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-rw-r--r--modules/brotli/enc/hash_forgetful_chain_inc.h293
1 files changed, 293 insertions, 0 deletions
diff --git a/modules/brotli/enc/hash_forgetful_chain_inc.h b/modules/brotli/enc/hash_forgetful_chain_inc.h
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+++ b/modules/brotli/enc/hash_forgetful_chain_inc.h
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+/* 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* BROTLI_RESTRICT data) {
+ const 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 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 {
+ uint16_t free_slot_idx[NUM_BANKS]; /* Up to 1KiB. Move to dynamic? */
+ size_t max_hops;
+
+ /* Shortcuts. */
+ void* extra;
+ HasherCommon* common;
+
+ /* --- Dynamic size members --- */
+
+ /* 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]; */
+} HashForgetfulChain;
+
+static uint32_t* FN(Addr)(void* extra) {
+ return (uint32_t*)extra;
+}
+
+static uint16_t* FN(Head)(void* extra) {
+ return (uint16_t*)(&FN(Addr)(extra)[BUCKET_SIZE]);
+}
+
+static uint8_t* FN(TinyHash)(void* extra) {
+ return (uint8_t*)(&FN(Head)(extra)[BUCKET_SIZE]);
+}
+
+static FN(Bank)* FN(Banks)(void* extra) {
+ return (FN(Bank)*)(&FN(TinyHash)(extra)[65536]);
+}
+
+static void FN(Initialize)(
+ HasherCommon* common, HashForgetfulChain* BROTLI_RESTRICT self,
+ const BrotliEncoderParams* params) {
+ self->common = common;
+ self->extra = common->extra;
+
+ self->max_hops = (params->quality > 6 ? 7u : 8u) << (params->quality - 4);
+}
+
+static void FN(Prepare)(
+ HashForgetfulChain* BROTLI_RESTRICT self, BROTLI_BOOL one_shot,
+ size_t input_size, const uint8_t* BROTLI_RESTRICT data) {
+ uint32_t* BROTLI_RESTRICT addr = FN(Addr)(self->extra);
+ uint16_t* BROTLI_RESTRICT head = FN(Head)(self->extra);
+ uint8_t* BROTLI_RESTRICT tiny_hash = FN(TinyHash)(self->extra);
+ /* Partial preparation is 100 times slower (per socket). */
+ size_t partial_prepare_threshold = BUCKET_SIZE >> 6;
+ if (one_shot && input_size <= partial_prepare_threshold) {
+ size_t i;
+ for (i = 0; i < input_size; ++i) {
+ size_t bucket = FN(HashBytes)(&data[i]);
+ /* See InitEmpty comment. */
+ addr[bucket] = 0xCCCCCCCC;
+ head[bucket] = 0xCCCC;
+ }
+ } else {
+ /* 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(addr, 0xCC, sizeof(uint32_t) * BUCKET_SIZE);
+ memset(head, 0, sizeof(uint16_t) * BUCKET_SIZE);
+ }
+ memset(tiny_hash, 0, sizeof(uint8_t) * 65536);
+ memset(self->free_slot_idx, 0, sizeof(self->free_slot_idx));
+}
+
+static BROTLI_INLINE size_t FN(HashMemAllocInBytes)(
+ const BrotliEncoderParams* params, BROTLI_BOOL one_shot,
+ size_t input_size) {
+ BROTLI_UNUSED(params);
+ BROTLI_UNUSED(one_shot);
+ BROTLI_UNUSED(input_size);
+ return sizeof(uint32_t) * BUCKET_SIZE + sizeof(uint16_t) * BUCKET_SIZE +
+ sizeof(uint8_t) * 65536 + sizeof(FN(Bank)) * NUM_BANKS;
+}
+
+/* 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) {
+ uint32_t* BROTLI_RESTRICT addr = FN(Addr)(self->extra);
+ uint16_t* BROTLI_RESTRICT head = FN(Head)(self->extra);
+ uint8_t* BROTLI_RESTRICT tiny_hash = FN(TinyHash)(self->extra);
+ FN(Bank)* BROTLI_RESTRICT banks = FN(Banks)(self->extra);
+ 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 - addr[key];
+ tiny_hash[(uint16_t)ix] = (uint8_t)key;
+ if (delta > 0xFFFF) delta = CAPPED_CHAINS ? 0 : 0xFFFF;
+ banks[bank].slots[idx].delta = (uint16_t)delta;
+ banks[bank].slots[idx].next = head[key];
+ addr[key] = (uint32_t)ix;
+ head[key] = (uint16_t)idx;
+}
+
+static BROTLI_INLINE void FN(StoreRange)(
+ HashForgetfulChain* BROTLI_RESTRICT self,
+ const uint8_t* BROTLI_RESTRICT 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* BROTLI_RESTRICT 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);
+ }
+}
+
+static BROTLI_INLINE void FN(PrepareDistanceCache)(
+ HashForgetfulChain* BROTLI_RESTRICT self,
+ int* BROTLI_RESTRICT distance_cache) {
+ BROTLI_UNUSED(self);
+ PrepareDistanceCache(distance_cache, 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)(
+ HashForgetfulChain* BROTLI_RESTRICT self,
+ 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 dictionary_distance, const size_t max_distance,
+ HasherSearchResult* BROTLI_RESTRICT out) {
+ uint32_t* BROTLI_RESTRICT addr = FN(Addr)(self->extra);
+ uint16_t* BROTLI_RESTRICT head = FN(Head)(self->extra);
+ uint8_t* BROTLI_RESTRICT tiny_hashes = FN(TinyHash)(self->extra);
+ FN(Bank)* BROTLI_RESTRICT banks = FN(Banks)(self->extra);
+ 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;
+ const size_t key = FN(HashBytes)(&data[cur_ix_masked]);
+ const uint8_t tiny_hash = (uint8_t)(key);
+ out->len = 0;
+ out->len_code_delta = 0;
+ /* Try last distance first. */
+ for (i = 0; i < NUM_LAST_DISTANCES_TO_CHECK; ++i) {
+ const size_t backward = (size_t)distance_cache[i];
+ size_t prev_ix = (cur_ix - backward);
+ /* For distance code 0 we want to consider 2-byte matches. */
+ if (i > 0 && tiny_hashes[(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);
+ 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 size_t bank = key & (NUM_BANKS - 1);
+ size_t backward = 0;
+ size_t hops = self->max_hops;
+ size_t delta = cur_ix - addr[key];
+ size_t slot = 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 = banks[bank].slots[last].next;
+ delta = 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;
+ }
+ }
+ }
+ }
+ FN(Store)(self, data, ring_buffer_mask, cur_ix);
+ }
+ if (out->score == min_score) {
+ SearchInStaticDictionary(dictionary,
+ self->common, &data[cur_ix_masked], max_length, dictionary_distance,
+ max_distance, out, BROTLI_FALSE);
+ }
+}
+
+#undef BANK_SIZE
+#undef BUCKET_SIZE
+#undef CAPPED_CHAINS
+
+#undef HashForgetfulChain
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-22 15:07:48 +0000