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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 02:57:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 02:57:58 +0000 |
commit | be1c7e50e1e8809ea56f2c9d472eccd8ffd73a97 (patch) | |
tree | 9754ff1ca740f6346cf8483ec915d4054bc5da2d /web/server/h2o/libh2o/deps/brotli/enc/block_splitter.cc | |
parent | Initial commit. (diff) | |
download | netdata-be1c7e50e1e8809ea56f2c9d472eccd8ffd73a97.tar.xz netdata-be1c7e50e1e8809ea56f2c9d472eccd8ffd73a97.zip |
Adding upstream version 1.44.3.upstream/1.44.3upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'web/server/h2o/libh2o/deps/brotli/enc/block_splitter.cc')
-rw-r--r-- | web/server/h2o/libh2o/deps/brotli/enc/block_splitter.cc | 389 |
1 files changed, 389 insertions, 0 deletions
diff --git a/web/server/h2o/libh2o/deps/brotli/enc/block_splitter.cc b/web/server/h2o/libh2o/deps/brotli/enc/block_splitter.cc new file mode 100644 index 00000000..8eaf9535 --- /dev/null +++ b/web/server/h2o/libh2o/deps/brotli/enc/block_splitter.cc @@ -0,0 +1,389 @@ +/* Copyright 2013 Google Inc. All Rights Reserved. + + Distributed under MIT license. + See file LICENSE for detail or copy at https://opensource.org/licenses/MIT +*/ + +// Block split point selection utilities. + +#include "./block_splitter.h" + +#include <assert.h> +#include <math.h> + +#include <algorithm> +#include <cstring> +#include <map> + +#include "./cluster.h" +#include "./command.h" +#include "./fast_log.h" +#include "./histogram.h" + +namespace brotli { + +static const size_t kMaxLiteralHistograms = 100; +static const size_t kMaxCommandHistograms = 50; +static const double kLiteralBlockSwitchCost = 28.1; +static const double kCommandBlockSwitchCost = 13.5; +static const double kDistanceBlockSwitchCost = 14.6; +static const size_t kLiteralStrideLength = 70; +static const size_t kCommandStrideLength = 40; +static const size_t kSymbolsPerLiteralHistogram = 544; +static const size_t kSymbolsPerCommandHistogram = 530; +static const size_t kSymbolsPerDistanceHistogram = 544; +static const size_t kMinLengthForBlockSplitting = 128; +static const size_t kIterMulForRefining = 2; +static const size_t kMinItersForRefining = 100; + +void CopyLiteralsToByteArray(const Command* cmds, + const size_t num_commands, + const uint8_t* data, + const size_t offset, + const size_t mask, + std::vector<uint8_t>* literals) { + // Count how many we have. + size_t total_length = 0; + for (size_t i = 0; i < num_commands; ++i) { + total_length += cmds[i].insert_len_; + } + if (total_length == 0) { + return; + } + + // Allocate. + literals->resize(total_length); + + // Loop again, and copy this time. + size_t pos = 0; + size_t from_pos = offset & mask; + for (size_t i = 0; i < num_commands && pos < total_length; ++i) { + size_t insert_len = cmds[i].insert_len_; + if (from_pos + insert_len > mask) { + size_t head_size = mask + 1 - from_pos; + memcpy(&(*literals)[pos], data + from_pos, head_size); + from_pos = 0; + pos += head_size; + insert_len -= head_size; + } + if (insert_len > 0) { + memcpy(&(*literals)[pos], data + from_pos, insert_len); + pos += insert_len; + } + from_pos = (from_pos + insert_len + cmds[i].copy_len_) & mask; + } +} + +void CopyCommandsToByteArray(const Command* cmds, + const size_t num_commands, + std::vector<uint16_t>* insert_and_copy_codes, + std::vector<uint16_t>* distance_prefixes) { + for (size_t i = 0; i < num_commands; ++i) { + const Command& cmd = cmds[i]; + insert_and_copy_codes->push_back(cmd.cmd_prefix_); + if (cmd.copy_len_ > 0 && cmd.cmd_prefix_ >= 128) { + distance_prefixes->push_back(cmd.dist_prefix_); + } + } +} + +inline static unsigned int MyRand(unsigned int* seed) { + *seed *= 16807U; + if (*seed == 0) { + *seed = 1; + } + return *seed; +} + +template<typename HistogramType, typename DataType> +void InitialEntropyCodes(const DataType* data, size_t length, + size_t literals_per_histogram, + size_t max_histograms, + size_t stride, + std::vector<HistogramType>* vec) { + size_t total_histograms = length / literals_per_histogram + 1; + if (total_histograms > max_histograms) { + total_histograms = max_histograms; + } + unsigned int seed = 7; + size_t block_length = length / total_histograms; + for (size_t i = 0; i < total_histograms; ++i) { + size_t pos = length * i / total_histograms; + if (i != 0) { + pos += MyRand(&seed) % block_length; + } + if (pos + stride >= length) { + pos = length - stride - 1; + } + HistogramType histo; + histo.Add(data + pos, stride); + vec->push_back(histo); + } +} + +template<typename HistogramType, typename DataType> +void RandomSample(unsigned int* seed, + const DataType* data, + size_t length, + size_t stride, + HistogramType* sample) { + size_t pos = 0; + if (stride >= length) { + pos = 0; + stride = length; + } else { + pos = MyRand(seed) % (length - stride + 1); + } + sample->Add(data + pos, stride); +} + +template<typename HistogramType, typename DataType> +void RefineEntropyCodes(const DataType* data, size_t length, + size_t stride, + std::vector<HistogramType>* vec) { + size_t iters = + kIterMulForRefining * length / stride + kMinItersForRefining; + unsigned int seed = 7; + iters = ((iters + vec->size() - 1) / vec->size()) * vec->size(); + for (size_t iter = 0; iter < iters; ++iter) { + HistogramType sample; + RandomSample(&seed, data, length, stride, &sample); + size_t ix = iter % vec->size(); + (*vec)[ix].AddHistogram(sample); + } +} + +inline static double BitCost(size_t count) { + return count == 0 ? -2.0 : FastLog2(count); +} + +template<typename DataType, int kSize> +void FindBlocks(const DataType* data, const size_t length, + const double block_switch_bitcost, + const std::vector<Histogram<kSize> > &vec, + uint8_t *block_id) { + if (vec.size() <= 1) { + for (size_t i = 0; i < length; ++i) { + block_id[i] = 0; + } + return; + } + size_t vecsize = vec.size(); + assert(vecsize <= 256); + double* insert_cost = new double[kSize * vecsize]; + memset(insert_cost, 0, sizeof(insert_cost[0]) * kSize * vecsize); + for (size_t j = 0; j < vecsize; ++j) { + insert_cost[j] = FastLog2(static_cast<uint32_t>(vec[j].total_count_)); + } + for (size_t i = kSize; i != 0;) { + --i; + for (size_t j = 0; j < vecsize; ++j) { + insert_cost[i * vecsize + j] = insert_cost[j] - BitCost(vec[j].data_[i]); + } + } + double *cost = new double[vecsize]; + memset(cost, 0, sizeof(cost[0]) * vecsize); + bool* switch_signal = new bool[length * vecsize]; + memset(switch_signal, 0, sizeof(switch_signal[0]) * length * vecsize); + // After each iteration of this loop, cost[k] will contain the difference + // between the minimum cost of arriving at the current byte position using + // entropy code k, and the minimum cost of arriving at the current byte + // position. This difference is capped at the block switch cost, and if it + // reaches block switch cost, it means that when we trace back from the last + // position, we need to switch here. + for (size_t byte_ix = 0; byte_ix < length; ++byte_ix) { + size_t ix = byte_ix * vecsize; + size_t insert_cost_ix = data[byte_ix] * vecsize; + double min_cost = 1e99; + for (size_t k = 0; k < vecsize; ++k) { + // We are coding the symbol in data[byte_ix] with entropy code k. + cost[k] += insert_cost[insert_cost_ix + k]; + if (cost[k] < min_cost) { + min_cost = cost[k]; + block_id[byte_ix] = static_cast<uint8_t>(k); + } + } + double block_switch_cost = block_switch_bitcost; + // More blocks for the beginning. + if (byte_ix < 2000) { + block_switch_cost *= 0.77 + 0.07 * static_cast<double>(byte_ix) / 2000; + } + for (size_t k = 0; k < vecsize; ++k) { + cost[k] -= min_cost; + if (cost[k] >= block_switch_cost) { + cost[k] = block_switch_cost; + switch_signal[ix + k] = true; + } + } + } + // Now trace back from the last position and switch at the marked places. + size_t byte_ix = length - 1; + size_t ix = byte_ix * vecsize; + uint8_t cur_id = block_id[byte_ix]; + while (byte_ix > 0) { + --byte_ix; + ix -= vecsize; + if (switch_signal[ix + cur_id]) { + cur_id = block_id[byte_ix]; + } + block_id[byte_ix] = cur_id; + } + delete[] insert_cost; + delete[] cost; + delete[] switch_signal; +} + +size_t RemapBlockIds(uint8_t* block_ids, const size_t length) { + std::map<uint8_t, uint8_t> new_id; + size_t next_id = 0; + for (size_t i = 0; i < length; ++i) { + if (new_id.find(block_ids[i]) == new_id.end()) { + new_id[block_ids[i]] = static_cast<uint8_t>(next_id); + ++next_id; + } + } + for (size_t i = 0; i < length; ++i) { + block_ids[i] = new_id[block_ids[i]]; + } + return next_id; +} + +template<typename HistogramType, typename DataType> +void BuildBlockHistograms(const DataType* data, const size_t length, + uint8_t* block_ids, + std::vector<HistogramType>* histograms) { + size_t num_types = RemapBlockIds(block_ids, length); + assert(num_types <= 256); + histograms->clear(); + histograms->resize(num_types); + for (size_t i = 0; i < length; ++i) { + (*histograms)[block_ids[i]].Add(data[i]); + } +} + +template<typename HistogramType, typename DataType> +void ClusterBlocks(const DataType* data, const size_t length, + uint8_t* block_ids) { + std::vector<HistogramType> histograms; + std::vector<uint32_t> block_index(length); + uint32_t cur_idx = 0; + HistogramType cur_histogram; + for (size_t i = 0; i < length; ++i) { + bool block_boundary = (i + 1 == length || block_ids[i] != block_ids[i + 1]); + block_index[i] = cur_idx; + cur_histogram.Add(data[i]); + if (block_boundary) { + histograms.push_back(cur_histogram); + cur_histogram.Clear(); + ++cur_idx; + } + } + std::vector<HistogramType> clustered_histograms; + std::vector<uint32_t> histogram_symbols; + // Block ids need to fit in one byte. + static const size_t kMaxNumberOfBlockTypes = 256; + ClusterHistograms(histograms, 1, histograms.size(), + kMaxNumberOfBlockTypes, + &clustered_histograms, + &histogram_symbols); + for (size_t i = 0; i < length; ++i) { + block_ids[i] = static_cast<uint8_t>(histogram_symbols[block_index[i]]); + } +} + +void BuildBlockSplit(const std::vector<uint8_t>& block_ids, BlockSplit* split) { + uint8_t cur_id = block_ids[0]; + uint8_t max_type = cur_id; + uint32_t cur_length = 1; + for (size_t i = 1; i < block_ids.size(); ++i) { + uint8_t next_id = block_ids[i]; + if (next_id != cur_id) { + split->types.push_back(cur_id); + split->lengths.push_back(cur_length); + max_type = std::max(max_type, next_id); + cur_id = next_id; + cur_length = 0; + } + ++cur_length; + } + split->types.push_back(cur_id); + split->lengths.push_back(cur_length); + split->num_types = static_cast<size_t>(max_type) + 1; +} + +template<typename HistogramType, typename DataType> +void SplitByteVector(const std::vector<DataType>& data, + const size_t literals_per_histogram, + const size_t max_histograms, + const size_t sampling_stride_length, + const double block_switch_cost, + BlockSplit* split) { + if (data.empty()) { + split->num_types = 1; + return; + } else if (data.size() < kMinLengthForBlockSplitting) { + split->num_types = 1; + split->types.push_back(0); + split->lengths.push_back(static_cast<uint32_t>(data.size())); + return; + } + std::vector<HistogramType> histograms; + // Find good entropy codes. + InitialEntropyCodes(&data[0], data.size(), + literals_per_histogram, + max_histograms, + sampling_stride_length, + &histograms); + RefineEntropyCodes(&data[0], data.size(), + sampling_stride_length, + &histograms); + // Find a good path through literals with the good entropy codes. + std::vector<uint8_t> block_ids(data.size()); + for (size_t i = 0; i < 10; ++i) { + FindBlocks(&data[0], data.size(), + block_switch_cost, + histograms, + &block_ids[0]); + BuildBlockHistograms(&data[0], data.size(), &block_ids[0], &histograms); + } + ClusterBlocks<HistogramType>(&data[0], data.size(), &block_ids[0]); + BuildBlockSplit(block_ids, split); +} + +void SplitBlock(const Command* cmds, + const size_t num_commands, + const uint8_t* data, + const size_t pos, + const size_t mask, + BlockSplit* literal_split, + BlockSplit* insert_and_copy_split, + BlockSplit* dist_split) { + // Create a continuous array of literals. + std::vector<uint8_t> literals; + CopyLiteralsToByteArray(cmds, num_commands, data, pos, mask, &literals); + + // Compute prefix codes for commands. + std::vector<uint16_t> insert_and_copy_codes; + std::vector<uint16_t> distance_prefixes; + CopyCommandsToByteArray(cmds, num_commands, + &insert_and_copy_codes, + &distance_prefixes); + + SplitByteVector<HistogramLiteral>( + literals, + kSymbolsPerLiteralHistogram, kMaxLiteralHistograms, + kLiteralStrideLength, kLiteralBlockSwitchCost, + literal_split); + SplitByteVector<HistogramCommand>( + insert_and_copy_codes, + kSymbolsPerCommandHistogram, kMaxCommandHistograms, + kCommandStrideLength, kCommandBlockSwitchCost, + insert_and_copy_split); + SplitByteVector<HistogramDistance>( + distance_prefixes, + kSymbolsPerDistanceHistogram, kMaxCommandHistograms, + kCommandStrideLength, kDistanceBlockSwitchCost, + dist_split); +} + +} // namespace brotli |