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diff --git a/web/server/h2o/libh2o/deps/brotli/enc/histogram.h b/web/server/h2o/libh2o/deps/brotli/enc/histogram.h
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+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+// Models the histograms of literals, commands and distance codes.
+
+#ifndef BROTLI_ENC_HISTOGRAM_H_
+#define BROTLI_ENC_HISTOGRAM_H_
+
+#include <cstring>
+#include <limits>
+#include <vector>
+#include "./context.h"
+#include "./command.h"
+#include "./fast_log.h"
+#include "./prefix.h"
+#include "./types.h"
+
+namespace brotli {
+
+struct BlockSplit;
+
+// A simple container for histograms of data in blocks.
+template<int kDataSize>
+struct Histogram {
+  Histogram() {
+    Clear();
+  }
+  void Clear() {
+    memset(data_, 0, sizeof(data_));
+    total_count_ = 0;
+    bit_cost_ = std::numeric_limits<double>::infinity();
+  }
+  void Add(size_t val) {
+    ++data_[val];
+    ++total_count_;
+  }
+  void Remove(size_t val) {
+    --data_[val];
+    --total_count_;
+  }
+  template<typename DataType>
+  void Add(const DataType *p, size_t n) {
+    total_count_ += n;
+    n += 1;
+    while(--n) ++data_[*p++];
+  }
+  void AddHistogram(const Histogram& v) {
+    total_count_ += v.total_count_;
+    for (size_t i = 0; i < kDataSize; ++i) {
+      data_[i] += v.data_[i];
+    }
+  }
+
+  uint32_t data_[kDataSize];
+  size_t total_count_;
+  double bit_cost_;
+};
+
+// Literal histogram.
+typedef Histogram<256> HistogramLiteral;
+// Prefix histograms.
+typedef Histogram<kNumCommandPrefixes> HistogramCommand;
+typedef Histogram<kNumDistancePrefixes> HistogramDistance;
+typedef Histogram<kNumBlockLenPrefixes> HistogramBlockLength;
+// Context map histogram, 256 Huffman tree indexes + 16 run length codes.
+typedef Histogram<272> HistogramContextMap;
+// Block type histogram, 256 block types + 2 special symbols.
+typedef Histogram<258> HistogramBlockType;
+
+static const size_t kLiteralContextBits = 6;
+static const size_t kDistanceContextBits = 2;
+
+void BuildHistograms(
+    const Command* cmds,
+    const size_t num_commands,
+    const BlockSplit& literal_split,
+    const BlockSplit& insert_and_copy_split,
+    const BlockSplit& dist_split,
+    const uint8_t* ringbuffer,
+    size_t pos,
+    size_t mask,
+    uint8_t prev_byte,
+    uint8_t prev_byte2,
+    const std::vector<ContextType>& context_modes,
+    std::vector<HistogramLiteral>* literal_histograms,
+    std::vector<HistogramCommand>* insert_and_copy_histograms,
+    std::vector<HistogramDistance>* copy_dist_histograms);
+
+}  // namespace brotli
+
+#endif  // BROTLI_ENC_HISTOGRAM_H_