+++ /dev/null
-## Persistent references
-
-An object reference that is independent of any `HandleScope` is a _persistent_ reference. Where a `Local` handle only lives as long as the `HandleScope` in which it was allocated, a `Persistent` handle remains valid until it is explicitly disposed.
-
-Due to the evolution of the V8 API, it is necessary for NAN to provide a wrapper implementation of the `Persistent` classes to supply compatibility across the V8 versions supported.
-
- - <a href="#api_nan_persistent_base"><b><code>Nan::PersistentBase & v8::PersistentBase</code></b></a>
- - <a href="#api_nan_non_copyable_persistent_traits"><b><code>Nan::NonCopyablePersistentTraits & v8::NonCopyablePersistentTraits</code></b></a>
- - <a href="#api_nan_copyable_persistent_traits"><b><code>Nan::CopyablePersistentTraits & v8::CopyablePersistentTraits</code></b></a>
- - <a href="#api_nan_persistent"><b><code>Nan::Persistent</code></b></a>
- - <a href="#api_nan_global"><b><code>Nan::Global</code></b></a>
- - <a href="#api_nan_weak_callback_info"><b><code>Nan::WeakCallbackInfo</code></b></a>
- - <a href="#api_nan_weak_callback_type"><b><code>Nan::WeakCallbackType</code></b></a>
-
-Also see the V8 Embedders Guide section on [Handles and Garbage Collection](https://developers.google.com/v8/embed#handles).
-
-<a name="api_nan_persistent_base"></a>
-### Nan::PersistentBase & v8::PersistentBase
-
-A persistent handle contains a reference to a storage cell in V8 which holds an object value and which is updated by the garbage collector whenever the object is moved. A new storage cell can be created using the constructor or `Nan::PersistentBase::Reset()`. Existing handles can be disposed using an argument-less `Nan::PersistentBase::Reset()`.
-
-Definition:
-
-_(note: this is implemented as `Nan::PersistentBase` for older versions of V8 and the native `v8::PersistentBase` is used for newer versions of V8)_
-
-```c++
-template<typename T> class PersistentBase {
- public:
- /**
- * If non-empty, destroy the underlying storage cell
- */
- void Reset();
-
- /**
- * If non-empty, destroy the underlying storage cell and create a new one with
- * the contents of another if it is also non-empty
- */
- template<typename S> void Reset(const v8::Local<S> &other);
-
- /**
- * If non-empty, destroy the underlying storage cell and create a new one with
- * the contents of another if it is also non-empty
- */
- template<typename S> void Reset(const PersistentBase<S> &other);
-
- /** Returns true if the handle is empty. */
- bool IsEmpty() const;
-
- /**
- * If non-empty, destroy the underlying storage cell
- * IsEmpty() will return true after this call.
- */
- void Empty();
-
- template<typename S> bool operator==(const PersistentBase<S> &that);
-
- template<typename S> bool operator==(const v8::Local<S> &that);
-
- template<typename S> bool operator!=(const PersistentBase<S> &that);
-
- template<typename S> bool operator!=(const v8::Local<S> &that);
-
- /**
- * Install a finalization callback on this object.
- * NOTE: There is no guarantee as to *when* or even *if* the callback is
- * invoked. The invocation is performed solely on a best effort basis.
- * As always, GC-based finalization should *not* be relied upon for any
- * critical form of resource management! At the moment you can either
- * specify a parameter for the callback or the location of two internal
- * fields in the dying object.
- */
- template<typename P>
- void SetWeak(P *parameter,
- typename WeakCallbackInfo<P>::Callback callback,
- WeakCallbackType type);
-
- void ClearWeak();
-
- /**
- * Marks the reference to this object independent. Garbage collector is free
- * to ignore any object groups containing this object. Weak callback for an
- * independent handle should not assume that it will be preceded by a global
- * GC prologue callback or followed by a global GC epilogue callback.
- */
- void MarkIndependent() const;
-
- bool IsIndependent() const;
-
- /** Checks if the handle holds the only reference to an object. */
- bool IsNearDeath() const;
-
- /** Returns true if the handle's reference is weak. */
- bool IsWeak() const
-};
-```
-
-See the V8 documentation for [`PersistentBase`](https://v8docs.nodesource.com/node-8.11/d4/dca/classv8_1_1_persistent_base.html) for further information.
-
-**Tip:** To get a `v8::Local` reference to the original object back from a `PersistentBase` or `Persistent` object:
-
-```c++
-v8::Local<v8::Object> object = Nan::New(persistent);
-```
-
-<a name="api_nan_non_copyable_persistent_traits"></a>
-### Nan::NonCopyablePersistentTraits & v8::NonCopyablePersistentTraits
-
-Default traits for `Nan::Persistent`. This class does not allow use of the a copy constructor or assignment operator. At present `kResetInDestructor` is not set, but that will change in a future version.
-
-Definition:
-
-_(note: this is implemented as `Nan::NonCopyablePersistentTraits` for older versions of V8 and the native `v8::NonCopyablePersistentTraits` is used for newer versions of V8)_
-
-```c++
-template<typename T> class NonCopyablePersistentTraits {
- public:
- typedef Persistent<T, NonCopyablePersistentTraits<T> > NonCopyablePersistent;
-
- static const bool kResetInDestructor = false;
-
- template<typename S, typename M>
- static void Copy(const Persistent<S, M> &source,
- NonCopyablePersistent *dest);
-
- template<typename O> static void Uncompilable();
-};
-```
-
-See the V8 documentation for [`NonCopyablePersistentTraits`](https://v8docs.nodesource.com/node-8.11/de/d73/classv8_1_1_non_copyable_persistent_traits.html) for further information.
-
-<a name="api_nan_copyable_persistent_traits"></a>
-### Nan::CopyablePersistentTraits & v8::CopyablePersistentTraits
-
-A helper class of traits to allow copying and assignment of `Persistent`. This will clone the contents of storage cell, but not any of the flags, etc..
-
-Definition:
-
-_(note: this is implemented as `Nan::CopyablePersistentTraits` for older versions of V8 and the native `v8::NonCopyablePersistentTraits` is used for newer versions of V8)_
-
-```c++
-template<typename T>
-class CopyablePersistentTraits {
- public:
- typedef Persistent<T, CopyablePersistentTraits<T> > CopyablePersistent;
-
- static const bool kResetInDestructor = true;
-
- template<typename S, typename M>
- static void Copy(const Persistent<S, M> &source,
- CopyablePersistent *dest);
-};
-```
-
-See the V8 documentation for [`CopyablePersistentTraits`](https://v8docs.nodesource.com/node-8.11/da/d5c/structv8_1_1_copyable_persistent_traits.html) for further information.
-
-<a name="api_nan_persistent"></a>
-### Nan::Persistent
-
-A type of `PersistentBase` which allows copy and assignment. Copy, assignment and destructor behavior is controlled by the traits class `M`.
-
-Definition:
-
-```c++
-template<typename T, typename M = NonCopyablePersistentTraits<T> >
-class Persistent;
-
-template<typename T, typename M> class Persistent : public PersistentBase<T> {
- public:
- /**
- * A Persistent with no storage cell.
- */
- Persistent();
-
- /**
- * Construct a Persistent from a v8::Local. When the v8::Local is non-empty, a
- * new storage cell is created pointing to the same object, and no flags are
- * set.
- */
- template<typename S> Persistent(v8::Local<S> that);
-
- /**
- * Construct a Persistent from a Persistent. When the Persistent is non-empty,
- * a new storage cell is created pointing to the same object, and no flags are
- * set.
- */
- Persistent(const Persistent &that);
-
- /**
- * The copy constructors and assignment operator create a Persistent exactly
- * as the Persistent constructor, but the Copy function from the traits class
- * is called, allowing the setting of flags based on the copied Persistent.
- */
- Persistent &operator=(const Persistent &that);
-
- template <typename S, typename M2>
- Persistent &operator=(const Persistent<S, M2> &that);
-
- /**
- * The destructor will dispose the Persistent based on the kResetInDestructor
- * flags in the traits class. Since not calling dispose can result in a
- * memory leak, it is recommended to always set this flag.
- */
- ~Persistent();
-};
-```
-
-See the V8 documentation for [`Persistent`](https://v8docs.nodesource.com/node-8.11/d2/d78/classv8_1_1_persistent.html) for further information.
-
-<a name="api_nan_global"></a>
-### Nan::Global
-
-A type of `PersistentBase` which has move semantics.
-
-```c++
-template<typename T> class Global : public PersistentBase<T> {
- public:
- /**
- * A Global with no storage cell.
- */
- Global();
-
- /**
- * Construct a Global from a v8::Local. When the v8::Local is non-empty, a new
- * storage cell is created pointing to the same object, and no flags are set.
- */
- template<typename S> Global(v8::Local<S> that);
- /**
- * Construct a Global from a PersistentBase. When the Persistent is non-empty,
- * a new storage cell is created pointing to the same object, and no flags are
- * set.
- */
- template<typename S> Global(const PersistentBase<S> &that);
-
- /**
- * Pass allows returning globals from functions, etc.
- */
- Global Pass();
-};
-```
-
-See the V8 documentation for [`Global`](https://v8docs.nodesource.com/node-8.11/d5/d40/classv8_1_1_global.html) for further information.
-
-<a name="api_nan_weak_callback_info"></a>
-### Nan::WeakCallbackInfo
-
-`Nan::WeakCallbackInfo` is used as an argument when setting a persistent reference as weak. You may need to free any external resources attached to the object. It is a mirror of `v8:WeakCallbackInfo` as found in newer versions of V8.
-
-Definition:
-
-```c++
-template<typename T> class WeakCallbackInfo {
- public:
- typedef void (*Callback)(const WeakCallbackInfo<T>& data);
-
- v8::Isolate *GetIsolate() const;
-
- /**
- * Get the parameter that was associated with the weak handle.
- */
- T *GetParameter() const;
-
- /**
- * Get pointer from internal field, index can be 0 or 1.
- */
- void *GetInternalField(int index) const;
-};
-```
-
-Example usage:
-
-```c++
-void weakCallback(const WeakCallbackInfo<int> &data) {
- int *parameter = data.GetParameter();
- delete parameter;
-}
-
-Persistent<v8::Object> obj;
-int *data = new int(0);
-obj.SetWeak(data, callback, WeakCallbackType::kParameter);
-```
-
-See the V8 documentation for [`WeakCallbackInfo`](https://v8docs.nodesource.com/node-8.11/d8/d06/classv8_1_1_weak_callback_info.html) for further information.
-
-<a name="api_nan_weak_callback_type"></a>
-### Nan::WeakCallbackType
-
-Represents the type of a weak callback.
-A weak callback of type `kParameter` makes the supplied parameter to `Nan::PersistentBase::SetWeak` available through `WeakCallbackInfo::GetParameter`.
-A weak callback of type `kInternalFields` uses up to two internal fields at indices 0 and 1 on the `Nan::PersistentBase<v8::Object>` being made weak.
-Note that only `v8::Object`s and derivatives can have internal fields.
-
-Definition:
-
-```c++
-enum class WeakCallbackType { kParameter, kInternalFields };
-```
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