Update brotli to v1.0.0-snapshot.

third_party/brotli/enc/hash_longest_match_quickly_inc.h

+/* NOLINT(build/header_guard) */
+/* Copyright 2010 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, BUCKET_SWEEP, USE_DICTIONARY */
+
+#define HashLongestMatchQuickly HASHER()
+
+#define BUCKET_SIZE (1 << BUCKET_BITS)
+
+#define HASH_MAP_SIZE (4 << BUCKET_BITS)
+
+static BROTLI_INLINE size_t FN(HashTypeLength)(void) { return 8; }
+static BROTLI_INLINE size_t FN(StoreLookahead)(void) { return 8; }
+
+/* HashBytes is the function that chooses the bucket to place
+   the address in. The HashLongestMatch and HashLongestMatchQuickly
+   classes have separate, different implementations of hashing. */
+static uint32_t FN(HashBytes)(const uint8_t *data) {
+  /* Computing a hash based on 5 bytes works much better for
+     qualities 1 and 3, where the next hash value is likely to replace */
+  uint64_t h = (BROTLI_UNALIGNED_LOAD64(data) << 24) * kHashMul32;
+  /* The higher bits contain more mixture from the multiplication,
+     so we take our results from there. */
+  return (uint32_t)(h >> (64 - BUCKET_BITS));
+}
+
+/* A (forgetful) hash table to the data seen by the compressor, to
+   help create backward references to previous data.
+
+   This is a hash map of fixed size (BUCKET_SIZE). Starting from the
+   given index, BUCKET_SWEEP buckets are used to store values of a key. */
+typedef struct HashLongestMatchQuickly {
+  uint32_t buckets_[BUCKET_SIZE + BUCKET_SWEEP];
+  /* True if buckets_ array needs to be initialized. */
+  BROTLI_BOOL is_dirty_;
+  DictionarySearchStatictics dict_search_stats_;
+} HashLongestMatchQuickly;
+
+static void FN(Reset)(HashLongestMatchQuickly* self) {
+  self->is_dirty_ = BROTLI_TRUE;
+  DictionarySearchStaticticsReset(&self->dict_search_stats_);
+}
+
+static void FN(InitEmpty)(HashLongestMatchQuickly* self) {
+  if (self->is_dirty_) {
+    /* It is not strictly necessary to fill this buffer here, but
+       not filling will make the results of the compression stochastic
+       (but correct). This is because random data would cause the
+       system to find accidentally good backward references here and there. */
+    memset(&self->buckets_[0], 0, sizeof(self->buckets_));
+    self->is_dirty_ = BROTLI_FALSE;
+  }
+}
+
+static void FN(InitForData)(HashLongestMatchQuickly* self, const uint8_t* data,
+    size_t num) {
+  size_t i;
+  for (i = 0; i < num; ++i) {
+    const uint32_t key = FN(HashBytes)(&data[i]);
+    memset(&self->buckets_[key], 0, BUCKET_SWEEP * sizeof(self->buckets_[0]));
+  }
+  if (num != 0) {
+    self->is_dirty_ = BROTLI_FALSE;
+  }
+}
+
+static void FN(Init)(
+    MemoryManager* m, HashLongestMatchQuickly* 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 = HASH_MAP_SIZE >> 7;
+  BROTLI_UNUSED(m);
+  BROTLI_UNUSED(params);
+  if (position == 0 && is_last && bytes <= kMaxBytesForPartialHashInit) {
+    FN(InitForData)(self, data, bytes);
+  } else {
+    FN(InitEmpty)(self);
+  }
+}
+
+/* Look at 5 bytes at &data[ix & mask].
+   Compute a hash from these, and store the value somewhere within
+   [ix .. ix+3]. */
+static BROTLI_INLINE void FN(Store)(HashLongestMatchQuickly* self,
+    const uint8_t *data, const size_t mask, const size_t ix) {
+  const uint32_t key = FN(HashBytes)(&data[ix & mask]);
+  /* Wiggle the value with the bucket sweep range. */
+  const uint32_t off = (ix >> 3) % BUCKET_SWEEP;
+  self->buckets_[key + off] = (uint32_t)ix;
+}
+
+static BROTLI_INLINE void FN(StoreRange)(HashLongestMatchQuickly* 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)(
+    HashLongestMatchQuickly* self, size_t num_bytes, size_t position,
+    const uint8_t* ringbuffer, size_t ringbuffer_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, ringbuffer_mask, position - 3);
+    FN(Store)(self, ringbuffer, ringbuffer_mask, position - 2);
+    FN(Store)(self, ringbuffer, ringbuffer_mask, position - 1);
+  }
+}
+
+/* Find a longest backward match of &data[cur_ix & ring_buffer_mask]
+   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 true if match is found, otherwise false. */
+static BROTLI_INLINE BROTLI_BOOL FN(FindLongestMatch)(
+    HashLongestMatchQuickly* 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 best_len_in = out->len;
+  const size_t cur_ix_masked = cur_ix & ring_buffer_mask;
+  const uint32_t key = FN(HashBytes)(&data[cur_ix_masked]);
+  int compare_char = data[cur_ix_masked + best_len_in];
+  score_t best_score = out->score;
+  size_t best_len = best_len_in;
+  size_t cached_backward = (size_t)distance_cache[0];
+  size_t prev_ix = cur_ix - cached_backward;
+  BROTLI_BOOL is_match_found = BROTLI_FALSE;
+  out->len_x_code = 0;
+  if (prev_ix < cur_ix) {
+    prev_ix &= (uint32_t)ring_buffer_mask;
+    if (compare_char == data[prev_ix + best_len]) {
+      size_t len = FindMatchLengthWithLimit(&data[prev_ix],
+                                            &data[cur_ix_masked],
+                                            max_length);
+      if (len >= 4) {
+        best_score = BackwardReferenceScoreUsingLastDistance(len, 0);
+        best_len = len;
+        out->len = len;
+        out->distance = cached_backward;
+        out->score = best_score;
+        compare_char = data[cur_ix_masked + best_len];
+        if (BUCKET_SWEEP == 1) {
+          self->buckets_[key] = (uint32_t)cur_ix;
+          return BROTLI_TRUE;
+        } else {
+          is_match_found = BROTLI_TRUE;
+        }
+      }
+    }
+  }
+  if (BUCKET_SWEEP == 1) {
+    size_t backward;
+    size_t len;
+    /* Only one to look for, don't bother to prepare for a loop. */
+    prev_ix = self->buckets_[key];
+    self->buckets_[key] = (uint32_t)cur_ix;
+    backward = cur_ix - prev_ix;
+    prev_ix &= (uint32_t)ring_buffer_mask;
+    if (compare_char != data[prev_ix + best_len_in]) {
+      return BROTLI_FALSE;
+    }
+    if (BROTLI_PREDICT_FALSE(backward == 0 || backward > max_backward)) {
+      return BROTLI_FALSE;
+    }
+    len = FindMatchLengthWithLimit(&data[prev_ix],
+                                   &data[cur_ix_masked],
+                                   max_length);
+    if (len >= 4) {
+      out->len = len;
+      out->distance = backward;
+      out->score = BackwardReferenceScore(len, backward);
+      return BROTLI_TRUE;
+    }
+  } else {
+    uint32_t *bucket = self->buckets_ + key;
+    int i;
+    prev_ix = *bucket++;
+    for (i = 0; i < BUCKET_SWEEP; ++i, prev_ix = *bucket++) {
+      const size_t backward = cur_ix - prev_ix;
+      size_t len;
+      prev_ix &= (uint32_t)ring_buffer_mask;
+      if (compare_char != data[prev_ix + best_len]) {
+        continue;
+      }
+      if (BROTLI_PREDICT_FALSE(backward == 0 || backward > max_backward)) {
+        continue;
+      }
+      len = FindMatchLengthWithLimit(&data[prev_ix],
+                                     &data[cur_ix_masked],
+                                     max_length);
+      if (len >= 4) {
+        const 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 = score;
+          compare_char = data[cur_ix_masked + best_len];
+          is_match_found = BROTLI_TRUE;
+        }
+      }
+    }
+  }
+  if (USE_DICTIONARY && !is_match_found) {
+    is_match_found = SearchInStaticDictionary(&self->dict_search_stats_,
+        &data[cur_ix_masked], max_length, max_backward, out, BROTLI_TRUE);
+  }
+  self->buckets_[key + ((cur_ix >> 3) % BUCKET_SWEEP)] = (uint32_t)cur_ix;
+  return is_match_found;
+}
+
+#undef HASH_MAP_SIZE
+#undef BUCKET_SIZE
+
+#undef HashLongestMatchQuickly