class a {
    void f(){};
}

a::a() {
    func1(this->f);
}

Pult_wrapper::Pult_wrapper() {
    l3=new Level3;
    if (l3) l3->registerCb(PC_PULT, (Level3Cb)(this->cbL3));
}

void Pult_wrapper::cbL3(unsigned short nTs, unsigned char *buf, unsigned short buf_len) {

}

typedef void (*Level3Cb)(unsigned short return_param, unsigned char *buf, unsigned short buf_len);

class Level3 {
    public:
        short registerCb(unsigned short type, Level3Cb cb);

typedef void (*Level3Cb)(unsigned short return_param, unsigned char *buf, unsigned short buf_len);

typedef void (ClassName::*Level3Cb)(unsigned short return_param, unsigned char *buf, unsigned short buf_len);

//timer
class TimerTask {
   public:
       virtual void timeout(void *param) =  0 ;
}

class Timer {
   public:
       int start(TimerTask *_tt, void *param, int sec, int usec, bool one=false);
}

...

//program
class TimerRegister public TimerTask {
   public:
       virtual void timeout(void *param) {
            MainClass *mc=(MainClass *)param;
  
            mc->...
            ....
       };
}

class MainClass{
      TimerRegister *timerRegister;
      Timer *timer;
   public:
      MainClass() {
          timer = newTimer;
          timer->start(timerRegister, this,  1 ,  1 );
      }
}