1  // Copyright (c) 2014-2022 The Bitcoin Core developers
 2  // Distributed under the MIT software license, see the accompanying
 3  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 4  
 5  #ifndef BITCOIN_TIMEDATA_H
 6  #define BITCOIN_TIMEDATA_H
 7  
 8  #include <algorithm>
 9  #include <cassert>
10  #include <cstdint>
11  #include <vector>
12  
13  static const int64_t DEFAULT_MAX_TIME_ADJUSTMENT = 70 * 60;
14  
15  class CNetAddr;
16  
17  /**
18   * Median filter over a stream of values.
19   * Returns the median of the last N numbers
20   */
21  template <typename T>
22  class CMedianFilter
23  {
24  private:
25      std::vector<T> vValues;
26      std::vector<T> vSorted;
27      unsigned int nSize;
28  
29  public:
30      CMedianFilter(unsigned int _size, T initial_value) : nSize(_size)
31      {
32          vValues.reserve(_size);
33          vValues.push_back(initial_value);
34          vSorted = vValues;
35      }
36  
37      void input(T value)
38      {
39          if (vValues.size() == nSize) {
40              vValues.erase(vValues.begin());
41          }
42          vValues.push_back(value);
43  
44          vSorted.resize(vValues.size());
45          std::copy(vValues.begin(), vValues.end(), vSorted.begin());
46          std::sort(vSorted.begin(), vSorted.end());
47      }
48  
49      T median() const
50      {
51          int vSortedSize = vSorted.size();
52          assert(vSortedSize > 0);
53          if (vSortedSize & 1) // Odd number of elements
54          {
55              return vSorted[vSortedSize / 2];
56          } else // Even number of elements
57          {
58              return (vSorted[vSortedSize / 2 - 1] + vSorted[vSortedSize / 2]) / 2;
59          }
60      }
61  
62      int size() const
63      {
64          return vValues.size();
65      }
66  
67      std::vector<T> sorted() const
68      {
69          return vSorted;
70      }
71  };
72  
73  /** Functions to keep track of adjusted P2P time */
74  int64_t GetTimeOffset();
75  void AddTimeData(const CNetAddr& ip, int64_t nTime);
76  
77  /**
78   * Reset the internal state of GetTimeOffset() and AddTimeData().
79   */
80  void TestOnlyResetTimeData();
81  
82  #endif // BITCOIN_TIMEDATA_H