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1 | /* NOLINT(build/header_guard) */\r |
2 | /* Copyright 2010 Google Inc. All Rights Reserved.\r | |
3 | \r | |
4 | Distributed under MIT license.\r | |
5 | See file LICENSE for detail or copy at https://opensource.org/licenses/MIT\r | |
6 | */\r | |
7 | \r | |
8 | /* template parameters: FN */\r | |
9 | \r | |
10 | /* A (forgetful) hash table to the data seen by the compressor, to\r | |
11 | help create backward references to previous data.\r | |
12 | \r | |
13 | This is a hash map of fixed size (bucket_size_) to a ring buffer of\r | |
14 | fixed size (block_size_). The ring buffer contains the last block_size_\r | |
15 | index positions of the given hash key in the compressed data. */\r | |
16 | \r | |
17 | #define HashLongestMatch HASHER()\r | |
18 | \r | |
19 | static BROTLI_INLINE size_t FN(HashTypeLength)(void) { return 8; }\r | |
20 | static BROTLI_INLINE size_t FN(StoreLookahead)(void) { return 8; }\r | |
21 | \r | |
22 | /* HashBytes is the function that chooses the bucket to place the address in. */\r | |
23 | static BROTLI_INLINE uint32_t FN(HashBytes)(const uint8_t* data,\r | |
24 | const uint64_t mask,\r | |
25 | const int shift) {\r | |
26 | const uint64_t h = (BROTLI_UNALIGNED_LOAD64LE(data) & mask) * kHashMul64Long;\r | |
27 | /* The higher bits contain more mixture from the multiplication,\r | |
28 | so we take our results from there. */\r | |
29 | return (uint32_t)(h >> shift);\r | |
30 | }\r | |
31 | \r | |
32 | typedef struct HashLongestMatch {\r | |
33 | /* Number of hash buckets. */\r | |
34 | size_t bucket_size_;\r | |
35 | /* Only block_size_ newest backward references are kept,\r | |
36 | and the older are forgotten. */\r | |
37 | size_t block_size_;\r | |
38 | /* Left-shift for computing hash bucket index from hash value. */\r | |
39 | int hash_shift_;\r | |
40 | /* Mask for selecting the next 4-8 bytes of input */\r | |
41 | uint64_t hash_mask_;\r | |
42 | /* Mask for accessing entries in a block (in a ring-buffer manner). */\r | |
43 | uint32_t block_mask_;\r | |
44 | \r | |
45 | /* --- Dynamic size members --- */\r | |
46 | \r | |
47 | /* Number of entries in a particular bucket. */\r | |
48 | /* uint16_t num[bucket_size]; */\r | |
49 | \r | |
50 | /* Buckets containing block_size_ of backward references. */\r | |
51 | /* uint32_t* buckets[bucket_size * block_size]; */\r | |
52 | } HashLongestMatch;\r | |
53 | \r | |
54 | static BROTLI_INLINE HashLongestMatch* FN(Self)(HasherHandle handle) {\r | |
55 | return (HashLongestMatch*)&(GetHasherCommon(handle)[1]);\r | |
56 | }\r | |
57 | \r | |
58 | static BROTLI_INLINE uint16_t* FN(Num)(HashLongestMatch* self) {\r | |
59 | return (uint16_t*)(&self[1]);\r | |
60 | }\r | |
61 | \r | |
62 | static BROTLI_INLINE uint32_t* FN(Buckets)(HashLongestMatch* self) {\r | |
63 | return (uint32_t*)(&FN(Num)(self)[self->bucket_size_]);\r | |
64 | }\r | |
65 | \r | |
66 | static void FN(Initialize)(\r | |
67 | HasherHandle handle, const BrotliEncoderParams* params) {\r | |
68 | HasherCommon* common = GetHasherCommon(handle);\r | |
69 | HashLongestMatch* self = FN(Self)(handle);\r | |
70 | BROTLI_UNUSED(params);\r | |
71 | self->hash_shift_ = 64 - common->params.bucket_bits;\r | |
72 | self->hash_mask_ = (~((uint64_t)0U)) >> (64 - 8 * common->params.hash_len);\r | |
73 | self->bucket_size_ = (size_t)1 << common->params.bucket_bits;\r | |
74 | self->block_size_ = (size_t)1 << common->params.block_bits;\r | |
75 | self->block_mask_ = (uint32_t)(self->block_size_ - 1);\r | |
76 | }\r | |
77 | \r | |
78 | static void FN(Prepare)(HasherHandle handle, BROTLI_BOOL one_shot,\r | |
79 | size_t input_size, const uint8_t* data) {\r | |
80 | HashLongestMatch* self = FN(Self)(handle);\r | |
81 | uint16_t* num = FN(Num)(self);\r | |
82 | /* Partial preparation is 100 times slower (per socket). */\r | |
83 | size_t partial_prepare_threshold = self->bucket_size_ >> 6;\r | |
84 | if (one_shot && input_size <= partial_prepare_threshold) {\r | |
85 | size_t i;\r | |
86 | for (i = 0; i < input_size; ++i) {\r | |
87 | const uint32_t key = FN(HashBytes)(&data[i], self->hash_mask_,\r | |
88 | self->hash_shift_);\r | |
89 | num[key] = 0;\r | |
90 | }\r | |
91 | } else {\r | |
92 | memset(num, 0, self->bucket_size_ * sizeof(num[0]));\r | |
93 | }\r | |
94 | }\r | |
95 | \r | |
96 | static BROTLI_INLINE size_t FN(HashMemAllocInBytes)(\r | |
97 | const BrotliEncoderParams* params, BROTLI_BOOL one_shot,\r | |
98 | size_t input_size) {\r | |
99 | size_t bucket_size = (size_t)1 << params->hasher.bucket_bits;\r | |
100 | size_t block_size = (size_t)1 << params->hasher.block_bits;\r | |
101 | BROTLI_UNUSED(one_shot);\r | |
102 | BROTLI_UNUSED(input_size);\r | |
103 | return sizeof(HashLongestMatch) + bucket_size * (2 + 4 * block_size);\r | |
104 | }\r | |
105 | \r | |
106 | /* Look at 4 bytes at &data[ix & mask].\r | |
107 | Compute a hash from these, and store the value of ix at that position. */\r | |
108 | static BROTLI_INLINE void FN(Store)(HasherHandle handle, const uint8_t* data,\r | |
109 | const size_t mask, const size_t ix) {\r | |
110 | HashLongestMatch* self = FN(Self)(handle);\r | |
111 | uint16_t* num = FN(Num)(self);\r | |
112 | const uint32_t key = FN(HashBytes)(&data[ix & mask], self->hash_mask_,\r | |
113 | self->hash_shift_);\r | |
114 | const size_t minor_ix = num[key] & self->block_mask_;\r | |
115 | const size_t offset =\r | |
116 | minor_ix + (key << GetHasherCommon(handle)->params.block_bits);\r | |
117 | FN(Buckets)(self)[offset] = (uint32_t)ix;\r | |
118 | ++num[key];\r | |
119 | }\r | |
120 | \r | |
121 | static BROTLI_INLINE void FN(StoreRange)(HasherHandle handle,\r | |
122 | const uint8_t* data, const size_t mask, const size_t ix_start,\r | |
123 | const size_t ix_end) {\r | |
124 | size_t i;\r | |
125 | for (i = ix_start; i < ix_end; ++i) {\r | |
126 | FN(Store)(handle, data, mask, i);\r | |
127 | }\r | |
128 | }\r | |
129 | \r | |
130 | static BROTLI_INLINE void FN(StitchToPreviousBlock)(HasherHandle handle,\r | |
131 | size_t num_bytes, size_t position, const uint8_t* ringbuffer,\r | |
132 | size_t ringbuffer_mask) {\r | |
133 | if (num_bytes >= FN(HashTypeLength)() - 1 && position >= 3) {\r | |
134 | /* Prepare the hashes for three last bytes of the last write.\r | |
135 | These could not be calculated before, since they require knowledge\r | |
136 | of both the previous and the current block. */\r | |
137 | FN(Store)(handle, ringbuffer, ringbuffer_mask, position - 3);\r | |
138 | FN(Store)(handle, ringbuffer, ringbuffer_mask, position - 2);\r | |
139 | FN(Store)(handle, ringbuffer, ringbuffer_mask, position - 1);\r | |
140 | }\r | |
141 | }\r | |
142 | \r | |
143 | static BROTLI_INLINE void FN(PrepareDistanceCache)(\r | |
144 | HasherHandle handle, int* BROTLI_RESTRICT distance_cache) {\r | |
145 | PrepareDistanceCache(distance_cache,\r | |
146 | GetHasherCommon(handle)->params.num_last_distances_to_check);\r | |
147 | }\r | |
148 | \r | |
149 | /* Find a longest backward match of &data[cur_ix] up to the length of\r | |
150 | max_length and stores the position cur_ix in the hash table.\r | |
151 | \r | |
152 | REQUIRES: FN(PrepareDistanceCache) must be invoked for current distance cache\r | |
153 | values; if this method is invoked repeatedly with the same distance\r | |
154 | cache values, it is enough to invoke FN(PrepareDistanceCache) once.\r | |
155 | \r | |
156 | Does not look for matches longer than max_length.\r | |
157 | Does not look for matches further away than max_backward.\r | |
158 | Writes the best match into |out|.\r | |
159 | |out|->score is updated only if a better match is found. */\r | |
160 | static BROTLI_INLINE void FN(FindLongestMatch)(HasherHandle handle,\r | |
161 | const BrotliEncoderDictionary* dictionary,\r | |
162 | const uint8_t* BROTLI_RESTRICT data, const size_t ring_buffer_mask,\r | |
163 | const int* BROTLI_RESTRICT distance_cache, const size_t cur_ix,\r | |
164 | const size_t max_length, const size_t max_backward, const size_t gap,\r | |
165 | const size_t max_distance, HasherSearchResult* BROTLI_RESTRICT out) {\r | |
166 | HasherCommon* common = GetHasherCommon(handle);\r | |
167 | HashLongestMatch* self = FN(Self)(handle);\r | |
168 | uint16_t* num = FN(Num)(self);\r | |
169 | uint32_t* buckets = FN(Buckets)(self);\r | |
170 | const size_t cur_ix_masked = cur_ix & ring_buffer_mask;\r | |
171 | /* Don't accept a short copy from far away. */\r | |
172 | score_t min_score = out->score;\r | |
173 | score_t best_score = out->score;\r | |
174 | size_t best_len = out->len;\r | |
175 | size_t i;\r | |
176 | out->len = 0;\r | |
177 | out->len_code_delta = 0;\r | |
178 | /* Try last distance first. */\r | |
179 | for (i = 0; i < (size_t)common->params.num_last_distances_to_check; ++i) {\r | |
180 | const size_t backward = (size_t)distance_cache[i];\r | |
181 | size_t prev_ix = (size_t)(cur_ix - backward);\r | |
182 | if (prev_ix >= cur_ix) {\r | |
183 | continue;\r | |
184 | }\r | |
185 | if (BROTLI_PREDICT_FALSE(backward > max_backward)) {\r | |
186 | continue;\r | |
187 | }\r | |
188 | prev_ix &= ring_buffer_mask;\r | |
189 | \r | |
190 | if (cur_ix_masked + best_len > ring_buffer_mask ||\r | |
191 | prev_ix + best_len > ring_buffer_mask ||\r | |
192 | data[cur_ix_masked + best_len] != data[prev_ix + best_len]) {\r | |
193 | continue;\r | |
194 | }\r | |
195 | {\r | |
196 | const size_t len = FindMatchLengthWithLimit(&data[prev_ix],\r | |
197 | &data[cur_ix_masked],\r | |
198 | max_length);\r | |
199 | if (len >= 3 || (len == 2 && i < 2)) {\r | |
200 | /* Comparing for >= 2 does not change the semantics, but just saves for\r | |
201 | a few unnecessary binary logarithms in backward reference score,\r | |
202 | since we are not interested in such short matches. */\r | |
203 | score_t score = BackwardReferenceScoreUsingLastDistance(len);\r | |
204 | if (best_score < score) {\r | |
205 | if (i != 0) score -= BackwardReferencePenaltyUsingLastDistance(i);\r | |
206 | if (best_score < score) {\r | |
207 | best_score = score;\r | |
208 | best_len = len;\r | |
209 | out->len = best_len;\r | |
210 | out->distance = backward;\r | |
211 | out->score = best_score;\r | |
212 | }\r | |
213 | }\r | |
214 | }\r | |
215 | }\r | |
216 | }\r | |
217 | {\r | |
218 | const uint32_t key = FN(HashBytes)(\r | |
219 | &data[cur_ix_masked], self->hash_mask_, self->hash_shift_);\r | |
220 | uint32_t* BROTLI_RESTRICT bucket =\r | |
221 | &buckets[key << common->params.block_bits];\r | |
222 | const size_t down =\r | |
223 | (num[key] > self->block_size_) ?\r | |
224 | (num[key] - self->block_size_) : 0u;\r | |
225 | for (i = num[key]; i > down;) {\r | |
226 | size_t prev_ix = bucket[--i & self->block_mask_];\r | |
227 | const size_t backward = cur_ix - prev_ix;\r | |
228 | if (BROTLI_PREDICT_FALSE(backward > max_backward)) {\r | |
229 | break;\r | |
230 | }\r | |
231 | prev_ix &= ring_buffer_mask;\r | |
232 | if (cur_ix_masked + best_len > ring_buffer_mask ||\r | |
233 | prev_ix + best_len > ring_buffer_mask ||\r | |
234 | data[cur_ix_masked + best_len] != data[prev_ix + best_len]) {\r | |
235 | continue;\r | |
236 | }\r | |
237 | {\r | |
238 | const size_t len = FindMatchLengthWithLimit(&data[prev_ix],\r | |
239 | &data[cur_ix_masked],\r | |
240 | max_length);\r | |
241 | if (len >= 4) {\r | |
242 | /* Comparing for >= 3 does not change the semantics, but just saves\r | |
243 | for a few unnecessary binary logarithms in backward reference\r | |
244 | score, since we are not interested in such short matches. */\r | |
245 | score_t score = BackwardReferenceScore(len, backward);\r | |
246 | if (best_score < score) {\r | |
247 | best_score = score;\r | |
248 | best_len = len;\r | |
249 | out->len = best_len;\r | |
250 | out->distance = backward;\r | |
251 | out->score = best_score;\r | |
252 | }\r | |
253 | }\r | |
254 | }\r | |
255 | }\r | |
256 | bucket[num[key] & self->block_mask_] = (uint32_t)cur_ix;\r | |
257 | ++num[key];\r | |
258 | }\r | |
259 | if (min_score == out->score) {\r | |
260 | SearchInStaticDictionary(dictionary,\r | |
261 | handle, &data[cur_ix_masked], max_length, max_backward + gap,\r | |
262 | max_distance, out, BROTLI_FALSE);\r | |
263 | }\r | |
264 | }\r | |
265 | \r | |
266 | #undef HashLongestMatch\r |