[api] Introduce ReturnValue::Get

include/v8.h

 // Copyright 2012 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.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 312 matching lines @@
   template<class F> friend class internal::CustomArguments;
   friend Local<Primitive> Undefined(Isolate* isolate);
   friend Local<Primitive> Null(Isolate* isolate);
   friend Local<Boolean> True(Isolate* isolate);
   friend Local<Boolean> False(Isolate* isolate);
   friend class HandleScope;
   friend class EscapableHandleScope;
   template <class F1, class F2, class F3>
   friend class PersistentValueMapBase;
   template<class F1, class F2> friend class PersistentValueVector;
+  template <class F>
+  friend class ReturnValue;
 
   explicit V8_INLINE Local(T* that) : val_(that) {}
   V8_INLINE static Local<T> New(Isolate* isolate, T* that);
   T* val_;
 };
 
 
 #if !defined(V8_IMMINENT_DEPRECATION_WARNINGS)
 // Local is an alias for Local for historical reasons.
 template <class T>
@@ skipping 2777 matching lines @@
   // Fast primitive setters
   V8_INLINE void Set(bool value);
   V8_INLINE void Set(double i);
   V8_INLINE void Set(int32_t i);
   V8_INLINE void Set(uint32_t i);
   // Fast JS primitive setters
   V8_INLINE void SetNull();
   V8_INLINE void SetUndefined();
   V8_INLINE void SetEmptyString();
   // Convenience getter for Isolate
-  V8_INLINE Isolate* GetIsolate();
+  V8_INLINE Isolate* GetIsolate() const;
 
   // Pointer setter: Uncompilable to prevent inadvertent misuse.
   template <typename S>
   V8_INLINE void Set(S* whatever);
 
+  // Getter. Creates a new Local<> so it comes with a certain performance
+  // hit. If the ReturnValue was not yet set, this will return the undefined
+  // value.
+  V8_INLINE Local<Value> Get() const;
+
  private:
   template<class F> friend class ReturnValue;
   template<class F> friend class FunctionCallbackInfo;
   template<class F> friend class PropertyCallbackInfo;
   template <class F, class G, class H>
   friend class PersistentValueMapBase;
   V8_INLINE void SetInternal(internal::Object* value) { *value_ = value; }
   V8_INLINE internal::Object* GetDefaultValue();
   V8_INLINE explicit ReturnValue(internal::Object** slot);
   internal::Object** value_;
@@ skipping 4181 matching lines @@
 
   static const int kIsolateEmbedderDataOffset = 0 * kApiPointerSize;
   static const int kAmountOfExternalAllocatedMemoryOffset =
       4 * kApiPointerSize;
   static const int kAmountOfExternalAllocatedMemoryAtLastGlobalGCOffset =
       kAmountOfExternalAllocatedMemoryOffset + kApiInt64Size;
   static const int kIsolateRootsOffset =
       kAmountOfExternalAllocatedMemoryAtLastGlobalGCOffset + kApiInt64Size +
       kApiPointerSize;
   static const int kUndefinedValueRootIndex = 4;
+  static const int kTheHoleValueRootIndex = 5;
   static const int kNullValueRootIndex = 6;
   static const int kTrueValueRootIndex = 7;
   static const int kFalseValueRootIndex = 8;
   static const int kEmptyStringRootIndex = 9;
 
   // The external allocation limit should be below 256 MB on all architectures
   // to avoid that resource-constrained embedders run low on memory.
   static const int kExternalAllocationLimit = 192 * 1024 * 1024;
 
   static const int kNodeClassIdOffset = 1 * kApiPointerSize;
@@ skipping 459 matching lines @@
   *value_ = *I::GetRoot(GetIsolate(), I::kUndefinedValueRootIndex);
 }
 
 template<typename T>
 void ReturnValue<T>::SetEmptyString() {
   TYPE_CHECK(T, String);
   typedef internal::Internals I;
   *value_ = *I::GetRoot(GetIsolate(), I::kEmptyStringRootIndex);
 }
 
-template<typename T>
-Isolate* ReturnValue<T>::GetIsolate() {
+template <typename T>
+Isolate* ReturnValue<T>::GetIsolate() const {
   // Isolate is always the pointer below the default value on the stack.
   return *reinterpret_cast<Isolate**>(&value_[-2]);
 }
 
-template<typename T>
-template<typename S>
+template <typename T>
+Local<Value> ReturnValue<T>::Get() const {
+  typedef internal::Internals I;
+  if (*value_ == *I::GetRoot(GetIsolate(), I::kTheHoleValueRootIndex))
+    return Local<Value>(*Undefined(GetIsolate()));
+  return Local<Value>::New(GetIsolate(), reinterpret_cast<Value*>(value_));
+}
+
+template <typename T>
+template <typename S>
 void ReturnValue<T>::Set(S* whatever) {
   // Uncompilable to prevent inadvertent misuse.
   TYPE_CHECK(S*, Primitive);
 }
 
 template<typename T>
 internal::Object* ReturnValue<T>::GetDefaultValue() {
   // Default value is always the pointer below value_ on the stack.
   return value_[-1];
 }
@@ skipping 915 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // INCLUDE_V8_H_