Add safe interface for collections of UniquePersistent

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index dd8f2685bc37115638f5332ddbefd42a79c16cea..cb9e172545660e56fb97124530b6c59810af74ce 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -412,6 +412,7 @@ template <class T> class Local : public Handle<T> {
   template<class F> friend class internal::CustomArguments;
   friend class HandleScope;
   friend class EscapableHandleScope;
+  template<class F1, class F2, class F3> friend class PersistentValueMap;
 
   V8_INLINE static Local<T> New(Isolate* isolate, T* that);
 };
@@ -527,7 +528,11 @@ template <class T> class PersistentBase {
       P* parameter,
       typename WeakCallbackData<S, P>::Callback callback);
 
-  V8_INLINE void ClearWeak();
+  template<typename P>
+  V8_INLINE P* ClearWeak();
+
+  // TODO(dcarney): remove this.
+  V8_INLINE void ClearWeak() { ClearWeak<void>(); }
 
   /**
    * Marks the reference to this object independent. Garbage collector is free
@@ -576,6 +581,7 @@ template <class T> class PersistentBase {
   template<class F> friend class UniquePersistent;
   template<class F> friend class PersistentBase;
   template<class F> friend class ReturnValue;
+  template<class F1, class F2, class F3> friend class PersistentValueMap;
 
   explicit V8_INLINE PersistentBase(T* val) : val_(val) {}
   PersistentBase(PersistentBase& other); // NOLINT
@@ -781,6 +787,7 @@ class UniquePersistent : public PersistentBase<T> {
   template<class S>
   V8_INLINE UniquePersistent& operator=(UniquePersistent<S> rhs) {
     TYPE_CHECK(T, S);
+    this->Reset();
     this->val_ = rhs.val_;
     rhs.val_ = 0;
     return *this;
@@ -800,6 +807,80 @@ class UniquePersistent : public PersistentBase<T> {
 };
 
 
+typedef uintptr_t PersistentContainerValue;
+static const uintptr_t kPersistentContainerNotFound = 0;
+
+/**
+ * A map wrapper that allows using UniquePersistent as a mapped value.
+ * C++11 embedders don't need this class, as they can use UniquePersistent
+ * directly in std containers.
+ **/
+template<class K, class V, class Traits>
+class PersistentValueMap {
+ public:
+  V8_INLINE explicit PersistentValueMap(Isolate* isolate) : isolate_(isolate) {}
+
+  V8_INLINE ~PersistentValueMap() { Clear(); }
+
+  V8_INLINE Isolate* GetIsolate() { return isolate_; }
+
+  V8_INLINE size_t Size() { return Traits::Size(&impl_); }
+
+  V8_INLINE Local<V> Get(const K& key) {
+    return Local<V>::New(isolate_, FromVal(Traits::Get(&impl_, key)));
+  }
+
+  UniquePersistent<V> Set(const K& key, Local<V> value) {
+    UniquePersistent<V> persistent(isolate_, value);
+    if (Traits::kIsWeak) {
+      persistent.template SetWeak<typename Traits::WeakCallbackDataType>(
+        Traits::WeakCallbackParameter(&impl_, key, value), WeakCallback);
+    }
+    PersistentContainerValue old_value =
+        Traits::Set(&impl_, key, ClearAndLeak(&persistent));
+    return Release(old_value).Pass();
+  }
+
+  V8_INLINE UniquePersistent<V> Remove(const K& key) {
+    return Release(Traits::Remove(&impl_, key)).Pass();
+  }
+
+  /**
+  * Traverses the map repeatedly,
+  * in case side effects of disposal cause insertions.
+  **/
+  void Clear();
+
+ private:
+  PersistentValueMap(PersistentValueMap&);
+  void operator=(PersistentValueMap&);
+
+  static void WeakCallback(
+      const WeakCallbackData<V, typename Traits::WeakCallbackDataType>& data);
+  V8_INLINE static V* FromVal(PersistentContainerValue v) {
+    return reinterpret_cast<V*>(v);
+  }
+  V8_INLINE static PersistentContainerValue ClearAndLeak(
+      UniquePersistent<V>* persistent) {
+    V* v = persistent->val_;
+    persistent->val_ = 0;
+    return reinterpret_cast<PersistentContainerValue>(v);
+  }
+  V8_INLINE static UniquePersistent<V> Release(PersistentContainerValue v) {
+    UniquePersistent<V> p;
+    p.val_ = FromVal(v);
+    if (Traits::kIsWeak && !p.IsEmpty()) {
+      Traits::DisposeCallbackData(
+          p.template ClearWeak<typename Traits::WeakCallbackDataType>());
+    }
+    return p.Pass();
+  }
+
+  Isolate* isolate_;
+  typename Traits::Impl impl_;
+};
+
+
  /**
  * A stack-allocated class that governs a number of local handles.
  * After a handle scope has been created, all local handles will be
@@ -4786,7 +4867,7 @@ class V8_EXPORT V8 {
   static void MakeWeak(internal::Object** global_handle,
                        void* data,
                        WeakCallback weak_callback);
-  static void ClearWeak(internal::Object** global_handle);
+  static void* ClearWeak(internal::Object** global_handle);
   static void Eternalize(Isolate* isolate,
                          Value* handle,
                          int* index);
@@ -5699,8 +5780,10 @@ void PersistentBase<T>::SetWeak(
 
 
 template <class T>
-void PersistentBase<T>::ClearWeak() {
-  V8::ClearWeak(reinterpret_cast<internal::Object**>(this->val_));
+template<typename P>
+P* PersistentBase<T>::ClearWeak() {
+  return reinterpret_cast<P*>(
+    V8::ClearWeak(reinterpret_cast<internal::Object**>(this->val_)));
 }
 
 
@@ -5753,6 +5836,37 @@ uint16_t PersistentBase<T>::WrapperClassId() const {
 }
 
 
+template<class K, class V, class Traits>
+void PersistentValueMap<K, V, Traits>::Clear() {
+  typedef typename Traits::Iterator It;
+  HandleScope handle_scope(isolate_);
+  // TODO(dcarney): figure out if this swap and loop is necessary.
+  while (!Traits::Empty(&impl_)) {
+    typename Traits::Impl impl;
+    Traits::Swap(impl_, impl);
+    for (It i = Traits::Begin(&impl); i != Traits::End(&impl); ++i) {
+      Traits::DisposeCallback(&impl, Release(Traits::Value(i)).Pass());
+    }
+  }
+}
+
+
+template<class K, class V, class Traits>
+void PersistentValueMap<K, V, Traits>::WeakCallback(
+    const WeakCallbackData<V, typename Traits::WeakCallbackDataType>& data) {
+  typename Traits::Impl* impl = Traits::ImplFromWeakCallbackData(data);
+  K key = Traits::KeyFromWeakCallbackData(data);
+  PersistentContainerValue value = Traits::Remove(impl, key);
+  // TODO(dcarney): this should be an const in Traits instead of kIsWeak.
+  if (data.GetValue().IsEmpty()) {  // Zombied handle.
+    // TODO(dcarney): zombie callback/push on zombie queue.
+  } else {
+    Traits::DisposeCallback(impl, Release(value).Pass());
+  }
+  Traits::DisposeCallbackData(data.GetParameter());
+}
+
+
 template<typename T>
 ReturnValue<T>::ReturnValue(internal::Object** slot) : value_(slot) {}