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| -rw-r--r-- | web/server/h2o/libh2o/deps/brotli/enc/backward_references.cc | 783 |
1 files changed, 783 insertions, 0 deletions
diff --git a/web/server/h2o/libh2o/deps/brotli/enc/backward_references.cc b/web/server/h2o/libh2o/deps/brotli/enc/backward_references.cc new file mode 100644 index 00000000..02d956dd --- /dev/null +++ b/web/server/h2o/libh2o/deps/brotli/enc/backward_references.cc @@ -0,0 +1,783 @@ +/* Copyright 2013 Google Inc. All Rights Reserved. + + Distributed under MIT license. + See file LICENSE for detail or copy at https://opensource.org/licenses/MIT +*/ + +// Function to find backward reference copies. + +#include "./backward_references.h" + +#include <algorithm> +#include <limits> +#include <vector> + +#include "./command.h" +#include "./fast_log.h" +#include "./literal_cost.h" + +namespace brotli { + +// The maximum length for which the zopflification uses distinct distances. +static const uint16_t kMaxZopfliLen = 325; + +static const double kInfinity = std::numeric_limits<double>::infinity(); + +// Histogram based cost model for zopflification. +class ZopfliCostModel { + public: + ZopfliCostModel() : min_cost_cmd_(kInfinity) {} + + void SetFromCommands(size_t num_bytes, + size_t position, + const uint8_t* ringbuffer, + size_t ringbuffer_mask, + const Command* commands, + size_t num_commands, + size_t last_insert_len) { + std::vector<uint32_t> histogram_literal(256, 0); + std::vector<uint32_t> histogram_cmd(kNumCommandPrefixes, 0); + std::vector<uint32_t> histogram_dist(kNumDistancePrefixes, 0); + + size_t pos = position - last_insert_len; + for (size_t i = 0; i < num_commands; i++) { + size_t inslength = commands[i].insert_len_; + size_t copylength = commands[i].copy_len_; + size_t distcode = commands[i].dist_prefix_; + size_t cmdcode = commands[i].cmd_prefix_; + + histogram_cmd[cmdcode]++; + if (cmdcode >= 128) histogram_dist[distcode]++; + + for (size_t j = 0; j < inslength; j++) { + histogram_literal[ringbuffer[(pos + j) & ringbuffer_mask]]++; + } + + pos += inslength + copylength; + } + + std::vector<double> cost_literal; + Set(histogram_literal, &cost_literal); + Set(histogram_cmd, &cost_cmd_); + Set(histogram_dist, &cost_dist_); + + for (uint32_t i = 0; i < kNumCommandPrefixes; ++i) { + min_cost_cmd_ = std::min(min_cost_cmd_, cost_cmd_[i]); + } + + literal_costs_.resize(num_bytes + 1); + literal_costs_[0] = 0.0; + for (size_t i = 0; i < num_bytes; ++i) { + literal_costs_[i + 1] = literal_costs_[i] + + cost_literal[ringbuffer[(position + i) & ringbuffer_mask]]; + } + } + + void SetFromLiteralCosts(size_t num_bytes, + size_t position, + const uint8_t* ringbuffer, + size_t ringbuffer_mask) { + std::vector<float> literal_cost(num_bytes + 1); + EstimateBitCostsForLiterals(position, num_bytes, ringbuffer_mask, + ringbuffer, &literal_cost[0]); + literal_costs_.resize(num_bytes + 1); + literal_costs_[0] = 0.0; + for (size_t i = 0; i < num_bytes; ++i) { + literal_costs_[i + 1] = literal_costs_[i] + literal_cost[i]; + } + cost_cmd_.resize(kNumCommandPrefixes); + cost_dist_.resize(kNumDistancePrefixes); + for (uint32_t i = 0; i < kNumCommandPrefixes; ++i) { + cost_cmd_[i] = FastLog2(11 + i); + } + for (uint32_t i = 0; i < kNumDistancePrefixes; ++i) { + cost_dist_[i] = FastLog2(20 + i); + } + min_cost_cmd_ = FastLog2(11); + } + + double GetCommandCost( + size_t dist_code, size_t length_code, size_t insert_length) const { + uint16_t inscode = GetInsertLengthCode(insert_length); + uint16_t copycode = GetCopyLengthCode(length_code); + uint16_t cmdcode = CombineLengthCodes(inscode, copycode, dist_code == 0); + uint16_t dist_symbol; + uint32_t distextra; + PrefixEncodeCopyDistance(dist_code, 0, 0, &dist_symbol, &distextra); + uint32_t distnumextra = distextra >> 24; + + double result = static_cast<double>( + kInsExtra[inscode] + kCopyExtra[copycode] + distnumextra); + result += cost_cmd_[cmdcode]; + if (cmdcode >= 128) result += cost_dist_[dist_symbol]; + return result; + } + + double GetLiteralCosts(size_t from, size_t to) const { + return literal_costs_[to] - literal_costs_[from]; + } + + double GetMinCostCmd() const { + return min_cost_cmd_; + } + + private: + void Set(const std::vector<uint32_t>& histogram, std::vector<double>* cost) { + cost->resize(histogram.size()); + size_t sum = 0; + for (size_t i = 0; i < histogram.size(); i++) { + sum += histogram[i]; + } + double log2sum = FastLog2(sum); + for (size_t i = 0; i < histogram.size(); i++) { + if (histogram[i] == 0) { + (*cost)[i] = log2sum + 2; + continue; + } + + // Shannon bits for this symbol. + (*cost)[i] = log2sum - FastLog2(histogram[i]); + + // Cannot be coded with less than 1 bit + if ((*cost)[i] < 1) (*cost)[i] = 1; + } + } + + std::vector<double> cost_cmd_; // The insert and copy length symbols. + std::vector<double> cost_dist_; + // Cumulative costs of literals per position in the stream. + std::vector<double> literal_costs_; + double min_cost_cmd_; +}; + +inline void SetDistanceCache(size_t distance, + size_t distance_code, + size_t max_distance, + const int* dist_cache, + int* result_dist_cache) { + if (distance <= max_distance && distance_code > 0) { + result_dist_cache[0] = static_cast<int>(distance); + memcpy(&result_dist_cache[1], dist_cache, 3 * sizeof(dist_cache[0])); + } else { + memcpy(result_dist_cache, dist_cache, 4 * sizeof(dist_cache[0])); + } +} + +inline size_t ComputeDistanceCode(size_t distance, + size_t max_distance, + int quality, + const int* dist_cache) { + if (distance <= max_distance) { + if (distance == static_cast<size_t>(dist_cache[0])) { + return 0; + } else if (distance == static_cast<size_t>(dist_cache[1])) { + return 1; + } else if (distance == static_cast<size_t>(dist_cache[2])) { + return 2; + } else if (distance == static_cast<size_t>(dist_cache[3])) { + return 3; + } else if (quality > 3 && distance >= 6) { + for (size_t k = 4; k < kNumDistanceShortCodes; ++k) { + size_t idx = kDistanceCacheIndex[k]; + size_t candidate = + static_cast<size_t>(dist_cache[idx] + kDistanceCacheOffset[k]); + static const size_t kLimits[16] = { 0, 0, 0, 0, + 6, 6, 11, 11, + 11, 11, 11, 11, + 12, 12, 12, 12 }; + if (distance == candidate && distance >= kLimits[k]) { + return k; + } + } + } + } + return distance + 15; +} + +struct ZopfliNode { + ZopfliNode() : length(1), + distance(0), + distance_code(0), + length_code(0), + insert_length(0), + cost(kInfinity) {} + + // best length to get up to this byte (not including this byte itself) + uint32_t length; + // distance associated with the length + uint32_t distance; + uint32_t distance_code; + int distance_cache[4]; + // length code associated with the length - usually the same as length, + // except in case of length-changing dictionary transformation. + uint32_t length_code; + // number of literal inserts before this copy + uint32_t insert_length; + // smallest cost to get to this byte from the beginning, as found so far + double cost; +}; + +inline void UpdateZopfliNode(ZopfliNode* nodes, size_t pos, size_t start_pos, + size_t len, size_t len_code, size_t dist, + size_t dist_code, size_t max_dist, + const int* dist_cache, double cost) { + ZopfliNode& next = nodes[pos + len]; + next.length = static_cast<uint32_t>(len); + next.length_code = static_cast<uint32_t>(len_code); + next.distance = static_cast<uint32_t>(dist); + next.distance_code = static_cast<uint32_t>(dist_code); + next.insert_length = static_cast<uint32_t>(pos - start_pos); + next.cost = cost; + SetDistanceCache(dist, dist_code, max_dist, dist_cache, + &next.distance_cache[0]); +} + +// Maintains the smallest 2^k cost difference together with their positions +class StartPosQueue { + public: + explicit StartPosQueue(int bits) + : mask_((1u << bits) - 1), q_(1 << bits), idx_(0) {} + + void Clear() { + idx_ = 0; + } + + void Push(size_t pos, double costdiff) { + if (costdiff == kInfinity) { + // We can't start a command from an unreachable start position. + // E.g. position 1 in a stream is always unreachable, because all commands + // have a copy of at least length 2. + return; + } + size_t offset = -idx_ & mask_; + ++idx_; + size_t len = size(); + q_[offset] = std::make_pair(pos, costdiff); + /* Restore the sorted order. In the list of |len| items at most |len - 1| + adjacent element comparisons / swaps are required. */ + for (size_t i = 1; i < len; ++i) { + if (q_[offset & mask_].second > q_[(offset + 1) & mask_].second) { + std::swap(q_[offset & mask_], q_[(offset + 1) & mask_]); + } + ++offset; + } + } + + size_t size() const { return std::min(idx_, mask_ + 1); } + + size_t GetStartPos(size_t k) const { + return q_[(k + 1 - idx_) & mask_].first; + } + + private: + const size_t mask_; + std::vector<std::pair<size_t, double> > q_; + size_t idx_; +}; + +// Returns the minimum possible copy length that can improve the cost of any +// future position. +size_t ComputeMinimumCopyLength(const StartPosQueue& queue, + const std::vector<ZopfliNode>& nodes, + const ZopfliCostModel& model, + size_t pos, + double min_cost_cmd) { + // Compute the minimum possible cost of reaching any future position. + const size_t start0 = queue.GetStartPos(0); + double min_cost = (nodes[start0].cost + + model.GetLiteralCosts(start0, pos) + + min_cost_cmd); + size_t len = 2; + size_t next_len_bucket = 4; + size_t next_len_offset = 10; + while (pos + len < nodes.size() && nodes[pos + len].cost <= min_cost) { + // We already reached (pos + len) with no more cost than the minimum + // possible cost of reaching anything from this pos, so there is no point in + // looking for lengths <= len. + ++len; + if (len == next_len_offset) { + // We reached the next copy length code bucket, so we add one more + // extra bit to the minimum cost. + min_cost += 1.0; + next_len_offset += next_len_bucket; + next_len_bucket *= 2; + } + } + return len; +} + +void ZopfliIterate(size_t num_bytes, + size_t position, + const uint8_t* ringbuffer, + size_t ringbuffer_mask, + const size_t max_backward_limit, + const ZopfliCostModel& model, + const std::vector<uint32_t>& num_matches, + const std::vector<BackwardMatch>& matches, + int* dist_cache, + size_t* last_insert_len, + Command* commands, + size_t* num_commands, + size_t* num_literals) { + const Command * const orig_commands = commands; + + std::vector<ZopfliNode> nodes(num_bytes + 1); + nodes[0].length = 0; + nodes[0].cost = 0; + memcpy(nodes[0].distance_cache, dist_cache, 4 * sizeof(dist_cache[0])); + + StartPosQueue queue(3); + const double min_cost_cmd = model.GetMinCostCmd(); + + size_t cur_match_pos = 0; + for (size_t i = 0; i + 3 < num_bytes; i++) { + size_t cur_ix = position + i; + size_t cur_ix_masked = cur_ix & ringbuffer_mask; + size_t max_distance = std::min(cur_ix, max_backward_limit); + size_t max_length = num_bytes - i; + + queue.Push(i, nodes[i].cost - model.GetLiteralCosts(0, i)); + + const size_t min_len = ComputeMinimumCopyLength(queue, nodes, model, + i, min_cost_cmd); + + // Go over the command starting positions in order of increasing cost + // difference. + for (size_t k = 0; k < 5 && k < queue.size(); ++k) { + const size_t start = queue.GetStartPos(k); + const double start_costdiff = + nodes[start].cost - model.GetLiteralCosts(0, start); + const int* dist_cache2 = &nodes[start].distance_cache[0]; + + // Look for last distance matches using the distance cache from this + // starting position. + size_t best_len = min_len - 1; + for (size_t j = 0; j < kNumDistanceShortCodes; ++j) { + const size_t idx = kDistanceCacheIndex[j]; + const size_t backward = + static_cast<size_t>(dist_cache2[idx] + kDistanceCacheOffset[j]); + size_t prev_ix = cur_ix - backward; + if (prev_ix >= cur_ix) { + continue; + } + if (PREDICT_FALSE(backward > max_distance)) { + continue; + } + prev_ix &= ringbuffer_mask; + + if (cur_ix_masked + best_len > ringbuffer_mask || + prev_ix + best_len > ringbuffer_mask || + ringbuffer[cur_ix_masked + best_len] != + ringbuffer[prev_ix + best_len]) { + continue; + } + const size_t len = + FindMatchLengthWithLimit(&ringbuffer[prev_ix], + &ringbuffer[cur_ix_masked], + max_length); + for (size_t l = best_len + 1; l <= len; ++l) { + const size_t inslen = i - start; + double cmd_cost = model.GetCommandCost(j, l, inslen); + double cost = start_costdiff + cmd_cost + model.GetLiteralCosts(0, i); + if (cost < nodes[i + l].cost) { + UpdateZopfliNode(&nodes[0], i, start, l, l, backward, j, + max_distance, dist_cache2, cost); + } + best_len = l; + } + } + + // At higher iterations look only for new last distance matches, since + // looking only for new command start positions with the same distances + // does not help much. + if (k >= 2) continue; + + // Loop through all possible copy lengths at this position. + size_t len = min_len; + for (size_t j = 0; j < num_matches[i]; ++j) { + BackwardMatch match = matches[cur_match_pos + j]; + size_t dist = match.distance; + bool is_dictionary_match = dist > max_distance; + // We already tried all possible last distance matches, so we can use + // normal distance code here. + size_t dist_code = dist + 15; + // Try all copy lengths up until the maximum copy length corresponding + // to this distance. If the distance refers to the static dictionary, or + // the maximum length is long enough, try only one maximum length. + size_t max_len = match.length(); + if (len < max_len && (is_dictionary_match || max_len > kMaxZopfliLen)) { + len = max_len; + } + for (; len <= max_len; ++len) { + size_t len_code = is_dictionary_match ? match.length_code() : len; + const size_t inslen = i - start; + double cmd_cost = model.GetCommandCost(dist_code, len_code, inslen); + double cost = start_costdiff + cmd_cost + model.GetLiteralCosts(0, i); + if (cost < nodes[i + len].cost) { + UpdateZopfliNode(&nodes[0], i, start, len, len_code, dist, + dist_code, max_distance, dist_cache2, cost); + } + } + } + } + + cur_match_pos += num_matches[i]; + + // The zopflification can be too slow in case of very long lengths, so in + // such case skip it all, it does not cost a lot of compression ratio. + if (num_matches[i] == 1 && + matches[cur_match_pos - 1].length() > kMaxZopfliLen) { + i += matches[cur_match_pos - 1].length() - 1; + queue.Clear(); + } + } + + std::vector<uint32_t> backwards; + size_t index = num_bytes; + while (nodes[index].cost == kInfinity) --index; + while (index != 0) { + size_t len = nodes[index].length + nodes[index].insert_length; + backwards.push_back(static_cast<uint32_t>(len)); + index -= len; + } + + std::vector<uint32_t> path; + for (size_t i = backwards.size(); i > 0; i--) { + path.push_back(backwards[i - 1]); + } + + size_t pos = 0; + for (size_t i = 0; i < path.size(); i++) { + const ZopfliNode& next = nodes[pos + path[i]]; + size_t copy_length = next.length; + size_t insert_length = next.insert_length; + pos += insert_length; + if (i == 0) { + insert_length += *last_insert_len; + *last_insert_len = 0; + } + size_t distance = next.distance; + size_t len_code = next.length_code; + size_t max_distance = std::min(position + pos, max_backward_limit); + bool is_dictionary = (distance > max_distance); + size_t dist_code = next.distance_code; + + Command cmd(insert_length, copy_length, len_code, dist_code); + *commands++ = cmd; + + if (!is_dictionary && dist_code > 0) { + dist_cache[3] = dist_cache[2]; + dist_cache[2] = dist_cache[1]; + dist_cache[1] = dist_cache[0]; + dist_cache[0] = static_cast<int>(distance); + } + + *num_literals += insert_length; + insert_length = 0; + pos += copy_length; + } + *last_insert_len += num_bytes - pos; + *num_commands += static_cast<size_t>(commands - orig_commands); +} + +template<typename Hasher> +void CreateBackwardReferences(size_t num_bytes, + size_t position, + bool is_last, + const uint8_t* ringbuffer, + size_t ringbuffer_mask, + const int quality, + const int lgwin, + 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 = (1 << lgwin) - 16; + + // Choose which init method is faster. + // memset is about 100 times faster than hasher->InitForData(). + const size_t kMaxBytesForPartialHashInit = Hasher::kHashMapSize >> 7; + if (position == 0 && is_last && num_bytes <= kMaxBytesForPartialHashInit) { + hasher->InitForData(ringbuffer, num_bytes); + } else { + hasher->Init(); + } + if (num_bytes >= 3 && 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. + hasher->Store(&ringbuffer[(position - 3) & ringbuffer_mask], + static_cast<uint32_t>(position - 3)); + hasher->Store(&ringbuffer[(position - 2) & ringbuffer_mask], + static_cast<uint32_t>(position - 2)); + hasher->Store(&ringbuffer[(position - 1) & ringbuffer_mask], + static_cast<uint32_t>(position - 1)); + } + const Command * const orig_commands = commands; + size_t insert_length = *last_insert_len; + size_t i = position & ringbuffer_mask; + const size_t i_diff = position - i; + const size_t i_end = i + num_bytes; + + // For speed up heuristics for random data. + const size_t random_heuristics_window_size = quality < 9 ? 64 : 512; + size_t apply_random_heuristics = i + random_heuristics_window_size; + + // Minimum score to accept a backward reference. + const int kMinScore = 4.0; + + while (i + Hasher::kHashTypeLength - 1 < i_end) { + size_t max_length = i_end - i; + size_t max_distance = std::min(i + i_diff, max_backward_limit); + size_t best_len = 0; + size_t best_len_code = 0; + size_t best_dist = 0; + double best_score = kMinScore; + bool match_found = hasher->FindLongestMatch( + ringbuffer, ringbuffer_mask, + dist_cache, static_cast<uint32_t>(i + i_diff), max_length, max_distance, + &best_len, &best_len_code, &best_dist, &best_score); + if (match_found) { + // Found a match. Let's look for something even better ahead. + int delayed_backward_references_in_row = 0; + for (;;) { + --max_length; + size_t best_len_2 = + quality < 5 ? std::min(best_len - 1, max_length) : 0; + size_t best_len_code_2 = 0; + size_t best_dist_2 = 0; + double best_score_2 = kMinScore; + max_distance = std::min(i + i_diff + 1, max_backward_limit); + match_found = hasher->FindLongestMatch( + ringbuffer, ringbuffer_mask, + dist_cache, static_cast<uint32_t>(i + i_diff + 1), + max_length, max_distance, + &best_len_2, &best_len_code_2, &best_dist_2, &best_score_2); + double cost_diff_lazy = 7.0; + if (match_found && best_score_2 >= best_score + cost_diff_lazy) { + // Ok, let's just write one byte for now and start a match from the + // next byte. + ++i; + ++insert_length; + best_len = best_len_2; + best_len_code = best_len_code_2; + best_dist = best_dist_2; + best_score = best_score_2; + if (++delayed_backward_references_in_row < 4) { + continue; + } + } + break; + } + apply_random_heuristics = + i + 2 * best_len + random_heuristics_window_size; + max_distance = std::min(i + i_diff, max_backward_limit); + // The first 16 codes are special shortcodes, and the minimum offset is 1. + size_t distance_code = + ComputeDistanceCode(best_dist, max_distance, quality, dist_cache); + if (best_dist <= 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] = static_cast<int>(best_dist); + } + Command cmd(insert_length, best_len, best_len_code, distance_code); + *commands++ = cmd; + *num_literals += insert_length; + insert_length = 0; + // Put the hash keys into the table, if there are enough + // bytes left. + for (size_t j = 2; j < best_len; ++j) { + hasher->Store(&ringbuffer[i + j], + static_cast<uint32_t>(i + i_diff + j)); + } + i += best_len; + } else { + ++insert_length; + ++i; + // 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 (i > apply_random_heuristics) { + // Going through uncompressible data, jump. + if (i > 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. + size_t i_jump = std::min(i + 16, i_end - 4); + for (; i < i_jump; i += 4) { + hasher->Store(ringbuffer + i, static_cast<uint32_t>(i + i_diff)); + insert_length += 4; + } + } else { + size_t i_jump = std::min(i + 8, i_end - 3); + for (; i < i_jump; i += 2) { + hasher->Store(ringbuffer + i, static_cast<uint32_t>(i + i_diff)); + insert_length += 2; + } + } + } + } + } + insert_length += i_end - i; + *last_insert_len = insert_length; + *num_commands += static_cast<size_t>(commands - orig_commands); +} + +void CreateBackwardReferences(size_t num_bytes, + size_t position, + bool is_last, + const uint8_t* ringbuffer, + size_t ringbuffer_mask, + const int quality, + const int lgwin, + Hashers* hashers, + int hash_type, + int* dist_cache, + size_t* last_insert_len, + Command* commands, + size_t* num_commands, + size_t* num_literals) { + bool zopflify = quality > 9; + if (zopflify) { + Hashers::H10* hasher = hashers->hash_h10; + hasher->Init(lgwin, position, num_bytes, is_last); + if (num_bytes >= 3 && position >= kMaxTreeCompLength) { + // Store the last `kMaxTreeCompLength - 1` positions in the hasher. + // These could not be calculated before, since they require knowledge + // of both the previous and the current block. + for (size_t i = position - kMaxTreeCompLength + 1; i < position; ++i) { + hasher->Store(ringbuffer, ringbuffer_mask, i, num_bytes + position - i); + } + } + // Set maximum distance, see section 9.1. of the spec. + const size_t max_backward_limit = (1 << lgwin) - 16; + std::vector<uint32_t> num_matches(num_bytes); + std::vector<BackwardMatch> matches(4 * num_bytes); + size_t cur_match_pos = 0; + for (size_t i = 0; i + 3 < num_bytes; ++i) { + size_t max_distance = std::min(position + i, max_backward_limit); + size_t max_length = num_bytes - i; + // Ensure that we have enough free slots. + if (matches.size() < cur_match_pos + Hashers::H10::kMaxNumMatches) { + matches.resize(cur_match_pos + Hashers::H10::kMaxNumMatches); + } + size_t num_found_matches = hasher->FindAllMatches( + ringbuffer, ringbuffer_mask, position + i, max_length, max_distance, + &matches[cur_match_pos]); + const size_t cur_match_end = cur_match_pos + num_found_matches; + for (size_t j = cur_match_pos; j + 1 < cur_match_end; ++j) { + assert(matches[j].length() < matches[j + 1].length()); + assert(matches[j].distance > max_distance || + matches[j].distance <= matches[j + 1].distance); + } + num_matches[i] = static_cast<uint32_t>(num_found_matches); + if (num_found_matches > 0) { + const size_t match_len = matches[cur_match_end - 1].length(); + if (match_len > kMaxZopfliLen) { + matches[cur_match_pos++] = matches[cur_match_end - 1]; + num_matches[i] = 1; + for (size_t j = 1; j < match_len; ++j) { + ++i; + if (match_len - j < 64) { + hasher->Store(ringbuffer, ringbuffer_mask, position + i, + num_bytes - i); + } + num_matches[i] = 0; + } + } else { + cur_match_pos = cur_match_end; + } + } + } + size_t orig_num_literals = *num_literals; + size_t orig_last_insert_len = *last_insert_len; + int orig_dist_cache[4] = { + dist_cache[0], dist_cache[1], dist_cache[2], dist_cache[3] + }; + size_t orig_num_commands = *num_commands; + static const size_t kIterations = 2; + for (size_t i = 0; i < kIterations; i++) { + ZopfliCostModel model; + if (i == 0) { + model.SetFromLiteralCosts(num_bytes, position, + ringbuffer, ringbuffer_mask); + } else { + model.SetFromCommands(num_bytes, position, + ringbuffer, ringbuffer_mask, + commands, *num_commands - orig_num_commands, + orig_last_insert_len); + } + *num_commands = orig_num_commands; + *num_literals = orig_num_literals; + *last_insert_len = orig_last_insert_len; + memcpy(dist_cache, orig_dist_cache, 4 * sizeof(dist_cache[0])); + ZopfliIterate(num_bytes, position, ringbuffer, ringbuffer_mask, + max_backward_limit, model, num_matches, matches, dist_cache, + last_insert_len, commands, num_commands, num_literals); + } + return; + } + + switch (hash_type) { + case 2: + CreateBackwardReferences<Hashers::H2>( + num_bytes, position, is_last, ringbuffer, ringbuffer_mask, + quality, lgwin, hashers->hash_h2, dist_cache, + last_insert_len, commands, num_commands, num_literals); + break; + case 3: + CreateBackwardReferences<Hashers::H3>( + num_bytes, position, is_last, ringbuffer, ringbuffer_mask, + quality, lgwin, hashers->hash_h3, dist_cache, + last_insert_len, commands, num_commands, num_literals); + break; + case 4: + CreateBackwardReferences<Hashers::H4>( + num_bytes, position, is_last, ringbuffer, ringbuffer_mask, + quality, lgwin, hashers->hash_h4, dist_cache, + last_insert_len, commands, num_commands, num_literals); + break; + case 5: + CreateBackwardReferences<Hashers::H5>( + num_bytes, position, is_last, ringbuffer, ringbuffer_mask, + quality, lgwin, hashers->hash_h5, dist_cache, + last_insert_len, commands, num_commands, num_literals); + break; + case 6: + CreateBackwardReferences<Hashers::H6>( + num_bytes, position, is_last, ringbuffer, ringbuffer_mask, + quality, lgwin, hashers->hash_h6, dist_cache, + last_insert_len, commands, num_commands, num_literals); + break; + case 7: + CreateBackwardReferences<Hashers::H7>( + num_bytes, position, is_last, ringbuffer, ringbuffer_mask, + quality, lgwin, hashers->hash_h7, dist_cache, + last_insert_len, commands, num_commands, num_literals); + break; + case 8: + CreateBackwardReferences<Hashers::H8>( + num_bytes, position, is_last, ringbuffer, ringbuffer_mask, + quality, lgwin, hashers->hash_h8, dist_cache, + last_insert_len, commands, num_commands, num_literals); + break; + case 9: + CreateBackwardReferences<Hashers::H9>( + num_bytes, position, is_last, ringbuffer, ringbuffer_mask, + quality, lgwin, hashers->hash_h9, dist_cache, + last_insert_len, commands, num_commands, num_literals); + break; + default: + break; + } +} + +} // namespace brotli |