src/node_persistent.h

#ifndef SRC_NODE_PERSISTENT_H_
#define SRC_NODE_PERSISTENT_H_

#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

#include "v8.h"

namespace node {

template <typename T>
struct ResetInDestructorPersistentTraits {
  static const bool kResetInDestructor = true;
  template <typename S, typename M>
  // Disallow copy semantics by leaving this unimplemented.
  inline static void Copy(
      const v8::Persistent<S, M>&,
      v8::Persistent<T, ResetInDestructorPersistentTraits<T>>*);
};

// v8::Persistent does not reset the object slot in its destructor.  That is
// acknowledged as a flaw in the V8 API and expected to change in the future
// but for now node::Persistent is the easier and safer alternative.
template <typename T>
using Persistent = v8::Persistent<T, ResetInDestructorPersistentTraits<T>>;

class PersistentToLocal {
 public:
  // If persistent.IsWeak() == false, then do not call persistent.Reset()
  // while the returned Local<T> is still in scope, it will destroy the
  // reference to the object.
  template <class TypeName>
  static inline v8::Local<TypeName> Default(
      v8::Isolate* isolate,
      const Persistent<TypeName>& persistent) {
    if (persistent.IsWeak()) {
      return PersistentToLocal::Weak(isolate, persistent);
    } else {
      return PersistentToLocal::Strong(persistent);
    }
  }

  // Unchecked conversion from a non-weak Persistent<T> to Local<T>,
  // use with care!
  //
  // Do not call persistent.Reset() while the returned Local<T> is still in
  // scope, it will destroy the reference to the object.
  template <class TypeName>
  static inline v8::Local<TypeName> Strong(
      const Persistent<TypeName>& persistent) {
    return *reinterpret_cast<v8::Local<TypeName>*>(
        const_cast<Persistent<TypeName>*>(&persistent));
  }

  template <class TypeName>
  static inline v8::Local<TypeName> Weak(
      v8::Isolate* isolate,
      const Persistent<TypeName>& persistent) {
    return v8::Local<TypeName>::New(isolate, persistent);
  }
};

}  // namespace node

#endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

#endif  // SRC_NODE_PERSISTENT_H_