src/FadingCounter.h

   1 /*
   2  * $Id$
   3  */
   4
   5 #ifndef SQUID_FADING_COUNTER_H
   6 #define SQUID_FADING_COUNTER_H
   7
   8 #include "Array.h"
   9
  10 /// Counts events, forgetting old ones. Usefull for "3 errors/minute" limits.
  11 class FadingCounter
  12 {
  13 public:
  14     FadingCounter();
  15
  16     /// 0=remember nothing; -1=forget nothing; new value triggers clear()
  17     void configure(double horizonSeconds);
  18
  19     void clear(); ///< forgets all events
  20
  21     int count(int howMany); ///< count fresh, return #events remembered
  22     int remembered() const { return total; } ///< possibly stale #events
  23
  24     /// read-only memory horizon in seconds; older events are forgotten
  25     double horizon;
  26
  27 private:
  28     const int precision; ///< #counting slots, controls measur. occuracy
  29     double delta; ///< sub-interval duration = horizon/precision
  30
  31     double lastTime; ///< time of the last update
  32     Vector<int> counters; ///< events per delta (possibly stale)
  33     int total; ///< number of remembered events (possibly stale)
  34 };
  35
  36 #endif /* SQUID_FADING_COUNTER_H */