1 files changed, 259 insertions, 0 deletions
diff --git a/modules/brotli/enc/hash_longest_match_inc.h b/modules/brotli/enc/hash_longest_match_inc.h
new file mode 100644
index 000000000..457f5a9ed
--- /dev/null
+++ b/modules/brotli/enc/hash_longest_match_inc.h
@@ -0,0 +1,259 @@
+/* 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 */
+
+/* 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()
+
+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 uint32_t FN(HashBytes)(const uint8_t* data, const int shift) {
+  uint32_t h = BROTLI_UNALIGNED_LOAD32LE(data) * kHashMul32;
+  /* The higher bits contain more mixture from the multiplication,
+     so we take our results from there. */
+  return (uint32_t)(h >> shift);
+}
+
+typedef struct HashLongestMatch {
+  /* Number of hash buckets. */
+  size_t bucket_size_;
+  /* Only block_size_ newest backward references are kept,
+     and the older are forgotten. */
+  size_t block_size_;
+  /* Left-shift for computing hash bucket index from hash value. */
+  int hash_shift_;
+  /* Mask for accessing entries in a block (in a ring-buffer manner). */
+  uint32_t block_mask_;
+
+  /* --- Dynamic size members --- */
+
+  /* Number of entries in a particular bucket. */
+  /* uint16_t num[bucket_size]; */
+
+  /* Buckets containing block_size_ of backward references. */
+  /* uint32_t* buckets[bucket_size * block_size]; */
+} HashLongestMatch;
+
+static BROTLI_INLINE HashLongestMatch* FN(Self)(HasherHandle handle) {
+  return (HashLongestMatch*)&(GetHasherCommon(handle)[1]);
+}
+
+static BROTLI_INLINE uint16_t* FN(Num)(HashLongestMatch* self) {
+  return (uint16_t*)(&self[1]);
+}
+
+static BROTLI_INLINE uint32_t* FN(Buckets)(HashLongestMatch* self) {
+  return (uint32_t*)(&FN(Num)(self)[self->bucket_size_]);
+}
+
+static void FN(Initialize)(
+    HasherHandle handle, const BrotliEncoderParams* params) {
+  HasherCommon* common = GetHasherCommon(handle);
+  HashLongestMatch* self = FN(Self)(handle);
+  BROTLI_UNUSED(params);
+  self->hash_shift_ = 32 - common->params.bucket_bits;
+  self->bucket_size_ = (size_t)1 << common->params.bucket_bits;
+  self->block_size_ = (size_t)1 << common->params.block_bits;
+  self->block_mask_ = (uint32_t)(self->block_size_ - 1);
+}
+
+static void FN(Prepare)(HasherHandle handle, BROTLI_BOOL one_shot,
+    size_t input_size, const uint8_t* data) {
+  HashLongestMatch* self = FN(Self)(handle);
+  uint16_t* num = FN(Num)(self);
+  /* Partial preparation is 100 times slower (per socket). */
+  size_t partial_prepare_threshold = self->bucket_size_ >> 6;
+  if (one_shot && input_size <= partial_prepare_threshold) {
+    size_t i;
+    for (i = 0; i < input_size; ++i) {
+      const uint32_t key = FN(HashBytes)(&data[i], self->hash_shift_);
+      num[key] = 0;
+    }
+  } else {
+    memset(num, 0, self->bucket_size_ * sizeof(num[0]));
+  }
+}
+
+static BROTLI_INLINE size_t FN(HashMemAllocInBytes)(
+    const BrotliEncoderParams* params, BROTLI_BOOL one_shot,
+    size_t input_size) {
+  size_t bucket_size = (size_t)1 << params->hasher.bucket_bits;
+  size_t block_size = (size_t)1 << params->hasher.block_bits;
+  BROTLI_UNUSED(one_shot);
+  BROTLI_UNUSED(input_size);
+  return sizeof(HashLongestMatch) + bucket_size * (2 + 4 * block_size);
+}
+
+/* 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)(HasherHandle handle, const uint8_t* data,
+    const size_t mask, const size_t ix) {
+  HashLongestMatch* self = FN(Self)(handle);
+  uint16_t* num = FN(Num)(self);
+  const uint32_t key = FN(HashBytes)(&data[ix & mask], self->hash_shift_);
+  const size_t minor_ix = num[key] & self->block_mask_;
+  const size_t offset =
+      minor_ix + (key << GetHasherCommon(handle)->params.block_bits);
+  FN(Buckets)(self)[offset] = (uint32_t)ix;
+  ++num[key];
+}
+
+static BROTLI_INLINE void FN(StoreRange)(HasherHandle handle,
+    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)(handle, data, mask, i);
+  }
+}
+
+static BROTLI_INLINE void FN(StitchToPreviousBlock)(HasherHandle handle,
+    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)(handle, ringbuffer, ringbuffer_mask, position - 3);
+    FN(Store)(handle, ringbuffer, ringbuffer_mask, position - 2);
+    FN(Store)(handle, ringbuffer, ringbuffer_mask, position - 1);
+  }
+}
+
+static BROTLI_INLINE void FN(PrepareDistanceCache)(
+    HasherHandle handle, int* BROTLI_RESTRICT distance_cache) {
+  PrepareDistanceCache(distance_cache,
+      GetHasherCommon(handle)->params.num_last_distances_to_check);
+}
+
+/* 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.
+
+   REQUIRES: FN(PrepareDistanceCache) must be invoked for current distance cache
+             values; if this method is invoked repeatedly with the same distance
+             cache values, it is enough to invoke FN(PrepareDistanceCache) once.
+
+   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|.
+   |out|->score is updated only if a better match is found. */
+static BROTLI_INLINE void FN(FindLongestMatch)(HasherHandle handle,
+    const BrotliEncoderDictionary* dictionary,
+    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,
+    const size_t gap, const size_t max_distance,
+    HasherSearchResult* BROTLI_RESTRICT out) {
+  HasherCommon* common = GetHasherCommon(handle);
+  HashLongestMatch* self = FN(Self)(handle);
+  uint16_t* num = FN(Num)(self);
+  uint32_t* buckets = FN(Buckets)(self);
+  const size_t cur_ix_masked = cur_ix & ring_buffer_mask;
+  /* Don't accept a short copy from far away. */
+  score_t min_score = out->score;
+  score_t best_score = out->score;
+  size_t best_len = out->len;
+  size_t i;
+  out->len = 0;
+  out->len_code_delta = 0;
+  /* Try last distance first. */
+  for (i = 0; i < (size_t)common->params.num_last_distances_to_check; ++i) {
+    const size_t backward = (size_t)distance_cache[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);
+        if (best_score < score) {
+          if (i != 0) score -= BackwardReferencePenaltyUsingLastDistance(i);
+          if (best_score < score) {
+            best_score = score;
+            best_len = len;
+            out->len = best_len;
+            out->distance = backward;
+            out->score = best_score;
+          }
+        }
+      }
+    }
+  }
+  {
+    const uint32_t key =
+        FN(HashBytes)(&data[cur_ix_masked], self->hash_shift_);
+    uint32_t* BROTLI_RESTRICT bucket =
+        &buckets[key << common->params.block_bits];
+    const size_t down =
+        (num[key] > self->block_size_) ? (num[key] - self->block_size_) : 0u;
+    for (i = num[key]; i > down;) {
+      size_t prev_ix = bucket[--i & self->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;
+          }
+        }
+      }
+    }
+    bucket[num[key] & self->block_mask_] = (uint32_t)cur_ix;
+    ++num[key];
+  }
+  if (min_score == out->score) {
+    SearchInStaticDictionary(dictionary,
+        handle, &data[cur_ix_masked], max_length, max_backward + gap,
+        max_distance, out, BROTLI_FALSE);
+  }
+}
+
+#undef HashLongestMatch