Index: third_party/brotli/enc/backward_references_inc.h |
diff --git a/third_party/brotli/enc/backward_references_inc.h b/third_party/brotli/enc/backward_references_inc.h |
new file mode 100644 |
index 0000000000000000000000000000000000000000..e4d4cd07847b3d3d6b7ae4faad0beb9ea87d761e |
--- /dev/null |
+++ b/third_party/brotli/enc/backward_references_inc.h |
@@ -0,0 +1,147 @@ |
+/* NOLINT(build/header_guard) */ |
+/* Copyright 2013 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 */ |
+ |
+#define Hasher HASHER() |
+ |
+static BROTLI_NOINLINE void FN(CreateBackwardReferences)( |
+ MemoryManager* m, size_t num_bytes, size_t position, BROTLI_BOOL is_last, |
+ const uint8_t* ringbuffer, size_t ringbuffer_mask, |
+ const BrotliEncoderParams* params, Hasher* hasher, int* dist_cache, |
+ size_t* last_insert_len, Command* commands, size_t* num_commands, |
+ size_t* num_literals) { |
+ /* Set maximum distance, see section 9.1. of the spec. */ |
+ const size_t max_backward_limit = MaxBackwardLimit(params->lgwin); |
+ |
+ const Command* const orig_commands = commands; |
+ size_t insert_length = *last_insert_len; |
+ const size_t pos_end = position + num_bytes; |
+ const size_t store_end = num_bytes >= FN(StoreLookahead)() ? |
+ position + num_bytes - FN(StoreLookahead)() + 1 : position; |
+ |
+ /* For speed up heuristics for random data. */ |
+ const size_t random_heuristics_window_size = |
+ LiteralSpreeLengthForSparseSearch(params); |
+ size_t apply_random_heuristics = position + random_heuristics_window_size; |
+ |
+ /* Minimum score to accept a backward reference. */ |
+ const score_t kMinScore = BROTLI_SCORE_BASE + 400; |
+ |
+ FN(Init)(m, hasher, ringbuffer, params, position, num_bytes, is_last); |
+ if (BROTLI_IS_OOM(m)) return; |
+ FN(StitchToPreviousBlock)(hasher, num_bytes, position, |
+ ringbuffer, ringbuffer_mask); |
+ |
+ while (position + FN(HashTypeLength)() < pos_end) { |
+ size_t max_length = pos_end - position; |
+ size_t max_distance = BROTLI_MIN(size_t, position, max_backward_limit); |
+ HasherSearchResult sr; |
+ sr.len = 0; |
+ sr.len_x_code = 0; |
+ sr.distance = 0; |
+ sr.score = kMinScore; |
+ if (FN(FindLongestMatch)(hasher, ringbuffer, ringbuffer_mask, dist_cache, |
+ position, max_length, max_distance, &sr)) { |
+ /* Found a match. Let's look for something even better ahead. */ |
+ int delayed_backward_references_in_row = 0; |
+ --max_length; |
+ for (;; --max_length) { |
+ const score_t cost_diff_lazy = 700; |
+ BROTLI_BOOL is_match_found; |
+ HasherSearchResult sr2; |
+ sr2.len = params->quality < MIN_QUALITY_FOR_EXTENSIVE_REFERENCE_SEARCH ? |
+ BROTLI_MIN(size_t, sr.len - 1, max_length) : 0; |
+ sr2.len_x_code = 0; |
+ sr2.distance = 0; |
+ sr2.score = kMinScore; |
+ max_distance = BROTLI_MIN(size_t, position + 1, max_backward_limit); |
+ is_match_found = FN(FindLongestMatch)(hasher, ringbuffer, |
+ ringbuffer_mask, dist_cache, position + 1, max_length, max_distance, |
+ &sr2); |
+ if (is_match_found && sr2.score >= sr.score + cost_diff_lazy) { |
+ /* Ok, let's just write one byte for now and start a match from the |
+ next byte. */ |
+ ++position; |
+ ++insert_length; |
+ sr = sr2; |
+ if (++delayed_backward_references_in_row < 4 && |
+ position + FN(HashTypeLength)() < pos_end) { |
+ continue; |
+ } |
+ } |
+ break; |
+ } |
+ apply_random_heuristics = |
+ position + 2 * sr.len + random_heuristics_window_size; |
+ max_distance = BROTLI_MIN(size_t, position, max_backward_limit); |
+ { |
+ /* The first 16 codes are special short-codes, |
+ and the minimum offset is 1. */ |
+ size_t distance_code = |
+ ComputeDistanceCode(sr.distance, max_distance, dist_cache); |
+ if (sr.distance <= max_distance && distance_code > 0) { |
+ dist_cache[3] = dist_cache[2]; |
+ dist_cache[2] = dist_cache[1]; |
+ dist_cache[1] = dist_cache[0]; |
+ dist_cache[0] = (int)sr.distance; |
+ } |
+ InitCommand(commands++, insert_length, sr.len, sr.len ^ sr.len_x_code, |
+ distance_code); |
+ } |
+ *num_literals += insert_length; |
+ insert_length = 0; |
+ /* Put the hash keys into the table, if there are enough bytes left. |
+ Depending on the hasher implementation, it can push all positions |
+ in the given range or only a subset of them. */ |
+ FN(StoreRange)(hasher, ringbuffer, ringbuffer_mask, position + 2, |
+ BROTLI_MIN(size_t, position + sr.len, store_end)); |
+ position += sr.len; |
+ } else { |
+ ++insert_length; |
+ ++position; |
+ /* If we have not seen matches for a long time, we can skip some |
+ match lookups. Unsuccessful match lookups are very very expensive |
+ and this kind of a heuristic speeds up compression quite |
+ a lot. */ |
+ if (position > apply_random_heuristics) { |
+ /* Going through uncompressible data, jump. */ |
+ if (position > |
+ apply_random_heuristics + 4 * random_heuristics_window_size) { |
+ /* It is quite a long time since we saw a copy, so we assume |
+ that this data is not compressible, and store hashes less |
+ often. Hashes of non compressible data are less likely to |
+ turn out to be useful in the future, too, so we store less of |
+ them to not to flood out the hash table of good compressible |
+ data. */ |
+ const size_t kMargin = |
+ BROTLI_MAX(size_t, FN(StoreLookahead)() - 1, 4); |
+ size_t pos_jump = |
+ BROTLI_MIN(size_t, position + 16, pos_end - kMargin); |
+ for (; position < pos_jump; position += 4) { |
+ FN(Store)(hasher, ringbuffer, ringbuffer_mask, position); |
+ insert_length += 4; |
+ } |
+ } else { |
+ const size_t kMargin = |
+ BROTLI_MAX(size_t, FN(StoreLookahead)() - 1, 2); |
+ size_t pos_jump = |
+ BROTLI_MIN(size_t, position + 8, pos_end - kMargin); |
+ for (; position < pos_jump; position += 2) { |
+ FN(Store)(hasher, ringbuffer, ringbuffer_mask, position); |
+ insert_length += 2; |
+ } |
+ } |
+ } |
+ } |
+ } |
+ insert_length += pos_end - position; |
+ *last_insert_len = insert_length; |
+ *num_commands += (size_t)(commands - orig_commands); |
+} |
+ |
+#undef Hasher |