// Copyright 2012 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

/** \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.
 *
 * For other documentation see http://code.google.com/apis/v8/
 */

#ifndef V8_H_
#define V8_H_

#include "v8stdint.h"

// We reserve the V8_* prefix for macros defined in V8 public API and
// assume there are no name conflicts with the embedder's code.

#ifdef V8_OS_WIN

// Setup for Windows DLL export/import. When building the V8 DLL the
// BUILDING_V8_SHARED needs to be defined. When building a program which uses
// the V8 DLL USING_V8_SHARED needs to be defined. When either building the V8
// static library or building a program which uses the V8 static library neither
// BUILDING_V8_SHARED nor USING_V8_SHARED should be defined.
#if defined(BUILDING_V8_SHARED) && defined(USING_V8_SHARED)
#error both BUILDING_V8_SHARED and USING_V8_SHARED are set - please check the\
  build configuration to ensure that at most one of these is set
#endif

#ifdef BUILDING_V8_SHARED
# define V8_EXPORT __declspec(dllexport)
#elif USING_V8_SHARED
# define V8_EXPORT __declspec(dllimport)
#else
# define V8_EXPORT
#endif  // BUILDING_V8_SHARED

#else  // V8_OS_WIN

// Setup for Linux shared library export.
#if V8_HAS_ATTRIBUTE_VISIBILITY && defined(V8_SHARED)
# ifdef BUILDING_V8_SHARED
#  define V8_EXPORT __attribute__ ((visibility("default")))
# else
#  define V8_EXPORT
# endif
#else
# define V8_EXPORT
#endif

#endif  // V8_OS_WIN

/**
 * The v8 JavaScript engine.
 */
namespace v8 {

class AccessorSignature;
class Array;
class Boolean;
class BooleanObject;
class Context;
class CpuProfiler;
class Data;
class Date;
class DeclaredAccessorDescriptor;
class External;
class Function;
class FunctionTemplate;
class HeapProfiler;
class ImplementationUtilities;
class Int32;
class Integer;
class Isolate;
class Number;
class NumberObject;
class Object;
class ObjectOperationDescriptor;
class ObjectTemplate;
class Primitive;
class RawOperationDescriptor;
class Signature;
class StackFrame;
class StackTrace;
class String;
class StringObject;
class Symbol;
class SymbolObject;
class Uint32;
class Utils;
class Value;
template <class T> class Handle;
template <class T> class Local;
template <class T> class Eternal;
template<class T> class NonCopyablePersistentTraits;
template<class T,
         class M = NonCopyablePersistentTraits<T> > class Persistent;
template<class T, class P> class WeakCallbackObject;
class FunctionTemplate;
class ObjectTemplate;
class Data;
template<typename T> class PropertyCallbackInfo;
class StackTrace;
class StackFrame;
class Isolate;
class DeclaredAccessorDescriptor;
class ObjectOperationDescriptor;
class RawOperationDescriptor;
class CallHandlerHelper;
class EscapableHandleScope;

namespace internal {
class Arguments;
class Heap;
class HeapObject;
class Isolate;
class Object;
template<typename T> class CustomArguments;
class PropertyCallbackArguments;
class FunctionCallbackArguments;
class GlobalHandles;
}


/**
 * General purpose unique identifier.
 */
class UniqueId {
 public:
  explicit UniqueId(intptr_t data)
      : data_(data) {}

  bool operator==(const UniqueId& other) const {
    return data_ == other.data_;
  }

  bool operator!=(const UniqueId& other) const {
    return data_ != other.data_;
  }

  bool operator<(const UniqueId& other) const {
    return data_ < other.data_;
  }

 private:
  intptr_t data_;
};

// --- Handles ---

#define TYPE_CHECK(T, S)                                       \
  while (false) {                                              \
    *(static_cast<T* volatile*>(0)) = static_cast<S*>(0);      \
  }


/**
 * An object reference managed by the v8 garbage collector.
 *
 * All objects returned from v8 have to be tracked by the garbage
 * collector so that it knows that the objects are still alive.  Also,
 * because the garbage collector may move objects, it is unsafe to
 * point directly to an object.  Instead, all objects are stored in
 * handles which are known by the garbage collector and updated
 * whenever an object moves.  Handles should always be passed by value
 * (except in cases like out-parameters) and they should never be
 * allocated on the heap.
 *
 * There are two types of handles: local and persistent handles.
 * Local handles are light-weight and transient and typically used in
 * local operations.  They are managed by HandleScopes.  Persistent
 * handles can be used when storing objects across several independent
 * operations and have to be explicitly deallocated when they're no
 * longer used.
 *
 * It is safe to extract the object stored in the handle by
 * dereferencing the handle (for instance, to extract the Object* from
 * a Handle<Object>); the value will still be governed by a handle
 * behind the scenes and the same rules apply to these values as to
 * their handles.
 */
template <class T> class Handle {
 public:
  /**
   * Creates an empty handle.
   */
  V8_INLINE Handle() : val_(0) {}

  /**
   * Creates a handle for the contents of the specified handle.  This
   * constructor allows you to pass handles as arguments by value and
   * to assign between handles.  However, if you try to assign between
   * incompatible handles, for instance from a Handle<String> to a
   * Handle<Number> it will cause a compile-time error.  Assigning
   * between compatible handles, for instance assigning a
   * Handle<String> to a variable declared as Handle<Value>, is legal
   * because String is a subclass of Value.
   */
  template <class S> V8_INLINE Handle(Handle<S> that)
      : val_(reinterpret_cast<T*>(*that)) {
    /**
     * This check fails when trying to convert between incompatible
     * handles. For example, converting from a Handle<String> to a
     * Handle<Number>.
     */
    TYPE_CHECK(T, S);
  }

  /**
   * Returns true if the handle is empty.
   */
  V8_INLINE bool IsEmpty() const { return val_ == 0; }

  /**
   * Sets the handle to be empty. IsEmpty() will then return true.
   */
  V8_INLINE void Clear() { val_ = 0; }

  V8_INLINE T* operator->() const { return val_; }

  V8_INLINE T* operator*() const { return val_; }

  /**
   * Checks whether two handles are the same.
   * Returns true if both are empty, or if the objects
   * to which they refer are identical.
   * The handles' references are not checked.
   */
  template <class S> V8_INLINE bool operator==(const Handle<S>& that) const {
    internal::Object** a = reinterpret_cast<internal::Object**>(**this);
    internal::Object** b = reinterpret_cast<internal::Object**>(*that);
    if (a == 0) return b == 0;
    if (b == 0) return false;
    return *a == *b;
  }

  template <class S> V8_INLINE bool operator==(
      const Persistent<S>& that) const {
    internal::Object** a = reinterpret_cast<internal::Object**>(**this);
    internal::Object** b = reinterpret_cast<internal::Object**>(*that);
    if (a == 0) return b == 0;
    if (b == 0) return false;
    return *a == *b;
  }

  /**
   * Checks whether two handles are different.
   * Returns true if only one of the handles is empty, or if
   * the objects to which they refer are different.
   * The handles' references are not checked.
   */
  template <class S> V8_INLINE bool operator!=(const Handle<S>& that) const {
    return !operator==(that);
  }

  template <class S> V8_INLINE bool operator!=(
      const Persistent<S>& that) const {
    return !operator==(that);
  }

  template <class S> V8_INLINE static Handle<T> Cast(Handle<S> that) {
#ifdef V8_ENABLE_CHECKS
    // If we're going to perform the type check then we have to check
    // that the handle isn't empty before doing the checked cast.
    if (that.IsEmpty()) return Handle<T>();
#endif
    return Handle<T>(T::Cast(*that));
  }

  template <class S> V8_INLINE Handle<S> As() {
    return Handle<S>::Cast(*this);
  }

  V8_INLINE static Handle<T> New(Isolate* isolate, Handle<T> that) {
    return New(isolate, that.val_);
  }
  V8_INLINE static Handle<T> New(Isolate* isolate, const Persistent<T>& that) {
    return New(isolate, that.val_);
  }

#ifndef V8_ALLOW_ACCESS_TO_RAW_HANDLE_CONSTRUCTOR

 private:
#endif
  /**
   * Creates a new handle for the specified value.
   */
  V8_INLINE explicit Handle(T* val) : val_(val) {}

 private:
  friend class Utils;
  template<class F, class M> friend class Persistent;
  template<class F> friend class Local;
  template<class F> friend class FunctionCallbackInfo;
  template<class F> friend class PropertyCallbackInfo;
  template<class F> friend class internal::CustomArguments;
  friend Handle<Primitive> Undefined(Isolate* isolate);
  friend Handle<Primitive> Null(Isolate* isolate);
  friend Handle<Boolean> True(Isolate* isolate);
  friend Handle<Boolean> False(Isolate* isolate);
  friend class Context;
  friend class HandleScope;

  V8_INLINE static Handle<T> New(Isolate* isolate, T* that);

  T* val_;
};


/**
 * A light-weight stack-allocated object handle.  All operations
 * that return objects from within v8 return them in local handles.  They
 * are created within HandleScopes, and all local handles allocated within a
 * handle scope are destroyed when the handle scope is destroyed.  Hence it
 * is not necessary to explicitly deallocate local handles.
 */
template <class T> class Local : public Handle<T> {
 public:
  V8_INLINE Local();
  template <class S> V8_INLINE Local(Local<S> that)
      : Handle<T>(reinterpret_cast<T*>(*that)) {
    /**
     * This check fails when trying to convert between incompatible
     * handles. For example, converting from a Handle<String> to a
     * Handle<Number>.
     */
    TYPE_CHECK(T, S);
  }


  template <class S> V8_INLINE static Local<T> Cast(Local<S> that) {
#ifdef V8_ENABLE_CHECKS
    // If we're going to perform the type check then we have to check
    // that the handle isn't empty before doing the checked cast.
    if (that.IsEmpty()) return Local<T>();
#endif
    return Local<T>(T::Cast(*that));
  }
  template <class S> V8_INLINE Local(Handle<S> that)
      : Handle<T>(reinterpret_cast<T*>(*that)) {
    TYPE_CHECK(T, S);
  }

  template <class S> V8_INLINE Local<S> As() {
    return Local<S>::Cast(*this);
  }

  /**
   * Create a local handle for the content of another handle.
   * The referee is kept alive by the local handle even when
   * the original handle is destroyed/disposed.
   */
  V8_INLINE static Local<T> New(Isolate* isolate, Handle<T> that);
  template<class M>
  V8_INLINE static Local<T> New(Isolate* isolate,
                                const Persistent<T, M>& that);

#ifndef V8_ALLOW_ACCESS_TO_RAW_HANDLE_CONSTRUCTOR

 private:
#endif
  template <class S> V8_INLINE Local(S* that) : Handle<T>(that) { }

 private:
  friend class Utils;
  template<class F> friend class Eternal;
  template<class F, class M> friend class Persistent;
  template<class F> friend class Handle;
  template<class F> friend class FunctionCallbackInfo;
  template<class F> friend class PropertyCallbackInfo;
  friend class String;
  friend class Object;
  friend class Context;
  template<class F> friend class internal::CustomArguments;
  friend class HandleScope;
  friend class EscapableHandleScope;

  V8_INLINE static Local<T> New(Isolate* isolate, T* that);
};


// Eternal handles are set-once handles that live for the life of the isolate.
template <class T> class Eternal {
 public:
  V8_INLINE Eternal() : index_(kInitialValue) { }
  template<class S>
  V8_INLINE Eternal(Isolate* isolate, Local<S> handle) : index_(kInitialValue) {
    Set(isolate, handle);
  }
  // Can only be safely called if already set.
  V8_INLINE Local<T> Get(Isolate* isolate);
  V8_INLINE bool IsEmpty() { return index_ == kInitialValue; }
  template<class S> V8_INLINE void Set(Isolate* isolate, Local<S> handle);

 private:
  static const int kInitialValue = -1;
  int index_;
};


template<class T, class P>
class WeakCallbackData {
 public:
  typedef void (*Callback)(const WeakCallbackData<T, P>& data);

  V8_INLINE Isolate* GetIsolate() const { return isolate_; }
  V8_INLINE Local<T> GetValue() const { return handle_; }
  V8_INLINE P* GetParameter() const { return parameter_; }

 private:
  friend class internal::GlobalHandles;
  WeakCallbackData(Isolate* isolate, Local<T> handle, P* parameter)
    : isolate_(isolate), handle_(handle), parameter_(parameter) { }
  Isolate* isolate_;
  Local<T> handle_;
  P* parameter_;
};


// TODO(dcarney): Remove this class.
template<typename T,
         typename P,
         typename M = NonCopyablePersistentTraits<T> >
class WeakReferenceCallbacks {
 public:
  typedef void (*Revivable)(Isolate* isolate,
                            Persistent<T, M>* object,
                            P* parameter);
};


/**
 * Default traits for Persistent. This class does not allow
 * use of the copy constructor or assignment operator.
 * At present kResetInDestructor is not set, but that will change in a future
 * version.
 */
template<class T>
class NonCopyablePersistentTraits {
 public:
  typedef Persistent<T, NonCopyablePersistentTraits<T> > NonCopyablePersistent;
  static const bool kResetInDestructor = false;
  template<class S, class M>
  V8_INLINE static void Copy(const Persistent<S, M>& source,
                             NonCopyablePersistent* dest) {
    Uncompilable<Object>();
  }
  // TODO(dcarney): come up with a good compile error here.
  template<class O> V8_INLINE static void Uncompilable() {
    TYPE_CHECK(O, Primitive);
  }
};


/**
 * Helper class traits to allow copying and assignment of Persistent.
 * This will clone the contents of storage cell, but not any of the flags, etc.
 */
template<class T>
struct CopyablePersistentTraits {
  typedef Persistent<T, CopyablePersistentTraits<T> > CopyablePersistent;
  static const bool kResetInDestructor = true;
  template<class S, class M>
  static V8_INLINE void Copy(const Persistent<S, M>& source,
                             CopyablePersistent* dest) {
    // do nothing, just allow copy
  }
};


/**
 * An object reference that is independent of any handle scope.  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.
 *
 * A persistent handle contains a reference to a storage cell within
 * the v8 engine 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 Persistent::Reset and
 * existing handles can be disposed using Persistent::Reset.
 *
 * Copy, assignment and destructor bevavior is controlled by the traits
 * class M.
 */
template <class T, class M> class Persistent {
 public:
  /**
   * A Persistent with no storage cell.
   */
  V8_INLINE Persistent() : val_(0) { }
  /**
   * Construct a Persistent from a Handle.
   * When the Handle is non-empty, a new storage cell is created
   * pointing to the same object, and no flags are set.
   */
  template <class S> V8_INLINE Persistent(Isolate* isolate, Handle<S> that)
      : val_(New(isolate, *that)) {
    TYPE_CHECK(T, S);
  }
  /**
   * 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.
   */
  template <class S, class M2>
  V8_INLINE Persistent(Isolate* isolate, const Persistent<S, M2>& that)
    : val_(New(isolate, *that)) {
    TYPE_CHECK(T, S);
  }
  /**
   * 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.
   */
  V8_INLINE Persistent(const Persistent& that) : val_(0) {
    Copy(that);
  }
  template <class S, class M2>
  V8_INLINE Persistent(const Persistent<S, M2>& that) : val_(0) {
    Copy(that);
  }
  V8_INLINE Persistent& operator=(const Persistent& that) { // NOLINT
    Copy(that);
    return *this;
  }
  template <class S, class M2>
  V8_INLINE Persistent& operator=(const Persistent<S, M2>& that) { // NOLINT
    Copy(that);
    return *this;
  }
  /**
   * 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.
   */
  V8_INLINE ~Persistent() {
    if (M::kResetInDestructor) Reset();
  }

  /**
   * If non-empty, destroy the underlying storage cell
   * IsEmpty() will return true after this call.
   */
  V8_INLINE void Reset();
  /**
   * If non-empty, destroy the underlying storage cell
   * and create a new one with the contents of other if other is non empty
   */
  template <class S>
  V8_INLINE void Reset(Isolate* isolate, const Handle<S>& other);
  /**
   * If non-empty, destroy the underlying storage cell
   * and create a new one with the contents of other if other is non empty
   */
  template <class S, class M2>
  V8_INLINE void Reset(Isolate* isolate, const Persistent<S, M2>& other);
  // TODO(dcarney): deprecate
  V8_INLINE void Dispose() { Reset(); }
  V8_DEPRECATED(V8_INLINE void Dispose(Isolate* isolate)) { Reset(); }

  V8_INLINE bool IsEmpty() const { return val_ == 0; }

  // TODO(dcarney): this is pretty useless, fix or remove
  template <class S>
  V8_INLINE static Persistent<T>& Cast(Persistent<S>& that) { // NOLINT
#ifdef V8_ENABLE_CHECKS
    // If we're going to perform the type check then we have to check
    // that the handle isn't empty before doing the checked cast.
    if (!that.IsEmpty()) T::Cast(*that);
#endif
    return reinterpret_cast<Persistent<T>&>(that);
  }

  // TODO(dcarney): this is pretty useless, fix or remove
  template <class S> V8_INLINE Persistent<S>& As() { // NOLINT
    return Persistent<S>::Cast(*this);
  }

  template <class S, class M2>
  V8_INLINE bool operator==(const Persistent<S, M2>& that) const {
    internal::Object** a = reinterpret_cast<internal::Object**>(**this);
    internal::Object** b = reinterpret_cast<internal::Object**>(*that);
    if (a == 0) return b == 0;
    if (b == 0) return false;
    return *a == *b;
  }

  template <class S> V8_INLINE bool operator==(const Handle<S>& that) const {
    internal::Object** a = reinterpret_cast<internal::Object**>(**this);
    internal::Object** b = reinterpret_cast<internal::Object**>(*that);
    if (a == 0) return b == 0;
    if (b == 0) return false;
    return *a == *b;
  }

  template <class S, class M2>
  V8_INLINE bool operator!=(const Persistent<S, M2>& that) const {
    return !operator==(that);
  }

  template <class S> V8_INLINE bool operator!=(const Handle<S>& that) const {
    return !operator==(that);
  }

  template<typename P>
  V8_INLINE void SetWeak(
      P* parameter,
      typename WeakCallbackData<T, P>::Callback callback);

  template<typename S, typename P>
  V8_INLINE void SetWeak(
      P* parameter,
      typename WeakCallbackData<S, P>::Callback callback);

  // TODO(dcarney): deprecate
  template<typename S, typename P>
  V8_INLINE void MakeWeak(
      P* parameter,
      typename WeakReferenceCallbacks<S, P>::Revivable callback);

  // TODO(dcarney): deprecate
  template<typename P>
  V8_INLINE void MakeWeak(
      P* parameter,
      typename WeakReferenceCallbacks<T, P>::Revivable callback);

  V8_INLINE void ClearWeak();

  V8_DEPRECATED(V8_INLINE void ClearWeak(Isolate* isolate)) { 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.
   */
  V8_INLINE void MarkIndependent();

  V8_DEPRECATED(V8_INLINE void MarkIndependent(Isolate* isolate)) {
    MarkIndependent();
  }

  /**
   * Marks the reference to this object partially dependent. Partially dependent
   * handles only depend on other partially dependent handles and these
   * dependencies are provided through object groups. It provides a way to build
   * smaller object groups for young objects that represent only a subset of all
   * external dependencies. This mark is automatically cleared after each
   * garbage collection.
   */
  V8_INLINE void MarkPartiallyDependent();

  V8_DEPRECATED(V8_INLINE void MarkPartiallyDependent(Isolate* isolate)) {
    MarkPartiallyDependent();
  }

  V8_INLINE bool IsIndependent() const;

  V8_DEPRECATED(V8_INLINE bool IsIndependent(Isolate* isolate) const) {
    return IsIndependent();
  }

  /** Checks if the handle holds the only reference to an object. */
  V8_INLINE bool IsNearDeath() const;

  V8_DEPRECATED(V8_INLINE bool IsNearDeath(Isolate* isolate) const) {
    return IsNearDeath();
  }

  /** Returns true if the handle's reference is weak.  */
  V8_INLINE bool IsWeak() const;

  V8_DEPRECATED(V8_INLINE bool IsWeak(Isolate* isolate) const) {
    return IsWeak();
  }

  /**
   * Assigns a wrapper class ID to the handle. See RetainedObjectInfo interface
   * description in v8-profiler.h for details.
   */
  V8_INLINE void SetWrapperClassId(uint16_t class_id);

  V8_DEPRECATED(
      V8_INLINE void SetWrapperClassId(Isolate * isolate, uint16_t class_id)) {
    SetWrapperClassId(class_id);
  }

  /**
   * Returns the class ID previously assigned to this handle or 0 if no class ID
   * was previously assigned.
   */
  V8_INLINE uint16_t WrapperClassId() const;

  V8_DEPRECATED(V8_INLINE uint16_t WrapperClassId(Isolate* isolate) const) {
    return WrapperClassId();
  }

  // TODO(dcarney): remove
  V8_INLINE T* ClearAndLeak();

  // TODO(dcarney): remove
  V8_INLINE void Clear() { val_ = 0; }

  // TODO(dcarney): remove
#ifndef V8_ALLOW_ACCESS_TO_RAW_HANDLE_CONSTRUCTOR

 private:
#endif
  template <class S> V8_INLINE Persistent(S* that) : val_(that) { }

  V8_INLINE T* operator*() const { return val_; }

 private:
  friend class Utils;
  template<class F> friend class Handle;
  template<class F> friend class Local;
  template<class F1, class F2> friend class Persistent;
  template<class F> friend class ReturnValue;

  V8_INLINE static T* New(Isolate* isolate, T* that);
  template<class S, class M2>
  V8_INLINE void Copy(const Persistent<S, M2>& that);

  T* val_;
};

 /**
 * A stack-allocated class that governs a number of local handles.
 * After a handle scope has been created, all local handles will be
 * allocated within that handle scope until either the handle scope is
 * deleted or another handle scope is created.  If there is already a
 * handle scope and a new one is created, all allocations will take
 * place in the new handle scope until it is deleted.  After that,
 * new handles will again be allocated in the original handle scope.
 *
 * After the handle scope of a local handle has been deleted the
 * garbage collector will no longer track the object stored in the
 * handle and may deallocate it.  The behavior of accessing a handle
 * for which the handle scope has been deleted is undefined.
 */
class V8_EXPORT HandleScope {
 public:
  HandleScope(Isolate* isolate);

  ~HandleScope();

  // TODO(dcarney): deprecated - use EscapableHandleScope::Escape.
  template <class T> Local<T> Close(Handle<T> value);

  /**
   * Counts the number of allocated handles.
   */
  static int NumberOfHandles();

 private:
  /**
   * Creates a new handle with the given value.
   */
  static internal::Object** CreateHandle(internal::Isolate* isolate,
                                         internal::Object* value);
  // Uses HeapObject to obtain the current Isolate.
  static internal::Object** CreateHandle(internal::HeapObject* heap_object,
                                         internal::Object* value);

  V8_INLINE HandleScope() {}
  void Initialize(Isolate* isolate);

  // Make it hard to create heap-allocated or illegal handle scopes by
  // disallowing certain operations.
  HandleScope(const HandleScope&);
  void operator=(const HandleScope&);
  void* operator new(size_t size);
  void operator delete(void*, size_t);

  // This Data class is accessible internally as HandleScopeData through a
  // typedef in the ImplementationUtilities class.
  class V8_EXPORT Data {
   public:
    internal::Object** next;
    internal::Object** limit;
    int level;
    V8_INLINE void Initialize() {
      next = limit = NULL;
      level = 0;
    }
  };

  void Leave();

  internal::Isolate* isolate_;
  internal::Object** prev_next_;
  internal::Object** prev_limit_;

  // TODO(dcarney): remove this field
  // Allow for the active closing of HandleScopes which allows to pass a handle
  // from the HandleScope being closed to the next top most HandleScope.
  bool is_closed_;
  internal::Object** RawClose(internal::Object** value);

  friend class ImplementationUtilities;
  friend class EscapableHandleScope;
  template<class F> friend class Handle;
  template<class F> friend class Local;
  friend class Object;
  friend class Context;
};


/**
 * A HandleScope which first allocates a handle in the current scope
 * which will be later filled with the escape value.
 */
class V8_EXPORT EscapableHandleScope : public HandleScope {
 public:
  EscapableHandleScope(Isolate* isolate);
  V8_INLINE ~EscapableHandleScope() {}

  /**
   * Pushes the value into the previous scope and returns a handle to it.
   * Cannot be called twice.
   */
  template <class T>
  V8_INLINE Local<T> Escape(Local<T> value) {
    internal::Object** slot =
        Escape(reinterpret_cast<internal::Object**>(*value));
    return Local<T>(reinterpret_cast<T*>(slot));
  }

 private:
  internal::Object** Escape(internal::Object** escape_value);

  // Make it hard to create heap-allocated or illegal handle scopes by
  // disallowing certain operations.
  EscapableHandleScope(const EscapableHandleScope&);
  void operator=(const EscapableHandleScope&);
  void* operator new(size_t size);
  void operator delete(void*, size_t);

  internal::Object** escape_slot_;
};


/**
 * A simple Maybe type, representing an object which may or may not have a
 * value.
 */
template<class T>
struct V8_EXPORT Maybe {
  Maybe() : has_value(false) {}
  explicit Maybe(T t) : has_value(true), value(t) {}
  Maybe(bool has, T t) : has_value(has), value(t) {}

  bool has_value;
  T value;
};


// --- Special objects ---


/**
 * The superclass of values and API object templates.
 */
class V8_EXPORT Data {
 private:
  Data();
};


/**
 * Pre-compilation data that can be associated with a script.  This
 * data can be calculated for a script in advance of actually
 * compiling it, and can be stored between compilations.  When script
 * data is given to the compile method compilation will be faster.
 */
class V8_EXPORT ScriptData {  // NOLINT
 public:
  virtual ~ScriptData() { }

  /**
   * Pre-compiles the specified script (context-independent).
   *
   * \param input Pointer to UTF-8 script source code.
   * \param length Length of UTF-8 script source code.
   */
  static ScriptData* PreCompile(const char* input, int length);

  /**
   * Pre-compiles the specified script (context-independent).
   *
   * NOTE: Pre-compilation using this method cannot happen on another thread
   * without using Lockers.
   *
   * \param source Script source code.
   */
  static ScriptData* PreCompile(Handle<String> source);

  /**
   * Load previous pre-compilation data.
   *
   * \param data Pointer to data returned by a call to Data() of a previous
   *   ScriptData. Ownership is not transferred.
   * \param length Length of data.
   */
  static ScriptData* New(const char* data, int length);

  /**
   * Returns the length of Data().
   */
  virtual int Length() = 0;

  /**
   * Returns a serialized representation of this ScriptData that can later be
   * passed to New(). NOTE: Serialized data is platform-dependent.
   */
  virtual const char* Data() = 0;

  /**
   * Returns true if the source code could not be parsed.
   */
  virtual bool HasError() = 0;
};


/**
 * The origin, within a file, of a script.
 */
class ScriptOrigin {
 public:
  V8_INLINE ScriptOrigin(
      Handle<Value> resource_name,
      Handle<Integer> resource_line_offset = Handle<Integer>(),
      Handle<Integer> resource_column_offset = Handle<Integer>(),
      Handle<Boolean> resource_is_shared_cross_origin = Handle<Boolean>())
      : resource_name_(resource_name),
        resource_line_offset_(resource_line_offset),
        resource_column_offset_(resource_column_offset),
        resource_is_shared_cross_origin_(resource_is_shared_cross_origin) { }
  V8_INLINE Handle<Value> ResourceName() const;
  V8_INLINE Handle<Integer> ResourceLineOffset() const;
  V8_INLINE Handle<Integer> ResourceColumnOffset() const;
  V8_INLINE Handle<Boolean> ResourceIsSharedCrossOrigin() const;
 private:
  Handle<Value> resource_name_;
  Handle<Integer> resource_line_offset_;
  Handle<Integer> resource_column_offset_;
  Handle<Boolean> resource_is_shared_cross_origin_;
};


/**
 * A compiled JavaScript script.
 */
class V8_EXPORT Script {
 public:
  /**
   * Compiles the specified script (context-independent).
   *
   * \param source Script source code.
   * \param origin Script origin, owned by caller, no references are kept
   *   when New() returns
   * \param pre_data Pre-parsing data, as obtained by ScriptData::PreCompile()
   *   using pre_data speeds compilation if it's done multiple times.
   *   Owned by caller, no references are kept when New() returns.
   * \param script_data Arbitrary data associated with script. Using
   *   this has same effect as calling SetData(), but allows data to be
   *   available to compile event handlers.
   * \return Compiled script object (context independent; when run it
   *   will use the currently entered context).
   */
  static Local<Script> New(Handle<String> source,
                           ScriptOrigin* origin = NULL,
                           ScriptData* pre_data = NULL,
                           Handle<String> script_data = Handle<String>());

  /**
   * Compiles the specified script using the specified file name
   * object (typically a string) as the script's origin.
   *
   * \param source Script source code.
   * \param file_name file name object (typically a string) to be used
   *   as the script's origin.
   * \return Compiled script object (context independent; when run it
   *   will use the currently entered context).
   */
  static Local<Script> New(Handle<String> source,
                           Handle<Value> file_name);

  /**
   * Compiles the specified script (bound to current context).
   *
   * \param source Script source code.
   * \param origin Script origin, owned by caller, no references are kept
   *   when Compile() returns
   * \param pre_data Pre-parsing data, as obtained by ScriptData::PreCompile()
   *   using pre_data speeds compilation if it's done multiple times.
   *   Owned by caller, no references are kept when Compile() returns.
   * \param script_data Arbitrary data associated with script. Using
   *   this has same effect as calling SetData(), but makes data available
   *   earlier (i.e. to compile event handlers).
   * \return Compiled script object, bound to the context that was active
   *   when this function was called.  When run it will always use this
   *   context.
   */
  static Local<Script> Compile(Handle<String> source,
                               ScriptOrigin* origin = NULL,
                               ScriptData* pre_data = NULL,
                               Handle<String> script_data = Handle<String>());

  /**
   * Compiles the specified script using the specified file name
   * object (typically a string) as the script's origin.
   *
   * \param source Script source code.
   * \param file_name File name to use as script's origin
   * \param script_data Arbitrary data associated with script. Using
   *   this has same effect as calling SetData(), but makes data available
   *   earlier (i.e. to compile event handlers).
   * \return Compiled script object, bound to the context that was active
   *   when this function was called.  When run it will always use this
   *   context.
   */
  static Local<Script> Compile(Handle<String> source,
                               Handle<Value> file_name,
                               Handle<String> script_data = Handle<String>());

  /**
   * Runs the script returning the resulting value.  If the script is
   * context independent (created using ::New) it will be run in the
   * currently entered context.  If it is context specific (created
   * using ::Compile) it will be run in the context in which it was
   * compiled.
   */
  Local<Value> Run();

  /**
   * Returns the script id value.
   * DEPRECATED: Please use GetId().
   */
  Local<Value> Id();

  /**
   * Returns the script id.
   */
  int GetId();

  /**
   * Associate an additional data object with the script. This is mainly used
   * with the debugger as this data object is only available through the
   * debugger API.
   */
  void SetData(Handle<String> data);

  /**
   * Returns the name value of one Script.
   */
  Handle<Value> GetScriptName();

  /**
   * Returns zero based line number of the code_pos location in the script.
   * -1 will be returned if no information available.
   */
  int GetLineNumber(int code_pos);

  static const int kNoScriptId = 0;
};


/**
 * An error message.
 */
class V8_EXPORT Message {
 public:
  Local<String> Get() const;
  Local<String> GetSourceLine() const;

  /**
   * Returns the resource name for the script from where the function causing
   * the error originates.
   */
  Handle<Value> GetScriptResourceName() const;

  /**
   * Returns the resource data for the script from where the function causing
   * the error originates.
   */
  Handle<Value> GetScriptData() const;

  /**
   * Exception stack trace. By default stack traces are not captured for
   * uncaught exceptions. SetCaptureStackTraceForUncaughtExceptions allows
   * to change this option.
   */
  Handle<StackTrace> GetStackTrace() const;

  /**
   * Returns the number, 1-based, of the line where the error occurred.
   */
  int GetLineNumber() const;

  /**
   * Returns the index within the script of the first character where
   * the error occurred.
   */
  int GetStartPosition() const;

  /**
   * Returns the index within the script of the last character where
   * the error occurred.
   */
  int GetEndPosition() const;

  /**
   * Returns the index within the line of the first character where
   * the error occurred.
   */
  int GetStartColumn() const;

  /**
   * Returns the index within the line of the last character where
   * the error occurred.
   */
  int GetEndColumn() const;

  /**
   * Passes on the value set by the embedder when it fed the script from which
   * this Message was generated to V8.
   */
  bool IsSharedCrossOrigin() const;

  // TODO(1245381): Print to a string instead of on a FILE.
  static void PrintCurrentStackTrace(FILE* out);

  static const int kNoLineNumberInfo = 0;
  static const int kNoColumnInfo = 0;
  static const int kNoScriptIdInfo = 0;
};


/**
 * Representation of a JavaScript stack trace. The information collected is a
 * snapshot of the execution stack and the information remains valid after
 * execution continues.
 */
class V8_EXPORT StackTrace {
 public:
  /**
   * Flags that determine what information is placed captured for each
   * StackFrame when grabbing the current stack trace.
   */
  enum StackTraceOptions {
    kLineNumber = 1,
    kColumnOffset = 1 << 1 | kLineNumber,
    kScriptName = 1 << 2,
    kFunctionName = 1 << 3,
    kIsEval = 1 << 4,
    kIsConstructor = 1 << 5,
    kScriptNameOrSourceURL = 1 << 6,
    kScriptId = 1 << 7,
    kOverview = kLineNumber | kColumnOffset | kScriptName | kFunctionName,
    kDetailed = kOverview | kIsEval | kIsConstructor | kScriptNameOrSourceURL
  };

  /**
   * Returns a StackFrame at a particular index.
   */
  Local<StackFrame> GetFrame(uint32_t index) const;

  /**
   * Returns the number of StackFrames.
   */
  int GetFrameCount() const;

  /**
   * Returns StackTrace as a v8::Array that contains StackFrame objects.
   */
  Local<Array> AsArray();

  /**
   * Grab a snapshot of the current JavaScript execution stack.
   *
   * \param frame_limit The maximum number of stack frames we want to capture.
   * \param options Enumerates the set of things we will capture for each
   *   StackFrame.
   */
  static Local<StackTrace> CurrentStackTrace(
      int frame_limit,
      StackTraceOptions options = kOverview);
};


/**
 * A single JavaScript stack frame.
 */
class V8_EXPORT StackFrame {
 public:
  /**
   * Returns the number, 1-based, of the line for the associate function call.
   * This method will return Message::kNoLineNumberInfo if it is unable to
   * retrieve the line number, or if kLineNumber was not passed as an option
   * when capturing the StackTrace.
   */
  int GetLineNumber() const;

  /**
   * Returns the 1-based column offset on the line for the associated function
   * call.
   * This method will return Message::kNoColumnInfo if it is unable to retrieve
   * the column number, or if kColumnOffset was not passed as an option when
   * capturing the StackTrace.
   */
  int GetColumn() const;

  /**
   * Returns the id of the script for the function for this StackFrame.
   * This method will return Message::kNoScriptIdInfo if it is unable to
   * retrieve the script id, or if kScriptId was not passed as an option when
   * capturing the StackTrace.
   */
  int GetScriptId() const;

  /**
   * Returns the name of the resource that contains the script for the
   * function for this StackFrame.
   */
  Local<String> GetScriptName() const;

  /**
   * Returns the name of the resource that contains the script for the
   * function for this StackFrame or sourceURL value if the script name
   * is undefined and its source ends with //# sourceURL=... string or
   * deprecated //@ sourceURL=... string.
   */
  Local<String> GetScriptNameOrSourceURL() const;

  /**
   * Returns the name of the function associated with this stack frame.
   */
  Local<String> GetFunctionName() const;

  /**
   * Returns whether or not the associated function is compiled via a call to
   * eval().
   */
  bool IsEval() const;

  /**
   * Returns whether or not the associated function is called as a
   * constructor via "new".
   */
  bool IsConstructor() const;
};


/**
 * A JSON Parser.
 */
class V8_EXPORT JSON {
 public:
  /**
   * Tries to parse the string |json_string| and returns it as value if
   * successful.
   *
   * \param json_string The string to parse.
   * \return The corresponding value if successfully parsed.
   */
  static Local<Value> Parse(Local<String> json_string);
};


// --- Value ---


/**
 * The superclass of all JavaScript values and objects.
 */
class V8_EXPORT Value : public Data {
 public:
  /**
   * Returns true if this value is the undefined value.  See ECMA-262
   * 4.3.10.
   */
  V8_INLINE bool IsUndefined() const;

  /**
   * Returns true if this value is the null value.  See ECMA-262
   * 4.3.11.
   */
  V8_INLINE bool IsNull() const;

   /**
   * Returns true if this value is true.
   */
  bool IsTrue() const;

  /**
   * Returns true if this value is false.
   */
  bool IsFalse() const;

  /**
   * Returns true if this value is an instance of the String type.
   * See ECMA-262 8.4.
   */
  V8_INLINE bool IsString() const;

  /**
   * Returns true if this value is a symbol.
   * This is an experimental feature.
   */
  bool IsSymbol() const;

  /**
   * Returns true if this value is a function.
   */
  bool IsFunction() const;

  /**
   * Returns true if this value is an array.
   */
  bool IsArray() const;

  /**
   * Returns true if this value is an object.
   */
  bool IsObject() const;

  /**
   * Returns true if this value is boolean.
   */
  bool IsBoolean() const;

  /**
   * Returns true if this value is a number.
   */
  bool IsNumber() const;

  /**
   * Returns true if this value is external.
   */
  bool IsExternal() const;

  /**
   * Returns true if this value is a 32-bit signed integer.
   */
  bool IsInt32() const;

  /**
   * Returns true if this value is a 32-bit unsigned integer.
   */
  bool IsUint32() const;

  /**
   * Returns true if this value is a Date.
   */
  bool IsDate() const;

  /**
   * Returns true if this value is a Boolean object.
   */
  bool IsBooleanObject() const;

  /**
   * Returns true if this value is a Number object.
   */
  bool IsNumberObject() const;

  /**
   * Returns true if this value is a String object.
   */
  bool IsStringObject() const;

  /**
   * Returns true if this value is a Symbol object.
   * This is an experimental feature.
   */
  bool IsSymbolObject() const;

  /**
   * Returns true if this value is a NativeError.
   */
  bool IsNativeError() const;

  /**
   * Returns true if this value is a RegExp.
   */
  bool IsRegExp() const;


  /**
   * Returns true if this value is an ArrayBuffer.
   * This is an experimental feature.
   */
  bool IsArrayBuffer() const;

  /**
   * Returns true if this value is an ArrayBufferView.
   * This is an experimental feature.
   */
  bool IsArrayBufferView() const;

  /**
   * Returns true if this value is one of TypedArrays.
   * This is an experimental feature.
   */
  bool IsTypedArray() const;

  /**
   * Returns true if this value is an Uint8Array.
   * This is an experimental feature.
   */
  bool IsUint8Array() const;

  /**
   * Returns true if this value is an Uint8ClampedArray.
   * This is an experimental feature.
   */
  bool IsUint8ClampedArray() const;

  /**
   * Returns true if this value is an Int8Array.
   * This is an experimental feature.
   */
  bool IsInt8Array() const;

  /**
   * Returns true if this value is an Uint16Array.
   * This is an experimental feature.
   */
  bool IsUint16Array() const;

  /**
   * Returns true if this value is an Int16Array.
   * This is an experimental feature.
   */
  bool IsInt16Array() const;

  /**
   * Returns true if this value is an Uint32Array.
   * This is an experimental feature.
   */
  bool IsUint32Array() const;

  /**
   * Returns true if this value is an Int32Array.
   * This is an experimental feature.
   */
  bool IsInt32Array() const;

  /**
   * Returns true if this value is a Float32Array.
   * This is an experimental feature.
   */
  bool IsFloat32Array() const;

  /**
   * Returns true if this value is a Float64Array.
   * This is an experimental feature.
   */
  bool IsFloat64Array() const;

  /**
   * Returns true if this value is a DataView.
   * This is an experimental feature.
   */
  bool IsDataView() const;

  Local<Boolean> ToBoolean() const;
  Local<Number> ToNumber() const;
  Local<String> ToString() const;
  Local<String> ToDetailString() const;
  Local<Object> ToObject() const;
  Local<Integer> ToInteger() const;
  Local<Uint32> ToUint32() const;
  Local<Int32> ToInt32() const;

  /**
   * Attempts to convert a string to an array index.
   * Returns an empty handle if the conversion fails.
   */
  Local<Uint32> ToArrayIndex() const;

  bool BooleanValue() const;
  double NumberValue() const;
  int64_t IntegerValue() const;
  uint32_t Uint32Value() const;
  int32_t Int32Value() const;

  /** JS == */
  bool Equals(Handle<Value> that) const;
  bool StrictEquals(Handle<Value> that) const;
  bool SameValue(Handle<Value> that) const;

  template <class T> V8_INLINE static Value* Cast(T* value);

 private:
  V8_INLINE bool QuickIsUndefined() const;
  V8_INLINE bool QuickIsNull() const;
  V8_INLINE bool QuickIsString() const;
  bool FullIsUndefined() const;
  bool FullIsNull() const;
  bool FullIsString() const;
};


/**
 * The superclass of primitive values.  See ECMA-262 4.3.2.
 */
class V8_EXPORT Primitive : public Value { };


/**
 * A primitive boolean value (ECMA-262, 4.3.14).  Either the true
 * or false value.
 */
class V8_EXPORT Boolean : public Primitive {
 public:
  bool Value() const;
  V8_INLINE static Handle<Boolean> New(bool value);
};


/**
 * A JavaScript string value (ECMA-262, 4.3.17).
 */
class V8_EXPORT String : public Primitive {
 public:
  enum Encoding {
    UNKNOWN_ENCODING = 0x1,
    TWO_BYTE_ENCODING = 0x0,
    ASCII_ENCODING = 0x4,
    ONE_BYTE_ENCODING = 0x4
  };
  /**
   * Returns the number of characters in this string.
   */
  int Length() const;

  /**
   * Returns the number of bytes in the UTF-8 encoded
   * representation of this string.
   */
  int Utf8Length() const;

  /**
   * This function is no longer useful.
   */
  V8_DEPRECATED(V8_INLINE bool MayContainNonAscii() const) { return true; }

  /**
   * Returns whether this string is known to contain only one byte data.
   * Does not read the string.
   * False negatives are possible.
   */
  bool IsOneByte() const;

  /**
   * Returns whether this string contain only one byte data.
   * Will read the entire string in some cases.
   */
  bool ContainsOnlyOneByte() const;

  /**
   * Write the contents of the string to an external buffer.
   * If no arguments are given, expects the buffer to be large
   * enough to hold the entire string and NULL terminator. Copies
   * the contents of the string and the NULL terminator into the
   * buffer.
   *
   * WriteUtf8 will not write partial UTF-8 sequences, preferring to stop
   * before the end of the buffer.
   *
   * Copies up to length characters into the output buffer.
   * Only null-terminates if there is enough space in the buffer.
   *
   * \param buffer The buffer into which the string will be copied.
   * \param start The starting position within the string at which
   * copying begins.
   * \param length The number of characters to copy from the string.  For
   *    WriteUtf8 the number of bytes in the buffer.
   * \param nchars_ref The number of characters written, can be NULL.
   * \param options Various options that might affect performance of this or
   *    subsequent operations.
   * \return The number of characters copied to the buffer excluding the null
   *    terminator.  For WriteUtf8: The number of bytes copied to the buffer
   *    including the null terminator (if written).
   */
  enum WriteOptions {
    NO_OPTIONS = 0,
    HINT_MANY_WRITES_EXPECTED = 1,
    NO_NULL_TERMINATION = 2,
    PRESERVE_ASCII_NULL = 4
  };

  // 16-bit character codes.
  int Write(uint16_t* buffer,
            int start = 0,
            int length = -1,
            int options = NO_OPTIONS) const;
  // ASCII characters.
  V8_DEPRECATED(int WriteAscii(char* buffer,
                               int start = 0,
                               int length = -1,
                               int options = NO_OPTIONS) const);
  // One byte characters.
  int WriteOneByte(uint8_t* buffer,
                   int start = 0,
                   int length = -1,
                   int options = NO_OPTIONS) const;
  // UTF-8 encoded characters.
  int WriteUtf8(char* buffer,
                int length = -1,
                int* nchars_ref = NULL,
                int options = NO_OPTIONS) const;

  /**
   * A zero length string.
   */
  static v8::Local<v8::String> Empty();
  V8_INLINE static v8::Local<v8::String> Empty(Isolate* isolate);

  /**
   * Returns true if the string is external
   */
  bool IsExternal() const;

  /**
   * Returns true if the string is both external and ASCII
   */
  bool IsExternalAscii() const;

  class V8_EXPORT ExternalStringResourceBase {  // NOLINT
   public:
    virtual ~ExternalStringResourceBase() {}

   protected:
    ExternalStringResourceBase() {}

    /**
     * Internally V8 will call this Dispose method when the external string
     * resource is no longer needed. The default implementation will use the
     * delete operator. This method can be overridden in subclasses to
     * control how allocated external string resources are disposed.
     */
    virtual void Dispose() { delete this; }

   private:
    // Disallow copying and assigning.
    ExternalStringResourceBase(const ExternalStringResourceBase&);
    void operator=(const ExternalStringResourceBase&);

    friend class v8::internal::Heap;
  };

  /**
   * An ExternalStringResource is a wrapper around a two-byte string
   * buffer that resides outside V8's heap. Implement an
   * ExternalStringResource to manage the life cycle of the underlying
   * buffer.  Note that the string data must be immutable.
   */
  class V8_EXPORT ExternalStringResource
      : public ExternalStringResourceBase {
   public:
    /**
     * Override the destructor to manage the life cycle of the underlying
     * buffer.
     */
    virtual ~ExternalStringResource() {}

    /**
     * The string data from the underlying buffer.
     */
    virtual const uint16_t* data() const = 0;

    /**
     * The length of the string. That is, the number of two-byte characters.
     */
    virtual size_t length() const = 0;

   protected:
    ExternalStringResource() {}
  };

  /**
   * An ExternalAsciiStringResource is a wrapper around an ASCII
   * string buffer that resides outside V8's heap. Implement an
   * ExternalAsciiStringResource to manage the life cycle of the
   * underlying buffer.  Note that the string data must be immutable
   * and that the data must be strict (7-bit) ASCII, not Latin-1 or
   * UTF-8, which would require special treatment internally in the
   * engine and, in the case of UTF-8, do not allow efficient indexing.
   * Use String::New or convert to 16 bit data for non-ASCII.
   */

  class V8_EXPORT ExternalAsciiStringResource
      : public ExternalStringResourceBase {
   public:
    /**
     * Override the destructor to manage the life cycle of the underlying
     * buffer.
     */
    virtual ~ExternalAsciiStringResource() {}
    /** The string data from the underlying buffer.*/
    virtual const char* data() const = 0;
    /** The number of ASCII characters in the string.*/
    virtual size_t length() const = 0;
   protected:
    ExternalAsciiStringResource() {}
  };

  typedef ExternalAsciiStringResource ExternalOneByteStringResource;

  /**
   * If the string is an external string, return the ExternalStringResourceBase
   * regardless of the encoding, otherwise return NULL.  The encoding of the
   * string is returned in encoding_out.
   */
  V8_INLINE ExternalStringResourceBase* GetExternalStringResourceBase(
      Encoding* encoding_out) const;

  /**
   * Get the ExternalStringResource for an external string.  Returns
   * NULL if IsExternal() doesn't return true.
   */
  V8_INLINE ExternalStringResource* GetExternalStringResource() const;

  /**
   * Get the ExternalAsciiStringResource for an external ASCII string.
   * Returns NULL if IsExternalAscii() doesn't return true.
   */
  const ExternalAsciiStringResource* GetExternalAsciiStringResource() const;

  V8_INLINE static String* Cast(v8::Value* obj);

  // TODO(dcarney): deprecate
  /**
   * Allocates a new string from either UTF-8 encoded or ASCII data.
   * The second parameter 'length' gives the buffer length. If omitted,
   * the function calls 'strlen' to determine the buffer length.
   */
  V8_INLINE static Local<String> New(const char* data, int length = -1);

  // TODO(dcarney): deprecate
  /** Allocates a new string from 16-bit character codes.*/
  V8_INLINE static Local<String> New(const uint16_t* data, int length = -1);

  // TODO(dcarney): deprecate
  /**
   * Creates an internalized string (historically called a "symbol",
   * not to be confused with ES6 symbols). Returns one if it exists already.
   */
  V8_INLINE static Local<String> NewSymbol(const char* data, int length = -1);

  enum NewStringType {
    kNormalString, kInternalizedString, kUndetectableString
  };

  /** Allocates a new string from UTF-8 data.*/
  static Local<String> NewFromUtf8(Isolate* isolate,
                                  const char* data,
                                  NewStringType type = kNormalString,
                                  int length = -1);

  /** Allocates a new string from Latin-1 data.*/
  static Local<String> NewFromOneByte(
      Isolate* isolate,
      const uint8_t* data,
      NewStringType type = kNormalString,
      int length = -1);

  /** Allocates a new string from UTF-16 data.*/
  static Local<String> NewFromTwoByte(
      Isolate* isolate,
      const uint16_t* data,
      NewStringType type = kNormalString,
      int length = -1);

  /**
   * Creates a new string by concatenating the left and the right strings
   * passed in as parameters.
   */
  static Local<String> Concat(Handle<String> left, Handle<String> right);

  /**
   * Creates a new external string using the data defined in the given
   * resource. When the external string is no longer live on V8's heap the
   * resource will be disposed by calling its Dispose method. The caller of
   * this function should not otherwise delete or modify the resource. Neither
   * should the underlying buffer be deallocated or modified except through the
   * destructor of the external string resource.
   */
  static Local<String> NewExternal(ExternalStringResource* resource);

  /**
   * Associate an external string resource with this string by transforming it
   * in place so that existing references to this string in the JavaScript heap
   * will use the external string resource. The external string resource's
   * character contents need to be equivalent to this string.
   * Returns true if the string has been changed to be an external string.
   * The string is not modified if the operation fails. See NewExternal for
   * information on the lifetime of the resource.
   */
  bool MakeExternal(ExternalStringResource* resource);

  /**
   * Creates a new external string using the ASCII data defined in the given
   * resource. When the external string is no longer live on V8's heap the
   * resource will be disposed by calling its Dispose method. The caller of
   * this function should not otherwise delete or modify the resource. Neither
   * should the underlying buffer be deallocated or modified except through the
   * destructor of the external string resource.
   */
  static Local<String> NewExternal(ExternalAsciiStringResource* resource);

  /**
   * Associate an external string resource with this string by transforming it
   * in place so that existing references to this string in the JavaScript heap
   * will use the external string resource. The external string resource's
   * character contents need to be equivalent to this string.
   * Returns true if the string has been changed to be an external string.
   * The string is not modified if the operation fails. See NewExternal for
   * information on the lifetime of the resource.
   */
  bool MakeExternal(ExternalAsciiStringResource* resource);

  /**
   * Returns true if this string can be made external.
   */
  bool CanMakeExternal();

  // TODO(dcarney): deprecate
  /** Creates an undetectable string from the supplied ASCII or UTF-8 data.*/
  V8_INLINE static Local<String> NewUndetectable(const char* data,
                                                 int length = -1);

  // TODO(dcarney): deprecate
  /** Creates an undetectable string from the supplied 16-bit character codes.*/
  V8_INLINE static Local<String> NewUndetectable(const uint16_t* data,
                                                 int length = -1);

  /**
   * Converts an object to a UTF-8-encoded character array.  Useful if
   * you want to print the object.  If conversion to a string fails
   * (e.g. due to an exception in the toString() method of the object)
   * then the length() method returns 0 and the * operator returns
   * NULL.
   */
  class V8_EXPORT Utf8Value {
   public:
    explicit Utf8Value(Handle<v8::Value> obj);
    ~Utf8Value();
    char* operator*() { return str_; }
    const char* operator*() const { return str_; }
    int length() const { return length_; }
   private:
    char* str_;
    int length_;

    // Disallow copying and assigning.
    Utf8Value(const Utf8Value&);
    void operator=(const Utf8Value&);
  };

  /**
   * Converts an object to an ASCII string.
   * Useful if you want to print the object.
   * If conversion to a string fails (eg. due to an exception in the toString()
   * method of the object) then the length() method returns 0 and the * operator
   * returns NULL.
   */
  class V8_EXPORT AsciiValue {
   public:
    // TODO(dcarney): deprecate
    explicit AsciiValue(Handle<v8::Value> obj);
    ~AsciiValue();
    char* operator*() { return str_; }
    const char* operator*() const { return str_; }
    int length() const { return length_; }
   private:
    char* str_;
    int length_;

    // Disallow copying and assigning.
    AsciiValue(const AsciiValue&);
    void operator=(const AsciiValue&);
  };

  /**
   * Converts an object to a two-byte string.
   * If conversion to a string fails (eg. due to an exception in the toString()
   * method of the object) then the length() method returns 0 and the * operator
   * returns NULL.
   */
  class V8_EXPORT Value {
   public:
    explicit Value(Handle<v8::Value> obj);
    ~Value();
    uint16_t* operator*() { return str_; }
    const uint16_t* operator*() const { return str_; }
    int length() const { return length_; }
   private:
    uint16_t* str_;
    int length_;

    // Disallow copying and assigning.
    Value(const Value&);
    void operator=(const Value&);
  };

 private:
  void VerifyExternalStringResourceBase(ExternalStringResourceBase* v,
                                        Encoding encoding) const;
  void VerifyExternalStringResource(ExternalStringResource* val) const;
  static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript symbol (ECMA-262 edition 6)
 *
 * This is an experimental feature. Use at your own risk.
 */
class V8_EXPORT Symbol : public Primitive {
 public:
  // Returns the print name string of the symbol, or undefined if none.
  Local<Value> Name() const;

  // Create a symbol without a print name.
  static Local<Symbol> New(Isolate* isolate);

  // Create a symbol with a print name.
  static Local<Symbol> New(Isolate *isolate, const char* data, int length = -1);

  V8_INLINE static Symbol* Cast(v8::Value* obj);
 private:
  Symbol();
  static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript number value (ECMA-262, 4.3.20)
 */
class V8_EXPORT Number : public Primitive {
 public:
  double Value() const;
  static Local<Number> New(double value);
  static Local<Number> New(Isolate* isolate, double value);
  V8_INLINE static Number* Cast(v8::Value* obj);
 private:
  Number();
  static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript value representing a signed integer.
 */
class V8_EXPORT Integer : public Number {
 public:
  static Local<Integer> New(int32_t value);
  static Local<Integer> NewFromUnsigned(uint32_t value);
  static Local<Integer> New(int32_t value, Isolate*);
  static Local<Integer> NewFromUnsigned(uint32_t value, Isolate*);
  int64_t Value() const;
  V8_INLINE static Integer* Cast(v8::Value* obj);
 private:
  Integer();
  static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript value representing a 32-bit signed integer.
 */
class V8_EXPORT Int32 : public Integer {
 public:
  int32_t Value() const;
 private:
  Int32();
};


/**
 * A JavaScript value representing a 32-bit unsigned integer.
 */
class V8_EXPORT Uint32 : public Integer {
 public:
  uint32_t Value() const;
 private:
  Uint32();
};


enum PropertyAttribute {
  None       = 0,
  ReadOnly   = 1 << 0,
  DontEnum   = 1 << 1,
  DontDelete = 1 << 2
};

enum ExternalArrayType {
  kExternalByteArray = 1,
  kExternalUnsignedByteArray,
  kExternalShortArray,
  kExternalUnsignedShortArray,
  kExternalIntArray,
  kExternalUnsignedIntArray,
  kExternalFloatArray,
  kExternalDoubleArray,
  kExternalPixelArray
};

/**
 * Accessor[Getter|Setter] are used as callback functions when
 * setting|getting a particular property. See Object and ObjectTemplate's
 * method SetAccessor.
 */
typedef void (*AccessorGetterCallback)(
    Local<String> property,
    const PropertyCallbackInfo<Value>& info);


typedef void (*AccessorSetterCallback)(
    Local<String> property,
    Local<Value> value,
    const PropertyCallbackInfo<void>& info);


/**
 * Access control specifications.
 *
 * Some accessors should be accessible across contexts.  These
 * accessors have an explicit access control parameter which specifies
 * the kind of cross-context access that should be allowed.
 *
 * Additionally, for security, accessors can prohibit overwriting by
 * accessors defined in JavaScript.  For objects that have such
 * accessors either locally or in their prototype chain it is not
 * possible to overwrite the accessor by using __defineGetter__ or
 * __defineSetter__ from JavaScript code.
 */
enum AccessControl {
  DEFAULT               = 0,
  ALL_CAN_READ          = 1,
  ALL_CAN_WRITE         = 1 << 1,
  PROHIBITS_OVERWRITING = 1 << 2
};


/**
 * A JavaScript object (ECMA-262, 4.3.3)
 */
class V8_EXPORT Object : public Value {
 public:
  bool Set(Handle<Value> key,
           Handle<Value> value,
           PropertyAttribute attribs = None);

  bool Set(uint32_t index, Handle<Value> value);

  // Sets a local property on this object bypassing interceptors and
  // overriding accessors or read-only properties.
  //
  // Note that if the object has an interceptor the property will be set
  // locally, but since the interceptor takes precedence the local property
  // will only be returned if the interceptor doesn't return a value.
  //
  // Note also that this only works for named properties.
  bool ForceSet(Handle<Value> key,
                Handle<Value> value,
                PropertyAttribute attribs = None);

  Local<Value> Get(Handle<Value> key);

  Local<Value> Get(uint32_t index);

  /**
   * Gets the property attributes of a property which can be None or
   * any combination of ReadOnly, DontEnum and DontDelete. Returns
   * None when the property doesn't exist.
   */
  PropertyAttribute GetPropertyAttributes(Handle<Value> key);

  bool Has(Handle<Value> key);

  bool Delete(Handle<Value> key);

  // Delete a property on this object bypassing interceptors and
  // ignoring dont-delete attributes.
  bool ForceDelete(Handle<Value> key);

  bool Has(uint32_t index);

  bool Delete(uint32_t index);

  bool SetAccessor(Handle<String> name,
                   AccessorGetterCallback getter,
                   AccessorSetterCallback setter = 0,
                   Handle<Value> data = Handle<Value>(),
                   AccessControl settings = DEFAULT,
                   PropertyAttribute attribute = None);

  // This function is not yet stable and should not be used at this time.
  bool SetDeclaredAccessor(Local<String> name,
                           Local<DeclaredAccessorDescriptor> descriptor,
                           PropertyAttribute attribute = None,
                           AccessControl settings = DEFAULT);

  /**
   * Returns an array containing the names of the enumerable properties
   * of this object, including properties from prototype objects.  The
   * array returned by this method contains the same values as would
   * be enumerated by a for-in statement over this object.
   */
  Local<Array> GetPropertyNames();

  /**
   * This function has the same functionality as GetPropertyNames but
   * the returned array doesn't contain the names of properties from
   * prototype objects.
   */
  Local<Array> GetOwnPropertyNames();

  /**
   * Get the prototype object.  This does not skip objects marked to
   * be skipped by __proto__ and it does not consult the security
   * handler.
   */
  Local<Value> GetPrototype();

  /**
   * Set the prototype object.  This does not skip objects marked to
   * be skipped by __proto__ and it does not consult the security
   * handler.
   */
  bool SetPrototype(Handle<Value> prototype);

  /**
   * Finds an instance of the given function template in the prototype
   * chain.
   */
  Local<Object> FindInstanceInPrototypeChain(Handle<FunctionTemplate> tmpl);

  /**
   * Call builtin Object.prototype.toString on this object.
   * This is different from Value::ToString() that may call
   * user-defined toString function. This one does not.
   */
  Local<String> ObjectProtoToString();

  /**
   * Returns the function invoked as a constructor for this object.
   * May be the null value.
   */
  Local<Value> GetConstructor();

  /**
   * Returns the name of the function invoked as a constructor for this object.
   */
  Local<String> GetConstructorName();

  /** Gets the number of internal fields for this Object. */
  int InternalFieldCount();

  /** Gets the value from an internal field. */
  V8_INLINE Local<Value> GetInternalField(int index);

  /** Sets the value in an internal field. */
  void SetInternalField(int index, Handle<Value> value);

  /**
   * Gets a 2-byte-aligned native pointer from an internal field. This field
   * must have been set by SetAlignedPointerInInternalField, everything else
   * leads to undefined behavior.
   */
  V8_INLINE void* GetAlignedPointerFromInternalField(int index);

  /**
   * Sets a 2-byte-aligned native pointer in an internal field. To retrieve such
   * a field, GetAlignedPointerFromInternalField must be used, everything else
   * leads to undefined behavior.
   */
  void SetAlignedPointerInInternalField(int index, void* value);

  // Testers for local properties.
  bool HasOwnProperty(Handle<String> key);
  bool HasRealNamedProperty(Handle<String> key);
  bool HasRealIndexedProperty(uint32_t index);
  bool HasRealNamedCallbackProperty(Handle<String> key);

  /**
   * If result.IsEmpty() no real property was located in the prototype chain.
   * This means interceptors in the prototype chain are not called.
   */
  Local<Value> GetRealNamedPropertyInPrototypeChain(Handle<String> key);

  /**
   * If result.IsEmpty() no real property was located on the object or
   * in the prototype chain.
   * This means interceptors in the prototype chain are not called.
   */
  Local<Value> GetRealNamedProperty(Handle<String> key);

  /** Tests for a named lookup interceptor.*/
  bool HasNamedLookupInterceptor();

  /** Tests for an index lookup interceptor.*/
  bool HasIndexedLookupInterceptor();

  /**
   * Turns on access check on the object if the object is an instance of
   * a template that has access check callbacks. If an object has no
   * access check info, the object cannot be accessed by anyone.
   */
  void TurnOnAccessCheck();

  /**
   * Returns the identity hash for this object. The current implementation
   * uses a hidden property on the object to store the identity hash.
   *
   * The return value will never be 0. Also, it is not guaranteed to be
   * unique.
   */
  int GetIdentityHash();

  /**
   * Access hidden properties on JavaScript objects. These properties are
   * hidden from the executing JavaScript and only accessible through the V8
   * C++ API. Hidden properties introduced by V8 internally (for example the
   * identity hash) are prefixed with "v8::".
   */
  bool SetHiddenValue(Handle<String> key, Handle<Value> value);
  Local<Value> GetHiddenValue(Handle<String> key);
  bool DeleteHiddenValue(Handle<String> key);

  /**
   * Returns true if this is an instance of an api function (one
   * created from a function created from a function template) and has
   * been modified since it was created.  Note that this method is
   * conservative and may return true for objects that haven't actually
   * been modified.
   */
  bool IsDirty();

  /**
   * Clone this object with a fast but shallow copy.  Values will point
   * to the same values as the original object.
   */
  Local<Object> Clone();

  /**
   * Returns the context in which the object was created.
   */
  Local<Context> CreationContext();

  /**
   * Set the backing store of the indexed properties to be managed by the
   * embedding layer. Access to the indexed properties will follow the rules
   * spelled out in CanvasPixelArray.
   * Note: The embedding program still owns the data and needs to ensure that
   *       the backing store is preserved while V8 has a reference.
   */
  void SetIndexedPropertiesToPixelData(uint8_t* data, int length);
  bool HasIndexedPropertiesInPixelData();
  uint8_t* GetIndexedPropertiesPixelData();
  int GetIndexedPropertiesPixelDataLength();

  /**
   * Set the backing store of the indexed properties to be managed by the
   * embedding layer. Access to the indexed properties will follow the rules
   * spelled out for the CanvasArray subtypes in the WebGL specification.
   * Note: The embedding program still owns the data and needs to ensure that
   *       the backing store is preserved while V8 has a reference.
   */
  void SetIndexedPropertiesToExternalArrayData(void* data,
                                               ExternalArrayType array_type,
                                               int number_of_elements);
  bool HasIndexedPropertiesInExternalArrayData();
  void* GetIndexedPropertiesExternalArrayData();
  ExternalArrayType GetIndexedPropertiesExternalArrayDataType();
  int GetIndexedPropertiesExternalArrayDataLength();

  /**
   * Checks whether a callback is set by the
   * ObjectTemplate::SetCallAsFunctionHandler method.
   * When an Object is callable this method returns true.
   */
  bool IsCallable();

  /**
   * Call an Object as a function if a callback is set by the
   * ObjectTemplate::SetCallAsFunctionHandler method.
   */
  Local<Value> CallAsFunction(Handle<Object> recv,
                              int argc,
                              Handle<Value> argv[]);

  /**
   * Call an Object as a constructor if a callback is set by the
   * ObjectTemplate::SetCallAsFunctionHandler method.
   * Note: This method behaves like the Function::NewInstance method.
   */
  Local<Value> CallAsConstructor(int argc, Handle<Value> argv[]);

  static Local<Object> New();
  V8_INLINE static Object* Cast(Value* obj);

 private:
  Object();
  static void CheckCast(Value* obj);
  Local<Value> SlowGetInternalField(int index);
  void* SlowGetAlignedPointerFromInternalField(int index);
};


/**
 * An instance of the built-in array constructor (ECMA-262, 15.4.2).
 */
class V8_EXPORT Array : public Object {
 public:
  uint32_t Length() const;

  /**
   * Clones an element at index |index|.  Returns an empty
   * handle if cloning fails (for any reason).
   */
  Local<Object> CloneElementAt(uint32_t index);

  /**
   * Creates a JavaScript array with the given length. If the length
   * is negative the returned array will have length 0.
   */
  static Local<Array> New(int length = 0);

  V8_INLINE static Array* Cast(Value* obj);
 private:
  Array();
  static void CheckCast(Value* obj);
};


template<typename T>
class ReturnValue {
 public:
  template <class S> V8_INLINE ReturnValue(const ReturnValue<S>& that)
      : value_(that.value_) {
    TYPE_CHECK(T, S);
  }
  // Handle setters
  template <typename S> V8_INLINE void Set(const Persistent<S>& handle);
  template <typename S> V8_INLINE void Set(const Handle<S> handle);
  // 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();

 private:
  template<class F> friend class ReturnValue;
  template<class F> friend class FunctionCallbackInfo;
  template<class F> friend class PropertyCallbackInfo;
  V8_INLINE internal::Object* GetDefaultValue();
  V8_INLINE explicit ReturnValue(internal::Object** slot);
  internal::Object** value_;
};


/**
 * The argument information given to function call callbacks.  This
 * class provides access to information about the context of the call,
 * including the receiver, the number and values of arguments, and
 * the holder of the function.
 */
template<typename T>
class FunctionCallbackInfo {
 public:
  V8_INLINE int Length() const;
  V8_INLINE Local<Value> operator[](int i) const;
  V8_INLINE Local<Function> Callee() const;
  V8_INLINE Local<Object> This() const;
  V8_INLINE Local<Object> Holder() const;
  V8_INLINE bool IsConstructCall() const;
  V8_INLINE Local<Value> Data() const;
  V8_INLINE Isolate* GetIsolate() const;
  V8_INLINE ReturnValue<T> GetReturnValue() const;
  // This shouldn't be public, but the arm compiler needs it.
  static const int kArgsLength = 7;

 protected:
  friend class internal::FunctionCallbackArguments;
  friend class internal::CustomArguments<FunctionCallbackInfo>;
  static const int kContextSaveIndex = 0;
  static const int kCalleeIndex = -1;
  static const int kDataIndex = -2;
  static const int kReturnValueIndex = -3;
  static const int kReturnValueDefaultValueIndex = -4;
  static const int kIsolateIndex = -5;
  static const int kHolderIndex = -6;

  V8_INLINE FunctionCallbackInfo(internal::Object** implicit_args,
                   internal::Object** values,
                   int length,
                   bool is_construct_call);
  internal::Object** implicit_args_;
  internal::Object** values_;
  int length_;
  bool is_construct_call_;
};


/**
 * The information passed to a property callback about the context
 * of the property access.
 */
template<typename T>
class PropertyCallbackInfo {
 public:
  V8_INLINE Isolate* GetIsolate() const;
  V8_INLINE Local<Value> Data() const;
  V8_INLINE Local<Object> This() const;
  V8_INLINE Local<Object> Holder() const;
  V8_INLINE ReturnValue<T> GetReturnValue() const;
  // This shouldn't be public, but the arm compiler needs it.
  static const int kArgsLength = 6;

 protected:
  friend class MacroAssembler;
  friend class internal::PropertyCallbackArguments;
  friend class internal::CustomArguments<PropertyCallbackInfo>;
  static const int kThisIndex = 0;
  static const int kDataIndex = -1;
  static const int kReturnValueIndex = -2;
  static const int kReturnValueDefaultValueIndex = -3;
  static const int kIsolateIndex = -4;
  static const int kHolderIndex = -5;

  V8_INLINE PropertyCallbackInfo(internal::Object** args) : args_(args) {}
  internal::Object** args_;
};


typedef void (*FunctionCallback)(const FunctionCallbackInfo<Value>& info);


/**
 * A JavaScript function object (ECMA-262, 15.3).
 */
class V8_EXPORT Function : public Object {
 public:
  /**
   * Create a function in the current execution context
   * for a given FunctionCallback.
   */
  static Local<Function> New(Isolate* isolate,
                             FunctionCallback callback,
                             Local<Value> data = Local<Value>(),
                             int length = 0);

  Local<Object> NewInstance() const;
  Local<Object> NewInstance(int argc, Handle<Value> argv[]) const;
  Local<Value> Call(Handle<Object> recv, int argc, Handle<Value> argv[]);
  void SetName(Handle<String> name);
  Handle<Value> GetName() const;

  /**
   * Name inferred from variable or property assignment of this function.
   * Used to facilitate debugging and profiling of JavaScript code written
   * in an OO style, where many functions are anonymous but are assigned
   * to object properties.
   */
  Handle<Value> GetInferredName() const;

  /**
   * Returns zero based line number of function body and
   * kLineOffsetNotFound if no information available.
   */
  int GetScriptLineNumber() const;
  /**
   * Returns zero based column number of function body and
   * kLineOffsetNotFound if no information available.
   */
  int GetScriptColumnNumber() const;

  /**
   * Returns scriptId object.
   * DEPRECATED: use ScriptId() instead.
   */
  Handle<Value> GetScriptId() const;

  /**
   * Returns scriptId.
   */
  int ScriptId() const;

  ScriptOrigin GetScriptOrigin() const;
  V8_INLINE static Function* Cast(Value* obj);
  static const int kLineOffsetNotFound;

 private:
  Function();
  static void CheckCast(Value* obj);
};

#ifndef V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT
// The number of required internal fields can be defined by embedder.
#define V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT 2
#endif

/**
 * An instance of the built-in ArrayBuffer constructor (ES6 draft 15.13.5).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT ArrayBuffer : public Object {
 public:
  /**
   * Allocator that V8 uses to allocate |ArrayBuffer|'s memory.
   * The allocator is a global V8 setting. It should be set with
   * V8::SetArrayBufferAllocator prior to creation of a first ArrayBuffer.
   *
   * This API is experimental and may change significantly.
   */
  class V8_EXPORT Allocator { // NOLINT
   public:
    virtual ~Allocator() {}

    /**
     * Allocate |length| bytes. Return NULL if allocation is not successful.
     * Memory should be initialized to zeroes.
     */
    virtual void* Allocate(size_t length) = 0;

    /**
     * Allocate |length| bytes. Return NULL if allocation is not successful.
     * Memory does not have to be initialized.
     */
    virtual void* AllocateUninitialized(size_t length) = 0;
    /**
     * Free the memory block of size |length|, pointed to by |data|.
     * That memory is guaranteed to be previously allocated by |Allocate|.
     */
    virtual void Free(void* data, size_t length) = 0;
  };

  /**
   * The contents of an |ArrayBuffer|. Externalization of |ArrayBuffer|
   * returns an instance of this class, populated, with a pointer to data
   * and byte length.
   *
   * The Data pointer of ArrayBuffer::Contents is always allocated with
   * Allocator::Allocate that is set with V8::SetArrayBufferAllocator.
   *
   * This API is experimental and may change significantly.
   */
  class V8_EXPORT Contents { // NOLINT
   public:
    Contents() : data_(NULL), byte_length_(0) {}

    void* Data() const { return data_; }
    size_t ByteLength() const { return byte_length_; }

   private:
    void* data_;
    size_t byte_length_;

    friend class ArrayBuffer;
  };


  /**
   * Data length in bytes.
   */
  size_t ByteLength() const;

  /**
   * Create a new ArrayBuffer. Allocate |byte_length| bytes.
   * Allocated memory will be owned by a created ArrayBuffer and
   * will be deallocated when it is garbage-collected,
   * unless the object is externalized.
   */
  static Local<ArrayBuffer> New(size_t byte_length);

  /**
   * Create a new ArrayBuffer over an existing memory block.
   * The created array buffer is immediately in externalized state.
   * The memory block will not be reclaimed when a created ArrayBuffer
   * is garbage-collected.
   */
  static Local<ArrayBuffer> New(void* data, size_t byte_length);

  /**
   * Returns true if ArrayBuffer is extrenalized, that is, does not
   * own its memory block.
   */
  bool IsExternal() const;

  /**
   * Neuters this ArrayBuffer and all its views (typed arrays).
   * Neutering sets the byte length of the buffer and all typed arrays to zero,
   * preventing JavaScript from ever accessing underlying backing store.
   * ArrayBuffer should have been externalized.
   */
  void Neuter();

  /**
   * Make this ArrayBuffer external. The pointer to underlying memory block
   * and byte length are returned as |Contents| structure. After ArrayBuffer
   * had been etxrenalized, it does no longer owns the memory block. The caller
   * should take steps to free memory when it is no longer needed.
   *
   * The memory block is guaranteed to be allocated with |Allocator::Allocate|
   * that has been set with V8::SetArrayBufferAllocator.
   */
  Contents Externalize();

  V8_INLINE static ArrayBuffer* Cast(Value* obj);

  static const int kInternalFieldCount = V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT;

 private:
  ArrayBuffer();
  static void CheckCast(Value* obj);
};


#ifndef V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT
// The number of required internal fields can be defined by embedder.
#define V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT 2
#endif


/**
 * A base class for an instance of one of "views" over ArrayBuffer,
 * including TypedArrays and DataView (ES6 draft 15.13).
 *
 * This API is experimental and may change significantly.
 */
class V8_EXPORT ArrayBufferView : public Object {
 public:
  /**
   * Returns underlying ArrayBuffer.
   */
  Local<ArrayBuffer> Buffer();
  /**
   * Byte offset in |Buffer|.
   */
  size_t ByteOffset();
  /**
   * Size of a view in bytes.
   */
  size_t ByteLength();
  /**
   * Base address of a view.
   */
  void* BaseAddress();

  V8_INLINE static ArrayBufferView* Cast(Value* obj);

  static const int kInternalFieldCount =
      V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT;

 private:
  ArrayBufferView();
  static void CheckCast(Value* obj);
};


/**
 * A base class for an instance of TypedArray series of constructors
 * (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT TypedArray : public ArrayBufferView {
 public:
  /**
   * Number of elements in this typed array
   * (e.g. for Int16Array, |ByteLength|/2).
   */
  size_t Length();

  V8_INLINE static TypedArray* Cast(Value* obj);

 private:
  TypedArray();
  static void CheckCast(Value* obj);
};


/**
 * An instance of Uint8Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Uint8Array : public TypedArray {
 public:
  static Local<Uint8Array> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Uint8Array* Cast(Value* obj);

 private:
  Uint8Array();
  static void CheckCast(Value* obj);
};


/**
 * An instance of Uint8ClampedArray constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Uint8ClampedArray : public TypedArray {
 public:
  static Local<Uint8ClampedArray> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Uint8ClampedArray* Cast(Value* obj);

 private:
  Uint8ClampedArray();
  static void CheckCast(Value* obj);
};

/**
 * An instance of Int8Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Int8Array : public TypedArray {
 public:
  static Local<Int8Array> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Int8Array* Cast(Value* obj);

 private:
  Int8Array();
  static void CheckCast(Value* obj);
};


/**
 * An instance of Uint16Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Uint16Array : public TypedArray {
 public:
  static Local<Uint16Array> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Uint16Array* Cast(Value* obj);

 private:
  Uint16Array();
  static void CheckCast(Value* obj);
};


/**
 * An instance of Int16Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Int16Array : public TypedArray {
 public:
  static Local<Int16Array> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Int16Array* Cast(Value* obj);

 private:
  Int16Array();
  static void CheckCast(Value* obj);
};


/**
 * An instance of Uint32Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Uint32Array : public TypedArray {
 public:
  static Local<Uint32Array> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Uint32Array* Cast(Value* obj);

 private:
  Uint32Array();
  static void CheckCast(Value* obj);
};


/**
 * An instance of Int32Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Int32Array : public TypedArray {
 public:
  static Local<Int32Array> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Int32Array* Cast(Value* obj);

 private:
  Int32Array();
  static void CheckCast(Value* obj);
};


/**
 * An instance of Float32Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Float32Array : public TypedArray {
 public:
  static Local<Float32Array> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Float32Array* Cast(Value* obj);

 private:
  Float32Array();
  static void CheckCast(Value* obj);
};


/**
 * An instance of Float64Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Float64Array : public TypedArray {
 public:
  static Local<Float64Array> New(Handle<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  V8_INLINE static Float64Array* Cast(Value* obj);

 private:
  Float64Array();
  static void CheckCast(Value* obj);
};


/**
 * An instance of DataView constructor (ES6 draft 15.13.7).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT DataView : public ArrayBufferView {
 public:
  static Local<DataView> New(Handle<ArrayBuffer> array_buffer,
                             size_t byte_offset, size_t length);
  V8_INLINE static DataView* Cast(Value* obj);

 private:
  DataView();
  static void CheckCast(Value* obj);
};


/**
 * An instance of the built-in Date constructor (ECMA-262, 15.9).
 */
class V8_EXPORT Date : public Object {
 public:
  static Local<Value> New(double time);

  // Deprecated, use Date::ValueOf() instead.
  // TODO(svenpanne) Actually deprecate when Chrome is adapted.
  double NumberValue() const { return ValueOf(); }

  /**
   * A specialization of Value::NumberValue that is more efficient
   * because we know the structure of this object.
   */
  double ValueOf() const;

  V8_INLINE static Date* Cast(v8::Value* obj);

  /**
   * Notification that the embedder has changed the time zone,
   * daylight savings time, or other date / time configuration
   * parameters.  V8 keeps a cache of various values used for
   * date / time computation.  This notification will reset
   * those cached values for the current context so that date /
   * time configuration changes would be reflected in the Date
   * object.
   *
   * This API should not be called more than needed as it will
   * negatively impact the performance of date operations.
   */
  static void DateTimeConfigurationChangeNotification();

 private:
  static void CheckCast(v8::Value* obj);
};


/**
 * A Number object (ECMA-262, 4.3.21).
 */
class V8_EXPORT NumberObject : public Object {
 public:
  static Local<Value> New(double value);

  // Deprecated, use NumberObject::ValueOf() instead.
  // TODO(svenpanne) Actually deprecate when Chrome is adapted.
  double NumberValue() const { return ValueOf(); }

  /**
   * Returns the Number held by the object.
   */
  double ValueOf() const;

  V8_INLINE static NumberObject* Cast(v8::Value* obj);

 private:
  static void CheckCast(v8::Value* obj);
};


/**
 * A Boolean object (ECMA-262, 4.3.15).
 */
class V8_EXPORT BooleanObject : public Object {
 public:
  static Local<Value> New(bool value);

  // Deprecated, use BooleanObject::ValueOf() instead.
  // TODO(svenpanne) Actually deprecate when Chrome is adapted.
  bool BooleanValue() const { return ValueOf(); }

  /**
   * Returns the Boolean held by the object.
   */
  bool ValueOf() const;

  V8_INLINE static BooleanObject* Cast(v8::Value* obj);

 private:
  static void CheckCast(v8::Value* obj);
};


/**
 * A String object (ECMA-262, 4.3.18).
 */
class V8_EXPORT StringObject : public Object {
 public:
  static Local<Value> New(Handle<String> value);

  // Deprecated, use StringObject::ValueOf() instead.
  // TODO(svenpanne) Actually deprecate when Chrome is adapted.
  Local<String> StringValue() const { return ValueOf(); }

  /**
   * Returns the String held by the object.
   */
  Local<String> ValueOf() const;

  V8_INLINE static StringObject* Cast(v8::Value* obj);

 private:
  static void CheckCast(v8::Value* obj);
};


/**
 * A Symbol object (ECMA-262 edition 6).
 *
 * This is an experimental feature. Use at your own risk.
 */
class V8_EXPORT SymbolObject : public Object {
 public:
  static Local<Value> New(Isolate* isolate, Handle<Symbol> value);

  // Deprecated, use SymbolObject::ValueOf() instead.
  // TODO(svenpanne) Actually deprecate when Chrome is adapted.
  Local<Symbol> SymbolValue() const { return ValueOf(); }

  /**
   * Returns the Symbol held by the object.
   */
  Local<Symbol> ValueOf() const;

  V8_INLINE static SymbolObject* Cast(v8::Value* obj);

 private:
  static void CheckCast(v8::Value* obj);
};


/**
 * An instance of the built-in RegExp constructor (ECMA-262, 15.10).
 */
class V8_EXPORT RegExp : public Object {
 public:
  /**
   * Regular expression flag bits. They can be or'ed to enable a set
   * of flags.
   */
  enum Flags {
    kNone = 0,
    kGlobal = 1,
    kIgnoreCase = 2,
    kMultiline = 4
  };

  /**
   * Creates a regular expression from the given pattern string and
   * the flags bit field. May throw a JavaScript exception as
   * described in ECMA-262, 15.10.4.1.
   *
   * For example,
   *   RegExp::New(v8::String::New("foo"),
   *               static_cast<RegExp::Flags>(kGlobal | kMultiline))
   * is equivalent to evaluating "/foo/gm".
   */
  static Local<RegExp> New(Handle<String> pattern, Flags flags);

  /**
   * Returns the value of the source property: a string representing
   * the regular expression.
   */
  Local<String> GetSource() const;

  /**
   * Returns the flags bit field.
   */
  Flags GetFlags() const;

  V8_INLINE static RegExp* Cast(v8::Value* obj);

 private:
  static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript value that wraps a C++ void*. This type of value is mainly used
 * to associate C++ data structures with JavaScript objects.
 */
class V8_EXPORT External : public Value {
 public:
  static Local<External> New(void* value);
  V8_INLINE static External* Cast(Value* obj);
  void* Value() const;
 private:
  static void CheckCast(v8::Value* obj);
};


// --- Templates ---


/**
 * The superclass of object and function templates.
 */
class V8_EXPORT Template : public Data {
 public:
  /** Adds a property to each instance created by this template.*/
  void Set(Handle<String> name, Handle<Data> value,
           PropertyAttribute attributes = None);
  V8_INLINE void Set(const char* name, Handle<Data> value);

  void SetAccessorProperty(
     Local<String> name,
     Local<FunctionTemplate> getter = Local<FunctionTemplate>(),
     Local<FunctionTemplate> setter = Local<FunctionTemplate>(),
     PropertyAttribute attribute = None,
     AccessControl settings = DEFAULT);

  /**
   * Whenever the property with the given name is accessed on objects
   * created from this Template the getter and setter callbacks
   * are called instead of getting and setting the property directly
   * on the JavaScript object.
   *
   * \param name The name of the property for which an accessor is added.
   * \param getter The callback to invoke when getting the property.
   * \param setter The callback to invoke when setting the property.
   * \param data A piece of data that will be passed to the getter and setter
   *   callbacks whenever they are invoked.
   * \param settings Access control settings for the accessor. This is a bit
   *   field consisting of one of more of
   *   DEFAULT = 0, ALL_CAN_READ = 1, or ALL_CAN_WRITE = 2.
   *   The default is to not allow cross-context access.
   *   ALL_CAN_READ means that all cross-context reads are allowed.
   *   ALL_CAN_WRITE means that all cross-context writes are allowed.
   *   The combination ALL_CAN_READ | ALL_CAN_WRITE can be used to allow all
   *   cross-context access.
   * \param attribute The attributes of the property for which an accessor
   *   is added.
   * \param signature The signature describes valid receivers for the accessor
   *   and is used to perform implicit instance checks against them. If the
   *   receiver is incompatible (i.e. is not an instance of the constructor as
   *   defined by FunctionTemplate::HasInstance()), an implicit TypeError is
   *   thrown and no callback is invoked.
   */
  void SetNativeDataProperty(Local<String> name,
                             AccessorGetterCallback getter,
                             AccessorSetterCallback setter = 0,
                             // TODO(dcarney): gcc can't handle Local below
                             Handle<Value> data = Handle<Value>(),
                             PropertyAttribute attribute = None,
                             Local<AccessorSignature> signature =
                                 Local<AccessorSignature>(),
                             AccessControl settings = DEFAULT);

  // This function is not yet stable and should not be used at this time.
  bool SetDeclaredAccessor(Local<String> name,
                           Local<DeclaredAccessorDescriptor> descriptor,
                           PropertyAttribute attribute = None,
                           Local<AccessorSignature> signature =
                               Local<AccessorSignature>(),
                           AccessControl settings = DEFAULT);

 private:
  Template();

  friend class ObjectTemplate;
  friend class FunctionTemplate;
};


/**
 * NamedProperty[Getter|Setter] are used as interceptors on object.
 * See ObjectTemplate::SetNamedPropertyHandler.
 */
typedef void (*NamedPropertyGetterCallback)(
    Local<String> property,
    const PropertyCallbackInfo<Value>& info);


/**
 * Returns the value if the setter intercepts the request.
 * Otherwise, returns an empty handle.
 */
typedef void (*NamedPropertySetterCallback)(
    Local<String> property,
    Local<Value> value,
    const PropertyCallbackInfo<Value>& info);


/**
 * Returns a non-empty handle if the interceptor intercepts the request.
 * The result is an integer encoding property attributes (like v8::None,
 * v8::DontEnum, etc.)
 */
typedef void (*NamedPropertyQueryCallback)(
    Local<String> property,
    const PropertyCallbackInfo<Integer>& info);


/**
 * Returns a non-empty handle if the deleter intercepts the request.
 * The return value is true if the property could be deleted and false
 * otherwise.
 */
typedef void (*NamedPropertyDeleterCallback)(
    Local<String> property,
    const PropertyCallbackInfo<Boolean>& info);


/**
 * Returns an array containing the names of the properties the named
 * property getter intercepts.
 */
typedef void (*NamedPropertyEnumeratorCallback)(
    const PropertyCallbackInfo<Array>& info);


/**
 * Returns the value of the property if the getter intercepts the
 * request.  Otherwise, returns an empty handle.
 */
typedef void (*IndexedPropertyGetterCallback)(
    uint32_t index,
    const PropertyCallbackInfo<Value>& info);


/**
 * Returns the value if the setter intercepts the request.
 * Otherwise, returns an empty handle.
 */
typedef void (*IndexedPropertySetterCallback)(
    uint32_t index,
    Local<Value> value,
    const PropertyCallbackInfo<Value>& info);


/**
 * Returns a non-empty handle if the interceptor intercepts the request.
 * The result is an integer encoding property attributes.
 */
typedef void (*IndexedPropertyQueryCallback)(
    uint32_t index,
    const PropertyCallbackInfo<Integer>& info);


/**
 * Returns a non-empty handle if the deleter intercepts the request.
 * The return value is true if the property could be deleted and false
 * otherwise.
 */
typedef void (*IndexedPropertyDeleterCallback)(
    uint32_t index,
    const PropertyCallbackInfo<Boolean>& info);


/**
 * Returns an array containing the indices of the properties the
 * indexed property getter intercepts.
 */
typedef void (*IndexedPropertyEnumeratorCallback)(
    const PropertyCallbackInfo<Array>& info);


/**
 * Access type specification.
 */
enum AccessType {
  ACCESS_GET,
  ACCESS_SET,
  ACCESS_HAS,
  ACCESS_DELETE,
  ACCESS_KEYS
};


/**
 * Returns true if cross-context access should be allowed to the named
 * property with the given key on the host object.
 */
typedef bool (*NamedSecurityCallback)(Local<Object> host,
                                      Local<Value> key,
                                      AccessType type,
                                      Local<Value> data);


/**
 * Returns true if cross-context access should be allowed to the indexed
 * property with the given index on the host object.
 */
typedef bool (*IndexedSecurityCallback)(Local<Object> host,
                                        uint32_t index,
                                        AccessType type,
                                        Local<Value> data);


/**
 * A FunctionTemplate is used to create functions at runtime. There
 * can only be one function created from a FunctionTemplate in a
 * context.  The lifetime of the created function is equal to the
 * lifetime of the context.  So in case the embedder needs to create
 * temporary functions that can be collected using Scripts is
 * preferred.
 *
 * A FunctionTemplate can have properties, these properties are added to the
 * function object when it is created.
 *
 * A FunctionTemplate has a corresponding instance template which is
 * used to create object instances when the function is used as a
 * constructor. Properties added to the instance template are added to
 * each object instance.
 *
 * A FunctionTemplate can have a prototype template. The prototype template
 * is used to create the prototype object of the function.
 *
 * The following example shows how to use a FunctionTemplate:
 *
 * \code
 *    v8::Local<v8::FunctionTemplate> t = v8::FunctionTemplate::New();
 *    t->Set("func_property", v8::Number::New(1));
 *
 *    v8::Local<v8::Template> proto_t = t->PrototypeTemplate();
 *    proto_t->Set("proto_method", v8::FunctionTemplate::New(InvokeCallback));
 *    proto_t->Set("proto_const", v8::Number::New(2));
 *
 *    v8::Local<v8::ObjectTemplate> instance_t = t->InstanceTemplate();
 *    instance_t->SetAccessor("instance_accessor", InstanceAccessorCallback);
 *    instance_t->SetNamedPropertyHandler(PropertyHandlerCallback, ...);
 *    instance_t->Set("instance_property", Number::New(3));
 *
 *    v8::Local<v8::Function> function = t->GetFunction();
 *    v8::Local<v8::Object> instance = function->NewInstance();
 * \endcode
 *
 * Let's use "function" as the JS variable name of the function object
 * and "instance" for the instance object created above.  The function
 * and the instance will have the following properties:
 *
 * \code
 *   func_property in function == true;
 *   function.func_property == 1;
 *
 *   function.prototype.proto_method() invokes 'InvokeCallback'
 *   function.prototype.proto_const == 2;
 *
 *   instance instanceof function == true;
 *   instance.instance_accessor calls 'InstanceAccessorCallback'
 *   instance.instance_property == 3;
 * \endcode
 *
 * A FunctionTemplate can inherit from another one by calling the
 * FunctionTemplate::Inherit method.  The following graph illustrates
 * the semantics of inheritance:
 *
 * \code
 *   FunctionTemplate Parent  -> Parent() . prototype -> { }
 *     ^                                                  ^
 *     | Inherit(Parent)                                  | .__proto__
 *     |                                                  |
 *   FunctionTemplate Child   -> Child()  . prototype -> { }
 * \endcode
 *
 * A FunctionTemplate 'Child' inherits from 'Parent', the prototype
 * object of the Child() function has __proto__ pointing to the
 * Parent() function's prototype object. An instance of the Child
 * function has all properties on Parent's instance templates.
 *
 * Let Parent be the FunctionTemplate initialized in the previous
 * section and create a Child FunctionTemplate by:
 *
 * \code
 *   Local<FunctionTemplate> parent = t;
 *   Local<FunctionTemplate> child = FunctionTemplate::New();
 *   child->Inherit(parent);
 *
 *   Local<Function> child_function = child->GetFunction();
 *   Local<Object> child_instance = child_function->NewInstance();
 * \endcode
 *
 * The Child function and Child instance will have the following
 * properties:
 *
 * \code
 *   child_func.prototype.__proto__ == function.prototype;
 *   child_instance.instance_accessor calls 'InstanceAccessorCallback'
 *   child_instance.instance_property == 3;
 * \endcode
 */
class V8_EXPORT FunctionTemplate : public Template {
 public:
  /** Creates a function template.*/
  static Local<FunctionTemplate> New(
      FunctionCallback callback = 0,
      Handle<Value> data = Handle<Value>(),
      Handle<Signature> signature = Handle<Signature>(),
      int length = 0);

  /** Returns the unique function instance in the current execution context.*/
  Local<Function> GetFunction();

  /**
   * Set the call-handler callback for a FunctionTemplate.  This
   * callback is called whenever the function created from this
   * FunctionTemplate is called.
   */
  void SetCallHandler(FunctionCallback callback,
                      Handle<Value> data = Handle<Value>());

  /** Set the predefined length property for the FunctionTemplate. */
  void SetLength(int length);

  /** Get the InstanceTemplate. */
  Local<ObjectTemplate> InstanceTemplate();

  /** Causes the function template to inherit from a parent function template.*/
  void Inherit(Handle<FunctionTemplate> parent);

  /**
   * A PrototypeTemplate is the template used to create the prototype object
   * of the function created by this template.
   */
  Local<ObjectTemplate> PrototypeTemplate();

  /**
   * Set the class name of the FunctionTemplate.  This is used for
   * printing objects created with the function created from the
   * FunctionTemplate as its constructor.
   */
  void SetClassName(Handle<String> name);

  /**
   * Determines whether the __proto__ accessor ignores instances of
   * the function template.  If instances of the function template are
   * ignored, __proto__ skips all instances and instead returns the
   * next object in the prototype chain.
   *
   * Call with a value of true to make the __proto__ accessor ignore
   * instances of the function template.  Call with a value of false
   * to make the __proto__ accessor not ignore instances of the
   * function template.  By default, instances of a function template
   * are not ignored.
   */
  void SetHiddenPrototype(bool value);

  /**
   * Sets the ReadOnly flag in the attributes of the 'prototype' property
   * of functions created from this FunctionTemplate to true.
   */
  void ReadOnlyPrototype();

  /**
   * Removes the prototype property from functions created from this
   * FunctionTemplate.
   */
  void RemovePrototype();

  /**
   * Returns true if the given object is an instance of this function
   * template.
   */
  bool HasInstance(Handle<Value> object);

 private:
  FunctionTemplate();
  friend class Context;
  friend class ObjectTemplate;
};


/**
 * An ObjectTemplate is used to create objects at runtime.
 *
 * Properties added to an ObjectTemplate are added to each object
 * created from the ObjectTemplate.
 */
class V8_EXPORT ObjectTemplate : public Template {
 public:
  /** Creates an ObjectTemplate. */
  static Local<ObjectTemplate> New();

  /** Creates a new instance of this template.*/
  Local<Object> NewInstance();

  /**
   * Sets an accessor on the object template.
   *
   * Whenever the property with the given name is accessed on objects
   * created from this ObjectTemplate the getter and setter callbacks
   * are called instead of getting and setting the property directly
   * on the JavaScript object.
   *
   * \param name The name of the property for which an accessor is added.
   * \param getter The callback to invoke when getting the property.
   * \param setter The callback to invoke when setting the property.
   * \param data A piece of data that will be passed to the getter and setter
   *   callbacks whenever they are invoked.
   * \param settings Access control settings for the accessor. This is a bit
   *   field consisting of one of more of
   *   DEFAULT = 0, ALL_CAN_READ = 1, or ALL_CAN_WRITE = 2.
   *   The default is to not allow cross-context access.
   *   ALL_CAN_READ means that all cross-context reads are allowed.
   *   ALL_CAN_WRITE means that all cross-context writes are allowed.
   *   The combination ALL_CAN_READ | ALL_CAN_WRITE can be used to allow all
   *   cross-context access.
   * \param attribute The attributes of the property for which an accessor
   *   is added.
   * \param signature The signature describes valid receivers for the accessor
   *   and is used to perform implicit instance checks against them. If the
   *   receiver is incompatible (i.e. is not an instance of the constructor as
   *   defined by FunctionTemplate::HasInstance()), an implicit TypeError is
   *   thrown and no callback is invoked.
   */
  void SetAccessor(Handle<String> name,
                   AccessorGetterCallback getter,
                   AccessorSetterCallback setter = 0,
                   Handle<Value> data = Handle<Value>(),
                   AccessControl settings = DEFAULT,
                   PropertyAttribute attribute = None,
                   Handle<AccessorSignature> signature =
                       Handle<AccessorSignature>());

  /**
   * Sets a named property handler on the object template.
   *
   * Whenever a named property is accessed on objects created from
   * this object template, the provided callback is invoked instead of
   * accessing the property directly on the JavaScript object.
   *
   * \param getter The callback to invoke when getting a property.
   * \param setter The callback to invoke when setting a property.
   * \param query The callback to invoke to check if a property is present,
   *   and if present, get its attributes.
   * \param deleter The callback to invoke when deleting a property.
   * \param enumerator The callback to invoke to enumerate all the named
   *   properties of an object.
   * \param data A piece of data that will be passed to the callbacks
   *   whenever they are invoked.
   */
  void SetNamedPropertyHandler(
      NamedPropertyGetterCallback getter,
      NamedPropertySetterCallback setter = 0,
      NamedPropertyQueryCallback query = 0,
      NamedPropertyDeleterCallback deleter = 0,
      NamedPropertyEnumeratorCallback enumerator = 0,
      Handle<Value> data = Handle<Value>());

  /**
   * Sets an indexed property handler on the object template.
   *
   * Whenever an indexed property is accessed on objects created from
   * this object template, the provided callback is invoked instead of
   * accessing the property directly on the JavaScript object.
   *
   * \param getter The callback to invoke when getting a property.
   * \param setter The callback to invoke when setting a property.
   * \param query The callback to invoke to check if an object has a property.
   * \param deleter The callback to invoke when deleting a property.
   * \param enumerator The callback to invoke to enumerate all the indexed
   *   properties of an object.
   * \param data A piece of data that will be passed to the callbacks
   *   whenever they are invoked.
   */
  void SetIndexedPropertyHandler(
      IndexedPropertyGetterCallback getter,
      IndexedPropertySetterCallback setter = 0,
      IndexedPropertyQueryCallback query = 0,
      IndexedPropertyDeleterCallback deleter = 0,
      IndexedPropertyEnumeratorCallback enumerator = 0,
      Handle<Value> data = Handle<Value>());

  /**
   * Sets the callback to be used when calling instances created from
   * this template as a function.  If no callback is set, instances
   * behave like normal JavaScript objects that cannot be called as a
   * function.
   */
  void SetCallAsFunctionHandler(FunctionCallback callback,
                                Handle<Value> data = Handle<Value>());

  /**
   * Mark object instances of the template as undetectable.
   *
   * In many ways, undetectable objects behave as though they are not
   * there.  They behave like 'undefined' in conditionals and when
   * printed.  However, properties can be accessed and called as on
   * normal objects.
   */
  void MarkAsUndetectable();

  /**
   * Sets access check callbacks on the object template.
   *
   * When accessing properties on instances of this object template,
   * the access check callback will be called to determine whether or
   * not to allow cross-context access to the properties.
   * The last parameter specifies whether access checks are turned
   * on by default on instances. If access checks are off by default,
   * they can be turned on on individual instances by calling
   * Object::TurnOnAccessCheck().
   */
  void SetAccessCheckCallbacks(NamedSecurityCallback named_handler,
                               IndexedSecurityCallback indexed_handler,
                               Handle<Value> data = Handle<Value>(),
                               bool turned_on_by_default = true);

  /**
   * Gets the number of internal fields for objects generated from
   * this template.
   */
  int InternalFieldCount();

  /**
   * Sets the number of internal fields for objects generated from
   * this template.
   */
  void SetInternalFieldCount(int value);

 private:
  ObjectTemplate();
  static Local<ObjectTemplate> New(Handle<FunctionTemplate> constructor);
  friend class FunctionTemplate;
};


/**
 * A Signature specifies which receivers and arguments are valid
 * parameters to a function.
 */
class V8_EXPORT Signature : public Data {
 public:
  static Local<Signature> New(Handle<FunctionTemplate> receiver =
                                  Handle<FunctionTemplate>(),
                              int argc = 0,
                              Handle<FunctionTemplate> argv[] = 0);
 private:
  Signature();
};


/**
 * An AccessorSignature specifies which receivers are valid parameters
 * to an accessor callback.
 */
class V8_EXPORT AccessorSignature : public Data {
 public:
  static Local<AccessorSignature> New(Handle<FunctionTemplate> receiver =
                                          Handle<FunctionTemplate>());
 private:
  AccessorSignature();
};


class V8_EXPORT DeclaredAccessorDescriptor : public Data {
 private:
  DeclaredAccessorDescriptor();
};


class V8_EXPORT ObjectOperationDescriptor : public Data {
 public:
  // This function is not yet stable and should not be used at this time.
  static Local<RawOperationDescriptor> NewInternalFieldDereference(
      Isolate* isolate,
      int internal_field);
 private:
  ObjectOperationDescriptor();
};


enum DeclaredAccessorDescriptorDataType {
    kDescriptorBoolType,
    kDescriptorInt8Type, kDescriptorUint8Type,
    kDescriptorInt16Type, kDescriptorUint16Type,
    kDescriptorInt32Type, kDescriptorUint32Type,
    kDescriptorFloatType, kDescriptorDoubleType
};


class V8_EXPORT RawOperationDescriptor : public Data {
 public:
  Local<DeclaredAccessorDescriptor> NewHandleDereference(Isolate* isolate);
  Local<RawOperationDescriptor> NewRawDereference(Isolate* isolate);
  Local<RawOperationDescriptor> NewRawShift(Isolate* isolate,
                                            int16_t byte_offset);
  Local<DeclaredAccessorDescriptor> NewPointerCompare(Isolate* isolate,
                                                      void* compare_value);
  Local<DeclaredAccessorDescriptor> NewPrimitiveValue(
      Isolate* isolate,
      DeclaredAccessorDescriptorDataType data_type,
      uint8_t bool_offset = 0);
  Local<DeclaredAccessorDescriptor> NewBitmaskCompare8(Isolate* isolate,
                                                       uint8_t bitmask,
                                                       uint8_t compare_value);
  Local<DeclaredAccessorDescriptor> NewBitmaskCompare16(
      Isolate* isolate,
      uint16_t bitmask,
      uint16_t compare_value);
  Local<DeclaredAccessorDescriptor> NewBitmaskCompare32(
      Isolate* isolate,
      uint32_t bitmask,
      uint32_t compare_value);

 private:
  RawOperationDescriptor();
};


/**
 * A utility for determining the type of objects based on the template
 * they were constructed from.
 */
class V8_EXPORT TypeSwitch : public Data {
 public:
  static Local<TypeSwitch> New(Handle<FunctionTemplate> type);
  static Local<TypeSwitch> New(int argc, Handle<FunctionTemplate> types[]);
  int match(Handle<Value> value);
 private:
  TypeSwitch();
};


// --- Extensions ---

class V8_EXPORT ExternalAsciiStringResourceImpl
    : public String::ExternalAsciiStringResource {
 public:
  ExternalAsciiStringResourceImpl() : data_(0), length_(0) {}
  ExternalAsciiStringResourceImpl(const char* data, size_t length)
      : data_(data), length_(length) {}
  const char* data() const { return data_; }
  size_t length() const { return length_; }

 private:
  const char* data_;
  size_t length_;
};

/**
 * Ignore
 */
class V8_EXPORT Extension {  // NOLINT
 public:
  // Note that the strings passed into this constructor must live as long
  // as the Extension itself.
  Extension(const char* name,
            const char* source = 0,
            int dep_count = 0,
            const char** deps = 0,
            int source_length = -1);
  virtual ~Extension() { }
  virtual v8::Handle<v8::FunctionTemplate>
      GetNativeFunction(v8::Handle<v8::String> name) {
    return v8::Handle<v8::FunctionTemplate>();
  }

  const char* name() const { return name_; }
  size_t source_length() const { return source_length_; }
  const String::ExternalAsciiStringResource* source() const {
    return &source_; }
  int dependency_count() { return dep_count_; }
  const char** dependencies() { return deps_; }
  void set_auto_enable(bool value) { auto_enable_ = value; }
  bool auto_enable() { return auto_enable_; }

 private:
  const char* name_;
  size_t source_length_;  // expected to initialize before source_
  ExternalAsciiStringResourceImpl source_;
  int dep_count_;
  const char** deps_;
  bool auto_enable_;

  // Disallow copying and assigning.
  Extension(const Extension&);
  void operator=(const Extension&);
};


void V8_EXPORT RegisterExtension(Extension* extension);


/**
 * Ignore
 */
class V8_EXPORT DeclareExtension {
 public:
  V8_INLINE DeclareExtension(Extension* extension) {
    RegisterExtension(extension);
  }
};


// --- Statics ---


Handle<Primitive> V8_EXPORT Undefined();
Handle<Primitive> V8_EXPORT Null();
Handle<Boolean> V8_EXPORT True();
Handle<Boolean> V8_EXPORT False();

V8_INLINE Handle<Primitive> Undefined(Isolate* isolate);
V8_INLINE Handle<Primitive> Null(Isolate* isolate);
V8_INLINE Handle<Boolean> True(Isolate* isolate);
V8_INLINE Handle<Boolean> False(Isolate* isolate);


/**
 * A set of constraints that specifies the limits of the runtime's memory use.
 * You must set the heap size before initializing the VM - the size cannot be
 * adjusted after the VM is initialized.
 *
 * If you are using threads then you should hold the V8::Locker lock while
 * setting the stack limit and you must set a non-default stack limit separately
 * for each thread.
 */
class V8_EXPORT ResourceConstraints {
 public:
  ResourceConstraints();
  int max_young_space_size() const { return max_young_space_size_; }
  void set_max_young_space_size(int value) { max_young_space_size_ = value; }
  int max_old_space_size() const { return max_old_space_size_; }
  void set_max_old_space_size(int value) { max_old_space_size_ = value; }
  int max_executable_size() { return max_executable_size_; }
  void set_max_executable_size(int value) { max_executable_size_ = value; }
  uint32_t* stack_limit() const { return stack_limit_; }
  // Sets an address beyond which the VM's stack may not grow.
  void set_stack_limit(uint32_t* value) { stack_limit_ = value; }

 private:
  int max_young_space_size_;
  int max_old_space_size_;
  int max_executable_size_;
  uint32_t* stack_limit_;
};


/**
 * Sets the given ResourceConstraints on the current isolate.
 */
bool V8_EXPORT SetResourceConstraints(ResourceConstraints* constraints);


// --- Exceptions ---


typedef void (*FatalErrorCallback)(const char* location, const char* message);


typedef void (*MessageCallback)(Handle<Message> message, Handle<Value> error);


// TODO(dcarney): remove. Use Isolate::ThrowException instead.
Handle<Value> V8_EXPORT ThrowException(Handle<Value> exception);

/**
 * Create new error objects by calling the corresponding error object
 * constructor with the message.
 */
class V8_EXPORT Exception {
 public:
  static Local<Value> RangeError(Handle<String> message);
  static Local<Value> ReferenceError(Handle<String> message);
  static Local<Value> SyntaxError(Handle<String> message);
  static Local<Value> TypeError(Handle<String> message);
  static Local<Value> Error(Handle<String> message);
};


// --- Counters Callbacks ---

typedef int* (*CounterLookupCallback)(const char* name);

typedef void* (*CreateHistogramCallback)(const char* name,
                                         int min,
                                         int max,
                                         size_t buckets);

typedef void (*AddHistogramSampleCallback)(void* histogram, int sample);

// --- Memory Allocation Callback ---
  enum ObjectSpace {
    kObjectSpaceNewSpace = 1 << 0,
    kObjectSpaceOldPointerSpace = 1 << 1,
    kObjectSpaceOldDataSpace = 1 << 2,
    kObjectSpaceCodeSpace = 1 << 3,
    kObjectSpaceMapSpace = 1 << 4,
    kObjectSpaceLoSpace = 1 << 5,

    kObjectSpaceAll = kObjectSpaceNewSpace | kObjectSpaceOldPointerSpace |
      kObjectSpaceOldDataSpace | kObjectSpaceCodeSpace | kObjectSpaceMapSpace |
      kObjectSpaceLoSpace
  };

  enum AllocationAction {
    kAllocationActionAllocate = 1 << 0,
    kAllocationActionFree = 1 << 1,
    kAllocationActionAll = kAllocationActionAllocate | kAllocationActionFree
  };

typedef void (*MemoryAllocationCallback)(ObjectSpace space,
                                         AllocationAction action,
                                         int size);

// --- Leave Script Callback ---
typedef void (*CallCompletedCallback)();

// --- Failed Access Check Callback ---
typedef void (*FailedAccessCheckCallback)(Local<Object> target,
                                          AccessType type,
                                          Local<Value> data);

// --- AllowCodeGenerationFromStrings callbacks ---

/**
 * Callback to check if code generation from strings is allowed. See
 * Context::AllowCodeGenerationFromStrings.
 */
typedef bool (*AllowCodeGenerationFromStringsCallback)(Local<Context> context);

// --- Garbage Collection Callbacks ---

/**
 * Applications can register callback functions which will be called
 * before and after a garbage collection.  Allocations are not
 * allowed in the callback functions, you therefore cannot manipulate
 * objects (set or delete properties for example) since it is possible
 * such operations will result in the allocation of objects.
 */
enum GCType {
  kGCTypeScavenge = 1 << 0,
  kGCTypeMarkSweepCompact = 1 << 1,
  kGCTypeAll = kGCTypeScavenge | kGCTypeMarkSweepCompact
};

enum GCCallbackFlags {
  kNoGCCallbackFlags = 0,
  kGCCallbackFlagCompacted = 1 << 0,
  kGCCallbackFlagConstructRetainedObjectInfos = 1 << 1
};

typedef void (*GCPrologueCallback)(GCType type, GCCallbackFlags flags);
typedef void (*GCEpilogueCallback)(GCType type, GCCallbackFlags flags);


/**
 * Collection of V8 heap information.
 *
 * Instances of this class can be passed to v8::V8::HeapStatistics to
 * get heap statistics from V8.
 */
class V8_EXPORT HeapStatistics {
 public:
  HeapStatistics();
  size_t total_heap_size() { return total_heap_size_; }
  size_t total_heap_size_executable() { return total_heap_size_executable_; }
  size_t total_physical_size() { return total_physical_size_; }
  size_t used_heap_size() { return used_heap_size_; }
  size_t heap_size_limit() { return heap_size_limit_; }

 private:
  size_t total_heap_size_;
  size_t total_heap_size_executable_;
  size_t total_physical_size_;
  size_t used_heap_size_;
  size_t heap_size_limit_;

  friend class V8;
  friend class Isolate;
};


class RetainedObjectInfo;

/**
 * Isolate represents an isolated instance of the V8 engine.  V8
 * isolates have completely separate states.  Objects from one isolate
 * must not be used in other isolates.  When V8 is initialized a
 * default isolate is implicitly created and entered.  The embedder
 * can create additional isolates and use them in parallel in multiple
 * threads.  An isolate can be entered by at most one thread at any
 * given time.  The Locker/Unlocker API must be used to synchronize.
 */
class V8_EXPORT Isolate {
 public:
  /**
   * Stack-allocated class which sets the isolate for all operations
   * executed within a local scope.
   */
  class V8_EXPORT Scope {
   public:
    explicit Scope(Isolate* isolate) : isolate_(isolate) {
      isolate->Enter();
    }

    ~Scope() { isolate_->Exit(); }

   private:
    Isolate* const isolate_;

    // Prevent copying of Scope objects.
    Scope(const Scope&);
    Scope& operator=(const Scope&);
  };

  /**
   * Creates a new isolate.  Does not change the currently entered
   * isolate.
   *
   * When an isolate is no longer used its resources should be freed
   * by calling Dispose().  Using the delete operator is not allowed.
   */
  static Isolate* New();

  /**
   * Returns the entered isolate for the current thread or NULL in
   * case there is no current isolate.
   */
  static Isolate* GetCurrent();

  /**
   * Methods below this point require holding a lock (using Locker) in
   * a multi-threaded environment.
   */

  /**
   * Sets this isolate as the entered one for the current thread.
   * Saves the previously entered one (if any), so that it can be
   * restored when exiting.  Re-entering an isolate is allowed.
   */
  void Enter();

  /**
   * Exits this isolate by restoring the previously entered one in the
   * current thread.  The isolate may still stay the same, if it was
   * entered more than once.
   *
   * Requires: this == Isolate::GetCurrent().
   */
  void Exit();

  /**
   * Disposes the isolate.  The isolate must not be entered by any
   * thread to be disposable.
   */
  void Dispose();

  /**
   * Associate embedder-specific data with the isolate
   */
  V8_INLINE void SetData(void* data);

  /**
   * Retrieve embedder-specific data from the isolate.
   * Returns NULL if SetData has never been called.
   */
  V8_INLINE void* GetData();

  /**
   * Get statistics about the heap memory usage.
   */
  void GetHeapStatistics(HeapStatistics* heap_statistics);

  /**
   * Adjusts the amount of registered external memory. Used to give V8 an
   * indication of the amount of externally allocated memory that is kept alive
   * by JavaScript objects. V8 uses this to decide when to perform global
   * garbage collections. Registering externally allocated memory will trigger
   * global garbage collections more often than it would otherwise in an attempt
   * to garbage collect the JavaScript objects that keep the externally
   * allocated memory alive.
   *
   * \param change_in_bytes the change in externally allocated memory that is
   *   kept alive by JavaScript objects.
   * \returns the adjusted value.
   */
  intptr_t AdjustAmountOfExternalAllocatedMemory(intptr_t change_in_bytes);

  /**
   * Returns heap profiler for this isolate. Will return NULL until the isolate
   * is initialized.
   */
  HeapProfiler* GetHeapProfiler();

  /**
   * Returns CPU profiler for this isolate. Will return NULL unless the isolate
   * is initialized. It is the embedder's responsibility to stop all CPU
   * profiling activities if it has started any.
   */
  CpuProfiler* GetCpuProfiler();

  /** Returns true if this isolate has a current context. */
  bool InContext();

  /** Returns the context that is on the top of the stack. */
  Local<Context> GetCurrentContext();

  /**
   * Returns the context of the calling JavaScript code.  That is the
   * context of the top-most JavaScript frame.  If there are no
   * JavaScript frames an empty handle is returned.
   */
  Local<Context> GetCallingContext();

  /** Returns the last entered context. */
  Local<Context> GetEnteredContext();

  /**
   * Schedules an exception to be thrown when returning to JavaScript.  When an
   * exception has been scheduled it is illegal to invoke any JavaScript
   * operation; the caller must return immediately and only after the exception
   * has been handled does it become legal to invoke JavaScript operations.
   */
  Local<Value> ThrowException(Local<Value> exception);

  /**
   * Allows the host application to group objects together. If one
   * object in the group is alive, all objects in the group are alive.
   * After each garbage collection, object groups are removed. It is
   * intended to be used in the before-garbage-collection callback
   * function, for instance to simulate DOM tree connections among JS
   * wrapper objects. Object groups for all dependent handles need to
   * be provided for kGCTypeMarkSweepCompact collections, for all other
   * garbage collection types it is sufficient to provide object groups
   * for partially dependent handles only.
   */
  void SetObjectGroupId(const Persistent<Value>& object,
                        UniqueId id);

  /**
   * Allows the host application to declare implicit references from an object
   * group to an object. If the objects of the object group are alive, the child
   * object is alive too. After each garbage collection, all implicit references
   * are removed. It is intended to be used in the before-garbage-collection
   * callback function.
   */
  void SetReferenceFromGroup(UniqueId id,
                             const Persistent<Value>& child);

  /**
   * Allows the host application to declare implicit references from an object
   * to another object. If the parent object is alive, the child object is alive
   * too. After each garbage collection, all implicit references are removed. It
   * is intended to be used in the before-garbage-collection callback function.
   */
  void SetReference(const Persistent<Object>& parent,
                    const Persistent<Value>& child);

  typedef void (*GCPrologueCallback)(Isolate* isolate,
                                     GCType type,
                                     GCCallbackFlags flags);
  typedef void (*GCEpilogueCallback)(Isolate* isolate,
                                     GCType type,
                                     GCCallbackFlags flags);

  /**
   * Enables the host application to receive a notification before a
   * garbage collection.  Allocations are not allowed in the
   * callback function, you therefore cannot manipulate objects (set
   * or delete properties for example) since it is possible such
   * operations will result in the allocation of objects. It is possible
   * to specify the GCType filter for your callback. But it is not possible to
   * register the same callback function two times with different
   * GCType filters.
   */
  void AddGCPrologueCallback(
      GCPrologueCallback callback, GCType gc_type_filter = kGCTypeAll);

  /**
   * This function removes callback which was installed by
   * AddGCPrologueCallback function.
   */
  void RemoveGCPrologueCallback(GCPrologueCallback callback);

  /**
   * Enables the host application to receive a notification after a
   * garbage collection.  Allocations are not allowed in the
   * callback function, you therefore cannot manipulate objects (set
   * or delete properties for example) since it is possible such
   * operations will result in the allocation of objects. It is possible
   * to specify the GCType filter for your callback. But it is not possible to
   * register the same callback function two times with different
   * GCType filters.
   */
  void AddGCEpilogueCallback(
      GCEpilogueCallback callback, GCType gc_type_filter = kGCTypeAll);

  /**
   * This function removes callback which was installed by
   * AddGCEpilogueCallback function.
   */
  void RemoveGCEpilogueCallback(GCEpilogueCallback callback);

 private:
  Isolate();
  Isolate(const Isolate&);
  ~Isolate();
  Isolate& operator=(const Isolate&);
  void* operator new(size_t size);
  void operator delete(void*, size_t);
};


class V8_EXPORT StartupData {
 public:
  enum CompressionAlgorithm {
    kUncompressed,
    kBZip2
  };

  const char* data;
  int compressed_size;
  int raw_size;
};


/**
 * A helper class for driving V8 startup data decompression.  It is based on
 * "CompressedStartupData" API functions from the V8 class.  It isn't mandatory
 * for an embedder to use this class, instead, API functions can be used
 * directly.
 *
 * For an example of the class usage, see the "shell.cc" sample application.
 */
class V8_EXPORT StartupDataDecompressor {  // NOLINT
 public:
  StartupDataDecompressor();
  virtual ~StartupDataDecompressor();
  int Decompress();

 protected:
  virtual int DecompressData(char* raw_data,
                             int* raw_data_size,
                             const char* compressed_data,
                             int compressed_data_size) = 0;

 private:
  char** raw_data;
};


/**
 * EntropySource is used as a callback function when v8 needs a source
 * of entropy.
 */
typedef bool (*EntropySource)(unsigned char* buffer, size_t length);


/**
 * ReturnAddressLocationResolver is used as a callback function when v8 is
 * resolving the location of a return address on the stack. Profilers that
 * change the return address on the stack can use this to resolve the stack
 * location to whereever the profiler stashed the original return address.
 *
 * \param return_addr_location points to a location on stack where a machine
 *    return address resides.
 * \returns either return_addr_location, or else a pointer to the profiler's
 *    copy of the original return address.
 *
 * \note the resolver function must not cause garbage collection.
 */
typedef uintptr_t (*ReturnAddressLocationResolver)(
    uintptr_t return_addr_location);


/**
 * FunctionEntryHook is the type of the profile entry hook called at entry to
 * any generated function when function-level profiling is enabled.
 *
 * \param function the address of the function that's being entered.
 * \param return_addr_location points to a location on stack where the machine
 *    return address resides. This can be used to identify the caller of
 *    \p function, and/or modified to divert execution when \p function exits.
 *
 * \note the entry hook must not cause garbage collection.
 */
typedef void (*FunctionEntryHook)(uintptr_t function,
                                  uintptr_t return_addr_location);


/**
 * A JIT code event is issued each time code is added, moved or removed.
 *
 * \note removal events are not currently issued.
 */
struct JitCodeEvent {
  enum EventType {
    CODE_ADDED,
    CODE_MOVED,
    CODE_REMOVED,
    CODE_ADD_LINE_POS_INFO,
    CODE_START_LINE_INFO_RECORDING,
    CODE_END_LINE_INFO_RECORDING
  };
  // Definition of the code position type. The "POSITION" type means the place
  // in the source code which are of interest when making stack traces to
  // pin-point the source location of a stack frame as close as possible.
  // The "STATEMENT_POSITION" means the place at the beginning of each
  // statement, and is used to indicate possible break locations.
  enum PositionType {
    POSITION,
    STATEMENT_POSITION
  };

  // Type of event.
  EventType type;
  // Start of the instructions.
  void* code_start;
  // Size of the instructions.
  size_t code_len;
  // Script info for CODE_ADDED event.
  Handle<Script> script;
  // User-defined data for *_LINE_INFO_* event. It's used to hold the source
  // code line information which is returned from the
  // CODE_START_LINE_INFO_RECORDING event. And it's passed to subsequent
  // CODE_ADD_LINE_POS_INFO and CODE_END_LINE_INFO_RECORDING events.
  void* user_data;

  struct name_t {
    // Name of the object associated with the code, note that the string is not
    // zero-terminated.
    const char* str;
    // Number of chars in str.
    size_t len;
  };

  struct line_info_t {
    // PC offset
    size_t offset;
    // Code postion
    size_t pos;
    // The position type.
    PositionType position_type;
  };

  union {
    // Only valid for CODE_ADDED.
    struct name_t name;

    // Only valid for CODE_ADD_LINE_POS_INFO
    struct line_info_t line_info;

    // New location of instructions. Only valid for CODE_MOVED.
    void* new_code_start;
  };
};

/**
 * Option flags passed to the SetJitCodeEventHandler function.
 */
enum JitCodeEventOptions {
  kJitCodeEventDefault = 0,
  // Generate callbacks for already existent code.
  kJitCodeEventEnumExisting = 1
};


/**
 * Callback function passed to SetJitCodeEventHandler.
 *
 * \param event code add, move or removal event.
 */
typedef void (*JitCodeEventHandler)(const JitCodeEvent* event);


/**
 * Interface for iterating through all external resources in the heap.
 */
class V8_EXPORT ExternalResourceVisitor {  // NOLINT
 public:
  virtual ~ExternalResourceVisitor() {}
  virtual void VisitExternalString(Handle<String> string) {}
};


/**
 * Interface for iterating through all the persistent handles in the heap.
 */
class V8_EXPORT PersistentHandleVisitor {  // NOLINT
 public:
  virtual ~PersistentHandleVisitor() {}
  virtual void VisitPersistentHandle(Persistent<Value>* value,
                                     uint16_t class_id) {}
};


/**
 * Asserts that no action is performed that could cause a handle's value
 * to be modified. Useful when otherwise unsafe handle operations need to
 * be performed.
 */
class V8_EXPORT AssertNoGCScope {
#ifndef DEBUG
  // TODO(yangguo): remove isolate argument.
  V8_INLINE AssertNoGCScope(Isolate* isolate) {}
#else
  AssertNoGCScope(Isolate* isolate);
  ~AssertNoGCScope();
 private:
  void* disallow_heap_allocation_;
#endif
};


/**
 * Container class for static utility functions.
 */
class V8_EXPORT V8 {
 public:
  /** Set the callback to invoke in case of fatal errors. */
  static void SetFatalErrorHandler(FatalErrorCallback that);

  /**
   * Set the callback to invoke to check if code generation from
   * strings should be allowed.
   */
  static void SetAllowCodeGenerationFromStringsCallback(
      AllowCodeGenerationFromStringsCallback that);

  /**
   * Set allocator to use for ArrayBuffer memory.
   * The allocator should be set only once. The allocator should be set
   * before any code tha uses ArrayBuffers is executed.
   * This allocator is used in all isolates.
   */
  static void SetArrayBufferAllocator(ArrayBuffer::Allocator* allocator);

  /**
   * Ignore out-of-memory exceptions.
   *
   * V8 running out of memory is treated as a fatal error by default.
   * This means that the fatal error handler is called and that V8 is
   * terminated.
   *
   * IgnoreOutOfMemoryException can be used to not treat an
   * out-of-memory situation as a fatal error.  This way, the contexts
   * that did not cause the out of memory problem might be able to
   * continue execution.
   */
  static void IgnoreOutOfMemoryException();

  /**
   * Check if V8 is dead and therefore unusable.  This is the case after
   * fatal errors such as out-of-memory situations.
   */
  static bool IsDead();

  /**
   * The following 4 functions are to be used when V8 is built with
   * the 'compress_startup_data' flag enabled. In this case, the
   * embedder must decompress startup data prior to initializing V8.
   *
   * This is how interaction with V8 should look like:
   *   int compressed_data_count = v8::V8::GetCompressedStartupDataCount();
   *   v8::StartupData* compressed_data =
   *     new v8::StartupData[compressed_data_count];
   *   v8::V8::GetCompressedStartupData(compressed_data);
   *   ... decompress data (compressed_data can be updated in-place) ...
   *   v8::V8::SetDecompressedStartupData(compressed_data);
   *   ... now V8 can be initialized
   *   ... make sure the decompressed data stays valid until V8 shutdown
   *
   * A helper class StartupDataDecompressor is provided. It implements
   * the protocol of the interaction described above, and can be used in
   * most cases instead of calling these API functions directly.
   */
  static StartupData::CompressionAlgorithm GetCompressedStartupDataAlgorithm();
  static int GetCompressedStartupDataCount();
  static void GetCompressedStartupData(StartupData* compressed_data);
  static void SetDecompressedStartupData(StartupData* decompressed_data);

  /**
   * Adds a message listener.
   *
   * The same message listener can be added more than once and in that
   * case it will be called more than once for each message.
   *
   * If data is specified, it will be passed to the callback when it is called.
   * Otherwise, the exception object will be passed to the callback instead.
   */
  static bool AddMessageListener(MessageCallback that,
                                 Handle<Value> data = Handle<Value>());

  /**
   * Remove all message listeners from the specified callback function.
   */
  static void RemoveMessageListeners(MessageCallback that);

  /**
   * Tells V8 to capture current stack trace when uncaught exception occurs
   * and report it to the message listeners. The option is off by default.
   */
  static void SetCaptureStackTraceForUncaughtExceptions(
      bool capture,
      int frame_limit = 10,
      StackTrace::StackTraceOptions options = StackTrace::kOverview);

  /**
   * Sets V8 flags from a string.
   */
  static void SetFlagsFromString(const char* str, int length);

  /**
   * Sets V8 flags from the command line.
   */
  static void SetFlagsFromCommandLine(int* argc,
                                      char** argv,
                                      bool remove_flags);

  /** Get the version string. */
  static const char* GetVersion();

  /**
   * Enables the host application to provide a mechanism for recording
   * statistics counters.
   */
  static void SetCounterFunction(CounterLookupCallback);

  /**
   * Enables the host application to provide a mechanism for recording
   * histograms. The CreateHistogram function returns a
   * histogram which will later be passed to the AddHistogramSample
   * function.
   */
  static void SetCreateHistogramFunction(CreateHistogramCallback);
  static void SetAddHistogramSampleFunction(AddHistogramSampleCallback);

  /** Callback function for reporting failed access checks.*/
  static void SetFailedAccessCheckCallbackFunction(FailedAccessCheckCallback);

  /**
   * Enables the host application to receive a notification before a
   * garbage collection.  Allocations are not allowed in the
   * callback function, you therefore cannot manipulate objects (set
   * or delete properties for example) since it is possible such
   * operations will result in the allocation of objects. It is possible
   * to specify the GCType filter for your callback. But it is not possible to
   * register the same callback function two times with different
   * GCType filters.
   */
  static void AddGCPrologueCallback(
      GCPrologueCallback callback, GCType gc_type_filter = kGCTypeAll);

  /**
   * This function removes callback which was installed by
   * AddGCPrologueCallback function.
   */
  static void RemoveGCPrologueCallback(GCPrologueCallback callback);

  /**
   * Enables the host application to receive a notification after a
   * garbage collection.  Allocations are not allowed in the
   * callback function, you therefore cannot manipulate objects (set
   * or delete properties for example) since it is possible such
   * operations will result in the allocation of objects. It is possible
   * to specify the GCType filter for your callback. But it is not possible to
   * register the same callback function two times with different
   * GCType filters.
   */
  static void AddGCEpilogueCallback(
      GCEpilogueCallback callback, GCType gc_type_filter = kGCTypeAll);

  /**
   * This function removes callback which was installed by
   * AddGCEpilogueCallback function.
   */
  static void RemoveGCEpilogueCallback(GCEpilogueCallback callback);

  /**
   * Enables the host application to provide a mechanism to be notified
   * and perform custom logging when V8 Allocates Executable Memory.
   */
  static void AddMemoryAllocationCallback(MemoryAllocationCallback callback,
                                          ObjectSpace space,
                                          AllocationAction action);

  /**
   * Removes callback that was installed by AddMemoryAllocationCallback.
   */
  static void RemoveMemoryAllocationCallback(MemoryAllocationCallback callback);

  /**
   * Adds a callback to notify the host application when a script finished
   * running.  If a script re-enters the runtime during executing, the
   * CallCompletedCallback is only invoked when the outer-most script
   * execution ends.  Executing scripts inside the callback do not trigger
   * further callbacks.
   */
  static void AddCallCompletedCallback(CallCompletedCallback callback);

  /**
   * Removes callback that was installed by AddCallCompletedCallback.
   */
  static void RemoveCallCompletedCallback(CallCompletedCallback callback);

  /**
   * Initializes from snapshot if possible. Otherwise, attempts to
   * initialize from scratch.  This function is called implicitly if
   * you use the API without calling it first.
   */
  static bool Initialize();

  /**
   * Allows the host application to provide a callback which can be used
   * as a source of entropy for random number generators.
   */
  static void SetEntropySource(EntropySource source);

  /**
   * Allows the host application to provide a callback that allows v8 to
   * cooperate with a profiler that rewrites return addresses on stack.
   */
  static void SetReturnAddressLocationResolver(
      ReturnAddressLocationResolver return_address_resolver);

  /**
   * Deprecated, use the variant with the Isolate parameter below instead.
   */
  V8_DEPRECATED(static bool SetFunctionEntryHook(FunctionEntryHook entry_hook));

  /**
   * Allows the host application to provide the address of a function that's
   * invoked on entry to every V8-generated function.
   * Note that \p entry_hook is invoked at the very start of each
   * generated function.
   *
   * \param isolate the isolate to operate on.
   * \param entry_hook a function that will be invoked on entry to every
   *   V8-generated function.
   * \returns true on success on supported platforms, false on failure.
   * \note Setting an entry hook can only be done very early in an isolates
   *   lifetime, and once set, the entry hook cannot be revoked.
   */
  static bool SetFunctionEntryHook(Isolate* isolate,
                                   FunctionEntryHook entry_hook);

  /**
   * Allows the host application to provide the address of a function that is
   * notified each time code is added, moved or removed.
   *
   * \param options options for the JIT code event handler.
   * \param event_handler the JIT code event handler, which will be invoked
   *     each time code is added, moved or removed.
   * \note \p event_handler won't get notified of existent code.
   * \note since code removal notifications are not currently issued, the
   *     \p event_handler may get notifications of code that overlaps earlier
   *     code notifications. This happens when code areas are reused, and the
   *     earlier overlapping code areas should therefore be discarded.
   * \note the events passed to \p event_handler and the strings they point to
   *     are not guaranteed to live past each call. The \p event_handler must
   *     copy strings and other parameters it needs to keep around.
   * \note the set of events declared in JitCodeEvent::EventType is expected to
   *     grow over time, and the JitCodeEvent structure is expected to accrue
   *     new members. The \p event_handler function must ignore event codes
   *     it does not recognize to maintain future compatibility.
   */
  static void SetJitCodeEventHandler(JitCodeEventOptions options,
                                     JitCodeEventHandler event_handler);

  // TODO(svenpanne) Really deprecate me when Chrome is fixed.
  /** Deprecated. Use Isolate::AdjustAmountOfExternalAllocatedMemory instead. */
  static intptr_t AdjustAmountOfExternalAllocatedMemory(
      intptr_t change_in_bytes);

  /**
   * Forcefully terminate the current thread of JavaScript execution
   * in the given isolate. If no isolate is provided, the default
   * isolate is used.
   *
   * This method can be used by any thread even if that thread has not
   * acquired the V8 lock with a Locker object.
   *
   * \param isolate The isolate in which to terminate the current JS execution.
   */
  static void TerminateExecution(Isolate* isolate = NULL);

  /**
   * Is V8 terminating JavaScript execution.
   *
   * Returns true if JavaScript execution is currently terminating
   * because of a call to TerminateExecution.  In that case there are
   * still JavaScript frames on the stack and the termination
   * exception is still active.
   *
   * \param isolate The isolate in which to check.
   */
  static bool IsExecutionTerminating(Isolate* isolate = NULL);

  /**
   * Resume execution capability in the given isolate, whose execution
   * was previously forcefully terminated using TerminateExecution().
   *
   * When execution is forcefully terminated using TerminateExecution(),
   * the isolate can not resume execution until all JavaScript frames
   * have propagated the uncatchable exception which is generated.  This
   * method allows the program embedding the engine to handle the
   * termination event and resume execution capability, even if
   * JavaScript frames remain on the stack.
   *
   * This method can be used by any thread even if that thread has not
   * acquired the V8 lock with a Locker object.
   *
   * \param isolate The isolate in which to resume execution capability.
   */
  static void CancelTerminateExecution(Isolate* isolate);

  /**
   * Releases any resources used by v8 and stops any utility threads
   * that may be running.  Note that disposing v8 is permanent, it
   * cannot be reinitialized.
   *
   * It should generally not be necessary to dispose v8 before exiting
   * a process, this should happen automatically.  It is only necessary
   * to use if the process needs the resources taken up by v8.
   */
  static bool Dispose();

  /** Deprecated. Use Isolate::GetHeapStatistics instead. */
  V8_DEPRECATED(static void GetHeapStatistics(HeapStatistics* heap_statistics));

  /**
   * Iterates through all external resources referenced from current isolate
   * heap.  GC is not invoked prior to iterating, therefore there is no
   * guarantee that visited objects are still alive.
   */
  static void VisitExternalResources(ExternalResourceVisitor* visitor);

  /**
   * Iterates through all the persistent handles in the current isolate's heap
   * that have class_ids.
   */
  static void VisitHandlesWithClassIds(PersistentHandleVisitor* visitor);

  /**
   * Iterates through all the persistent handles in the current isolate's heap
   * that have class_ids and are candidates to be marked as partially dependent
   * handles. This will visit handles to young objects created since the last
   * garbage collection but is free to visit an arbitrary superset of these
   * objects.
   */
  static void VisitHandlesForPartialDependence(
      Isolate* isolate, PersistentHandleVisitor* visitor);

  /**
   * Optional notification that the embedder is idle.
   * V8 uses the notification to reduce memory footprint.
   * This call can be used repeatedly if the embedder remains idle.
   * Returns true if the embedder should stop calling IdleNotification
   * until real work has been done.  This indicates that V8 has done
   * as much cleanup as it will be able to do.
   *
   * The hint argument specifies the amount of work to be done in the function
   * on scale from 1 to 1000. There is no guarantee that the actual work will
   * match the hint.
   */
  static bool IdleNotification(int hint = 1000);

  /**
   * Optional notification that the system is running low on memory.
   * V8 uses these notifications to attempt to free memory.
   */
  static void LowMemoryNotification();

  /**
   * Optional notification that a context has been disposed. V8 uses
   * these notifications to guide the GC heuristic. Returns the number
   * of context disposals - including this one - since the last time
   * V8 had a chance to clean up.
   */
  static int ContextDisposedNotification();

  /**
   * Initialize the ICU library bundled with V8. The embedder should only
   * invoke this method when using the bundled ICU. Returns true on success.
   */
  static bool InitializeICU();

 private:
  V8();

  static internal::Object** GlobalizeReference(internal::Isolate* isolate,
                                               internal::Object** handle);
  static internal::Object** CopyPersistent(internal::Object** handle);
  static void DisposeGlobal(internal::Object** global_handle);
  typedef WeakReferenceCallbacks<Value, void>::Revivable RevivableCallback;
  typedef WeakCallbackData<Value, void>::Callback WeakCallback;
  static void MakeWeak(internal::Object** global_handle,
                       void* data,
                       WeakCallback weak_callback,
                       RevivableCallback weak_reference_callback);
  static void ClearWeak(internal::Object** global_handle);
  static void Eternalize(Isolate* isolate,
                         Value* handle,
                         int* index);
  static Local<Value> GetEternal(Isolate* isolate, int index);

  template <class T> friend class Handle;
  template <class T> friend class Local;
  template <class T> friend class Eternal;
  template <class T, class M> friend class Persistent;
  friend class Context;
};


/**
 * An external exception handler.
 */
class V8_EXPORT TryCatch {
 public:
  /**
   * Creates a new try/catch block and registers it with v8.  Note that
   * all TryCatch blocks should be stack allocated because the memory
   * location itself is compared against JavaScript try/catch blocks.
   */
  TryCatch();

  /**
   * Unregisters and deletes this try/catch block.
   */
  ~TryCatch();

  /**
   * Returns true if an exception has been caught by this try/catch block.
   */
  bool HasCaught() const;

  /**
   * For certain types of exceptions, it makes no sense to continue execution.
   *
   * If CanContinue returns false, the correct action is to perform any C++
   * cleanup needed and then return.  If CanContinue returns false and
   * HasTerminated returns true, it is possible to call
   * CancelTerminateExecution in order to continue calling into the engine.
   */
  bool CanContinue() const;

  /**
   * Returns true if an exception has been caught due to script execution
   * being terminated.
   *
   * There is no JavaScript representation of an execution termination
   * exception.  Such exceptions are thrown when the TerminateExecution
   * methods are called to terminate a long-running script.
   *
   * If such an exception has been thrown, HasTerminated will return true,
   * indicating that it is possible to call CancelTerminateExecution in order
   * to continue calling into the engine.
   */
  bool HasTerminated() const;

  /**
   * Throws the exception caught by this TryCatch in a way that avoids
   * it being caught again by this same TryCatch.  As with ThrowException
   * it is illegal to execute any JavaScript operations after calling
   * ReThrow; the caller must return immediately to where the exception
   * is caught.
   */
  Handle<Value> ReThrow();

  /**
   * Returns the exception caught by this try/catch block.  If no exception has
   * been caught an empty handle is returned.
   *
   * The returned handle is valid until this TryCatch block has been destroyed.
   */
  Local<Value> Exception() const;

  /**
   * Returns the .stack property of the thrown object.  If no .stack
   * property is present an empty handle is returned.
   */
  Local<Value> StackTrace() const;

  /**
   * Returns the message associated with this exception.  If there is
   * no message associated an empty handle is returned.
   *
   * The returned handle is valid until this TryCatch block has been
   * destroyed.
   */
  Local<v8::Message> Message() const;

  /**
   * Clears any exceptions that may have been caught by this try/catch block.
   * After this method has been called, HasCaught() will return false.
   *
   * It is not necessary to clear a try/catch block before using it again; if
   * another exception is thrown the previously caught exception will just be
   * overwritten.  However, it is often a good idea since it makes it easier
   * to determine which operation threw a given exception.
   */
  void Reset();

  /**
   * Set verbosity of the external exception handler.
   *
   * By default, exceptions that are caught by an external exception
   * handler are not reported.  Call SetVerbose with true on an
   * external exception handler to have exceptions caught by the
   * handler reported as if they were not caught.
   */
  void SetVerbose(bool value);

  /**
   * Set whether or not this TryCatch should capture a Message object
   * which holds source information about where the exception
   * occurred.  True by default.
   */
  void SetCaptureMessage(bool value);

 private:
  // Make it hard to create heap-allocated TryCatch blocks.
  TryCatch(const TryCatch&);
  void operator=(const TryCatch&);
  void* operator new(size_t size);
  void operator delete(void*, size_t);

  v8::internal::Isolate* isolate_;
  void* next_;
  void* exception_;
  void* message_obj_;
  void* message_script_;
  int message_start_pos_;
  int message_end_pos_;
  bool is_verbose_ : 1;
  bool can_continue_ : 1;
  bool capture_message_ : 1;
  bool rethrow_ : 1;
  bool has_terminated_ : 1;

  friend class v8::internal::Isolate;
};


// --- Context ---


/**
 * Ignore
 */
class V8_EXPORT ExtensionConfiguration {
 public:
  ExtensionConfiguration(int name_count, const char* names[])
      : name_count_(name_count), names_(names) { }
 private:
  friend class ImplementationUtilities;
  int name_count_;
  const char** names_;
};


/**
 * A sandboxed execution context with its own set of built-in objects
 * and functions.
 */
class V8_EXPORT Context {
 public:
  /**
   * Returns the global proxy object or global object itself for
   * detached contexts.
   *
   * Global proxy object is a thin wrapper whose prototype points to
   * actual context's global object with the properties like Object, etc.
   * This is done that way for security reasons (for more details see
   * https://wiki.mozilla.org/Gecko:SplitWindow).
   *
   * Please note that changes to global proxy object prototype most probably
   * would break VM---v8 expects only global object as a prototype of
   * global proxy object.
   *
   * If DetachGlobal() has been invoked, Global() would return actual global
   * object until global is reattached with ReattachGlobal().
   */
  Local<Object> Global();

  /**
   * Detaches the global object from its context before
   * the global object can be reused to create a new context.
   */
  void DetachGlobal();

  /**
   * Reattaches a global object to a context.  This can be used to
   * restore the connection between a global object and a context
   * after DetachGlobal has been called.
   *
   * \param global_object The global object to reattach to the
   *   context.  For this to work, the global object must be the global
   *   object that was associated with this context before a call to
   *   DetachGlobal.
   */
  void ReattachGlobal(Handle<Object> global_object);

  /**
   * Creates a new context and returns a handle to the newly allocated
   * context.
   *
   * \param isolate The isolate in which to create the context.
   *
   * \param extensions An optional extension configuration containing
   * the extensions to be installed in the newly created context.
   *
   * \param global_template An optional object template from which the
   * global object for the newly created context will be created.
   *
   * \param global_object An optional global object to be reused for
   * the newly created context. This global object must have been
   * created by a previous call to Context::New with the same global
   * template. The state of the global object will be completely reset
   * and only object identify will remain.
   */
  static Local<Context> New(
      Isolate* isolate,
      ExtensionConfiguration* extensions = NULL,
      Handle<ObjectTemplate> global_template = Handle<ObjectTemplate>(),
      Handle<Value> global_object = Handle<Value>());

  // TODO(dcarney):  Remove this function.
  /** Deprecated. Use Isolate::GetEnteredContext */
  static Local<Context> GetEntered();

  // TODO(dcarney) Remove this function.
  /** Deprecated. Use Isolate::GetCurrentContext instead. */
  static Local<Context> GetCurrent();

  // TODO(dcarney) Remove this function.
  /** Deprecated. Use Isolate::GetCallingContext instead. */
  static Local<Context> GetCalling();

  /**
   * Sets the security token for the context.  To access an object in
   * another context, the security tokens must match.
   */
  void SetSecurityToken(Handle<Value> token);

  /** Restores the security token to the default value. */
  void UseDefaultSecurityToken();

  /** Returns the security token of this context.*/
  Handle<Value> GetSecurityToken();

  /**
   * Enter this context.  After entering a context, all code compiled
   * and run is compiled and run in this context.  If another context
   * is already entered, this old context is saved so it can be
   * restored when the new context is exited.
   */
  void Enter();

  /**
   * Exit this context.  Exiting the current context restores the
   * context that was in place when entering the current context.
   */
  void Exit();

  /** Returns true if the context has experienced an out of memory situation. */
  bool HasOutOfMemoryException();

  // TODO(dcarney) Remove this function.
  /** Deprecated. Use Isolate::InContext instead. */
  static bool InContext();

  /** Returns an isolate associated with a current context. */
  v8::Isolate* GetIsolate();

  /**
   * Gets the embedder data with the given index, which must have been set by a
   * previous call to SetEmbedderData with the same index. Note that index 0
   * currently has a special meaning for Chrome's debugger.
   */
  V8_INLINE Local<Value> GetEmbedderData(int index);

  /**
   * Sets the embedder data with the given index, growing the data as
   * needed. Note that index 0 currently has a special meaning for Chrome's
   * debugger.
   */
  void SetEmbedderData(int index, Handle<Value> value);

  /**
   * Gets a 2-byte-aligned native pointer from the embedder data with the given
   * index, which must have bees set by a previous call to
   * SetAlignedPointerInEmbedderData with the same index. Note that index 0
   * currently has a special meaning for Chrome's debugger.
   */
  V8_INLINE void* GetAlignedPointerFromEmbedderData(int index);

  /**
   * Sets a 2-byte-aligned native pointer in the embedder data with the given
   * index, growing the data as needed. Note that index 0 currently has a
   * special meaning for Chrome's debugger.
   */
  void SetAlignedPointerInEmbedderData(int index, void* value);

  /**
   * Control whether code generation from strings is allowed. Calling
   * this method with false will disable 'eval' and the 'Function'
   * constructor for code running in this context. If 'eval' or the
   * 'Function' constructor are used an exception will be thrown.
   *
   * If code generation from strings is not allowed the
   * V8::AllowCodeGenerationFromStrings callback will be invoked if
   * set before blocking the call to 'eval' or the 'Function'
   * constructor. If that callback returns true, the call will be
   * allowed, otherwise an exception will be thrown. If no callback is
   * set an exception will be thrown.
   */
  void AllowCodeGenerationFromStrings(bool allow);

  /**
   * Returns true if code generation from strings is allowed for the context.
   * For more details see AllowCodeGenerationFromStrings(bool) documentation.
   */
  bool IsCodeGenerationFromStringsAllowed();

  /**
   * Sets the error description for the exception that is thrown when
   * code generation from strings is not allowed and 'eval' or the 'Function'
   * constructor are called.
   */
  void SetErrorMessageForCodeGenerationFromStrings(Handle<String> message);

  /**
   * Stack-allocated class which sets the execution context for all
   * operations executed within a local scope.
   */
  class Scope {
   public:
    explicit V8_INLINE Scope(Handle<Context> context) : context_(context) {
      context_->Enter();
    }
    // TODO(dcarney): deprecate
    V8_INLINE Scope(Isolate* isolate, Persistent<Context>& context) // NOLINT
    : context_(Handle<Context>::New(isolate, context)) {
      context_->Enter();
    }
    V8_INLINE ~Scope() { context_->Exit(); }

   private:
    Handle<Context> context_;
  };

 private:
  friend class Value;
  friend class Script;
  friend class Object;
  friend class Function;

  Local<Value> SlowGetEmbedderData(int index);
  void* SlowGetAlignedPointerFromEmbedderData(int index);
};


/**
 * Multiple threads in V8 are allowed, but only one thread at a time is allowed
 * to use any given V8 isolate, see the comments in the Isolate class. The
 * definition of 'using a V8 isolate' includes accessing handles or holding onto
 * object pointers obtained from V8 handles while in the particular V8 isolate.
 * It is up to the user of V8 to ensure, perhaps with locking, that this
 * constraint is not violated. In addition to any other synchronization
 * mechanism that may be used, the v8::Locker and v8::Unlocker classes must be
 * used to signal thead switches to V8.
 *
 * v8::Locker is a scoped lock object. While it's active, i.e. between its
 * construction and destruction, the current thread is allowed to use the locked
 * isolate. V8 guarantees that an isolate can be locked by at most one thread at
 * any time. In other words, the scope of a v8::Locker is a critical section.
 *
 * Sample usage:
* \code
 * ...
 * {
 *   v8::Locker locker(isolate);
 *   v8::Isolate::Scope isolate_scope(isolate);
 *   ...
 *   // Code using V8 and isolate goes here.
 *   ...
 * } // Destructor called here
 * \endcode
 *
 * If you wish to stop using V8 in a thread A you can do this either by
 * destroying the v8::Locker object as above or by constructing a v8::Unlocker
 * object:
 *
 * \code
 * {
 *   isolate->Exit();
 *   v8::Unlocker unlocker(isolate);
 *   ...
 *   // Code not using V8 goes here while V8 can run in another thread.
 *   ...
 * } // Destructor called here.
 * isolate->Enter();
 * \endcode
 *
 * The Unlocker object is intended for use in a long-running callback from V8,
 * where you want to release the V8 lock for other threads to use.
 *
 * The v8::Locker is a recursive lock, i.e. you can lock more than once in a
 * given thread. This can be useful if you have code that can be called either
 * from code that holds the lock or from code that does not. The Unlocker is
 * not recursive so you can not have several Unlockers on the stack at once, and
 * you can not use an Unlocker in a thread that is not inside a Locker's scope.
 *
 * An unlocker will unlock several lockers if it has to and reinstate the
 * correct depth of locking on its destruction, e.g.:
 *
 * \code
 * // V8 not locked.
 * {
 *   v8::Locker locker(isolate);
 *   Isolate::Scope isolate_scope(isolate);
 *   // V8 locked.
 *   {
 *     v8::Locker another_locker(isolate);
 *     // V8 still locked (2 levels).
 *     {
 *       isolate->Exit();
 *       v8::Unlocker unlocker(isolate);
 *       // V8 not locked.
 *     }
 *     isolate->Enter();
 *     // V8 locked again (2 levels).
 *   }
 *   // V8 still locked (1 level).
 * }
 * // V8 Now no longer locked.
 * \endcode
 */
class V8_EXPORT Unlocker {
 public:
  /**
   * Initialize Unlocker for a given Isolate.
   */
  V8_INLINE explicit Unlocker(Isolate* isolate) { Initialize(isolate); }

  /** Deprecated. Use Isolate version instead. */
  V8_DEPRECATED(Unlocker());

  ~Unlocker();
 private:
  void Initialize(Isolate* isolate);

  internal::Isolate* isolate_;
};


class V8_EXPORT Locker {
 public:
  /**
   * Initialize Locker for a given Isolate.
   */
  V8_INLINE explicit Locker(Isolate* isolate) { Initialize(isolate); }

  /** Deprecated. Use Isolate version instead. */
  V8_DEPRECATED(Locker());

  ~Locker();

  /**
   * Start preemption.
   *
   * When preemption is started, a timer is fired every n milliseconds
   * that will switch between multiple threads that are in contention
   * for the V8 lock.
   */
  static void StartPreemption(int every_n_ms);

  /**
   * Stop preemption.
   */
  static void StopPreemption();

  /**
   * Returns whether or not the locker for a given isolate, is locked by the
   * current thread.
   */
  static bool IsLocked(Isolate* isolate);

  /**
   * Returns whether v8::Locker is being used by this V8 instance.
   */
  static bool IsActive();

 private:
  void Initialize(Isolate* isolate);

  bool has_lock_;
  bool top_level_;
  internal::Isolate* isolate_;

  static bool active_;

  // Disallow copying and assigning.
  Locker(const Locker&);
  void operator=(const Locker&);
};


/**
 * A struct for exporting HeapStats data from V8, using "push" model.
 */
struct HeapStatsUpdate;


/**
 * An interface for exporting data from V8, using "push" model.
 */
class V8_EXPORT OutputStream {  // NOLINT
 public:
  enum OutputEncoding {
    kAscii = 0  // 7-bit ASCII.
  };
  enum WriteResult {
    kContinue = 0,
    kAbort = 1
  };
  virtual ~OutputStream() {}
  /** Notify about the end of stream. */
  virtual void EndOfStream() = 0;
  /** Get preferred output chunk size. Called only once. */
  virtual int GetChunkSize() { return 1024; }
  /** Get preferred output encoding. Called only once. */
  virtual OutputEncoding GetOutputEncoding() { return kAscii; }
  /**
   * Writes the next chunk of snapshot data into the stream. Writing
   * can be stopped by returning kAbort as function result. EndOfStream
   * will not be called in case writing was aborted.
   */
  virtual WriteResult WriteAsciiChunk(char* data, int size) = 0;
  /**
   * Writes the next chunk of heap stats data into the stream. Writing
   * can be stopped by returning kAbort as function result. EndOfStream
   * will not be called in case writing was aborted.
   */
  virtual WriteResult WriteHeapStatsChunk(HeapStatsUpdate* data, int count) {
    return kAbort;
  };
};


/**
 * An interface for reporting progress and controlling long-running
 * activities.
 */
class V8_EXPORT ActivityControl {  // NOLINT
 public:
  enum ControlOption {
    kContinue = 0,
    kAbort = 1
  };
  virtual ~ActivityControl() {}
  /**
   * Notify about current progress. The activity can be stopped by
   * returning kAbort as the callback result.
   */
  virtual ControlOption ReportProgressValue(int done, int total) = 0;
};


// --- Implementation ---


namespace internal {

const int kApiPointerSize = sizeof(void*);  // NOLINT
const int kApiIntSize = sizeof(int);  // NOLINT

// Tag information for HeapObject.
const int kHeapObjectTag = 1;
const int kHeapObjectTagSize = 2;
const intptr_t kHeapObjectTagMask = (1 << kHeapObjectTagSize) - 1;

// Tag information for Smi.
const int kSmiTag = 0;
const int kSmiTagSize = 1;
const intptr_t kSmiTagMask = (1 << kSmiTagSize) - 1;

template <size_t ptr_size> struct SmiTagging;

template<int kSmiShiftSize>
V8_INLINE internal::Object* IntToSmi(int value) {
  int smi_shift_bits = kSmiTagSize + kSmiShiftSize;
  intptr_t tagged_value =
      (static_cast<intptr_t>(value) << smi_shift_bits) | kSmiTag;
  return reinterpret_cast<internal::Object*>(tagged_value);
}

// Smi constants for 32-bit systems.
template <> struct SmiTagging<4> {
  static const int kSmiShiftSize = 0;
  static const int kSmiValueSize = 31;
  V8_INLINE static int SmiToInt(internal::Object* value) {
    int shift_bits = kSmiTagSize + kSmiShiftSize;
    // Throw away top 32 bits and shift down (requires >> to be sign extending).
    return static_cast<int>(reinterpret_cast<intptr_t>(value)) >> shift_bits;
  }
  V8_INLINE static internal::Object* IntToSmi(int value) {
    return internal::IntToSmi<kSmiShiftSize>(value);
  }
  V8_INLINE static bool IsValidSmi(intptr_t value) {
    // To be representable as an tagged small integer, the two
    // most-significant bits of 'value' must be either 00 or 11 due to
    // sign-extension. To check this we add 01 to the two
    // most-significant bits, and check if the most-significant bit is 0
    //
    // CAUTION: The original code below:
    // bool result = ((value + 0x40000000) & 0x80000000) == 0;
    // may lead to incorrect results according to the C language spec, and
    // in fact doesn't work correctly with gcc4.1.1 in some cases: The
    // compiler may produce undefined results in case of signed integer
    // overflow. The computation must be done w/ unsigned ints.
    return static_cast<uintptr_t>(value + 0x40000000U) < 0x80000000U;
  }
};

// Smi constants for 64-bit systems.
template <> struct SmiTagging<8> {
  static const int kSmiShiftSize = 31;
  static const int kSmiValueSize = 32;
  V8_INLINE static int SmiToInt(internal::Object* value) {
    int shift_bits = kSmiTagSize + kSmiShiftSize;
    // Shift down and throw away top 32 bits.
    return static_cast<int>(reinterpret_cast<intptr_t>(value) >> shift_bits);
  }
  V8_INLINE static internal::Object* IntToSmi(int value) {
    return internal::IntToSmi<kSmiShiftSize>(value);
  }
  V8_INLINE static bool IsValidSmi(intptr_t value) {
    // To be representable as a long smi, the value must be a 32-bit integer.
    return (value == static_cast<int32_t>(value));
  }
};

typedef SmiTagging<kApiPointerSize> PlatformSmiTagging;
const int kSmiShiftSize = PlatformSmiTagging::kSmiShiftSize;
const int kSmiValueSize = PlatformSmiTagging::kSmiValueSize;
V8_INLINE static bool SmiValuesAre31Bits() { return kSmiValueSize == 31; }
V8_INLINE static bool SmiValuesAre32Bits() { return kSmiValueSize == 32; }

/**
 * This class exports constants and functionality from within v8 that
 * is necessary to implement inline functions in the v8 api.  Don't
 * depend on functions and constants defined here.
 */
class Internals {
 public:
  // These values match non-compiler-dependent values defined within
  // the implementation of v8.
  static const int kHeapObjectMapOffset = 0;
  static const int kMapInstanceTypeOffset = 1 * kApiPointerSize + kApiIntSize;
  static const int kStringResourceOffset = 3 * kApiPointerSize;

  static const int kOddballKindOffset = 3 * kApiPointerSize;
  static const int kForeignAddressOffset = kApiPointerSize;
  static const int kJSObjectHeaderSize = 3 * kApiPointerSize;
  static const int kFixedArrayHeaderSize = 2 * kApiPointerSize;
  static const int kContextHeaderSize = 2 * kApiPointerSize;
  static const int kContextEmbedderDataIndex = 65;
  static const int kFullStringRepresentationMask = 0x07;
  static const int kStringEncodingMask = 0x4;
  static const int kExternalTwoByteRepresentationTag = 0x02;
  static const int kExternalAsciiRepresentationTag = 0x06;

  static const int kIsolateEmbedderDataOffset = 1 * kApiPointerSize;
  static const int kIsolateRootsOffset = 3 * kApiPointerSize;
  static const int kUndefinedValueRootIndex = 5;
  static const int kNullValueRootIndex = 7;
  static const int kTrueValueRootIndex = 8;
  static const int kFalseValueRootIndex = 9;
  static const int kEmptyStringRootIndex = 131;

  static const int kNodeClassIdOffset = 1 * kApiPointerSize;
  static const int kNodeFlagsOffset = 1 * kApiPointerSize + 3;
  static const int kNodeStateMask = 0xf;
  static const int kNodeStateIsWeakValue = 2;
  static const int kNodeStateIsPendingValue = 3;
  static const int kNodeStateIsNearDeathValue = 4;
  static const int kNodeIsIndependentShift = 4;
  static const int kNodeIsPartiallyDependentShift = 5;

  static const int kJSObjectType = 0xb1;
  static const int kFirstNonstringType = 0x80;
  static const int kOddballType = 0x83;
  static const int kForeignType = 0x87;

  static const int kUndefinedOddballKind = 5;
  static const int kNullOddballKind = 3;

  V8_EXPORT static void CheckInitializedImpl(v8::Isolate* isolate);
  V8_INLINE static void CheckInitialized(v8::Isolate* isolate) {
#ifdef V8_ENABLE_CHECKS
    CheckInitializedImpl(isolate);
#endif
  }

  V8_INLINE static bool HasHeapObjectTag(internal::Object* value) {
    return ((reinterpret_cast<intptr_t>(value) & kHeapObjectTagMask) ==
            kHeapObjectTag);
  }

  V8_INLINE static int SmiValue(internal::Object* value) {
    return PlatformSmiTagging::SmiToInt(value);
  }

  V8_INLINE static internal::Object* IntToSmi(int value) {
    return PlatformSmiTagging::IntToSmi(value);
  }

  V8_INLINE static bool IsValidSmi(intptr_t value) {
    return PlatformSmiTagging::IsValidSmi(value);
  }

  V8_INLINE static int GetInstanceType(internal::Object* obj) {
    typedef internal::Object O;
    O* map = ReadField<O*>(obj, kHeapObjectMapOffset);
    return ReadField<uint8_t>(map, kMapInstanceTypeOffset);
  }

  V8_INLINE static int GetOddballKind(internal::Object* obj) {
    typedef internal::Object O;
    return SmiValue(ReadField<O*>(obj, kOddballKindOffset));
  }

  V8_INLINE static bool IsExternalTwoByteString(int instance_type) {
    int representation = (instance_type & kFullStringRepresentationMask);
    return representation == kExternalTwoByteRepresentationTag;
  }

  V8_INLINE static uint8_t GetNodeFlag(internal::Object** obj, int shift) {
      uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
      return *addr & static_cast<uint8_t>(1U << shift);
  }

  V8_INLINE static void UpdateNodeFlag(internal::Object** obj,
                                       bool value, int shift) {
      uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
      uint8_t mask = static_cast<uint8_t>(1 << shift);
      *addr = static_cast<uint8_t>((*addr & ~mask) | (value << shift));
  }

  V8_INLINE static uint8_t GetNodeState(internal::Object** obj) {
    uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
    return *addr & kNodeStateMask;
  }

  V8_INLINE static void UpdateNodeState(internal::Object** obj,
                                        uint8_t value) {
    uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
    *addr = static_cast<uint8_t>((*addr & ~kNodeStateMask) | value);
  }

  V8_INLINE static void SetEmbedderData(v8::Isolate* isolate, void* data) {
    uint8_t* addr = reinterpret_cast<uint8_t*>(isolate) +
        kIsolateEmbedderDataOffset;
    *reinterpret_cast<void**>(addr) = data;
  }

  V8_INLINE static void* GetEmbedderData(v8::Isolate* isolate) {
    uint8_t* addr = reinterpret_cast<uint8_t*>(isolate) +
        kIsolateEmbedderDataOffset;
    return *reinterpret_cast<void**>(addr);
  }

  V8_INLINE static internal::Object** GetRoot(v8::Isolate* isolate,
                                              int index) {
    uint8_t* addr = reinterpret_cast<uint8_t*>(isolate) + kIsolateRootsOffset;
    return reinterpret_cast<internal::Object**>(addr + index * kApiPointerSize);
  }

  template <typename T> V8_INLINE static T ReadField(Object* ptr, int offset) {
    uint8_t* addr = reinterpret_cast<uint8_t*>(ptr) + offset - kHeapObjectTag;
    return *reinterpret_cast<T*>(addr);
  }

  template <typename T>
  V8_INLINE static T ReadEmbedderData(Context* context, int index) {
    typedef internal::Object O;
    typedef internal::Internals I;
    O* ctx = *reinterpret_cast<O**>(context);
    int embedder_data_offset = I::kContextHeaderSize +
        (internal::kApiPointerSize * I::kContextEmbedderDataIndex);
    O* embedder_data = I::ReadField<O*>(ctx, embedder_data_offset);
    int value_offset =
        I::kFixedArrayHeaderSize + (internal::kApiPointerSize * index);
    return I::ReadField<T>(embedder_data, value_offset);
  }

  V8_INLINE static bool CanCastToHeapObject(void* o) { return false; }
  V8_INLINE static bool CanCastToHeapObject(Context* o) { return true; }
  V8_INLINE static bool CanCastToHeapObject(String* o) { return true; }
  V8_INLINE static bool CanCastToHeapObject(Object* o) { return true; }
  V8_INLINE static bool CanCastToHeapObject(Message* o) { return true; }
  V8_INLINE static bool CanCastToHeapObject(StackTrace* o) { return true; }
  V8_INLINE static bool CanCastToHeapObject(StackFrame* o) { return true; }
};

}  // namespace internal


template <class T>
Local<T>::Local() : Handle<T>() { }


template <class T>
Local<T> Local<T>::New(Isolate* isolate, Handle<T> that) {
  return New(isolate, that.val_);
}

template <class T>
template <class M>
Local<T> Local<T>::New(Isolate* isolate, const Persistent<T, M>& that) {
  return New(isolate, that.val_);
}

template <class T>
Handle<T> Handle<T>::New(Isolate* isolate, T* that) {
  if (that == NULL) return Handle<T>();
  T* that_ptr = that;
  internal::Object** p = reinterpret_cast<internal::Object**>(that_ptr);
  return Handle<T>(reinterpret_cast<T*>(HandleScope::CreateHandle(
      reinterpret_cast<internal::Isolate*>(isolate), *p)));
}


template <class T>
Local<T> Local<T>::New(Isolate* isolate, T* that) {
  if (that == NULL) return Local<T>();
  T* that_ptr = that;
  internal::Object** p = reinterpret_cast<internal::Object**>(that_ptr);
  return Local<T>(reinterpret_cast<T*>(HandleScope::CreateHandle(
      reinterpret_cast<internal::Isolate*>(isolate), *p)));
}


template<class T>
template<class S>
void Eternal<T>::Set(Isolate* isolate, Local<S> handle) {
  TYPE_CHECK(T, S);
  V8::Eternalize(isolate, reinterpret_cast<Value*>(*handle), &this->index_);
}


template<class T>
Local<T> Eternal<T>::Get(Isolate* isolate) {
  return Local<T>(reinterpret_cast<T*>(*V8::GetEternal(isolate, index_)));
}


template <class T, class M>
T* Persistent<T, M>::New(Isolate* isolate, T* that) {
  if (that == NULL) return NULL;
  internal::Object** p = reinterpret_cast<internal::Object**>(that);
  return reinterpret_cast<T*>(
      V8::GlobalizeReference(reinterpret_cast<internal::Isolate*>(isolate),
                             p));
}


template <class T, class M>
template <class S, class M2>
void Persistent<T, M>::Copy(const Persistent<S, M2>& that) {
  TYPE_CHECK(T, S);
  Reset();
  if (that.IsEmpty()) return;
  internal::Object** p = reinterpret_cast<internal::Object**>(that.val_);
  this->val_ = reinterpret_cast<T*>(V8::CopyPersistent(p));
  M::Copy(that, this);
}


template <class T, class M>
bool Persistent<T, M>::IsIndependent() const {
  typedef internal::Internals I;
  if (this->IsEmpty()) return false;
  return I::GetNodeFlag(reinterpret_cast<internal::Object**>(this->val_),
                        I::kNodeIsIndependentShift);
}


template <class T, class M>
bool Persistent<T, M>::IsNearDeath() const {
  typedef internal::Internals I;
  if (this->IsEmpty()) return false;
  uint8_t node_state =
      I::GetNodeState(reinterpret_cast<internal::Object**>(this->val_));
  return node_state == I::kNodeStateIsNearDeathValue ||
      node_state == I::kNodeStateIsPendingValue;
}


template <class T, class M>
bool Persistent<T, M>::IsWeak() const {
  typedef internal::Internals I;
  if (this->IsEmpty()) return false;
  return I::GetNodeState(reinterpret_cast<internal::Object**>(this->val_)) ==
      I::kNodeStateIsWeakValue;
}


template <class T, class M>
void Persistent<T, M>::Reset() {
  if (this->IsEmpty()) return;
  V8::DisposeGlobal(reinterpret_cast<internal::Object**>(this->val_));
  val_ = 0;
}


template <class T, class M>
template <class S>
void Persistent<T, M>::Reset(Isolate* isolate, const Handle<S>& other) {
  TYPE_CHECK(T, S);
  Reset();
  if (other.IsEmpty()) return;
  this->val_ = New(isolate, other.val_);
}


template <class T,  class M>
template <class S, class M2>
void Persistent<T, M>::Reset(Isolate* isolate,
                             const Persistent<S, M2>& other) {
  TYPE_CHECK(T, S);
  Reset();
  if (other.IsEmpty()) return;
  this->val_ = New(isolate, other.val_);
}


template <class T, class M>
template <typename S, typename P>
void Persistent<T, M>::SetWeak(
    P* parameter,
    typename WeakCallbackData<S, P>::Callback callback) {
  TYPE_CHECK(S, T);
  typedef typename WeakCallbackData<Value, void>::Callback Callback;
  V8::MakeWeak(reinterpret_cast<internal::Object**>(this->val_),
               parameter,
               reinterpret_cast<Callback>(callback),
               NULL);
}


template <class T, class M>
template <typename P>
void Persistent<T, M>::SetWeak(
    P* parameter,
    typename WeakCallbackData<T, P>::Callback callback) {
  SetWeak<T, P>(parameter, callback);
}


template <class T, class M>
template <typename S, typename P>
void Persistent<T, M>::MakeWeak(
    P* parameters,
    typename WeakReferenceCallbacks<S, P>::Revivable callback) {
  TYPE_CHECK(S, T);
  typedef typename WeakReferenceCallbacks<Value, void>::Revivable Revivable;
  V8::MakeWeak(reinterpret_cast<internal::Object**>(this->val_),
               parameters,
               NULL,
               reinterpret_cast<Revivable>(callback));
}


template <class T, class M>
template <typename P>
void Persistent<T, M>::MakeWeak(
    P* parameters,
    typename WeakReferenceCallbacks<T, P>::Revivable callback) {
  MakeWeak<T, P>(parameters, callback);
}


template <class T, class M>
void Persistent<T, M>::ClearWeak() {
  V8::ClearWeak(reinterpret_cast<internal::Object**>(this->val_));
}


template <class T, class M>
void Persistent<T, M>::MarkIndependent() {
  typedef internal::Internals I;
  if (this->IsEmpty()) return;
  I::UpdateNodeFlag(reinterpret_cast<internal::Object**>(this->val_),
                    true,
                    I::kNodeIsIndependentShift);
}


template <class T, class M>
void Persistent<T, M>::MarkPartiallyDependent() {
  typedef internal::Internals I;
  if (this->IsEmpty()) return;
  I::UpdateNodeFlag(reinterpret_cast<internal::Object**>(this->val_),
                    true,
                    I::kNodeIsPartiallyDependentShift);
}


template <class T, class M>
T* Persistent<T, M>::ClearAndLeak() {
  T* old;
  old = val_;
  val_ = NULL;
  return old;
}


template <class T, class M>
void Persistent<T, M>::SetWrapperClassId(uint16_t class_id) {
  typedef internal::Internals I;
  if (this->IsEmpty()) return;
  internal::Object** obj = reinterpret_cast<internal::Object**>(this->val_);
  uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + I::kNodeClassIdOffset;
  *reinterpret_cast<uint16_t*>(addr) = class_id;
}


template <class T, class M>
uint16_t Persistent<T, M>::WrapperClassId() const {
  typedef internal::Internals I;
  if (this->IsEmpty()) return 0;
  internal::Object** obj = reinterpret_cast<internal::Object**>(this->val_);
  uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + I::kNodeClassIdOffset;
  return *reinterpret_cast<uint16_t*>(addr);
}


template<typename T>
ReturnValue<T>::ReturnValue(internal::Object** slot) : value_(slot) {}

template<typename T>
template<typename S>
void ReturnValue<T>::Set(const Persistent<S>& handle) {
  TYPE_CHECK(T, S);
  if (V8_UNLIKELY(handle.IsEmpty())) {
    *value_ = GetDefaultValue();
  } else {
    *value_ = *reinterpret_cast<internal::Object**>(*handle);
  }
}

template<typename T>
template<typename S>
void ReturnValue<T>::Set(const Handle<S> handle) {
  TYPE_CHECK(T, S);
  if (V8_UNLIKELY(handle.IsEmpty())) {
    *value_ = GetDefaultValue();
  } else {
    *value_ = *reinterpret_cast<internal::Object**>(*handle);
  }
}

template<typename T>
void ReturnValue<T>::Set(double i) {
  TYPE_CHECK(T, Number);
  Set(Number::New(GetIsolate(), i));
}

template<typename T>
void ReturnValue<T>::Set(int32_t i) {
  TYPE_CHECK(T, Integer);
  typedef internal::Internals I;
  if (V8_LIKELY(I::IsValidSmi(i))) {
    *value_ = I::IntToSmi(i);
    return;
  }
  Set(Integer::New(i, GetIsolate()));
}

template<typename T>
void ReturnValue<T>::Set(uint32_t i) {
  TYPE_CHECK(T, Integer);
  typedef internal::Internals I;
  // Can't simply use INT32_MAX here for whatever reason.
  bool fits_into_int32_t = (i & (1U << 31)) == 0;
  if (V8_LIKELY(fits_into_int32_t)) {
    Set(static_cast<int32_t>(i));
    return;
  }
  Set(Integer::NewFromUnsigned(i, GetIsolate()));
}

template<typename T>
void ReturnValue<T>::Set(bool value) {
  TYPE_CHECK(T, Boolean);
  typedef internal::Internals I;
  int root_index;
  if (value) {
    root_index = I::kTrueValueRootIndex;
  } else {
    root_index = I::kFalseValueRootIndex;
  }
  *value_ = *I::GetRoot(GetIsolate(), root_index);
}

template<typename T>
void ReturnValue<T>::SetNull() {
  TYPE_CHECK(T, Primitive);
  typedef internal::Internals I;
  *value_ = *I::GetRoot(GetIsolate(), I::kNullValueRootIndex);
}

template<typename T>
void ReturnValue<T>::SetUndefined() {
  TYPE_CHECK(T, Primitive);
  typedef internal::Internals I;
  *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() {
  // Isolate is always the pointer below the default value on the stack.
  return *reinterpret_cast<Isolate**>(&value_[-2]);
}

template<typename T>
internal::Object* ReturnValue<T>::GetDefaultValue() {
  // Default value is always the pointer below value_ on the stack.
  return value_[-1];
}


template<typename T>
FunctionCallbackInfo<T>::FunctionCallbackInfo(internal::Object** implicit_args,
                                              internal::Object** values,
                                              int length,
                                              bool is_construct_call)
    : implicit_args_(implicit_args),
      values_(values),
      length_(length),
      is_construct_call_(is_construct_call) { }


template<typename T>
Local<Value> FunctionCallbackInfo<T>::operator[](int i) const {
  if (i < 0 || length_ <= i) return Local<Value>(*Undefined(GetIsolate()));
  return Local<Value>(reinterpret_cast<Value*>(values_ - i));
}


template<typename T>
Local<Function> FunctionCallbackInfo<T>::Callee() const {
  return Local<Function>(reinterpret_cast<Function*>(
      &implicit_args_[kCalleeIndex]));
}


template<typename T>
Local<Object> FunctionCallbackInfo<T>::This() const {
  return Local<Object>(reinterpret_cast<Object*>(values_ + 1));
}


template<typename T>
Local<Object> FunctionCallbackInfo<T>::Holder() const {
  return Local<Object>(reinterpret_cast<Object*>(
      &implicit_args_[kHolderIndex]));
}


template<typename T>
Local<Value> FunctionCallbackInfo<T>::Data() const {
  return Local<Value>(reinterpret_cast<Value*>(&implicit_args_[kDataIndex]));
}


template<typename T>
Isolate* FunctionCallbackInfo<T>::GetIsolate() const {
  return *reinterpret_cast<Isolate**>(&implicit_args_[kIsolateIndex]);
}


template<typename T>
ReturnValue<T> FunctionCallbackInfo<T>::GetReturnValue() const {
  return ReturnValue<T>(&implicit_args_[kReturnValueIndex]);
}


template<typename T>
bool FunctionCallbackInfo<T>::IsConstructCall() const {
  return is_construct_call_;
}


template<typename T>
int FunctionCallbackInfo<T>::Length() const {
  return length_;
}


template <class T>
Local<T> HandleScope::Close(Handle<T> value) {
  internal::Object** before = reinterpret_cast<internal::Object**>(*value);
  internal::Object** after = RawClose(before);
  return Local<T>(reinterpret_cast<T*>(after));
}

Handle<Value> ScriptOrigin::ResourceName() const {
  return resource_name_;
}


Handle<Integer> ScriptOrigin::ResourceLineOffset() const {
  return resource_line_offset_;
}


Handle<Integer> ScriptOrigin::ResourceColumnOffset() const {
  return resource_column_offset_;
}

Handle<Boolean> ScriptOrigin::ResourceIsSharedCrossOrigin() const {
  return resource_is_shared_cross_origin_;
}


Handle<Boolean> Boolean::New(bool value) {
  Isolate* isolate = Isolate::GetCurrent();
  return value ? True(isolate) : False(isolate);
}


void Template::Set(const char* name, v8::Handle<Data> value) {
  Set(v8::String::New(name), value);
}


Local<Value> Object::GetInternalField(int index) {
#ifndef V8_ENABLE_CHECKS
  typedef internal::Object O;
  typedef internal::HeapObject HO;
  typedef internal::Internals I;
  O* obj = *reinterpret_cast<O**>(this);
  // Fast path: If the object is a plain JSObject, which is the common case, we
  // know where to find the internal fields and can return the value directly.
  if (I::GetInstanceType(obj) == I::kJSObjectType) {
    int offset = I::kJSObjectHeaderSize + (internal::kApiPointerSize * index);
    O* value = I::ReadField<O*>(obj, offset);
    O** result = HandleScope::CreateHandle(reinterpret_cast<HO*>(obj), value);
    return Local<Value>(reinterpret_cast<Value*>(result));
  }
#endif
  return SlowGetInternalField(index);
}


void* Object::GetAlignedPointerFromInternalField(int index) {
#ifndef V8_ENABLE_CHECKS
  typedef internal::Object O;
  typedef internal::Internals I;
  O* obj = *reinterpret_cast<O**>(this);
  // Fast path: If the object is a plain JSObject, which is the common case, we
  // know where to find the internal fields and can return the value directly.
  if (V8_LIKELY(I::GetInstanceType(obj) == I::kJSObjectType)) {
    int offset = I::kJSObjectHeaderSize + (internal::kApiPointerSize * index);
    return I::ReadField<void*>(obj, offset);
  }
#endif
  return SlowGetAlignedPointerFromInternalField(index);
}


String* String::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<String*>(value);
}


Local<String> String::Empty(Isolate* isolate) {
  typedef internal::Object* S;
  typedef internal::Internals I;
  I::CheckInitialized(isolate);
  S* slot = I::GetRoot(isolate, I::kEmptyStringRootIndex);
  return Local<String>(reinterpret_cast<String*>(slot));
}


Local<String> String::New(const char* data, int length) {
  return NewFromUtf8(Isolate::GetCurrent(), data, kNormalString, length);
}


Local<String> String::New(const uint16_t* data, int length) {
  return NewFromTwoByte(Isolate::GetCurrent(), data, kNormalString, length);
}


Local<String> String::NewSymbol(const char* data, int length) {
  return NewFromUtf8(Isolate::GetCurrent(), data, kInternalizedString, length);
}


Local<String> String::NewUndetectable(const char* data, int length) {
  return NewFromUtf8(Isolate::GetCurrent(), data, kUndetectableString, length);
}


Local<String> String::NewUndetectable(const uint16_t* data, int length) {
  return NewFromTwoByte(
      Isolate::GetCurrent(), data, kUndetectableString, length);
}


String::ExternalStringResource* String::GetExternalStringResource() const {
  typedef internal::Object O;
  typedef internal::Internals I;
  O* obj = *reinterpret_cast<O**>(const_cast<String*>(this));
  String::ExternalStringResource* result;
  if (I::IsExternalTwoByteString(I::GetInstanceType(obj))) {
    void* value = I::ReadField<void*>(obj, I::kStringResourceOffset);
    result = reinterpret_cast<String::ExternalStringResource*>(value);
  } else {
    result = NULL;
  }
#ifdef V8_ENABLE_CHECKS
  VerifyExternalStringResource(result);
#endif
  return result;
}


String::ExternalStringResourceBase* String::GetExternalStringResourceBase(
    String::Encoding* encoding_out) const {
  typedef internal::Object O;
  typedef internal::Internals I;
  O* obj = *reinterpret_cast<O**>(const_cast<String*>(this));
  int type = I::GetInstanceType(obj) & I::kFullStringRepresentationMask;
  *encoding_out = static_cast<Encoding>(type & I::kStringEncodingMask);
  ExternalStringResourceBase* resource = NULL;
  if (type == I::kExternalAsciiRepresentationTag ||
      type == I::kExternalTwoByteRepresentationTag) {
    void* value = I::ReadField<void*>(obj, I::kStringResourceOffset);
    resource = static_cast<ExternalStringResourceBase*>(value);
  }
#ifdef V8_ENABLE_CHECKS
    VerifyExternalStringResourceBase(resource, *encoding_out);
#endif
  return resource;
}


bool Value::IsUndefined() const {
#ifdef V8_ENABLE_CHECKS
  return FullIsUndefined();
#else
  return QuickIsUndefined();
#endif
}

bool Value::QuickIsUndefined() const {
  typedef internal::Object O;
  typedef internal::Internals I;
  O* obj = *reinterpret_cast<O**>(const_cast<Value*>(this));
  if (!I::HasHeapObjectTag(obj)) return false;
  if (I::GetInstanceType(obj) != I::kOddballType) return false;
  return (I::GetOddballKind(obj) == I::kUndefinedOddballKind);
}


bool Value::IsNull() const {
#ifdef V8_ENABLE_CHECKS
  return FullIsNull();
#else
  return QuickIsNull();
#endif
}

bool Value::QuickIsNull() const {
  typedef internal::Object O;
  typedef internal::Internals I;
  O* obj = *reinterpret_cast<O**>(const_cast<Value*>(this));
  if (!I::HasHeapObjectTag(obj)) return false;
  if (I::GetInstanceType(obj) != I::kOddballType) return false;
  return (I::GetOddballKind(obj) == I::kNullOddballKind);
}


bool Value::IsString() const {
#ifdef V8_ENABLE_CHECKS
  return FullIsString();
#else
  return QuickIsString();
#endif
}

bool Value::QuickIsString() const {
  typedef internal::Object O;
  typedef internal::Internals I;
  O* obj = *reinterpret_cast<O**>(const_cast<Value*>(this));
  if (!I::HasHeapObjectTag(obj)) return false;
  return (I::GetInstanceType(obj) < I::kFirstNonstringType);
}


template <class T> Value* Value::Cast(T* value) {
  return static_cast<Value*>(value);
}


Symbol* Symbol::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Symbol*>(value);
}


Number* Number::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Number*>(value);
}


Integer* Integer::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Integer*>(value);
}


Date* Date::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Date*>(value);
}


StringObject* StringObject::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<StringObject*>(value);
}


SymbolObject* SymbolObject::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<SymbolObject*>(value);
}


NumberObject* NumberObject::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<NumberObject*>(value);
}


BooleanObject* BooleanObject::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<BooleanObject*>(value);
}


RegExp* RegExp::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<RegExp*>(value);
}


Object* Object::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Object*>(value);
}


Array* Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Array*>(value);
}


ArrayBuffer* ArrayBuffer::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<ArrayBuffer*>(value);
}


ArrayBufferView* ArrayBufferView::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<ArrayBufferView*>(value);
}


TypedArray* TypedArray::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<TypedArray*>(value);
}


Uint8Array* Uint8Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Uint8Array*>(value);
}


Int8Array* Int8Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Int8Array*>(value);
}


Uint16Array* Uint16Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Uint16Array*>(value);
}


Int16Array* Int16Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Int16Array*>(value);
}


Uint32Array* Uint32Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Uint32Array*>(value);
}


Int32Array* Int32Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Int32Array*>(value);
}


Float32Array* Float32Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Float32Array*>(value);
}


Float64Array* Float64Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Float64Array*>(value);
}


Uint8ClampedArray* Uint8ClampedArray::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Uint8ClampedArray*>(value);
}


DataView* DataView::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<DataView*>(value);
}


Function* Function::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<Function*>(value);
}


External* External::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
  CheckCast(value);
#endif
  return static_cast<External*>(value);
}


template<typename T>
Isolate* PropertyCallbackInfo<T>::GetIsolate() const {
  return *reinterpret_cast<Isolate**>(&args_[kIsolateIndex]);
}


template<typename T>
Local<Value> PropertyCallbackInfo<T>::Data() const {
  return Local<Value>(reinterpret_cast<Value*>(&args_[kDataIndex]));
}


template<typename T>
Local<Object> PropertyCallbackInfo<T>::This() const {
  return Local<Object>(reinterpret_cast<Object*>(&args_[kThisIndex]));
}


template<typename T>
Local<Object> PropertyCallbackInfo<T>::Holder() const {
  return Local<Object>(reinterpret_cast<Object*>(&args_[kHolderIndex]));
}


template<typename T>
ReturnValue<T> PropertyCallbackInfo<T>::GetReturnValue() const {
  return ReturnValue<T>(&args_[kReturnValueIndex]);
}


Handle<Primitive> Undefined(Isolate* isolate) {
  typedef internal::Object* S;
  typedef internal::Internals I;
  I::CheckInitialized(isolate);
  S* slot = I::GetRoot(isolate, I::kUndefinedValueRootIndex);
  return Handle<Primitive>(reinterpret_cast<Primitive*>(slot));
}


Handle<Primitive> Null(Isolate* isolate) {
  typedef internal::Object* S;
  typedef internal::Internals I;
  I::CheckInitialized(isolate);
  S* slot = I::GetRoot(isolate, I::kNullValueRootIndex);
  return Handle<Primitive>(reinterpret_cast<Primitive*>(slot));
}


Handle<Boolean> True(Isolate* isolate) {
  typedef internal::Object* S;
  typedef internal::Internals I;
  I::CheckInitialized(isolate);
  S* slot = I::GetRoot(isolate, I::kTrueValueRootIndex);
  return Handle<Boolean>(reinterpret_cast<Boolean*>(slot));
}


Handle<Boolean> False(Isolate* isolate) {
  typedef internal::Object* S;
  typedef internal::Internals I;
  I::CheckInitialized(isolate);
  S* slot = I::GetRoot(isolate, I::kFalseValueRootIndex);
  return Handle<Boolean>(reinterpret_cast<Boolean*>(slot));
}


void Isolate::SetData(void* data) {
  typedef internal::Internals I;
  I::SetEmbedderData(this, data);
}


void* Isolate::GetData() {
  typedef internal::Internals I;
  return I::GetEmbedderData(this);
}


Local<Value> Context::GetEmbedderData(int index) {
#ifndef V8_ENABLE_CHECKS
  typedef internal::Object O;
  typedef internal::HeapObject HO;
  typedef internal::Internals I;
  HO* context = *reinterpret_cast<HO**>(this);
  O** result =
      HandleScope::CreateHandle(context, I::ReadEmbedderData<O*>(this, index));
  return Local<Value>(reinterpret_cast<Value*>(result));
#else
  return SlowGetEmbedderData(index);
#endif
}


void* Context::GetAlignedPointerFromEmbedderData(int index) {
#ifndef V8_ENABLE_CHECKS
  typedef internal::Internals I;
  return I::ReadEmbedderData<void*>(this, index);
#else
  return SlowGetAlignedPointerFromEmbedderData(index);
#endif
}


/**
 * \example shell.cc
 * A simple shell that takes a list of expressions on the
 * command-line and executes them.
 */


/**
 * \example process.cc
 */


}  // namespace v8


#undef TYPE_CHECK


#endif  // V8_H_