--- /dev/null
+/* NOLINT(build/header_guard) */\r
+/* Copyright 2010 Google Inc. All Rights Reserved.\r
+\r
+ Distributed under MIT license.\r
+ See file LICENSE for detail or copy at https://opensource.org/licenses/MIT\r
+*/\r
+\r
+/* template parameters: FN */\r
+\r
+/* A (forgetful) hash table to the data seen by the compressor, to\r
+ help create backward references to previous data.\r
+\r
+ This is a hash map of fixed size (bucket_size_) to a ring buffer of\r
+ fixed size (block_size_). The ring buffer contains the last block_size_\r
+ index positions of the given hash key in the compressed data. */\r
+\r
+#define HashLongestMatch HASHER()\r
+\r
+static BROTLI_INLINE size_t FN(HashTypeLength)(void) { return 8; }\r
+static BROTLI_INLINE size_t FN(StoreLookahead)(void) { return 8; }\r
+\r
+/* HashBytes is the function that chooses the bucket to place the address in. */\r
+static BROTLI_INLINE uint32_t FN(HashBytes)(const uint8_t* data,\r
+ const uint64_t mask,\r
+ const int shift) {\r
+ const uint64_t h = (BROTLI_UNALIGNED_LOAD64LE(data) & mask) * kHashMul64Long;\r
+ /* The higher bits contain more mixture from the multiplication,\r
+ so we take our results from there. */\r
+ return (uint32_t)(h >> shift);\r
+}\r
+\r
+typedef struct HashLongestMatch {\r
+ /* Number of hash buckets. */\r
+ size_t bucket_size_;\r
+ /* Only block_size_ newest backward references are kept,\r
+ and the older are forgotten. */\r
+ size_t block_size_;\r
+ /* Left-shift for computing hash bucket index from hash value. */\r
+ int hash_shift_;\r
+ /* Mask for selecting the next 4-8 bytes of input */\r
+ uint64_t hash_mask_;\r
+ /* Mask for accessing entries in a block (in a ring-buffer manner). */\r
+ uint32_t block_mask_;\r
+\r
+ /* --- Dynamic size members --- */\r
+\r
+ /* Number of entries in a particular bucket. */\r
+ /* uint16_t num[bucket_size]; */\r
+\r
+ /* Buckets containing block_size_ of backward references. */\r
+ /* uint32_t* buckets[bucket_size * block_size]; */\r
+} HashLongestMatch;\r
+\r
+static BROTLI_INLINE HashLongestMatch* FN(Self)(HasherHandle handle) {\r
+ return (HashLongestMatch*)&(GetHasherCommon(handle)[1]);\r
+}\r
+\r
+static BROTLI_INLINE uint16_t* FN(Num)(HashLongestMatch* self) {\r
+ return (uint16_t*)(&self[1]);\r
+}\r
+\r
+static BROTLI_INLINE uint32_t* FN(Buckets)(HashLongestMatch* self) {\r
+ return (uint32_t*)(&FN(Num)(self)[self->bucket_size_]);\r
+}\r
+\r
+static void FN(Initialize)(\r
+ HasherHandle handle, const BrotliEncoderParams* params) {\r
+ HasherCommon* common = GetHasherCommon(handle);\r
+ HashLongestMatch* self = FN(Self)(handle);\r
+ BROTLI_UNUSED(params);\r
+ self->hash_shift_ = 64 - common->params.bucket_bits;\r
+ self->hash_mask_ = (~((uint64_t)0U)) >> (64 - 8 * common->params.hash_len);\r
+ self->bucket_size_ = (size_t)1 << common->params.bucket_bits;\r
+ self->block_size_ = (size_t)1 << common->params.block_bits;\r
+ self->block_mask_ = (uint32_t)(self->block_size_ - 1);\r
+}\r
+\r
+static void FN(Prepare)(HasherHandle handle, BROTLI_BOOL one_shot,\r
+ size_t input_size, const uint8_t* data) {\r
+ HashLongestMatch* self = FN(Self)(handle);\r
+ uint16_t* num = FN(Num)(self);\r
+ /* Partial preparation is 100 times slower (per socket). */\r
+ size_t partial_prepare_threshold = self->bucket_size_ >> 6;\r
+ if (one_shot && input_size <= partial_prepare_threshold) {\r
+ size_t i;\r
+ for (i = 0; i < input_size; ++i) {\r
+ const uint32_t key = FN(HashBytes)(&data[i], self->hash_mask_,\r
+ self->hash_shift_);\r
+ num[key] = 0;\r
+ }\r
+ } else {\r
+ memset(num, 0, self->bucket_size_ * sizeof(num[0]));\r
+ }\r
+}\r
+\r
+static BROTLI_INLINE size_t FN(HashMemAllocInBytes)(\r
+ const BrotliEncoderParams* params, BROTLI_BOOL one_shot,\r
+ size_t input_size) {\r
+ size_t bucket_size = (size_t)1 << params->hasher.bucket_bits;\r
+ size_t block_size = (size_t)1 << params->hasher.block_bits;\r
+ BROTLI_UNUSED(one_shot);\r
+ BROTLI_UNUSED(input_size);\r
+ return sizeof(HashLongestMatch) + bucket_size * (2 + 4 * block_size);\r
+}\r
+\r
+/* Look at 4 bytes at &data[ix & mask].\r
+ Compute a hash from these, and store the value of ix at that position. */\r
+static BROTLI_INLINE void FN(Store)(HasherHandle handle, const uint8_t* data,\r
+ const size_t mask, const size_t ix) {\r
+ HashLongestMatch* self = FN(Self)(handle);\r
+ uint16_t* num = FN(Num)(self);\r
+ const uint32_t key = FN(HashBytes)(&data[ix & mask], self->hash_mask_,\r
+ self->hash_shift_);\r
+ const size_t minor_ix = num[key] & self->block_mask_;\r
+ const size_t offset =\r
+ minor_ix + (key << GetHasherCommon(handle)->params.block_bits);\r
+ FN(Buckets)(self)[offset] = (uint32_t)ix;\r
+ ++num[key];\r
+}\r
+\r
+static BROTLI_INLINE void FN(StoreRange)(HasherHandle handle,\r
+ const uint8_t* data, const size_t mask, const size_t ix_start,\r
+ const size_t ix_end) {\r
+ size_t i;\r
+ for (i = ix_start; i < ix_end; ++i) {\r
+ FN(Store)(handle, data, mask, i);\r
+ }\r
+}\r
+\r
+static BROTLI_INLINE void FN(StitchToPreviousBlock)(HasherHandle handle,\r
+ size_t num_bytes, size_t position, const uint8_t* ringbuffer,\r
+ size_t ringbuffer_mask) {\r
+ if (num_bytes >= FN(HashTypeLength)() - 1 && position >= 3) {\r
+ /* Prepare the hashes for three last bytes of the last write.\r
+ These could not be calculated before, since they require knowledge\r
+ of both the previous and the current block. */\r
+ FN(Store)(handle, ringbuffer, ringbuffer_mask, position - 3);\r
+ FN(Store)(handle, ringbuffer, ringbuffer_mask, position - 2);\r
+ FN(Store)(handle, ringbuffer, ringbuffer_mask, position - 1);\r
+ }\r
+}\r
+\r
+static BROTLI_INLINE void FN(PrepareDistanceCache)(\r
+ HasherHandle handle, int* BROTLI_RESTRICT distance_cache) {\r
+ PrepareDistanceCache(distance_cache,\r
+ GetHasherCommon(handle)->params.num_last_distances_to_check);\r
+}\r
+\r
+/* Find a longest backward match of &data[cur_ix] up to the length of\r
+ max_length and stores the position cur_ix in the hash table.\r
+\r
+ REQUIRES: FN(PrepareDistanceCache) must be invoked for current distance cache\r
+ values; if this method is invoked repeatedly with the same distance\r
+ cache values, it is enough to invoke FN(PrepareDistanceCache) once.\r
+\r
+ Does not look for matches longer than max_length.\r
+ Does not look for matches further away than max_backward.\r
+ Writes the best match into |out|.\r
+ |out|->score is updated only if a better match is found. */\r
+static BROTLI_INLINE void FN(FindLongestMatch)(HasherHandle handle,\r
+ const BrotliEncoderDictionary* dictionary,\r
+ const uint8_t* BROTLI_RESTRICT data, const size_t ring_buffer_mask,\r
+ const int* BROTLI_RESTRICT distance_cache, const size_t cur_ix,\r
+ const size_t max_length, const size_t max_backward, const size_t gap,\r
+ const size_t max_distance, HasherSearchResult* BROTLI_RESTRICT out) {\r
+ HasherCommon* common = GetHasherCommon(handle);\r
+ HashLongestMatch* self = FN(Self)(handle);\r
+ uint16_t* num = FN(Num)(self);\r
+ uint32_t* buckets = FN(Buckets)(self);\r
+ const size_t cur_ix_masked = cur_ix & ring_buffer_mask;\r
+ /* Don't accept a short copy from far away. */\r
+ score_t min_score = out->score;\r
+ score_t best_score = out->score;\r
+ size_t best_len = out->len;\r
+ size_t i;\r
+ out->len = 0;\r
+ out->len_code_delta = 0;\r
+ /* Try last distance first. */\r
+ for (i = 0; i < (size_t)common->params.num_last_distances_to_check; ++i) {\r
+ const size_t backward = (size_t)distance_cache[i];\r
+ size_t prev_ix = (size_t)(cur_ix - backward);\r
+ if (prev_ix >= cur_ix) {\r
+ continue;\r
+ }\r
+ if (BROTLI_PREDICT_FALSE(backward > max_backward)) {\r
+ continue;\r
+ }\r
+ prev_ix &= ring_buffer_mask;\r
+\r
+ if (cur_ix_masked + best_len > ring_buffer_mask ||\r
+ prev_ix + best_len > ring_buffer_mask ||\r
+ data[cur_ix_masked + best_len] != data[prev_ix + best_len]) {\r
+ continue;\r
+ }\r
+ {\r
+ const size_t len = FindMatchLengthWithLimit(&data[prev_ix],\r
+ &data[cur_ix_masked],\r
+ max_length);\r
+ if (len >= 3 || (len == 2 && i < 2)) {\r
+ /* Comparing for >= 2 does not change the semantics, but just saves for\r
+ a few unnecessary binary logarithms in backward reference score,\r
+ since we are not interested in such short matches. */\r
+ score_t score = BackwardReferenceScoreUsingLastDistance(len);\r
+ if (best_score < score) {\r
+ if (i != 0) score -= BackwardReferencePenaltyUsingLastDistance(i);\r
+ if (best_score < score) {\r
+ best_score = score;\r
+ best_len = len;\r
+ out->len = best_len;\r
+ out->distance = backward;\r
+ out->score = best_score;\r
+ }\r
+ }\r
+ }\r
+ }\r
+ }\r
+ {\r
+ const uint32_t key = FN(HashBytes)(\r
+ &data[cur_ix_masked], self->hash_mask_, self->hash_shift_);\r
+ uint32_t* BROTLI_RESTRICT bucket =\r
+ &buckets[key << common->params.block_bits];\r
+ const size_t down =\r
+ (num[key] > self->block_size_) ?\r
+ (num[key] - self->block_size_) : 0u;\r
+ for (i = num[key]; i > down;) {\r
+ size_t prev_ix = bucket[--i & self->block_mask_];\r
+ const size_t backward = cur_ix - prev_ix;\r
+ if (BROTLI_PREDICT_FALSE(backward > max_backward)) {\r
+ break;\r
+ }\r
+ prev_ix &= ring_buffer_mask;\r
+ if (cur_ix_masked + best_len > ring_buffer_mask ||\r
+ prev_ix + best_len > ring_buffer_mask ||\r
+ data[cur_ix_masked + best_len] != data[prev_ix + best_len]) {\r
+ continue;\r
+ }\r
+ {\r
+ const size_t len = FindMatchLengthWithLimit(&data[prev_ix],\r
+ &data[cur_ix_masked],\r
+ max_length);\r
+ if (len >= 4) {\r
+ /* Comparing for >= 3 does not change the semantics, but just saves\r
+ for a few unnecessary binary logarithms in backward reference\r
+ score, since we are not interested in such short matches. */\r
+ score_t score = BackwardReferenceScore(len, backward);\r
+ if (best_score < score) {\r
+ best_score = score;\r
+ best_len = len;\r
+ out->len = best_len;\r
+ out->distance = backward;\r
+ out->score = best_score;\r
+ }\r
+ }\r
+ }\r
+ }\r
+ bucket[num[key] & self->block_mask_] = (uint32_t)cur_ix;\r
+ ++num[key];\r
+ }\r
+ if (min_score == out->score) {\r
+ SearchInStaticDictionary(dictionary,\r
+ handle, &data[cur_ix_masked], max_length, max_backward + gap,\r
+ max_distance, out, BROTLI_FALSE);\r
+ }\r
+}\r
+\r
+#undef HashLongestMatch\r
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