summaryrefslogtreecommitdiffstats
path: root/Utilities/cmliblzma/liblzma/lz/lz_encoder.h
blob: dcb4b2c5bb63effba14bec29a5e9910822645aba (plain)
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
///////////////////////////////////////////////////////////////////////////////
//
/// \file       lz_encoder.h
/// \brief      LZ in window and match finder API
///
//  Authors:    Igor Pavlov
//              Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef LZMA_LZ_ENCODER_H
#define LZMA_LZ_ENCODER_H

#include "common.h"


/// A table of these is used by the LZ-based encoder to hold
/// the length-distance pairs found by the match finder.
typedef struct {
	uint32_t len;
	uint32_t dist;
} lzma_match;


typedef struct lzma_mf_s lzma_mf;
struct lzma_mf_s {
	///////////////
	// In Window //
	///////////////

	/// Pointer to buffer with data to be compressed
	uint8_t *buffer;

	/// Total size of the allocated buffer (that is, including all
	/// the extra space)
	uint32_t size;

	/// Number of bytes that must be kept available in our input history.
	/// That is, once keep_size_before bytes have been processed,
	/// buffer[read_pos - keep_size_before] is the oldest byte that
	/// must be available for reading.
	uint32_t keep_size_before;

	/// Number of bytes that must be kept in buffer after read_pos.
	/// That is, read_pos <= write_pos - keep_size_after as long as
	/// action is LZMA_RUN; when action != LZMA_RUN, read_pos is allowed
	/// to reach write_pos so that the last bytes get encoded too.
	uint32_t keep_size_after;

	/// Match finders store locations of matches using 32-bit integers.
	/// To avoid adjusting several megabytes of integers every time the
	/// input window is moved with move_window, we only adjust the
	/// offset of the buffer. Thus, buffer[value_in_hash_table - offset]
	/// is the byte pointed by value_in_hash_table.
	uint32_t offset;

	/// buffer[read_pos] is the next byte to run through the match
	/// finder. This is incremented in the match finder once the byte
	/// has been processed.
	uint32_t read_pos;

	/// Number of bytes that have been ran through the match finder, but
	/// which haven't been encoded by the LZ-based encoder yet.
	uint32_t read_ahead;

	/// As long as read_pos is less than read_limit, there is enough
	/// input available in buffer for at least one encoding loop.
	///
	/// Because of the stateful API, read_limit may and will get greater
	/// than read_pos quite often. This is taken into account when
	/// calculating the value for keep_size_after.
	uint32_t read_limit;

	/// buffer[write_pos] is the first byte that doesn't contain valid
	/// uncompressed data; that is, the next input byte will be copied
	/// to buffer[write_pos].
	uint32_t write_pos;

	/// Number of bytes not hashed before read_pos. This is needed to
	/// restart the match finder after LZMA_SYNC_FLUSH.
	uint32_t pending;

	//////////////////
	// Match Finder //
	//////////////////

	/// Find matches. Returns the number of distance-length pairs written
	/// to the matches array. This is called only via lzma_mf_find().
	uint32_t (*find)(lzma_mf *mf, lzma_match *matches);

	/// Skips num bytes. This is like find() but doesn't make the
	/// distance-length pairs available, thus being a little faster.
	/// This is called only via mf_skip().
	void (*skip)(lzma_mf *mf, uint32_t num);

	uint32_t *hash;
	uint32_t *son;
	uint32_t cyclic_pos;
	uint32_t cyclic_size; // Must be dictionary size + 1.
	uint32_t hash_mask;

	/// Maximum number of loops in the match finder
	uint32_t depth;

	/// Maximum length of a match that the match finder will try to find.
	uint32_t nice_len;

	/// Maximum length of a match supported by the LZ-based encoder.
	/// If the longest match found by the match finder is nice_len,
	/// mf_find() tries to expand it up to match_len_max bytes.
	uint32_t match_len_max;

	/// When running out of input, binary tree match finders need to know
	/// if it is due to flushing or finishing. The action is used also
	/// by the LZ-based encoders themselves.
	lzma_action action;

	/// Number of elements in hash[]
	uint32_t hash_size_sum;

	/// Number of elements in son[]
	uint32_t sons_count;
};


typedef struct {
	/// Extra amount of data to keep available before the "actual"
	/// dictionary.
	size_t before_size;

	/// Size of the history buffer
	size_t dict_size;

	/// Extra amount of data to keep available after the "actual"
	/// dictionary.
	size_t after_size;

	/// Maximum length of a match that the LZ-based encoder can accept.
	/// This is used to extend matches of length nice_len to the
	/// maximum possible length.
	size_t match_len_max;

	/// Match finder will search matches up to this length.
	/// This must be less than or equal to match_len_max.
	size_t nice_len;

	/// Type of the match finder to use
	lzma_match_finder match_finder;

	/// Maximum search depth
	uint32_t depth;

	/// TODO: Comment
	const uint8_t *preset_dict;

	uint32_t preset_dict_size;

} lzma_lz_options;


// The total usable buffer space at any moment outside the match finder:
// before_size + dict_size + after_size + match_len_max
//
// In reality, there's some extra space allocated to prevent the number of
// memmove() calls reasonable. The bigger the dict_size is, the bigger
// this extra buffer will be since with bigger dictionaries memmove() would
// also take longer.
//
// A single encoder loop in the LZ-based encoder may call the match finder
// (mf_find() or mf_skip()) at most after_size times. In other words,
// a single encoder loop may increment lzma_mf.read_pos at most after_size
// times. Since matches are looked up to
// lzma_mf.buffer[lzma_mf.read_pos + match_len_max - 1], the total
// amount of extra buffer needed after dict_size becomes
// after_size + match_len_max.
//
// before_size has two uses. The first one is to keep literals available
// in cases when the LZ-based encoder has made some read ahead.
// TODO: Maybe this could be changed by making the LZ-based encoders to
// store the actual literals as they do with length-distance pairs.
//
// Algorithms such as LZMA2 first try to compress a chunk, and then check
// if the encoded result is smaller than the uncompressed one. If the chunk
// was uncompressible, it is better to store it in uncompressed form in
// the output stream. To do this, the whole uncompressed chunk has to be
// still available in the history buffer. before_size achieves that.


typedef struct {
	/// Data specific to the LZ-based encoder
	lzma_coder *coder;

	/// Function to encode from *dict to out[]
	lzma_ret (*code)(lzma_coder *LZMA_RESTRICT coder,
			lzma_mf *LZMA_RESTRICT mf, uint8_t *LZMA_RESTRICT out,
			size_t *LZMA_RESTRICT out_pos, size_t out_size);

	/// Free allocated resources
	void (*end)(lzma_coder *coder, lzma_allocator *allocator);

	/// Update the options in the middle of the encoding.
	lzma_ret (*options_update)(lzma_coder *coder,
			const lzma_filter *filter);

} lzma_lz_encoder;


// Basic steps:
//  1. Input gets copied into the dictionary.
//  2. Data in dictionary gets run through the match finder byte by byte.
//  3. The literals and matches are encoded using e.g. LZMA.
//
// The bytes that have been ran through the match finder, but not encoded yet,
// are called `read ahead'.


/// Get pointer to the first byte not ran through the match finder
static inline uint8_t *
mf_ptr(const lzma_mf *mf)
{
	return mf->buffer + mf->read_pos;
}


/// Get the number of bytes that haven't been ran through the match finder yet.
static inline uint32_t
mf_avail(const lzma_mf *mf)
{
	return mf->write_pos - mf->read_pos;
}


/// Get the number of bytes that haven't been encoded yet (some of these
/// bytes may have been ran through the match finder though).
static inline uint32_t
mf_unencoded(const lzma_mf *mf)
{
	return mf->write_pos - mf->read_pos + mf->read_ahead;
}


/// Calculate the absolute offset from the beginning of the most recent
/// dictionary reset. Only the lowest four bits are important, so there's no
/// problem that we don't know the 64-bit size of the data encoded so far.
///
/// NOTE: When moving the input window, we need to do it so that the lowest
/// bits of dict->read_pos are not modified to keep this macro working
/// as intended.
static inline uint32_t
mf_position(const lzma_mf *mf)
{
	return mf->read_pos - mf->read_ahead;
}


/// Since everything else begins with mf_, use it also for lzma_mf_find().
#define mf_find lzma_mf_find


/// Skip the given number of bytes. This is used when a good match was found.
/// For example, if mf_find() finds a match of 200 bytes long, the first byte
/// of that match was already consumed by mf_find(), and the rest 199 bytes
/// have to be skipped with mf_skip(mf, 199).
static inline void
mf_skip(lzma_mf *mf, uint32_t amount)
{
	if (amount != 0) {
		mf->skip(mf, amount);
		mf->read_ahead += amount;
	}
}


/// Copies at most *left number of bytes from the history buffer
/// to out[]. This is needed by LZMA2 to encode uncompressed chunks.
static inline void
mf_read(lzma_mf *mf, uint8_t *out, size_t *out_pos, size_t out_size,
		size_t *left)
{
	const size_t out_avail = out_size - *out_pos;
	const size_t copy_size = my_min(out_avail, *left);

	assert(mf->read_ahead == 0);
	assert(mf->read_pos >= *left);

	memcpy(out + *out_pos, mf->buffer + mf->read_pos - *left,
			copy_size);

	*out_pos += copy_size;
	*left -= copy_size;
	return;
}


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));


extern uint64_t lzma_lz_encoder_memusage(const lzma_lz_options *lz_options);


// These are only for LZ encoder's internal use.
extern uint32_t lzma_mf_find(
		lzma_mf *mf, uint32_t *count, lzma_match *matches);

extern uint32_t lzma_mf_hc3_find(lzma_mf *dict, lzma_match *matches);
extern void lzma_mf_hc3_skip(lzma_mf *dict, uint32_t amount);

extern uint32_t lzma_mf_hc4_find(lzma_mf *dict, lzma_match *matches);
extern void lzma_mf_hc4_skip(lzma_mf *dict, uint32_t amount);

extern uint32_t lzma_mf_bt2_find(lzma_mf *dict, lzma_match *matches);
extern void lzma_mf_bt2_skip(lzma_mf *dict, uint32_t amount);

extern uint32_t lzma_mf_bt3_find(lzma_mf *dict, lzma_match *matches);
extern void lzma_mf_bt3_skip(lzma_mf *dict, uint32_t amount);

extern uint32_t lzma_mf_bt4_find(lzma_mf *dict, lzma_match *matches);
extern void lzma_mf_bt4_skip(lzma_mf *dict, uint32_t amount);

#endif