src/RateLimiter.hpp

   1 /*
   2 Copyright_License {
   3
   4   XCSoar Glide Computer - http://www.xcsoar.org/
   5   Copyright (C) 2000-2013 The XCSoar Project
   6   A detailed list of copyright holders can be found in the file "AUTHORS".
   7
   8   This program is free software; you can redistribute it and/or
   9   modify it under the terms of the GNU General Public License
  10   as published by the Free Software Foundation; either version 2
  11   of the License, or (at your option) any later version.
  12
  13   This program is distributed in the hope that it will be useful,
  14   but WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16   GNU General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with this program; if not, write to the Free Software
  20   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  21 }
  22 */
  23
  24 #ifndef XCSOAR_RATE_LIMITER_HPP
  25 #define XCSOAR_RATE_LIMITER_HPP
  26
  27 #include "Event/Timer.hpp"
  28 #include "Time/PeriodClock.hpp"
  29
  30 /**
  31  * A class that limits the rate at which events are processed.  It
  32  * postpones processing for a certain amount of time, and combines
  33  * several events.
  34  *
  35  * Due to its use of timers and the event queue, this class can only
  36  * be used in the main thread.
  37  */
  38 class RateLimiter : private Timer {
  39   /**
  40    * Remember the last Run() invocation.
  41    */
  42   PeriodClock clock;
  43
  44   unsigned period_ms, delay_ms;
  45
  46 public:
  47   /**
  48    * Constructor.
  49    *
  50    * @param period_ms the minimum duration between two invocations
  51    * @param delay_ms an event is delayed by this duration to combine
  52    * consecutive invocations
  53    */
  54   RateLimiter(unsigned _period_ms, unsigned _delay_ms=0);
  55
  56   /**
  57    * Destructor.  Discards any pending events.
  58    */
  59   ~RateLimiter() {
  60     Cancel();
  61   }
  62
  63   void Trigger();
  64
  65   using Timer::Cancel;
  66
  67 protected:
  68   virtual void Run() = 0;
  69
  70 private:
  71   /* virtual methods from class Timer */
  72   virtual void OnTimer() override;
  73 };
  74
  75 #endif