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      1 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file. See the AUTHORS file for names of contributors.
      4 
      5 #ifndef STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
      6 #define STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
      7 
      8 #include <string>
      9 
     10 namespace leveldb {
     11 
     12 class Histogram {
     13  public:
     14   Histogram() { }
     15   ~Histogram() { }
     16 
     17   void Clear();
     18   void Add(double value);
     19   void Merge(const Histogram& other);
     20 
     21   std::string ToString() const;
     22 
     23  private:
     24   double min_;
     25   double max_;
     26   double num_;
     27   double sum_;
     28   double sum_squares_;
     29 
     30   enum { kNumBuckets = 154 };
     31   static const double kBucketLimit[kNumBuckets];
     32   double buckets_[kNumBuckets];
     33 
     34   double Median() const;
     35   double Percentile(double p) const;
     36   double Average() const;
     37   double StandardDeviation() const;
     38 };
     39 
     40 }  // namespace leveldb
     41 
     42 #endif  // STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
     43