1// SPDX-License-Identifier: 0BSD
2
3///////////////////////////////////////////////////////////////////////////////
4//
5/// \file       lz_encoder.h
6/// \brief      LZ in window and match finder API
7///
8//  Authors:    Igor Pavlov
9//              Lasse Collin
10//
11///////////////////////////////////////////////////////////////////////////////
12
13#ifndef LZMA_LZ_ENCODER_H
14#define LZMA_LZ_ENCODER_H
15
16#include "common.h"
17
18
19// For now, the dictionary size is limited to 1.5 GiB. This may grow
20// in the future if needed, but it needs a little more work than just
21// changing this check.
22#define IS_ENC_DICT_SIZE_VALID(size) \
23	((size) >= LZMA_DICT_SIZE_MIN \
24		&& (size) <= (UINT32_C(1) << 30) + (UINT32_C(1) << 29))
25
26
27/// A table of these is used by the LZ-based encoder to hold
28/// the length-distance pairs found by the match finder.
29typedef struct {
30	uint32_t len;
31	uint32_t dist;
32} lzma_match;
33
34
35typedef struct lzma_mf_s lzma_mf;
36struct lzma_mf_s {
37	///////////////
38	// In Window //
39	///////////////
40
41	/// Pointer to buffer with data to be compressed
42	uint8_t *buffer;
43
44	/// Total size of the allocated buffer (that is, including all
45	/// the extra space)
46	uint32_t size;
47
48	/// Number of bytes that must be kept available in our input history.
49	/// That is, once keep_size_before bytes have been processed,
50	/// buffer[read_pos - keep_size_before] is the oldest byte that
51	/// must be available for reading.
52	uint32_t keep_size_before;
53
54	/// Number of bytes that must be kept in buffer after read_pos.
55	/// That is, read_pos <= write_pos - keep_size_after as long as
56	/// action is LZMA_RUN; when action != LZMA_RUN, read_pos is allowed
57	/// to reach write_pos so that the last bytes get encoded too.
58	uint32_t keep_size_after;
59
60	/// Match finders store locations of matches using 32-bit integers.
61	/// To avoid adjusting several megabytes of integers every time the
62	/// input window is moved with move_window, we only adjust the
63	/// offset of the buffer. Thus, buffer[value_in_hash_table - offset]
64	/// is the byte pointed by value_in_hash_table.
65	uint32_t offset;
66
67	/// buffer[read_pos] is the next byte to run through the match
68	/// finder. This is incremented in the match finder once the byte
69	/// has been processed.
70	uint32_t read_pos;
71
72	/// Number of bytes that have been ran through the match finder, but
73	/// which haven't been encoded by the LZ-based encoder yet.
74	uint32_t read_ahead;
75
76	/// As long as read_pos is less than read_limit, there is enough
77	/// input available in buffer for at least one encoding loop.
78	///
79	/// Because of the stateful API, read_limit may and will get greater
80	/// than read_pos quite often. This is taken into account when
81	/// calculating the value for keep_size_after.
82	uint32_t read_limit;
83
84	/// buffer[write_pos] is the first byte that doesn't contain valid
85	/// uncompressed data; that is, the next input byte will be copied
86	/// to buffer[write_pos].
87	uint32_t write_pos;
88
89	/// Number of bytes not hashed before read_pos. This is needed to
90	/// restart the match finder after LZMA_SYNC_FLUSH.
91	uint32_t pending;
92
93	//////////////////
94	// Match Finder //
95	//////////////////
96
97	/// Find matches. Returns the number of distance-length pairs written
98	/// to the matches array. This is called only via lzma_mf_find().
99	uint32_t (*find)(lzma_mf *mf, lzma_match *matches);
100
101	/// Skips num bytes. This is like find() but doesn't make the
102	/// distance-length pairs available, thus being a little faster.
103	/// This is called only via mf_skip().
104	void (*skip)(lzma_mf *mf, uint32_t num);
105
106	uint32_t *hash;
107	uint32_t *son;
108	uint32_t cyclic_pos;
109	uint32_t cyclic_size; // Must be dictionary size + 1.
110	uint32_t hash_mask;
111
112	/// Maximum number of loops in the match finder
113	uint32_t depth;
114
115	/// Maximum length of a match that the match finder will try to find.
116	uint32_t nice_len;
117
118	/// Maximum length of a match supported by the LZ-based encoder.
119	/// If the longest match found by the match finder is nice_len,
120	/// mf_find() tries to expand it up to match_len_max bytes.
121	uint32_t match_len_max;
122
123	/// When running out of input, binary tree match finders need to know
124	/// if it is due to flushing or finishing. The action is used also
125	/// by the LZ-based encoders themselves.
126	lzma_action action;
127
128	/// Number of elements in hash[]
129	uint32_t hash_count;
130
131	/// Number of elements in son[]
132	uint32_t sons_count;
133};
134
135
136typedef struct {
137	/// Extra amount of data to keep available before the "actual"
138	/// dictionary.
139	size_t before_size;
140
141	/// Size of the history buffer
142	size_t dict_size;
143
144	/// Extra amount of data to keep available after the "actual"
145	/// dictionary.
146	size_t after_size;
147
148	/// Maximum length of a match that the LZ-based encoder can accept.
149	/// This is used to extend matches of length nice_len to the
150	/// maximum possible length.
151	size_t match_len_max;
152
153	/// Match finder will search matches up to this length.
154	/// This must be less than or equal to match_len_max.
155	size_t nice_len;
156
157	/// Type of the match finder to use
158	lzma_match_finder match_finder;
159
160	/// Maximum search depth
161	uint32_t depth;
162
163	/// Initial dictionary for the match finder to search.
164	const uint8_t *preset_dict;
165
166	/// If the preset dictionary is NULL, this value is ignored.
167	/// Otherwise this member must indicate the preset dictionary's
168	/// buffer size. If this size is larger than dict_size, then only
169	/// the dict_size sized tail of the preset_dict will be used.
170	uint32_t preset_dict_size;
171
172} lzma_lz_options;
173
174
175// The total usable buffer space at any moment outside the match finder:
176// before_size + dict_size + after_size + match_len_max
177//
178// In reality, there's some extra space allocated to prevent the number of
179// memmove() calls reasonable. The bigger the dict_size is, the bigger
180// this extra buffer will be since with bigger dictionaries memmove() would
181// also take longer.
182//
183// A single encoder loop in the LZ-based encoder may call the match finder
184// (mf_find() or mf_skip()) at most after_size times. In other words,
185// a single encoder loop may increment lzma_mf.read_pos at most after_size
186// times. Since matches are looked up to
187// lzma_mf.buffer[lzma_mf.read_pos + match_len_max - 1], the total
188// amount of extra buffer needed after dict_size becomes
189// after_size + match_len_max.
190//
191// before_size has two uses. The first one is to keep literals available
192// in cases when the LZ-based encoder has made some read ahead.
193// TODO: Maybe this could be changed by making the LZ-based encoders to
194// store the actual literals as they do with length-distance pairs.
195//
196// Algorithms such as LZMA2 first try to compress a chunk, and then check
197// if the encoded result is smaller than the uncompressed one. If the chunk
198// was incompressible, it is better to store it in uncompressed form in
199// the output stream. To do this, the whole uncompressed chunk has to be
200// still available in the history buffer. before_size achieves that.
201
202
203typedef struct {
204	/// Data specific to the LZ-based encoder
205	void *coder;
206
207	/// Function to encode from *dict to out[]
208	lzma_ret (*code)(void *coder,
209			lzma_mf *restrict mf, uint8_t *restrict out,
210			size_t *restrict out_pos, size_t out_size);
211
212	/// Free allocated resources
213	void (*end)(void *coder, const lzma_allocator *allocator);
214
215	/// Update the options in the middle of the encoding.
216	lzma_ret (*options_update)(void *coder, const lzma_filter *filter);
217
218	/// Set maximum allowed output size
219	lzma_ret (*set_out_limit)(void *coder, uint64_t *uncomp_size,
220			uint64_t out_limit);
221
222} lzma_lz_encoder;
223
224
225// Basic steps:
226//  1. Input gets copied into the dictionary.
227//  2. Data in dictionary gets run through the match finder byte by byte.
228//  3. The literals and matches are encoded using e.g. LZMA.
229//
230// The bytes that have been ran through the match finder, but not encoded yet,
231// are called 'read ahead'.
232
233
234/// Get how many bytes the match finder hashes in its initial step.
235/// This is also the minimum nice_len value with the match finder.
236static inline uint32_t
237mf_get_hash_bytes(lzma_match_finder match_finder)
238{
239	return (uint32_t)match_finder & 0x0F;
240}
241
242
243/// Get pointer to the first byte not ran through the match finder
244static inline const uint8_t *
245mf_ptr(const lzma_mf *mf)
246{
247	return mf->buffer + mf->read_pos;
248}
249
250
251/// Get the number of bytes that haven't been ran through the match finder yet.
252static inline uint32_t
253mf_avail(const lzma_mf *mf)
254{
255	return mf->write_pos - mf->read_pos;
256}
257
258
259/// Get the number of bytes that haven't been encoded yet (some of these
260/// bytes may have been ran through the match finder though).
261static inline uint32_t
262mf_unencoded(const lzma_mf *mf)
263{
264	return mf->write_pos - mf->read_pos + mf->read_ahead;
265}
266
267
268/// Calculate the absolute offset from the beginning of the most recent
269/// dictionary reset. Only the lowest four bits are important, so there's no
270/// problem that we don't know the 64-bit size of the data encoded so far.
271///
272/// NOTE: When moving the input window, we need to do it so that the lowest
273/// bits of dict->read_pos are not modified to keep this macro working
274/// as intended.
275static inline uint32_t
276mf_position(const lzma_mf *mf)
277{
278	return mf->read_pos - mf->read_ahead;
279}
280
281
282/// Since everything else begins with mf_, use it also for lzma_mf_find().
283#define mf_find lzma_mf_find
284
285
286/// Skip the given number of bytes. This is used when a good match was found.
287/// For example, if mf_find() finds a match of 200 bytes long, the first byte
288/// of that match was already consumed by mf_find(), and the rest 199 bytes
289/// have to be skipped with mf_skip(mf, 199).
290static inline void
291mf_skip(lzma_mf *mf, uint32_t amount)
292{
293	if (amount != 0) {
294		mf->skip(mf, amount);
295		mf->read_ahead += amount;
296	}
297}
298
299
300/// Copies at most *left number of bytes from the history buffer
301/// to out[]. This is needed by LZMA2 to encode uncompressed chunks.
302static inline void
303mf_read(lzma_mf *mf, uint8_t *out, size_t *out_pos, size_t out_size,
304		size_t *left)
305{
306	const size_t out_avail = out_size - *out_pos;
307	const size_t copy_size = my_min(out_avail, *left);
308
309	assert(mf->read_ahead == 0);
310	assert(mf->read_pos >= *left);
311
312	memcpy(out + *out_pos, mf->buffer + mf->read_pos - *left,
313			copy_size);
314
315	*out_pos += copy_size;
316	*left -= copy_size;
317	return;
318}
319
320
321extern lzma_ret lzma_lz_encoder_init(
322		lzma_next_coder *next, const lzma_allocator *allocator,
323		const lzma_filter_info *filters,
324		lzma_ret (*lz_init)(lzma_lz_encoder *lz,
325			const lzma_allocator *allocator,
326			lzma_vli id, const void *options,
327			lzma_lz_options *lz_options));
328
329
330extern uint64_t lzma_lz_encoder_memusage(const lzma_lz_options *lz_options);
331
332
333// These are only for LZ encoder's internal use.
334extern uint32_t lzma_mf_find(
335		lzma_mf *mf, uint32_t *count, lzma_match *matches);
336
337extern uint32_t lzma_mf_hc3_find(lzma_mf *dict, lzma_match *matches);
338extern void lzma_mf_hc3_skip(lzma_mf *dict, uint32_t amount);
339
340extern uint32_t lzma_mf_hc4_find(lzma_mf *dict, lzma_match *matches);
341extern void lzma_mf_hc4_skip(lzma_mf *dict, uint32_t amount);
342
343extern uint32_t lzma_mf_bt2_find(lzma_mf *dict, lzma_match *matches);
344extern void lzma_mf_bt2_skip(lzma_mf *dict, uint32_t amount);
345
346extern uint32_t lzma_mf_bt3_find(lzma_mf *dict, lzma_match *matches);
347extern void lzma_mf_bt3_skip(lzma_mf *dict, uint32_t amount);
348
349extern uint32_t lzma_mf_bt4_find(lzma_mf *dict, lzma_match *matches);
350extern void lzma_mf_bt4_skip(lzma_mf *dict, uint32_t amount);
351
352#endif
353