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Unified Diff: third_party/brotli/enc/hash_longest_match_quickly_inc.h

Issue 2537133002: Update brotli to v1.0.0-snapshot. (Closed)
Patch Set: Fixed typo Created 4 years ago
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Index: third_party/brotli/enc/hash_longest_match_quickly_inc.h
diff --git a/third_party/brotli/enc/hash_longest_match_quickly_inc.h b/third_party/brotli/enc/hash_longest_match_quickly_inc.h
new file mode 100644
index 0000000000000000000000000000000000000000..801ab22a1c1e1f572b63e39f7248a6a4ffa12003
--- /dev/null
+++ b/third_party/brotli/enc/hash_longest_match_quickly_inc.h
@@ -0,0 +1,230 @@
+/* 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
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