Listing 3

class TimeEvent;  //forward declaration.
class TimeEventSource : public EventSource <TimeEvent>
{
public:
    TimeEventSource() {};
    ~TimeEventSource() {};
};
//call back declaration with specific signature.
typedef void (*timerCallback)(time_t timer);

class TimeEvent : public Event <TimeEventSource>
{
public:
    explicit TimeEvent(unsigned int timer, timerCallback cb = NULL, bool
periodic = false):m_timer(timer), m_callBack(cb)
        {   setRestore(periodic);
        activateEvent();
        }
    void    eventProcess(); // impl of virtual,
    bool    eventTrigged();
    bool    activateEvent();
    void    deactivateEvent() {};

    time_t  getTimer() const { return m_timer;}
    time_t  getExpireTime() const { return m_expireTime;}
    void        setExpireTime(time_t t) {m_expireTime = t;}
    ~TimeEvent () {}
private:
    unsigned int m_timer;
    time_t m_expireTime;
    timerCallback m_callBack;
};
TimeEventSource  Event<TimeEventSource>::theEventSource;
bool TimeEvent::activateEvent()
{   time_t current_time = time(NULL);
        setExpireTime(current_time + getTimer());
        setTimeStamp(getExpireTime());//for position in dispatch queue
    theEventSource.addEvent(this);//put it on polling queue
    return true;
}
void TimeEvent::eventProcess()
{   if (m_callBack != NULL) (*m_callBack)(m_timer);
    if (IsRestore())    
        activateEvent();  //re-activated
    else
        delete this; //all objects of this class are created with 
                 //"new" operator, so self delete is valid.
}
bool TimeEvent::eventTrigged()
{   time_t current_time = time(NULL);
    time_t time_remaind = getExpireTime() - current_time;
    if (time_remaind <= 0)
        return true;
    else
        return false;
}