Update brotli to v1.0.0-snapshot.

third_party/brotli/enc/hash_forgetful_chain_inc.h

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