timer.h

// Timer.h
// Timer class to perform actions periodically. There is no set
// maximum number of timers available. The number of timers is limited
// only by memory and CPU.
// David O'Connor, Feb 15, 2014

struct _Timer {
  unsigned long lastTime;
  unsigned long interval;
  int status;
  void (*action)(int);
};

class Timer {
  public:
    Timer();
    
    // Call this function to start a timer. Interval is in milliseconds.
    // The timer number will be passed to the callback. If you want the
    // timer to run only when triggered, use an interval of 0.
    int startTimer(unsigned long interval, void (*action)(int));
    
    // Call this function to stop a timer. Can be used in the callback
    // function for a "one shot" timer.
    void stopTimer(int index);
    
    // Use this function to trigger a timer. Useful in interrupt handlers when
    // you have a lot of work to do also when you want to do something
    // periodically or when an event happens.
    void triggerTimer(int index);
    
    // Call this function in loop to run all your timers.
    void runTimers();
  private:
    struct _Timer *_timers;
    int getIndex();
    int timerCount;
};