src/FadingCounter.h

   1 #ifndef SQUID_FADING_COUNTER_H
   2 #define SQUID_FADING_COUNTER_H
   3
   4 #include "base/Vector.h"
   5
   6 /// Counts events, forgetting old ones. Usefull for "3 errors/minute" limits.
   7 class FadingCounter
   8 {
   9 public:
  10     FadingCounter();
  11
  12     /// 0=remember nothing; -1=forget nothing; new value triggers clear()
  13     void configure(double horizonSeconds);
  14
  15     void clear(); ///< forgets all events
  16
  17     int count(int howMany); ///< count fresh, return #events remembered
  18     int remembered() const { return total; } ///< possibly stale #events
  19
  20     /// read-only memory horizon in seconds; older events are forgotten
  21     double horizon;
  22
  23 private:
  24     const int precision; ///< #counting slots, controls measur. occuracy
  25     double delta; ///< sub-interval duration = horizon/precision
  26
  27     double lastTime; ///< time of the last update
  28     Vector<int> counters; ///< events per delta (possibly stale)
  29     int total; ///< number of remembered events (possibly stale)
  30 };
  31
  32 #endif /* SQUID_FADING_COUNTER_H */