Update brotli to v1.0.0-snapshot.

third_party/brotli/enc/hash_longest_match_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, BLOCK_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.
+
+   This is a hash map of fixed size (BUCKET_SIZE) to a ring buffer of
+   fixed size (BLOCK_SIZE). The ring buffer contains the last BLOCK_SIZE
+   index positions of the given hash key in the compressed data. */
+
+#define HashLongestMatch HASHER()
+
+/* Number of hash buckets. */
+#define BUCKET_SIZE (1 << BUCKET_BITS)
+
+/* Only BLOCK_SIZE newest backward references are kept,
+   and the older are forgotten. */
+#define BLOCK_SIZE (1u << BLOCK_BITS)
+
+/* Mask for accessing entries in a block (in a ring-buffer manner). */
+#define BLOCK_MASK ((1 << BLOCK_BITS) - 1)
+
+#define HASH_MAP_SIZE (2 << BUCKET_BITS)
+
+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. The HashLongestMatch and HashLongestMatchQuickly
+   classes have separate, different implementations of hashing. */
+static uint32_t FN(HashBytes)(const uint8_t *data) {
+  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 HashLongestMatch {
+  /* Number of entries in a particular bucket. */
+  uint16_t num_[BUCKET_SIZE];
+
+  /* Buckets containing BLOCK_SIZE of backward references. */
+  uint32_t buckets_[BLOCK_SIZE << BUCKET_BITS];
+
+  /* True if num_ array needs to be initialized. */
+  BROTLI_BOOL is_dirty_;
+
+  DictionarySearchStatictics dict_search_stats_;
+} HashLongestMatch;
+
+static void FN(Reset)(HashLongestMatch* self) {
+  self->is_dirty_ = BROTLI_TRUE;
+  DictionarySearchStaticticsReset(&self->dict_search_stats_);
+}
+
+static void FN(InitEmpty)(HashLongestMatch* self) {
+  if (self->is_dirty_) {
+    memset(self->num_, 0, sizeof(self->num_));
+    self->is_dirty_ = BROTLI_FALSE;
+  }
+}
+
+static void FN(InitForData)(HashLongestMatch* 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]);
+    self->num_[key] = 0;
+  }
+  if (num != 0) {
+    self->is_dirty_ = BROTLI_FALSE;
+  }
+}
+
+static void FN(Init)(
+    MemoryManager* m, HashLongestMatch* 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 4 bytes at &data[ix & mask].
+   Compute a hash from these, and store the value of ix at that position. */
+static BROTLI_INLINE void FN(Store)(HashLongestMatch* self, const uint8_t *data,
+    const size_t mask, const size_t ix) {
+  const uint32_t key = FN(HashBytes)(&data[ix & mask]);
+  const size_t minor_ix = self->num_[key] & BLOCK_MASK;
+  self->buckets_[minor_ix + (key << BLOCK_BITS)] = (uint32_t)ix;
+  ++self->num_[key];
+}
+
+static BROTLI_INLINE void FN(StoreRange)(HashLongestMatch* 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)(HashLongestMatch* 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] 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 when match is found, otherwise false. */
+static BROTLI_INLINE BROTLI_BOOL FN(FindLongestMatch)(HashLongestMatch* 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;
+  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 = (size_t)(cur_ix - backward);
+    if (prev_ix >= cur_ix) {
+      continue;
+    }
+    if (BROTLI_PREDICT_FALSE(backward > max_backward)) {
+      continue;
+    }
+    prev_ix &= ring_buffer_mask;
+
+    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 >= 3 || (len == 2 && i < 2)) {
+        /* Comparing for >= 2 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 = 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 uint32_t key = FN(HashBytes)(&data[cur_ix_masked]);
+    uint32_t* BROTLI_RESTRICT bucket = &self->buckets_[key << BLOCK_BITS];
+    const size_t down =
+        (self->num_[key] > BLOCK_SIZE) ? (self->num_[key] - BLOCK_SIZE) : 0u;
+    for (i = self->num_[key]; i > down;) {
+      size_t prev_ix = bucket[--i & BLOCK_MASK];
+      const size_t backward = cur_ix - prev_ix;
+      if (BROTLI_PREDICT_FALSE(backward > max_backward)) {
+        break;
+      }
+      prev_ix &= ring_buffer_mask;
+      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;
+          }
+        }
+      }
+    }
+    bucket[self->num_[key] & BLOCK_MASK] = (uint32_t)cur_ix;
+    ++self->num_[key];
+  }
+  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 HASH_MAP_SIZE
+#undef BLOCK_MASK
+#undef BLOCK_SIZE
+#undef BUCKET_SIZE
+
+#undef HashLongestMatch