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