问Node.js和C/C++集成:如何正确实现回调？

EN

class PiWorker : public NanAsyncWorker {
 public:
  PiWorker(NanCallback *callback, int points)
    : NanAsyncWorker(callback), points(points) {}
  ~PiWorker() {}

  // Executed inside the worker-thread.
  // It is not safe to access V8, or V8 data structures
  // here, so everything we need for input and output
  // should go on `this`.
  void Execute () {
    estimate = Estimate(points);
  }

  // Executed when the async work is complete
  // this function will be run inside the main event loop
  // so it is safe to use V8 again
  void HandleOKCallback () {
    NanScope();

    Local<Value> argv[] = {
        NanNull()
      , NanNew<Number>(estimate)
    };

    callback->Call(2, argv);
  };

 private:
  int points;
  double estimate;
};

// Asynchronous access to the `Estimate()` function
NAN_METHOD(CalculateAsync) {
  NanScope();

  int points = args[0]->Uint32Value();
  NanCallback *callback = new NanCallback(args[1].As<Function>());

  NanAsyncQueueWorker(new PiWorker(callback, points));
  NanReturnUndefined();
}