#ifndef _TIMER_H
#define _TIMER_H
#pragma interface
#undef hz
class Timer {
  unsigned long target;		// system tick count to call timerEvent at
  Timer *nextTimer;
  char active;
public:
  Timer() { active = 0; }
  virtual void timerEvent() = 0;
  static unsigned long ticks();	// check timers, return system clock ticks
  static void wait(struct timeval &);
  void timer(unsigned long ticks);
  void timer(int t) { timer((unsigned long)t); }
  void timer(double t) { timer((unsigned long)t); }
  static const double hz;	// ticks per second
  // true if target occurred before tick count
  int before(unsigned long ticks) const {
    return ((ticks - target) & 0x80000000L) == 0;
  }
  virtual ~Timer() { timer(0UL); }
};
#endif