	coder->mf.write_pos = write_pos;

	// If end of stream has been reached or flushing completed, we allow
	// the encoder to process all the input (that is, read_pos is allowed
	// to reach write_pos). Otherwise we keep keep_size_after bytes
	// available as prebuffer.
	if (ret == LZMA_STREAM_END) {
		assert(*in_pos == in_size);
		ret = LZMA_OK;
		coder->mf.action = action;
		coder->mf.read_limit = coder->mf.write_pos;

	} else if (coder->mf.write_pos > coder->mf.keep_size_after) {
		// This needs to be done conditionally, because if we got
		// only little new input, there may be too little input
		// to do any encoding yet.
		coder->mf.read_limit = coder->mf.write_pos
				- coder->mf.keep_size_after;
	}

	// Restart the match finder after finished LZMA_SYNC_FLUSH.
	if (coder->mf.pending > 0
			&& coder->mf.read_pos < coder->mf.read_limit) {
		// Match finder may update coder->pending and expects it to
		// start from zero, so use a temporary variable.
		const size_t pending = coder->mf.pending;
		coder->mf.pending = 0;

		// Rewind read_pos so that the match finder can hash
		// the pending bytes.
		assert(coder->mf.read_pos >= pending);
		coder->mf.read_pos -= pending;

		// Call the skip function directly instead of using
		// mf_skip(), since we don't want to touch mf->read_ahead.
		coder->mf.skip(&coder->mf, pending);
	}

	return ret;
}


static lzma_ret
lz_encode(lzma_coder *coder, lzma_allocator *allocator,
		const uint8_t *restrict in, size_t *restrict in_pos,
		size_t in_size,
		uint8_t *restrict out, size_t *restrict out_pos,
		size_t out_size, lzma_action action)
{
	while (*out_pos < out_size
			&& (*in_pos < in_size || action != LZMA_RUN)) {
		// Read more data to coder->mf.buffer if needed.
		if (coder->mf.action == LZMA_RUN && coder->mf.read_pos
				>= coder->mf.read_limit)
			return_if_error(fill_window(coder, allocator,
					in, in_pos, in_size, action));

		// Encode
		const lzma_ret ret = coder->lz.code(coder->lz.coder,
				&coder->mf, out, out_pos, out_size);
		if (ret != LZMA_OK) {
			// Setting this to LZMA_RUN for cases when we are
			// flushing. It doesn't matter when finishing or if
			// an error occurred.
			coder->mf.action = LZMA_RUN;
			return ret;
		}
	}

	return LZMA_OK;
}


static bool
lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
		const lzma_lz_options *lz_options)
{
	// For now, the dictionary size is limited to 1.5 GiB. This may grow
	// in the future if needed, but it needs a little more work than just
	// changing this check.
	if (lz_options->dict_size < LZMA_DICT_SIZE_MIN
			|| lz_options->dict_size
				> (UINT32_C(1) << 30) + (UINT32_C(1) << 29)
			|| lz_options->nice_len > lz_options->match_len_max)
		return true;

	mf->keep_size_before = lz_options->before_size + lz_options->dict_size;

	mf->keep_size_after = lz_options->after_size
			+ lz_options->match_len_max;

	// To avoid constant memmove()s, allocate some extra space. Since
	// memmove()s become more expensive when the size of the buffer
	// increases, we reserve more space when a large dictionary is
	// used to make the memmove() calls rarer.
	//
	// This works with dictionaries up to about 3 GiB. If bigger
	// dictionary is wanted, some extra work is needed:
	//   - Several variables in lzma_mf have to be changed from uint32_t
	//     to size_t.
	//   - Memory usage calculation needs something too, e.g. use uint64_t
	//     for mf->size.
	uint32_t reserve = lz_options->dict_size / 2;
	if (reserve > (UINT32_C(1) << 30))
		reserve /= 2;

	reserve += (lz_options->before_size + lz_options->match_len_max
			+ lz_options->after_size) / 2 + (UINT32_C(1) << 19);

	const uint32_t old_size = mf->size;
	mf->size = mf->keep_size_before + reserve + mf->keep_size_after;

	// Deallocate the old history buffer if it exists but has different
	// size than what is needed now.
	if (mf->buffer != NULL && old_size != mf->size) {
		lzma_free(mf->buffer, allocator);
		mf->buffer = NULL;
	}

	// Match finder options
	mf->match_len_max = lz_options->match_len_max;
	mf->nice_len = lz_options->nice_len;

	// cyclic_size has to stay smaller than 2 Gi. Note that this doesn't
	// mean limiting dictionary size to less than 2 GiB. With a match
	// finder that uses multibyte resolution (hashes start at e.g. every
	// fourth byte), cyclic_size would stay below 2 Gi even when
	// dictionary size is greater than 2 GiB.
	//
	// It would be possible to allow cyclic_size >= 2 Gi, but then we
	// would need to be careful to use 64-bit types in various places
	// (size_t could do since we would need bigger than 32-bit address
	// space anyway). It would also require either zeroing a multigigabyte
	// buffer at initialization (waste of time and RAM) or allow
	// normalization in lz_encoder_mf.c to access uninitialized
	// memory to keep the code simpler. The current way is simple and
	// still allows pretty big dictionaries, so I don't expect these
	// limits to change.
	mf->cyclic_size = lz_options->dict_size + 1;

	// Validate the match finder ID and setup the function pointers.
	switch (lz_options->match_finder) {
#ifdef HAVE_MF_HC3
	case LZMA_MF_HC3:
		mf->find = &lzma_mf_hc3_find;
		mf->skip = &lzma_mf_hc3_skip;
		break;
#endif
#ifdef HAVE_MF_HC4
	case LZMA_MF_HC4:
		mf->find = &lzma_mf_hc4_find;
		mf->skip = &lzma_mf_hc4_skip;
		break;
#endif
#ifdef HAVE_MF_BT2
	case LZMA_MF_BT2:
		mf->find = &lzma_mf_bt2_find;
		mf->skip = &lzma_mf_bt2_skip;
		break;
#endif
#ifdef HAVE_MF_BT3
	case LZMA_MF_BT3:
		mf->find = &lzma_mf_bt3_find;
		mf->skip = &lzma_mf_bt3_skip;
		break;
#endif
#ifdef HAVE_MF_BT4
	case LZMA_MF_BT4:
		mf->find = &lzma_mf_bt4_find;
		mf->skip = &lzma_mf_bt4_skip;
		break;
#endif

	default:
		return true;
	}

	// Calculate the sizes of mf->hash and mf->son and check that
	// nice_len is big enough for the selected match finder.
	const uint32_t hash_bytes = lz_options->match_finder & 0x0F;
	if (hash_bytes > mf->nice_len)
		return true;

	const bool is_bt = (lz_options->match_finder & 0x10) != 0;
	uint32_t hs;

	if (hash_bytes == 2) {
		hs = 0xFFFF;
	} else {
		// Round dictionary size up to the next 2^n - 1 so it can
		// be used as a hash mask.
		hs = lz_options->dict_size - 1;
		hs |= hs >> 1;
		hs |= hs >> 2;
		hs |= hs >> 4;
		hs |= hs >> 8;
		hs >>= 1;
		hs |= 0xFFFF;

		if (hs > (UINT32_C(1) << 24)) {
			if (hash_bytes == 3)
				hs = (UINT32_C(1) << 24) - 1;
			else
				hs >>= 1;
		}
	}

	mf->hash_mask = hs;

	++hs;
	if (hash_bytes > 2)
		hs += HASH_2_SIZE;
	if (hash_bytes > 3)
		hs += HASH_3_SIZE;
/*
	No match finder uses this at the moment.
	if (mf->hash_bytes > 4)
		hs += HASH_4_SIZE;
*/

	// If the above code calculating hs is modified, make sure that
	// this assertion stays valid (UINT32_MAX / 5 is not strictly the
	// exact limit). If it doesn't, you need to calculate that
	// hash_size_sum + sons_count cannot overflow.
	assert(hs < UINT32_MAX / 5);

	const uint32_t old_count = mf->hash_size_sum + mf->sons_count;
	mf->hash_size_sum = hs;
	mf->sons_count = mf->cyclic_size;
	if (is_bt)
		mf->sons_count *= 2;

	const uint32_t new_count = mf->hash_size_sum + mf->sons_count;

	// Deallocate the old hash array if it exists and has different size
	// than what is needed now.
	if (old_count != new_count) {
		lzma_free(mf->hash, allocator);
		mf->hash = NULL;
	}

	// Maximum number of match finder cycles
	mf->depth = lz_options->depth;
	if (mf->depth == 0) {
		mf->depth = 16 + (mf->nice_len / 2);
		if (!is_bt)
			mf->depth /= 2;
	}

	return false;
}


static bool
lz_encoder_init(lzma_mf *mf, lzma_allocator *allocator,
		const lzma_lz_options *lz_options)
{
	// Allocate the history buffer.
	if (mf->buffer == NULL) {
		mf->buffer = lzma_alloc(mf->size, allocator);
		if (mf->buffer == NULL)
			return true;
	}

	// Use cyclic_size as initial mf->offset. This allows
	// avoiding a few branches in the match finders. The downside is
	// that match finder needs to be normalized more often, which may
	// hurt performance with huge dictionaries.
	mf->offset = mf->cyclic_size;
	mf->read_pos = 0;
	mf->read_ahead = 0;
	mf->read_limit = 0;
	mf->write_pos = 0;
	mf->pending = 0;

	// Allocate match finder's hash array.
	const size_t alloc_count = mf->hash_size_sum + mf->sons_count;

#if UINT32_MAX >= SIZE_MAX / 4
	// Check for integer overflow. (Huge dictionaries are not
	// possible on 32-bit CPU.)
	if (alloc_count > SIZE_MAX / sizeof(uint32_t))
		return true;
#endif

	if (mf->hash == NULL) {
		mf->hash = lzma_alloc(alloc_count * sizeof(uint32_t),
				allocator);
		if (mf->hash == NULL)
			return true;
	}

	mf->son = mf->hash + mf->hash_size_sum;
	mf->cyclic_pos = 0;

	// Initialize the hash table. Since EMPTY_HASH_VALUE is zero, we
	// can use memset().
/*
	for (uint32_t i = 0; i < hash_size_sum; ++i)
		mf->hash[i] = EMPTY_HASH_VALUE;
*/
	memzero(mf->hash, (size_t)(mf->hash_size_sum) * sizeof(uint32_t));

	// We don't need to initialize mf->son, but not doing that will
	// make Valgrind complain in normalization (see normalize() in
	// lz_encoder_mf.c).
	//
	// Skipping this initialization is *very* good when big dictionary is
	// used but only small amount of data gets actually compressed: most
	// of the mf->hash won't get actually allocated by the kernel, so
	// we avoid wasting RAM and improve initialization speed a lot.
	//memzero(mf->son, (size_t)(mf->sons_count) * sizeof(uint32_t));

	// Handle preset dictionary.
	if (lz_options->preset_dict != NULL
			&& lz_options->preset_dict_size > 0) {
		// If the preset dictionary is bigger than the actual
		// dictionary, use only the tail.
		mf->write_pos = my_min(lz_options->preset_dict_size, mf->size);
		memcpy(mf->buffer, lz_options->preset_dict
				+ lz_options->preset_dict_size - mf->write_pos,
				mf->write_pos);
		mf->action = LZMA_SYNC_FLUSH;
		mf->skip(mf, mf->write_pos);
	}

	mf->action = LZMA_RUN;

	return false;
}


extern uint64_t
lzma_lz_encoder_memusage(const lzma_lz_options *lz_options)
{
	// Old buffers must not exist when calling lz_encoder_prepare().
	lzma_mf mf = {
		.buffer = NULL,
		.hash = NULL,
		.hash_size_sum = 0,
		.sons_count = 0,
	};

	// Setup the size information into mf.
	if (lz_encoder_prepare(&mf, NULL, lz_options))
		return UINT64_MAX;

	// Calculate the memory usage.
	return (uint64_t)(mf.hash_size_sum + mf.sons_count)
				* sizeof(uint32_t)
			+ (uint64_t)(mf.size) + sizeof(lzma_coder);
}


static void
lz_encoder_end(lzma_coder *coder, lzma_allocator *allocator)
{
	lzma_next_end(&coder->next, allocator);

	lzma_free(coder->mf.hash, allocator);
	lzma_free(coder->mf.buffer, allocator);

	if (coder->lz.end != NULL)
		coder->lz.end(coder->lz.coder, allocator);
	else
		lzma_free(coder->lz.coder, allocator);

	lzma_free(coder, allocator);
	return;
}


static lzma_ret
lz_encoder_update(lzma_coder *coder, lzma_allocator *allocator,
		const lzma_filter *filters_null lzma_attribute((unused)),
		const lzma_filter *reversed_filters)
{
	if (coder->lz.options_update == NULL)
		return LZMA_PROG_ERROR;

	return_if_error(coder->lz.options_update(
			coder->lz.coder, reversed_filters));

	return lzma_next_filter_update(
			&coder->next, allocator, reversed_filters + 1);
}


extern lzma_ret
lzma_lz_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
		const lzma_filter_info *filters,
		lzma_ret (*lz_init)(lzma_lz_encoder *lz,
			lzma_allocator *allocator, const void *options,
			lzma_lz_options *lz_options))
{
#ifdef HAVE_SMALL
	// We need that the CRC32 table has been initialized.
	lzma_crc32_init();
#endif

	// Allocate and initialize the base data structure.
	if (next->coder == NULL) {
		next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
		if (next->coder == NULL)
			return LZMA_MEM_ERROR;

		next->code = &lz_encode;
		next->end = &lz_encoder_end;
		next->update = &lz_encoder_update;

		next->coder->lz.coder = NULL;
		next->coder->lz.code = NULL;
		next->coder->lz.end = NULL;

		next->coder->mf.buffer = NULL;
		next->coder->mf.hash = NULL;
		next->coder->mf.hash_size_sum = 0;
		next->coder->mf.sons_count = 0;

		next->coder->next = LZMA_NEXT_CODER_INIT;
	}

	// Initialize the LZ-based encoder.
	lzma_lz_options lz_options;
	return_if_error(lz_init(&next->coder->lz, allocator,
			filters[0].options, &lz_options));

	// Setup the size information into next->coder->mf and deallocate
	// old buffers if they have wrong size.
	if (lz_encoder_prepare(&next->coder->mf, allocator, &lz_options))
		return LZMA_OPTIONS_ERROR;

	// Allocate new buffers if needed, and do the rest of
	// the initialization.
	if (lz_encoder_init(&next->coder->mf, allocator, &lz_options))
		return LZMA_MEM_ERROR;

	// Initialize the next filter in the chain, if any.
	return lzma_next_filter_init(&next->coder->next, allocator,
			filters + 1);
}


extern LZMA_API(lzma_bool)
lzma_mf_is_supported(lzma_match_finder mf)
{
	bool ret = false;

#ifdef HAVE_MF_HC3
	if (mf == LZMA_MF_HC3)
		ret = true;
#endif

#ifdef HAVE_MF_HC4
	if (mf == LZMA_MF_HC4)
		ret = true;
#endif

#ifdef HAVE_MF_BT2
	if (mf == LZMA_MF_BT2)
		ret = true;
#endif

#ifdef HAVE_MF_BT3
	if (mf == LZMA_MF_BT3)
		ret = true;
#endif

#ifdef HAVE_MF_BT4
	if (mf == LZMA_MF_BT4)
		ret = true;
#endif

	return ret;
}