Index: third_party/brotli/enc/hash_forgetful_chain_inc.h |
diff --git a/third_party/brotli/enc/hash_forgetful_chain_inc.h b/third_party/brotli/enc/hash_forgetful_chain_inc.h |
new file mode 100644 |
index 0000000000000000000000000000000000000000..131aa05c8824a6a1bfbb7888dbdbc541208ff3ff |
--- /dev/null |
+++ b/third_party/brotli/enc/hash_forgetful_chain_inc.h |
@@ -0,0 +1,250 @@ |
+/* NOLINT(build/header_guard) */ |
+/* Copyright 2016 Google Inc. All Rights Reserved. |
+ |
+ Distributed under MIT license. |
+ See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
+*/ |
+ |
+/* template parameters: FN, BUCKET_BITS, NUM_BANKS, BANK_BITS, |
+ NUM_LAST_DISTANCES_TO_CHECK */ |
+ |
+/* A (forgetful) hash table to the data seen by the compressor, to |
+ help create backward references to previous data. |
+ |
+ Hashes are stored in chains which are bucketed to groups. Group of chains |
+ share a storage "bank". When more than "bank size" chain nodes are added, |
+ oldest nodes are replaced; this way several chains may share a tail. */ |
+ |
+#define HashForgetfulChain HASHER() |
+ |
+#define BANK_SIZE (1 << BANK_BITS) |
+ |
+/* Number of hash buckets. */ |
+#define BUCKET_SIZE (1 << BUCKET_BITS) |
+ |
+#define CAPPED_CHAINS 0 |
+ |
+static BROTLI_INLINE size_t FN(HashTypeLength)(void) { return 4; } |
+static BROTLI_INLINE size_t FN(StoreLookahead)(void) { return 4; } |
+ |
+/* HashBytes is the function that chooses the bucket to place the address in.*/ |
+static BROTLI_INLINE size_t FN(HashBytes)(const uint8_t *data) { |
+ const uint32_t h = BROTLI_UNALIGNED_LOAD32(data) * kHashMul32; |
+ /* The higher bits contain more mixture from the multiplication, |
+ so we take our results from there. */ |
+ return h >> (32 - BUCKET_BITS); |
+} |
+ |
+typedef struct FN(Slot) { |
+ uint16_t delta; |
+ uint16_t next; |
+} FN(Slot); |
+ |
+typedef struct FN(Bank) { |
+ FN(Slot) slots[BANK_SIZE]; |
+} FN(Bank); |
+ |
+typedef struct HashForgetfulChain { |
+ uint32_t addr[BUCKET_SIZE]; |
+ uint16_t head[BUCKET_SIZE]; |
+ /* Truncated hash used for quick rejection of "distance cache" candidates. */ |
+ uint8_t tiny_hash[65536]; |
+ FN(Bank) banks[NUM_BANKS]; |
+ uint16_t free_slot_idx[NUM_BANKS]; |
+ BROTLI_BOOL is_dirty_; |
+ DictionarySearchStatictics dict_search_stats_; |
+ size_t max_hops; |
+} HashForgetfulChain; |
+ |
+static void FN(Reset)(HashForgetfulChain* self) { |
+ self->is_dirty_ = BROTLI_TRUE; |
+ DictionarySearchStaticticsReset(&self->dict_search_stats_); |
+} |
+ |
+static void FN(InitEmpty)(HashForgetfulChain* self) { |
+ if (self->is_dirty_) { |
+ /* Fill |addr| array with 0xCCCCCCCC value. Because of wrapping, position |
+ processed by hasher never reaches 3GB + 64M; this makes all new chains |
+ to be terminated after the first node. */ |
+ memset(self->addr, 0xCC, sizeof(self->addr)); |
+ memset(self->head, 0, sizeof(self->head)); |
+ memset(self->tiny_hash, 0, sizeof(self->tiny_hash)); |
+ memset(self->free_slot_idx, 0, sizeof(self->free_slot_idx)); |
+ self->is_dirty_ = BROTLI_FALSE; |
+ } |
+} |
+ |
+static void FN(InitForData)(HashForgetfulChain* self, const uint8_t* data, |
+ size_t num) { |
+ size_t i; |
+ for (i = 0; i < num; ++i) { |
+ size_t bucket = FN(HashBytes)(&data[i]); |
+ /* See InitEmpty comment. */ |
+ self->addr[bucket] = 0xCCCCCCCC; |
+ self->head[bucket] = 0xCCCC; |
+ } |
+ memset(self->tiny_hash, 0, sizeof(self->tiny_hash)); |
+ memset(self->free_slot_idx, 0, sizeof(self->free_slot_idx)); |
+ if (num != 0) { |
+ self->is_dirty_ = BROTLI_FALSE; |
+ } |
+} |
+ |
+static void FN(Init)( |
+ MemoryManager* m, HashForgetfulChain* self, const uint8_t* data, |
+ const BrotliEncoderParams* params, size_t position, size_t bytes, |
+ BROTLI_BOOL is_last) { |
+ /* Choose which initialization method is faster. |
+ Init() is about 100 times faster than InitForData(). */ |
+ const size_t kMaxBytesForPartialHashInit = BUCKET_SIZE >> 6; |
+ BROTLI_UNUSED(m); |
+ self->max_hops = (params->quality > 6 ? 7u : 8u) << (params->quality - 4); |
+ if (position == 0 && is_last && bytes <= kMaxBytesForPartialHashInit) { |
+ FN(InitForData)(self, data, bytes); |
+ } else { |
+ FN(InitEmpty)(self); |
+ } |
+} |
+ |
+/* Look at 4 bytes at &data[ix & mask]. Compute a hash from these, and prepend |
+ node to corresponding chain; also update tiny_hash for current position. */ |
+static BROTLI_INLINE void FN(Store)(HashForgetfulChain* BROTLI_RESTRICT self, |
+ const uint8_t* BROTLI_RESTRICT data, const size_t mask, const size_t ix) { |
+ const size_t key = FN(HashBytes)(&data[ix & mask]); |
+ const size_t bank = key & (NUM_BANKS - 1); |
+ const size_t idx = self->free_slot_idx[bank]++ & (BANK_SIZE - 1); |
+ size_t delta = ix - self->addr[key]; |
+ self->tiny_hash[(uint16_t)ix] = (uint8_t)key; |
+ if (delta > 0xFFFF) delta = CAPPED_CHAINS ? 0 : 0xFFFF; |
+ self->banks[bank].slots[idx].delta = (uint16_t)delta; |
+ self->banks[bank].slots[idx].next = self->head[key]; |
+ self->addr[key] = (uint32_t)ix; |
+ self->head[key] = (uint16_t)idx; |
+} |
+ |
+static BROTLI_INLINE void FN(StoreRange)(HashForgetfulChain* self, |
+ const uint8_t *data, const size_t mask, const size_t ix_start, |
+ const size_t ix_end) { |
+ size_t i; |
+ for (i = ix_start; i < ix_end; ++i) { |
+ FN(Store)(self, data, mask, i); |
+ } |
+} |
+ |
+static BROTLI_INLINE void FN(StitchToPreviousBlock)(HashForgetfulChain* self, |
+ size_t num_bytes, size_t position, const uint8_t* ringbuffer, |
+ size_t ring_buffer_mask) { |
+ if (num_bytes >= FN(HashTypeLength)() - 1 && position >= 3) { |
+ /* Prepare the hashes for three last bytes of the last write. |
+ These could not be calculated before, since they require knowledge |
+ of both the previous and the current block. */ |
+ FN(Store)(self, ringbuffer, ring_buffer_mask, position - 3); |
+ FN(Store)(self, ringbuffer, ring_buffer_mask, position - 2); |
+ FN(Store)(self, ringbuffer, ring_buffer_mask, position - 1); |
+ } |
+} |
+ |
+/* Find a longest backward match of &data[cur_ix] up to the length of |
+ max_length and stores the position cur_ix in the hash table. |
+ |
+ Does not look for matches longer than max_length. |
+ Does not look for matches further away than max_backward. |
+ Writes the best match into |out|. |
+ Returns 1 when match is found, otherwise 0. */ |
+static BROTLI_INLINE BROTLI_BOOL FN(FindLongestMatch)( |
+ HashForgetfulChain* self, const uint8_t* BROTLI_RESTRICT data, |
+ const size_t ring_buffer_mask, const int* BROTLI_RESTRICT distance_cache, |
+ const size_t cur_ix, const size_t max_length, const size_t max_backward, |
+ HasherSearchResult* BROTLI_RESTRICT out) { |
+ const size_t cur_ix_masked = cur_ix & ring_buffer_mask; |
+ BROTLI_BOOL is_match_found = BROTLI_FALSE; |
+ /* Don't accept a short copy from far away. */ |
+ score_t best_score = out->score; |
+ size_t best_len = out->len; |
+ size_t i; |
+ const size_t key = FN(HashBytes)(&data[cur_ix_masked]); |
+ const uint8_t tiny_hash = (uint8_t)(key); |
+ out->len = 0; |
+ out->len_x_code = 0; |
+ /* Try last distance first. */ |
+ for (i = 0; i < NUM_LAST_DISTANCES_TO_CHECK; ++i) { |
+ const size_t idx = kDistanceCacheIndex[i]; |
+ const size_t backward = |
+ (size_t)(distance_cache[idx] + kDistanceCacheOffset[i]); |
+ size_t prev_ix = (cur_ix - backward); |
+ /* For distance code 0 we want to consider 2-byte matches. */ |
+ if (i > 0 && self->tiny_hash[(uint16_t)prev_ix] != tiny_hash) continue; |
+ if (prev_ix >= cur_ix || backward > max_backward) { |
+ continue; |
+ } |
+ prev_ix &= ring_buffer_mask; |
+ { |
+ const size_t len = FindMatchLengthWithLimit(&data[prev_ix], |
+ &data[cur_ix_masked], |
+ max_length); |
+ if (len >= 2) { |
+ score_t score = BackwardReferenceScoreUsingLastDistance(len, i); |
+ if (best_score < score) { |
+ best_score = score; |
+ best_len = len; |
+ out->len = best_len; |
+ out->distance = backward; |
+ out->score = best_score; |
+ is_match_found = BROTLI_TRUE; |
+ } |
+ } |
+ } |
+ } |
+ { |
+ const size_t bank = key & (NUM_BANKS - 1); |
+ size_t backward = 0; |
+ size_t hops = self->max_hops; |
+ size_t delta = cur_ix - self->addr[key]; |
+ size_t slot = self->head[key]; |
+ while (hops--) { |
+ size_t prev_ix; |
+ size_t last = slot; |
+ backward += delta; |
+ if (backward > max_backward || (CAPPED_CHAINS && !delta)) break; |
+ prev_ix = (cur_ix - backward) & ring_buffer_mask; |
+ slot = self->banks[bank].slots[last].next; |
+ delta = self->banks[bank].slots[last].delta; |
+ if (cur_ix_masked + best_len > ring_buffer_mask || |
+ prev_ix + best_len > ring_buffer_mask || |
+ data[cur_ix_masked + best_len] != data[prev_ix + best_len]) { |
+ continue; |
+ } |
+ { |
+ const size_t len = FindMatchLengthWithLimit(&data[prev_ix], |
+ &data[cur_ix_masked], |
+ max_length); |
+ if (len >= 4) { |
+ /* Comparing for >= 3 does not change the semantics, but just saves |
+ for a few unnecessary binary logarithms in backward reference |
+ score, since we are not interested in such short matches. */ |
+ score_t score = BackwardReferenceScore(len, backward); |
+ if (best_score < score) { |
+ best_score = score; |
+ best_len = len; |
+ out->len = best_len; |
+ out->distance = backward; |
+ out->score = best_score; |
+ is_match_found = BROTLI_TRUE; |
+ } |
+ } |
+ } |
+ } |
+ FN(Store)(self, data, ring_buffer_mask, cur_ix); |
+ } |
+ if (!is_match_found) { |
+ is_match_found = SearchInStaticDictionary(&self->dict_search_stats_, |
+ &data[cur_ix_masked], max_length, max_backward, out, BROTLI_FALSE); |
+ } |
+ return is_match_found; |
+} |
+ |
+#undef BANK_SIZE |
+#undef BUCKET_SIZE |
+#undef CAPPED_CHAINS |
+ |
+#undef HashForgetfulChain |