node_object_wrap.h

#ifndef object_wrap_h
#define object_wrap_h

#include <v8.h>
#include <assert.h>

namespace node {

class ObjectWrap {
 public:
  ObjectWrap ( ) {
    refs_ = 0;
  }


  virtual ~ObjectWrap ( ) {
    if (!handle_.IsEmpty()) {
      assert(handle_.IsNearDeath());
      handle_.ClearWeak();
      handle_->SetInternalField(0, v8::Undefined());
      handle_.Dispose();
      handle_.Clear();
    }
  }


  template <class T>
  static inline T* Unwrap (v8::Handle<v8::Object> handle) {
    assert(!handle.IsEmpty());
    assert(handle->InternalFieldCount() > 0);
    return static_cast<T*>(handle->GetPointerFromInternalField(0));
  }


  v8::Persistent<v8::Object> handle_; // ro

 protected:
  inline void Wrap (v8::Handle<v8::Object> handle) {
    assert(handle_.IsEmpty());
    assert(handle->InternalFieldCount() > 0);
    handle_ = v8::Persistent<v8::Object>::New(handle);
    handle_->SetPointerInInternalField(0, this);
    MakeWeak();
  }


  inline void MakeWeak (void) {
    handle_.MakeWeak(this, WeakCallback);
  }

  /* Ref() marks the object as being attached to an event loop.
   * Refed objects will not be garbage collected, even if
   * all references are lost.
   */
  virtual void Ref() {
    assert(!handle_.IsEmpty());
    refs_++;
    handle_.ClearWeak();
  }

  /* Unref() marks an object as detached from the event loop.  This is its
   * default state.  When an object with a "weak" reference changes from
   * attached to detached state it will be freed. Be careful not to access
   * the object after making this call as it might be gone!
   * (A "weak reference" means an object that only has a
   * persistant handle.)
   *
   * DO NOT CALL THIS FROM DESTRUCTOR
   */
  virtual void Unref() {
    assert(!handle_.IsEmpty());
    assert(!handle_.IsWeak());
    assert(refs_ > 0);
    if (--refs_ == 0) { MakeWeak(); }
  }


  int refs_; // ro


 private:
  static void WeakCallback (v8::Persistent<v8::Value> value, void *data) {
    ObjectWrap *obj = static_cast<ObjectWrap*>(data);
    assert(value == obj->handle_);
    assert(!obj->refs_);
    assert(value.IsNearDeath());
    delete obj;
  }
};

} // namespace node
#endif // object_wrap_h