Designs decisions: Programming model for a socket-based networking framework...

What model do you like better: Asynchronous state-machine based on 
callbacks, or single-threaded model backed by user-space threads? Its a 
difference between something like this:


class IO_Callbacks {
  virtual void On_Send(...) = 0;
  virtual void On_Receive(...) = 0;
  // [...];
};


class My_Connection : public IO_Callbacks {
  void On_Send(...) {
    // [handle the event];
  }

  void On_Recv(...) {
    // [handle the event];
  }
};





or:



void My_Connection(...) {
  for (;;) {
    if (! IO_Receive(...)) {
      break;
    }

    if (! IO_Send(...)) {
      break;
    }
  }
}



I have to admit that the latter is easier to reason about. I can't make up

my mind! Dammit!

;^(...