src/FadingCounter.h

   1 /*
   2  * Copyright (C) 1996-2015 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_FADING_COUNTER_H
  10 #define SQUID_FADING_COUNTER_H
  11
  12 #include <vector>
  13
  14 /// Counts events, forgetting old ones. Usefull for "3 errors/minute" limits.
  15 class FadingCounter
  16 {
  17 public:
  18     FadingCounter();
  19
  20     /// 0=remember nothing; -1=forget nothing; new value triggers clear()
  21     void configure(double horizonSeconds);
  22
  23     void clear(); ///< forgets all events
  24
  25     int count(int howMany); ///< count fresh, return #events remembered
  26     int remembered() const { return total; } ///< possibly stale #events
  27
  28     /// read-only memory horizon in seconds; older events are forgotten
  29     double horizon;
  30
  31 private:
  32     const int precision; ///< #counting slots, controls measur. occuracy
  33     double delta; ///< sub-interval duration = horizon/precision
  34
  35     double lastTime; ///< time of the last update
  36     std::vector<int> counters; ///< events per delta (possibly stale)
  37     int total; ///< number of remembered events (possibly stale)
  38 };
  39
  40 #endif /* SQUID_FADING_COUNTER_H */
  41