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diff --git a/external/v8/include/v8-util.h b/external/v8/include/v8-util.h
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+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_UTIL_H_
+#define V8_UTIL_H_
+
+#include "v8.h"
+#include <map>
+#include <vector>
+
+/**
+ * Support for Persistent containers.
+ *
+ * C++11 embedders can use STL containers with UniquePersistent values,
+ * but pre-C++11 does not support the required move semantic and hence
+ * may want these container classes.
+ */
+namespace v8 {
+
+typedef uintptr_t PersistentContainerValue;
+static const uintptr_t kPersistentContainerNotFound = 0;
+enum PersistentContainerCallbackType {
+  kNotWeak,
+  kWeak
+};
+
+
+/**
+ * A default trait implemenation for PersistentValueMap which uses std::map
+ * as a backing map.
+ *
+ * Users will have to implement their own weak callbacks & dispose traits.
+ */
+template<typename K, typename V>
+class StdMapTraits {
+ public:
+  // STL map & related:
+  typedef std::map<K, PersistentContainerValue> Impl;
+  typedef typename Impl::iterator Iterator;
+
+  static bool Empty(Impl* impl) { return impl->empty(); }
+  static size_t Size(Impl* impl) { return impl->size(); }
+  static void Swap(Impl& a, Impl& b) { std::swap(a, b); }  // NOLINT
+  static Iterator Begin(Impl* impl) { return impl->begin(); }
+  static Iterator End(Impl* impl) { return impl->end(); }
+  static K Key(Iterator it) { return it->first; }
+  static PersistentContainerValue Value(Iterator it) { return it->second; }
+  static PersistentContainerValue Set(Impl* impl, K key,
+      PersistentContainerValue value) {
+    std::pair<Iterator, bool> res = impl->insert(std::make_pair(key, value));
+    PersistentContainerValue old_value = kPersistentContainerNotFound;
+    if (!res.second) {
+      old_value = res.first->second;
+      res.first->second = value;
+    }
+    return old_value;
+  }
+  static PersistentContainerValue Get(Impl* impl, K key) {
+    Iterator it = impl->find(key);
+    if (it == impl->end()) return kPersistentContainerNotFound;
+    return it->second;
+  }
+  static PersistentContainerValue Remove(Impl* impl, K key) {
+    Iterator it = impl->find(key);
+    if (it == impl->end()) return kPersistentContainerNotFound;
+    PersistentContainerValue value = it->second;
+    impl->erase(it);
+    return value;
+  }
+};
+
+
+/**
+ * A default trait implementation for PersistentValueMap, which inherits
+ * a std:map backing map from StdMapTraits and holds non-weak persistent
+ * objects and has no special Dispose handling.
+ *
+ * You should not derive from this class, since MapType depends on the
+ * surrounding class, and hence a subclass cannot simply inherit the methods.
+ */
+template<typename K, typename V>
+class DefaultPersistentValueMapTraits : public StdMapTraits<K, V> {
+ public:
+  // Weak callback & friends:
+  static const PersistentContainerCallbackType kCallbackType = kNotWeak;
+  typedef PersistentValueMap<K, V, DefaultPersistentValueMapTraits<K, V> >
+      MapType;
+  typedef void WeakCallbackDataType;
+
+  static WeakCallbackDataType* WeakCallbackParameter(
+      MapType* map, const K& key, Local<V> value) {
+    return NULL;
+  }
+  static MapType* MapFromWeakCallbackData(
+          const WeakCallbackData<V, WeakCallbackDataType>& data) {
+    return NULL;
+  }
+  static K KeyFromWeakCallbackData(
+      const WeakCallbackData<V, WeakCallbackDataType>& data) {
+    return K();
+  }
+  static void DisposeCallbackData(WeakCallbackDataType* data) { }
+  static void Dispose(Isolate* isolate, UniquePersistent<V> value, K key) { }
+};
+
+
+/**
+ * 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.
+ *
+ * The map relies on a backing map, whose type and accessors are described
+ * by the Traits class. The backing map will handle values of type
+ * PersistentContainerValue, with all conversion into and out of V8
+ * handles being transparently handled by this class.
+ */
+template<typename K, typename V, typename Traits>
+class PersistentValueMap {
+ public:
+  explicit PersistentValueMap(Isolate* isolate) : isolate_(isolate) {}
+
+  ~PersistentValueMap() { Clear(); }
+
+  Isolate* GetIsolate() { return isolate_; }
+
+  /**
+   * Return size of the map.
+   */
+  size_t Size() { return Traits::Size(&impl_); }
+
+  /**
+   * Return whether the map holds weak persistents.
+   */
+  bool IsWeak() { return Traits::kCallbackType != kNotWeak; }
+
+  /**
+   * Get value stored in map.
+   */
+  Local<V> Get(const K& key) {
+    return Local<V>::New(isolate_, FromVal(Traits::Get(&impl_, key)));
+  }
+
+  /**
+   * Check whether a value is contained in the map.
+   */
+  bool Contains(const K& key) {
+    return Traits::Get(&impl_, key) != kPersistentContainerNotFound;
+  }
+
+  /**
+   * Get value stored in map and set it in returnValue.
+   * Return true if a value was found.
+   */
+  bool SetReturnValue(const K& key,
+      ReturnValue<Value> returnValue) {
+    return SetReturnValueFromVal(&returnValue, Traits::Get(&impl_, key));
+  }
+
+  /**
+   * Call Isolate::SetReference with the given parent and the map value.
+   */
+  void SetReference(const K& key,
+      const Persistent<Object>& parent) {
+    GetIsolate()->SetReference(
+      reinterpret_cast<internal::Object**>(parent.val_),
+      reinterpret_cast<internal::Object**>(FromVal(Traits::Get(&impl_, key))));
+  }
+
+  /**
+   * Put value into map. Depending on Traits::kIsWeak, the value will be held
+   * by the map strongly or weakly.
+   * Returns old value as UniquePersistent.
+   */
+  UniquePersistent<V> Set(const K& key, Local<V> value) {
+    UniquePersistent<V> persistent(isolate_, value);
+    return SetUnique(key, &persistent);
+  }
+
+  /**
+   * Put value into map, like Set(const K&, Local<V>).
+   */
+  UniquePersistent<V> Set(const K& key, UniquePersistent<V> value) {
+    return SetUnique(key, &value);
+  }
+
+  /**
+   * Return value for key and remove it from the map.
+   */
+  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() {
+    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::Dispose(isolate_, Release(Traits::Value(i)).Pass(),
+                        Traits::Key(i));
+      }
+    }
+  }
+
+  /**
+   * Helper class for GetReference/SetWithReference. Do not use outside
+   * that context.
+   */
+  class PersistentValueReference {
+   public:
+    PersistentValueReference() : value_(kPersistentContainerNotFound) { }
+    PersistentValueReference(const PersistentValueReference& other)
+        : value_(other.value_) { }
+
+    Local<V> NewLocal(Isolate* isolate) const {
+      return Local<V>::New(isolate, FromVal(value_));
+    }
+    bool IsEmpty() const {
+      return value_ == kPersistentContainerNotFound;
+    }
+    template<typename T>
+    bool SetReturnValue(ReturnValue<T> returnValue) {
+      return SetReturnValueFromVal(&returnValue, value_);
+    }
+    void Reset() {
+      value_ = kPersistentContainerNotFound;
+    }
+    void operator=(const PersistentValueReference& other) {
+      value_ = other.value_;
+    }
+
+   private:
+    friend class PersistentValueMap;
+
+    explicit PersistentValueReference(PersistentContainerValue value)
+        : value_(value) { }
+
+    void operator=(PersistentContainerValue value) {
+      value_ = value;
+    }
+
+    PersistentContainerValue value_;
+  };
+
+  /**
+   * Get a reference to a map value. This enables fast, repeated access
+   * to a value stored in the map while the map remains unchanged.
+   *
+   * Careful: This is potentially unsafe, so please use with care.
+   * The value will become invalid if the value for this key changes
+   * in the underlying map, as a result of Set or Remove for the same
+   * key; as a result of the weak callback for the same key; or as a
+   * result of calling Clear() or destruction of the map.
+   */
+  PersistentValueReference GetReference(const K& key) {
+    return PersistentValueReference(Traits::Get(&impl_, key));
+  }
+
+  /**
+   * Put a value into the map and update the reference.
+   * Restrictions of GetReference apply here as well.
+   */
+  UniquePersistent<V> Set(const K& key, UniquePersistent<V> value,
+                          PersistentValueReference* reference) {
+    *reference = Leak(&value);
+    return SetUnique(key, &value);
+  }
+
+ private:
+  PersistentValueMap(PersistentValueMap&);
+  void operator=(PersistentValueMap&);
+
+  /**
+   * Put the value into the map, and set the 'weak' callback when demanded
+   * by the Traits class.
+   */
+  UniquePersistent<V> SetUnique(const K& key, UniquePersistent<V>* persistent) {
+    if (Traits::kCallbackType != kNotWeak) {
+      Local<V> value(Local<V>::New(isolate_, *persistent));
+      persistent->template SetWeak<typename Traits::WeakCallbackDataType>(
+        Traits::WeakCallbackParameter(this, key, value), WeakCallback);
+    }
+    PersistentContainerValue old_value =
+        Traits::Set(&impl_, key, ClearAndLeak(persistent));
+    return Release(old_value).Pass();
+  }
+
+  static void WeakCallback(
+      const WeakCallbackData<V, typename Traits::WeakCallbackDataType>& data) {
+    if (Traits::kCallbackType != kNotWeak) {
+      PersistentValueMap<K, V, Traits>* persistentValueMap =
+          Traits::MapFromWeakCallbackData(data);
+      K key = Traits::KeyFromWeakCallbackData(data);
+      Traits::Dispose(data.GetIsolate(),
+                      persistentValueMap->Remove(key).Pass(), key);
+      Traits::DisposeCallbackData(data.GetParameter());
+    }
+  }
+
+  static V* FromVal(PersistentContainerValue v) {
+    return reinterpret_cast<V*>(v);
+  }
+
+  static bool SetReturnValueFromVal(
+      ReturnValue<Value>* returnValue, PersistentContainerValue value) {
+    bool hasValue = value != kPersistentContainerNotFound;
+    if (hasValue) {
+      returnValue->SetInternal(
+          *reinterpret_cast<internal::Object**>(FromVal(value)));
+    }
+    return hasValue;
+  }
+
+  static PersistentContainerValue ClearAndLeak(
+      UniquePersistent<V>* persistent) {
+    V* v = persistent->val_;
+    persistent->val_ = 0;
+    return reinterpret_cast<PersistentContainerValue>(v);
+  }
+
+  static PersistentContainerValue Leak(
+      UniquePersistent<V>* persistent) {
+    return reinterpret_cast<PersistentContainerValue>(persistent->val_);
+  }
+
+  /**
+   * Return a container value as UniquePersistent and make sure the weak
+   * callback is properly disposed of. All remove functionality should go
+   * through this.
+   */
+  static UniquePersistent<V> Release(PersistentContainerValue v) {
+    UniquePersistent<V> p;
+    p.val_ = FromVal(v);
+    if (Traits::kCallbackType != kNotWeak && p.IsWeak()) {
+      Traits::DisposeCallbackData(
+          p.template ClearWeak<typename Traits::WeakCallbackDataType>());
+    }
+    return p.Pass();
+  }
+
+  Isolate* isolate_;
+  typename Traits::Impl impl_;
+};
+
+
+/**
+ * A map that uses UniquePersistent as value and std::map as the backing
+ * implementation. Persistents are held non-weak.
+ *
+ * C++11 embedders don't need this class, as they can use
+ * UniquePersistent directly in std containers.
+ */
+template<typename K, typename V,
+    typename Traits = DefaultPersistentValueMapTraits<K, V> >
+class StdPersistentValueMap : public PersistentValueMap<K, V, Traits> {
+ public:
+  explicit StdPersistentValueMap(Isolate* isolate)
+      : PersistentValueMap<K, V, Traits>(isolate) {}
+};
+
+
+class DefaultPersistentValueVectorTraits {
+ public:
+  typedef std::vector<PersistentContainerValue> Impl;
+
+  static void Append(Impl* impl, PersistentContainerValue value) {
+    impl->push_back(value);
+  }
+  static bool IsEmpty(const Impl* impl) {
+    return impl->empty();
+  }
+  static size_t Size(const Impl* impl) {
+    return impl->size();
+  }
+  static PersistentContainerValue Get(const Impl* impl, size_t i) {
+    return (i < impl->size()) ? impl->at(i) : kPersistentContainerNotFound;
+  }
+  static void ReserveCapacity(Impl* impl, size_t capacity) {
+    impl->reserve(capacity);
+  }
+  static void Clear(Impl* impl) {
+    impl->clear();
+  }
+};
+
+
+/**
+ * A vector wrapper that safely stores UniquePersistent values.
+ * C++11 embedders don't need this class, as they can use UniquePersistent
+ * directly in std containers.
+ *
+ * This class relies on a backing vector implementation, whose type and methods
+ * are described by the Traits class. The backing map will handle values of type
+ * PersistentContainerValue, with all conversion into and out of V8
+ * handles being transparently handled by this class.
+ */
+template<typename V, typename Traits = DefaultPersistentValueVectorTraits>
+class PersistentValueVector {
+ public:
+  explicit PersistentValueVector(Isolate* isolate) : isolate_(isolate) { }
+
+  ~PersistentValueVector() {
+    Clear();
+  }
+
+  /**
+   * Append a value to the vector.
+   */
+  void Append(Local<V> value) {
+    UniquePersistent<V> persistent(isolate_, value);
+    Traits::Append(&impl_, ClearAndLeak(&persistent));
+  }
+
+  /**
+   * Append a persistent's value to the vector.
+   */
+  void Append(UniquePersistent<V> persistent) {
+    Traits::Append(&impl_, ClearAndLeak(&persistent));
+  }
+
+  /**
+   * Are there any values in the vector?
+   */
+  bool IsEmpty() const {
+    return Traits::IsEmpty(&impl_);
+  }
+
+  /**
+   * How many elements are in the vector?
+   */
+  size_t Size() const {
+    return Traits::Size(&impl_);
+  }
+
+  /**
+   * Retrieve the i-th value in the vector.
+   */
+  Local<V> Get(size_t index) const {
+    return Local<V>::New(isolate_, FromVal(Traits::Get(&impl_, index)));
+  }
+
+  /**
+   * Remove all elements from the vector.
+   */
+  void Clear() {
+    size_t length = Traits::Size(&impl_);
+    for (size_t i = 0; i < length; i++) {
+      UniquePersistent<V> p;
+      p.val_ = FromVal(Traits::Get(&impl_, i));
+    }
+    Traits::Clear(&impl_);
+  }
+
+  /**
+   * Reserve capacity in the vector.
+   * (Efficiency gains depend on the backing implementation.)
+   */
+  void ReserveCapacity(size_t capacity) {
+    Traits::ReserveCapacity(&impl_, capacity);
+  }
+
+ private:
+  static PersistentContainerValue ClearAndLeak(
+      UniquePersistent<V>* persistent) {
+    V* v = persistent->val_;
+    persistent->val_ = 0;
+    return reinterpret_cast<PersistentContainerValue>(v);
+  }
+
+  static V* FromVal(PersistentContainerValue v) {
+    return reinterpret_cast<V*>(v);
+  }
+
+  Isolate* isolate_;
+  typename Traits::Impl impl_;
+};
+
+}  // namespace v8
+
+#endif  // V8_UTIL_H_