v8.h

Go to the documentation of this file.

// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/** \mainpage V8 API Reference Guide
 *
 * V8 is Google's open source JavaScript engine.
 *
 * This set of documents provides reference material generated from the
 * V8 header file, include/v8.h.
 *
 * For other documentation see http://code.google.com/apis/v8/
 */

#ifndef V8_H_
#define V8_H_

#include <stddef.h>
#include <stdint.h>
#include <stdio.h>

#include "v8-version.h"
#include "v8config.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 External;
class Function;
class FunctionTemplate;
class HeapProfiler;
class ImplementationUtilities;
class Int32;
class Integer;
class Isolate;
template <class T>
class Maybe;
class Name;
class Number;
class NumberObject;
class Object;
class ObjectOperationDescriptor;
class ObjectTemplate;
class Platform;
class Primitive;
class Promise;
class RawOperationDescriptor;
class Script;
class SharedArrayBuffer;
class Signature;
class StartupData;
class StackFrame;
class StackTrace;
class String;
class StringObject;
class Symbol;
class SymbolObject;
class Uint32;
class Utils;
class Value;
template <class T> class Local;
template <class T>
class MaybeLocal;
template <class T> class Eternal;
template<class T> class NonCopyablePersistentTraits;
template<class T> class PersistentBase;
template<class T,
         class M = NonCopyablePersistentTraits<T> > class Persistent;
template <class T>
class Global;
template<class K, class V, class T> class PersistentValueMap;
template <class K, class V, class T>
class PersistentValueMapBase;
template <class K, class V, class T>
class GlobalValueMap;
template<class V, class T> class PersistentValueVector;
template<class T, class P> class WeakCallbackObject;
class FunctionTemplate;
class ObjectTemplate;
class Data;
template<typename T> class FunctionCallbackInfo;
template<typename T> class PropertyCallbackInfo;
class StackTrace;
class StackFrame;
class Isolate;
class CallHandlerHelper;
class EscapableHandleScope;
template<typename T> class ReturnValue;

namespace internal {
class Arguments;
class Heap;
class HeapObject;
class Isolate;
class Object;
struct StreamedSource;
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 Local<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 Local {
 public:
  V8_INLINE Local() : val_(0) {}
  template <class S>
  V8_INLINE Local(Local<S> that)
      : val_(reinterpret_cast<T*>(*that)) {
    /**
     * This check fails when trying to convert between incompatible
     * handles. For example, converting from a Local<String> to a
     * Local<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 Local<S>& that) const {
    internal::Object** a = reinterpret_cast<internal::Object**>(this->val_);
    internal::Object** b = reinterpret_cast<internal::Object**>(that.val_);
    if (a == 0) return b == 0;
    if (b == 0) return false;
    return *a == *b;
  }

  template <class S> V8_INLINE bool operator==(
      const PersistentBase<S>& that) const {
    internal::Object** a = reinterpret_cast<internal::Object**>(this->val_);
    internal::Object** b = reinterpret_cast<internal::Object**>(that.val_);
    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 Local<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 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<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, Local<T> that);
  V8_INLINE static Local<T> New(Isolate* isolate,
                                const PersistentBase<T>& that);

 private:
  friend class Utils;
  template<class F> friend class Eternal;
  template<class F> friend class PersistentBase;
  template<class F, class M> friend class Persistent;
  template<class F> friend class Local;
  template <class F>
  friend class MaybeLocal;
  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 Local<Primitive> Undefined(Isolate* isolate);
  friend Local<Primitive> Null(Isolate* isolate);
  friend Local<Boolean> True(Isolate* isolate);
  friend Local<Boolean> False(Isolate* isolate);
  friend class HandleScope;
  friend class EscapableHandleScope;
  template <class F1, class F2, class F3>
  friend class PersistentValueMapBase;
  template<class F1, class F2> friend class PersistentValueVector;

  template <class S>
  V8_INLINE Local(S* that)
      : val_(that) {}
  V8_INLINE static Local<T> New(Isolate* isolate, T* that);
  T* val_;
};


#if !defined(V8_IMMINENT_DEPRECATION_WARNINGS)
// Local is an alias for Local for historical reasons.
template <class T>
using Handle = Local<T>;
#endif


/**
 * A MaybeLocal<> is a wrapper around Local<> that enforces a check whether
 * the Local<> is empty before it can be used.
 *
 * If an API method returns a MaybeLocal<>, the API method can potentially fail
 * either because an exception is thrown, or because an exception is pending,
 * e.g. because a previous API call threw an exception that hasn't been caught
 * yet, or because a TerminateExecution exception was thrown. In that case, an
 * empty MaybeLocal is returned.
 */
template <class T>
class MaybeLocal {
 public:
  V8_INLINE MaybeLocal() : val_(nullptr) {}
  template <class S>
  V8_INLINE MaybeLocal(Local<S> that)
      : val_(reinterpret_cast<T*>(*that)) {
    TYPE_CHECK(T, S);
  }

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

  template <class S>
  V8_WARN_UNUSED_RESULT V8_INLINE bool ToLocal(Local<S>* out) const {
    out->val_ = IsEmpty() ? nullptr : this->val_;
    return !IsEmpty();
  }

  // Will crash if the MaybeLocal<> is empty.
  V8_INLINE Local<T> ToLocalChecked();

  template <class S>
  V8_INLINE Local<S> FromMaybe(Local<S> default_value) const {
    return IsEmpty() ? default_value : Local<S>(val_);
  }

 private:
  T* val_;
};


// 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_;
};


static const int kInternalFieldsInWeakCallback = 2;


template <typename T>
class WeakCallbackInfo {
 public:
  typedef void (*Callback)(const WeakCallbackInfo<T>& data);

  WeakCallbackInfo(Isolate* isolate, T* parameter,
                   void* internal_fields[kInternalFieldsInWeakCallback],
                   Callback* callback)
      : isolate_(isolate), parameter_(parameter), callback_(callback) {
    for (int i = 0; i < kInternalFieldsInWeakCallback; ++i) {
      internal_fields_[i] = internal_fields[i];
    }
  }

  V8_INLINE Isolate* GetIsolate() const { return isolate_; }
  V8_INLINE T* GetParameter() const { return parameter_; }
  V8_INLINE void* GetInternalField(int index) const;

  V8_INLINE V8_DEPRECATE_SOON("use indexed version",
                              void* GetInternalField1() const) {
    return internal_fields_[0];
  }
  V8_INLINE V8_DEPRECATE_SOON("use indexed version",
                              void* GetInternalField2() const) {
    return internal_fields_[1];
  }

  bool IsFirstPass() const { return callback_ != nullptr; }

  // When first called, the embedder MUST Reset() the Global which triggered the
  // callback. The Global itself is unusable for anything else. No v8 other api
  // calls may be called in the first callback. Should additional work be
  // required, the embedder must set a second pass callback, which will be
  // called after all the initial callbacks are processed.
  // Calling SetSecondPassCallback on the second pass will immediately crash.
  void SetSecondPassCallback(Callback callback) const { *callback_ = callback; }

 private:
  Isolate* isolate_;
  T* parameter_;
  Callback* callback_;
  void* internal_fields_[kInternalFieldsInWeakCallback];
};


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

  WeakCallbackData(Isolate* isolate, P* parameter, Local<T> handle)
      : isolate_(isolate), parameter_(parameter), handle_(handle) {}

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

 private:
  Isolate* isolate_;
  P* parameter_;
  Local<T> handle_;
};


// TODO(dcarney): delete this with WeakCallbackData
template <class T>
using PhantomCallbackData = WeakCallbackInfo<T>;


enum class WeakCallbackType { kParameter, kInternalFields };


/**
 * 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 PersistentBase 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 PersistentBase::Reset and
 * existing handles can be disposed using PersistentBase::Reset.
 *
 */
template <class T> class PersistentBase {
 public:
  /**
   * 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 Local<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>
  V8_INLINE void Reset(Isolate* isolate, const PersistentBase<S>& other);

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

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

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

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

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

  /**
   *  Install a finalization callback on this object.
   *  NOTE: There is no guarantee as to *when* or even *if* the callback is
   *  invoked. The invocation is performed solely on a best effort basis.
   *  As always, GC-based finalization should *not* be relied upon for any
   *  critical form of resource management!
   */
  template <typename P>
  V8_INLINE V8_DEPRECATE_SOON(
      "use WeakCallbackInfo version",
      void SetWeak(P* parameter,
                   typename WeakCallbackData<T, P>::Callback callback));

  template <typename S, typename P>
  V8_INLINE V8_DEPRECATE_SOON(
      "use WeakCallbackInfo version",
      void SetWeak(P* parameter,
                   typename WeakCallbackData<S, P>::Callback callback));

  // Phantom persistents work like weak persistents, except that the pointer to
  // the object being collected is not available in the finalization callback.
  // This enables the garbage collector to collect the object and any objects
  // it references transitively in one GC cycle. At the moment you can either
  // specify a parameter for the callback or the location of two internal
  // fields in the dying object.
  template <typename P>
  V8_INLINE V8_DEPRECATE_SOON(
      "use SetWeak",
      void SetPhantom(P* parameter,
                      typename WeakCallbackInfo<P>::Callback callback,
                      int internal_field_index1 = -1,
                      int internal_field_index2 = -1));

  template <typename P>
  V8_INLINE void SetWeak(P* parameter,
                         typename WeakCallbackInfo<P>::Callback callback,
                         WeakCallbackType type);

  template<typename P>
  V8_INLINE P* ClearWeak();

  // TODO(dcarney): remove this.
  V8_INLINE void ClearWeak() { ClearWeak<void>(); }

  /**
   * Marks the reference to this object independent. Garbage collector is free
   * 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();

  /**
   * 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_INLINE bool IsIndependent() const;

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

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

  /**
   * 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);

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

 private:
  friend class Isolate;
  friend class Utils;
  template<class F> friend class Local;
  template<class F1, class F2> friend class Persistent;
  template <class F>
  friend class Global;
  template<class F> friend class PersistentBase;
  template<class F> friend class ReturnValue;
  template <class F1, class F2, class F3>
  friend class PersistentValueMapBase;
  template<class F1, class F2> friend class PersistentValueVector;
  friend class Object;

  explicit V8_INLINE PersistentBase(T* val) : val_(val) {}
  PersistentBase(PersistentBase& other) = delete;  // NOLINT
  void operator=(PersistentBase&) = delete;
  V8_INLINE static T* New(Isolate* isolate, T* that);

  T* val_;
};


/**
 * 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
  }
};


/**
 * A PersistentBase which allows copy and assignment.
 *
 * Copy, assignment and destructor bevavior is controlled by the traits
 * class M.
 *
 * Note: Persistent class hierarchy is subject to future changes.
 */
template <class T, class M> class Persistent : public PersistentBase<T> {
 public:
  /**
   * A Persistent with no storage cell.
   */
  V8_INLINE Persistent() : PersistentBase<T>(0) { }
  /**
   * Construct a Persistent from a Local.
   * When the Local 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, Local<S> that)
      : PersistentBase<T>(PersistentBase<T>::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)
    : PersistentBase<T>(PersistentBase<T>::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) : PersistentBase<T>(0) {
    Copy(that);
  }
  template <class S, class M2>
  V8_INLINE Persistent(const Persistent<S, M2>& that) : PersistentBase<T>(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) this->Reset();
  }

  // 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);
  }

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

  template <class S> V8_INLINE Persistent(S* that) : PersistentBase<T>(that) { }
  V8_INLINE T* operator*() const { return this->val_; }
  template<class S, class M2>
  V8_INLINE void Copy(const Persistent<S, M2>& that);
};


/**
 * A PersistentBase which has move semantics.
 *
 * Note: Persistent class hierarchy is subject to future changes.
 */
template <class T>
class Global : public PersistentBase<T> {
 public:
  /**
   * A Global with no storage cell.
   */
  V8_INLINE Global() : PersistentBase<T>(nullptr) {}
  /**
   * Construct a Global from a Local.
   * When the Local is non-empty, a new storage cell is created
   * pointing to the same object, and no flags are set.
   */
  template <class S>
  V8_INLINE Global(Isolate* isolate, Local<S> that)
      : PersistentBase<T>(PersistentBase<T>::New(isolate, *that)) {
    TYPE_CHECK(T, S);
  }
  /**
   * Construct a Global from a PersistentBase.
   * When the Persistent is non-empty, a new storage cell is created
   * pointing to the same object, and no flags are set.
   */
  template <class S>
  V8_INLINE Global(Isolate* isolate, const PersistentBase<S>& that)
      : PersistentBase<T>(PersistentBase<T>::New(isolate, that.val_)) {
    TYPE_CHECK(T, S);
  }
  /**
   * Move constructor.
   */
  V8_INLINE Global(Global&& other) : PersistentBase<T>(other.val_) {
    other.val_ = nullptr;
  }
  V8_INLINE ~Global() { this->Reset(); }
  /**
   * Move via assignment.
   */
  template <class S>
  V8_INLINE Global& operator=(Global<S>&& rhs) {
    TYPE_CHECK(T, S);
    if (this != &rhs) {
      this->Reset();
      this->val_ = rhs.val_;
      rhs.val_ = nullptr;
    }
    return *this;
  }
  /**
   * Pass allows returning uniques from functions, etc.
   */
  Global Pass() { return static_cast<Global&&>(*this); }

  /*
   * For compatibility with Chromium's base::Bind (base::Passed).
   */
  typedef void MoveOnlyTypeForCPP03;

 private:
  template <class F>
  friend class ReturnValue;
  Global(Global&) = delete;
  void operator=(Global&) = delete;
  V8_INLINE T* operator*() const { return this->val_; }
};


// UniquePersistent is an alias for Global for historical reason.
template <class T>
using UniquePersistent = Global<T>;


 /**
 * 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();

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

  V8_INLINE Isolate* GetIsolate() const {
    return reinterpret_cast<Isolate*>(isolate_);
  }

 protected:
  V8_INLINE HandleScope() {}

  void Initialize(Isolate* isolate);

  static internal::Object** CreateHandle(internal::Isolate* isolate,
                                         internal::Object* value);

 private:
  // Uses heap_object to obtain the current Isolate.
  static internal::Object** CreateHandle(internal::HeapObject* heap_object,
                                         internal::Object* value);

  // 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);

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

  // Local::New uses CreateHandle with an Isolate* parameter.
  template<class F> friend class Local;

  // Object::GetInternalField and Context::GetEmbedderData use CreateHandle with
  // a HeapObject* in their shortcuts.
  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_;
};

class V8_EXPORT SealHandleScope {
 public:
  SealHandleScope(Isolate* isolate);
  ~SealHandleScope();

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

  internal::Isolate* isolate_;
  int prev_level_;
  internal::Object** prev_limit_;
};


// --- Special objects ---


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


/**
 * The optional attributes of ScriptOrigin.
 */
class ScriptOriginOptions {
 public:
  V8_INLINE ScriptOriginOptions(bool is_embedder_debug_script = false,
                                bool is_shared_cross_origin = false,
                                bool is_opaque = false)
      : flags_((is_embedder_debug_script ? kIsEmbedderDebugScript : 0) |
               (is_shared_cross_origin ? kIsSharedCrossOrigin : 0) |
               (is_opaque ? kIsOpaque : 0)) {}
  V8_INLINE ScriptOriginOptions(int flags)
      : flags_(flags &
               (kIsEmbedderDebugScript | kIsSharedCrossOrigin | kIsOpaque)) {}
  bool IsEmbedderDebugScript() const {
    return (flags_ & kIsEmbedderDebugScript) != 0;
  }
  bool IsSharedCrossOrigin() const {
    return (flags_ & kIsSharedCrossOrigin) != 0;
  }
  bool IsOpaque() const { return (flags_ & kIsOpaque) != 0; }
  int Flags() const { return flags_; }

 private:
  enum {
    kIsEmbedderDebugScript = 1,
    kIsSharedCrossOrigin = 1 << 1,
    kIsOpaque = 1 << 2
  };
  const int flags_;
};

/**
 * The origin, within a file, of a script.
 */
class ScriptOrigin {
 public:
  V8_INLINE ScriptOrigin(
      Local<Value> resource_name,
      Local<Integer> resource_line_offset = Local<Integer>(),
      Local<Integer> resource_column_offset = Local<Integer>(),
      Local<Boolean> resource_is_shared_cross_origin = Local<Boolean>(),
      Local<Integer> script_id = Local<Integer>(),
      Local<Boolean> resource_is_embedder_debug_script = Local<Boolean>(),
      Local<Value> source_map_url = Local<Value>(),
      Local<Boolean> resource_is_opaque = Local<Boolean>());
  V8_INLINE Local<Value> ResourceName() const;
  V8_INLINE Local<Integer> ResourceLineOffset() const;
  V8_INLINE Local<Integer> ResourceColumnOffset() const;
  /**
    * Returns true for embedder's debugger scripts
    */
  V8_INLINE Local<Integer> ScriptID() const;
  V8_INLINE Local<Value> SourceMapUrl() const;
  V8_INLINE ScriptOriginOptions Options() const { return options_; }

 private:
  Local<Value> resource_name_;
  Local<Integer> resource_line_offset_;
  Local<Integer> resource_column_offset_;
  ScriptOriginOptions options_;
  Local<Integer> script_id_;
  Local<Value> source_map_url_;
};


/**
 * A compiled JavaScript script, not yet tied to a Context.
 */
class V8_EXPORT UnboundScript {
 public:
  /**
   * Binds the script to the currently entered context.
   */
  Local<Script> BindToCurrentContext();

  int GetId();
  Local<Value> GetScriptName();

  /**
   * Data read from magic sourceURL comments.
   */
  Local<Value> GetSourceURL();
  /**
   * Data read from magic sourceMappingURL comments.
   */
  Local<Value> GetSourceMappingURL();

  /**
   * 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;
};


/**
 * A compiled JavaScript script, tied to a Context which was active when the
 * script was compiled.
 */
class V8_EXPORT Script {
 public:
  /**
   * A shorthand for ScriptCompiler::Compile().
   */
  static V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<Script> Compile(Local<String> source,
                            ScriptOrigin* origin = nullptr));
  static V8_WARN_UNUSED_RESULT MaybeLocal<Script> Compile(
      Local<Context> context, Local<String> source,
      ScriptOrigin* origin = nullptr);

  static Local<Script> V8_DEPRECATE_SOON("Use maybe version",
                                         Compile(Local<String> source,
                                                 Local<String> file_name));

  /**
   * Runs the script returning the resulting value. It will be run in the
   * context in which it was created (ScriptCompiler::CompileBound or
   * UnboundScript::BindToCurrentContext()).
   */
  V8_DEPRECATE_SOON("Use maybe version", Local<Value> Run());
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> Run(Local<Context> context);

  /**
   * Returns the corresponding context-unbound script.
   */
  Local<UnboundScript> GetUnboundScript();

  V8_DEPRECATED("Use GetUnboundScript()->GetId()",
                int GetId()) {
    return GetUnboundScript()->GetId();
  }
};


/**
 * For compiling scripts.
 */
class V8_EXPORT ScriptCompiler {
 public:
  /**
   * Compilation data that the embedder can cache and pass back to speed up
   * future compilations. The data is produced if the CompilerOptions passed to
   * the compilation functions in ScriptCompiler contains produce_data_to_cache
   * = true. The data to cache can then can be retrieved from
   * UnboundScript.
   */
  struct V8_EXPORT CachedData {
    enum BufferPolicy {
      BufferNotOwned,
      BufferOwned
    };

    CachedData()
        : data(NULL),
          length(0),
          rejected(false),
          buffer_policy(BufferNotOwned) {}

    // If buffer_policy is BufferNotOwned, the caller keeps the ownership of
    // data and guarantees that it stays alive until the CachedData object is
    // destroyed. If the policy is BufferOwned, the given data will be deleted
    // (with delete[]) when the CachedData object is destroyed.
    CachedData(const uint8_t* data, int length,
               BufferPolicy buffer_policy = BufferNotOwned);
    ~CachedData();
    // TODO(marja): Async compilation; add constructors which take a callback
    // which will be called when V8 no longer needs the data.
    const uint8_t* data;
    int length;
    bool rejected;
    BufferPolicy buffer_policy;

   private:
    // Prevent copying. Not implemented.
    CachedData(const CachedData&);
    CachedData& operator=(const CachedData&);
  };

  /**
   * Source code which can be then compiled to a UnboundScript or Script.
   */
  class Source {
   public:
    // Source takes ownership of CachedData.
    V8_INLINE Source(Local<String> source_string, const ScriptOrigin& origin,
           CachedData* cached_data = NULL);
    V8_INLINE Source(Local<String> source_string,
                     CachedData* cached_data = NULL);
    V8_INLINE ~Source();

    // Ownership of the CachedData or its buffers is *not* transferred to the
    // caller. The CachedData object is alive as long as the Source object is
    // alive.
    V8_INLINE const CachedData* GetCachedData() const;

   private:
    friend class ScriptCompiler;
    // Prevent copying. Not implemented.
    Source(const Source&);
    Source& operator=(const Source&);

    Local<String> source_string;

    // Origin information
    Local<Value> resource_name;
    Local<Integer> resource_line_offset;
    Local<Integer> resource_column_offset;
    ScriptOriginOptions resource_options;
    Local<Value> source_map_url;

    // Cached data from previous compilation (if a kConsume*Cache flag is
    // set), or hold newly generated cache data (kProduce*Cache flags) are
    // set when calling a compile method.
    CachedData* cached_data;
  };

  /**
   * For streaming incomplete script data to V8. The embedder should implement a
   * subclass of this class.
   */
  class V8_EXPORT ExternalSourceStream {
   public:
    virtual ~ExternalSourceStream() {}

    /**
     * V8 calls this to request the next chunk of data from the embedder. This
     * function will be called on a background thread, so it's OK to block and
     * wait for the data, if the embedder doesn't have data yet. Returns the
     * length of the data returned. When the data ends, GetMoreData should
     * return 0. Caller takes ownership of the data.
     *
     * When streaming UTF-8 data, V8 handles multi-byte characters split between
     * two data chunks, but doesn't handle multi-byte characters split between
     * more than two data chunks. The embedder can avoid this problem by always
     * returning at least 2 bytes of data.
     *
     * If the embedder wants to cancel the streaming, they should make the next
     * GetMoreData call return 0. V8 will interpret it as end of data (and most
     * probably, parsing will fail). The streaming task will return as soon as
     * V8 has parsed the data it received so far.
     */
    virtual size_t GetMoreData(const uint8_t** src) = 0;

    /**
     * V8 calls this method to set a 'bookmark' at the current position in
     * the source stream, for the purpose of (maybe) later calling
     * ResetToBookmark. If ResetToBookmark is called later, then subsequent
     * calls to GetMoreData should return the same data as they did when
     * SetBookmark was called earlier.
     *
     * The embedder may return 'false' to indicate it cannot provide this
     * functionality.
     */
    virtual bool SetBookmark();

    /**
     * V8 calls this to return to a previously set bookmark.
     */
    virtual void ResetToBookmark();
  };


  /**
   * Source code which can be streamed into V8 in pieces. It will be parsed
   * while streaming. It can be compiled after the streaming is complete.
   * StreamedSource must be kept alive while the streaming task is ran (see
   * ScriptStreamingTask below).
   */
  class V8_EXPORT StreamedSource {
   public:
    enum Encoding { ONE_BYTE, TWO_BYTE, UTF8 };

    StreamedSource(ExternalSourceStream* source_stream, Encoding encoding);
    ~StreamedSource();

    // Ownership of the CachedData or its buffers is *not* transferred to the
    // caller. The CachedData object is alive as long as the StreamedSource
    // object is alive.
    const CachedData* GetCachedData() const;

    internal::StreamedSource* impl() const { return impl_; }

   private:
    // Prevent copying. Not implemented.
    StreamedSource(const StreamedSource&);
    StreamedSource& operator=(const StreamedSource&);

    internal::StreamedSource* impl_;
  };

  /**
   * A streaming task which the embedder must run on a background thread to
   * stream scripts into V8. Returned by ScriptCompiler::StartStreamingScript.
   */
  class ScriptStreamingTask {
   public:
    virtual ~ScriptStreamingTask() {}
    virtual void Run() = 0;
  };

  enum CompileOptions {
    kNoCompileOptions = 0,
    kProduceParserCache,
    kConsumeParserCache,
    kProduceCodeCache,
    kConsumeCodeCache
  };

  /**
   * Compiles the specified script (context-independent).
   * Cached data as part of the source object can be optionally produced to be
   * consumed later to speed up compilation of identical source scripts.
   *
   * Note that when producing cached data, the source must point to NULL for
   * cached data. When consuming cached data, the cached data must have been
   * produced by the same version of V8.
   *
   * \param source Script source code.
   * \return Compiled script object (context independent; for running it must be
   *   bound to a context).
   */
  static V8_DEPRECATE_SOON("Use maybe version",
                           Local<UnboundScript> CompileUnbound(
                               Isolate* isolate, Source* source,
                               CompileOptions options = kNoCompileOptions));
  static V8_WARN_UNUSED_RESULT MaybeLocal<UnboundScript> CompileUnboundScript(
      Isolate* isolate, Source* source,
      CompileOptions options = kNoCompileOptions);

  /**
   * Compiles the specified script (bound to current context).
   *
   * \param source Script source code.
   * \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 this function returns.
   * \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 V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<Script> Compile(Isolate* isolate, Source* source,
                            CompileOptions options = kNoCompileOptions));
  static V8_WARN_UNUSED_RESULT MaybeLocal<Script> Compile(
      Local<Context> context, Source* source,
      CompileOptions options = kNoCompileOptions);

  /**
   * Returns a task which streams script data into V8, or NULL if the script
   * cannot be streamed. The user is responsible for running the task on a
   * background thread and deleting it. When ran, the task starts parsing the
   * script, and it will request data from the StreamedSource as needed. When
   * ScriptStreamingTask::Run exits, all data has been streamed and the script
   * can be compiled (see Compile below).
   *
   * This API allows to start the streaming with as little data as possible, and
   * the remaining data (for example, the ScriptOrigin) is passed to Compile.
   */
  static ScriptStreamingTask* StartStreamingScript(
      Isolate* isolate, StreamedSource* source,
      CompileOptions options = kNoCompileOptions);

  /**
   * Compiles a streamed script (bound to current context).
   *
   * This can only be called after the streaming has finished
   * (ScriptStreamingTask has been run). V8 doesn't construct the source string
   * during streaming, so the embedder needs to pass the full source here.
   */
  static V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<Script> Compile(Isolate* isolate, StreamedSource* source,
                            Local<String> full_source_string,
                            const ScriptOrigin& origin));
  static V8_WARN_UNUSED_RESULT MaybeLocal<Script> Compile(
      Local<Context> context, StreamedSource* source,
      Local<String> full_source_string, const ScriptOrigin& origin);

  /**
   * Return a version tag for CachedData for the current V8 version & flags.
   *
   * This value is meant only for determining whether a previously generated
   * CachedData instance is still valid; the tag has no other meaing.
   *
   * Background: The data carried by CachedData may depend on the exact
   *   V8 version number or currently compiler flags. This means when
   *   persisting CachedData, the embedder must take care to not pass in
   *   data from another V8 version, or the same version with different
   *   features enabled.
   *
   *   The easiest way to do so is to clear the embedder's cache on any
   *   such change.
   *
   *   Alternatively, this tag can be stored alongside the cached data and
   *   compared when it is being used.
   */
  static uint32_t CachedDataVersionTag();

  /**
   * Compile an ES6 module.
   *
   * This is an experimental feature.
   *
   * TODO(adamk): Script is likely the wrong return value for this;
   * should return some new Module type.
   */
  static V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<Script> CompileModule(Isolate* isolate, Source* source,
                                  CompileOptions options = kNoCompileOptions));
  static V8_WARN_UNUSED_RESULT MaybeLocal<Script> CompileModule(
      Local<Context> context, Source* source,
      CompileOptions options = kNoCompileOptions);

  /**
   * Compile a function for a given context. This is equivalent to running
   *
   * with (obj) {
   *   return function(args) { ... }
   * }
   *
   * It is possible to specify multiple context extensions (obj in the above
   * example).
   */
  static V8_DEPRECATE_SOON("Use maybe version",
                           Local<Function> CompileFunctionInContext(
                               Isolate* isolate, Source* source,
                               Local<Context> context, size_t arguments_count,
                               Local<String> arguments[],
                               size_t context_extension_count,
                               Local<Object> context_extensions[]));
  static V8_WARN_UNUSED_RESULT MaybeLocal<Function> CompileFunctionInContext(
      Local<Context> context, Source* source, size_t arguments_count,
      Local<String> arguments[], size_t context_extension_count,
      Local<Object> context_extensions[]);

 private:
  static V8_WARN_UNUSED_RESULT MaybeLocal<UnboundScript> CompileUnboundInternal(
      Isolate* isolate, Source* source, CompileOptions options, bool is_module);
};


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

  V8_DEPRECATE_SOON("Use maybe version", Local<String> GetSourceLine() const);
  V8_WARN_UNUSED_RESULT MaybeLocal<String> GetSourceLine(
      Local<Context> context) const;

  /**
   * Returns the origin for the script from where the function causing the
   * error originates.
   */
  ScriptOrigin GetScriptOrigin() const;

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

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

  /**
   * Returns the number, 1-based, of the line where the error occurred.
   */
  V8_DEPRECATE_SOON("Use maybe version", int GetLineNumber() const);
  V8_WARN_UNUSED_RESULT Maybe<int> GetLineNumber(Local<Context> context) 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.
   */
  V8_DEPRECATE_SOON("Use maybe version", int GetStartColumn() const);
  V8_WARN_UNUSED_RESULT Maybe<int> GetStartColumn(Local<Context> context) const;

  /**
   * Returns the index within the line of the last character where
   * the error occurred.
   */
  V8_DEPRECATE_SOON("Use maybe version", int GetEndColumn() const);
  V8_WARN_UNUSED_RESULT Maybe<int> GetEndColumn(Local<Context> context) 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;
  bool IsOpaque() const;

  // TODO(1245381): Print to a string instead of on a FILE.
  static void PrintCurrentStackTrace(Isolate* isolate, 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,
    kExposeFramesAcrossSecurityOrigins = 1 << 8,
    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(
      Isolate* isolate,
      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 StateTag represents a possible state of the VM.
enum StateTag { JS, GC, COMPILER, OTHER, EXTERNAL, IDLE };


// A RegisterState represents the current state of registers used
// by the sampling profiler API.
struct RegisterState {
  RegisterState() : pc(NULL), sp(NULL), fp(NULL) {}
  void* pc;  // Instruction pointer.
  void* sp;  // Stack pointer.
  void* fp;  // Frame pointer.
};


// The output structure filled up by GetStackSample API function.
struct SampleInfo {
  size_t frames_count;
  StateTag vm_state;
};


/**
 * 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 V8_DEPRECATE_SOON("Use maybe version",
                           Local<Value> Parse(Local<String> json_string));
  static V8_WARN_UNUSED_RESULT MaybeLocal<Value> Parse(
      Isolate* isolate, Local<String> json_string);
};


/**
 * A map whose keys are referenced weakly. It is similar to JavaScript WeakMap
 * but can be created without entering a v8::Context and hence shouldn't
 * escape to JavaScript.
 */
class V8_EXPORT NativeWeakMap : public Data {
 public:
  static Local<NativeWeakMap> New(Isolate* isolate);
  void Set(Local<Value> key, Local<Value> value);
  Local<Value> Get(Local<Value> key);
  bool Has(Local<Value> key);
  bool Delete(Local<Value> key);
};


// --- 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 a symbol or a string.
   * This is an experimental feature.
   */
  bool IsName() 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 an Arguments object.
   */
  bool IsArgumentsObject() 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 a Generator function.
   * This is an experimental feature.
   */
  bool IsGeneratorFunction() const;

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

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

  /**
   * Returns true if this value is a Map.
   */
  bool IsMap() const;

  /**
   * Returns true if this value is a Set.
   */
  bool IsSet() const;

  /**
   * Returns true if this value is a Map Iterator.
   */
  bool IsMapIterator() const;

  /**
   * Returns true if this value is a Set Iterator.
   */
  bool IsSetIterator() const;

  /**
   * Returns true if this value is a WeakMap.
   */
  bool IsWeakMap() const;

  /**
   * Returns true if this value is a WeakSet.
   */
  bool IsWeakSet() 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 SIMD Float32x4.
   * This is an experimental feature.
   */
  bool IsFloat32x4() const;

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

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


  V8_WARN_UNUSED_RESULT MaybeLocal<Boolean> ToBoolean(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT MaybeLocal<Number> ToNumber(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT MaybeLocal<String> ToString(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT MaybeLocal<String> ToDetailString(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT MaybeLocal<Object> ToObject(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT MaybeLocal<Integer> ToInteger(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT MaybeLocal<Uint32> ToUint32(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT MaybeLocal<Int32> ToInt32(Local<Context> context) const;

  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Boolean> ToBoolean(Isolate* isolate) const);
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Number> ToNumber(Isolate* isolate) const);
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<String> ToString(Isolate* isolate) const);
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<String> ToDetailString(Isolate* isolate) const);
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Object> ToObject(Isolate* isolate) const);
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Integer> ToInteger(Isolate* isolate) const);
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Uint32> ToUint32(Isolate* isolate) const);
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Int32> ToInt32(Isolate* isolate) const);

  inline V8_DEPRECATE_SOON("Use maybe version",
                           Local<Boolean> ToBoolean() const);
  inline V8_DEPRECATE_SOON("Use maybe version", Local<Number> ToNumber() const);
  inline V8_DEPRECATE_SOON("Use maybe version", Local<String> ToString() const);
  inline V8_DEPRECATE_SOON("Use maybe version",
                           Local<String> ToDetailString() const);
  inline V8_DEPRECATE_SOON("Use maybe version", Local<Object> ToObject() const);
  inline V8_DEPRECATE_SOON("Use maybe version",
                           Local<Integer> ToInteger() const);
  inline V8_DEPRECATE_SOON("Use maybe version", Local<Uint32> ToUint32() const);
  inline V8_DEPRECATE_SOON("Use maybe version", Local<Int32> ToInt32() const);

  /**
   * Attempts to convert a string to an array index.
   * Returns an empty handle if the conversion fails.
   */
  V8_DEPRECATE_SOON("Use maybe version", Local<Uint32> ToArrayIndex() const);
  V8_WARN_UNUSED_RESULT MaybeLocal<Uint32> ToArrayIndex(
      Local<Context> context) const;

  V8_WARN_UNUSED_RESULT Maybe<bool> BooleanValue(Local<Context> context) const;
  V8_WARN_UNUSED_RESULT Maybe<double> NumberValue(Local<Context> context) const;
  V8_WARN_UNUSED_RESULT Maybe<int64_t> IntegerValue(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT Maybe<uint32_t> Uint32Value(
      Local<Context> context) const;
  V8_WARN_UNUSED_RESULT Maybe<int32_t> Int32Value(Local<Context> context) const;

  V8_DEPRECATE_SOON("Use maybe version", bool BooleanValue() const);
  V8_DEPRECATE_SOON("Use maybe version", double NumberValue() const);
  V8_DEPRECATE_SOON("Use maybe version", int64_t IntegerValue() const);
  V8_DEPRECATE_SOON("Use maybe version", uint32_t Uint32Value() const);
  V8_DEPRECATE_SOON("Use maybe version", int32_t Int32Value() const);

  /** JS == */
  V8_DEPRECATE_SOON("Use maybe version", bool Equals(Local<Value> that) const);
  V8_WARN_UNUSED_RESULT Maybe<bool> Equals(Local<Context> context,
                                           Local<Value> that) const;
  bool StrictEquals(Local<Value> that) const;
  bool SameValue(Local<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 Boolean* Cast(v8::Value* obj);
  V8_INLINE static Local<Boolean> New(Isolate* isolate, bool value);

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


/**
 * A superclass for symbols and strings.
 */
class V8_EXPORT Name : public Primitive {
 public:
  /**
   * Returns the identity hash for this object. The current implementation
   * uses an inline 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();

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


enum class NewStringType { kNormal, kInternalized };


/**
 * A JavaScript string value (ECMA-262, 4.3.17).
 */
class V8_EXPORT String : public Name {
 public:
  static const int kMaxLength = (1 << 28) - 16;

  enum Encoding {
    UNKNOWN_ENCODING = 0x1,
    TWO_BYTE_ENCODING = 0x0,
    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;

  /**
   * 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_ONE_BYTE_NULL = 4,
    // Used by WriteUtf8 to replace orphan surrogate code units with the
    // unicode replacement character. Needs to be set to guarantee valid UTF-8
    // output.
    REPLACE_INVALID_UTF8 = 8
  };

  // 16-bit character codes.
  int Write(uint16_t* 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.
   */
  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 one-byte.
   */
  bool IsExternalOneByte() 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 ExternalOneByteStringResource is a wrapper around an one-byte
   * string buffer that resides outside V8's heap. Implement an
   * ExternalOneByteStringResource to manage the life cycle of the
   * underlying buffer.  Note that the string data must be immutable
   * and that the data must be Latin-1 and not UTF-8, which would require
   * special treatment internally in the engine and do not allow efficient
   * indexing.  Use String::New or convert to 16 bit data for non-Latin1.
   */

  class V8_EXPORT ExternalOneByteStringResource
      : public ExternalStringResourceBase {
   public:
    /**
     * Override the destructor to manage the life cycle of the underlying
     * buffer.
     */
    virtual ~ExternalOneByteStringResource() {}
    /** The string data from the underlying buffer.*/
    virtual const char* data() const = 0;
    /** The number of Latin-1 characters in the string.*/
    virtual size_t length() const = 0;
   protected:
    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 ExternalOneByteStringResource for an external one-byte string.
   * Returns NULL if IsExternalOneByte() doesn't return true.
   */
  const ExternalOneByteStringResource* GetExternalOneByteStringResource() const;

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

  // TODO(dcarney): remove with deprecation of New functions.
  enum NewStringType {
    kNormalString = static_cast<int>(v8::NewStringType::kNormal),
    kInternalizedString = static_cast<int>(v8::NewStringType::kInternalized)
  };

  /** Allocates a new string from UTF-8 data.*/
  static V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<String> NewFromUtf8(Isolate* isolate, const char* data,
                                NewStringType type = kNormalString,
                                int length = -1));

  /** Allocates a new string from UTF-8 data. Only returns an empty value when
   * length > kMaxLength. **/
  static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewFromUtf8(
      Isolate* isolate, const char* data, v8::NewStringType type,
      int length = -1);

  /** Allocates a new string from Latin-1 data.*/
  static V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<String> NewFromOneByte(Isolate* isolate, const uint8_t* data,
                                   NewStringType type = kNormalString,
                                   int length = -1));

  /** Allocates a new string from Latin-1 data.  Only returns an empty value
   * when length > kMaxLength. **/
  static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewFromOneByte(
      Isolate* isolate, const uint8_t* data, v8::NewStringType type,
      int length = -1);

  /** Allocates a new string from UTF-16 data.*/
  static V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<String> NewFromTwoByte(Isolate* isolate, const uint16_t* data,
                                   NewStringType type = kNormalString,
                                   int length = -1));

  /** Allocates a new string from UTF-16 data. Only returns an empty value when
   * length > kMaxLength. **/
  static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewFromTwoByte(
      Isolate* isolate, const uint16_t* data, v8::NewStringType type,
      int length = -1);

  /**
   * Creates a new string by concatenating the left and the right strings
   * passed in as parameters.
   */
  static Local<String> Concat(Local<String> left, Local<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 V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<String> NewExternal(Isolate* isolate,
                                ExternalStringResource* resource));
  static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewExternalTwoByte(
      Isolate* isolate, 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 one-byte 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 V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<String> NewExternal(Isolate* isolate,
                                ExternalOneByteStringResource* resource));
  static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewExternalOneByte(
      Isolate* isolate, ExternalOneByteStringResource* 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(ExternalOneByteStringResource* resource);

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

  /**
   * 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(Local<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 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(Local<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 Name {
 public:
  // Returns the print name string of the symbol, or undefined if none.
  Local<Value> Name() const;

  // Create a symbol. If name is not empty, it will be used as the description.
  static Local<Symbol> New(
      Isolate *isolate, Local<String> name = Local<String>());

  // Access global symbol registry.
  // Note that symbols created this way are never collected, so
  // they should only be used for statically fixed properties.
  // Also, there is only one global name space for the names used as keys.
  // To minimize the potential for clashes, use qualified names as keys.
  static Local<Symbol> For(Isolate *isolate, Local<String> name);

  // Retrieve a global symbol. Similar to |For|, but using a separate
  // registry that is not accessible by (and cannot clash with) JavaScript code.
  static Local<Symbol> ForApi(Isolate *isolate, Local<String> name);

  // Well-known symbols
  static Local<Symbol> GetIterator(Isolate* isolate);
  static Local<Symbol> GetUnscopables(Isolate* isolate);
  static Local<Symbol> GetToStringTag(Isolate* isolate);

  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(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(Isolate* isolate, int32_t value);
  static Local<Integer> NewFromUnsigned(Isolate* isolate, uint32_t value);
  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;
  V8_INLINE static Int32* Cast(v8::Value* obj);

 private:
  Int32();
  static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript value representing a 32-bit unsigned integer.
 */
class V8_EXPORT Uint32 : public Integer {
 public:
  uint32_t Value() const;
  V8_INLINE static Uint32* Cast(v8::Value* obj);

 private:
  Uint32();
  static void CheckCast(v8::Value* obj);
};


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

/**
 * 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 (*AccessorNameGetterCallback)(
    Local<Name> property,
    const PropertyCallbackInfo<Value>& info);


typedef void (*AccessorSetterCallback)(
    Local<String> property,
    Local<Value> value,
    const PropertyCallbackInfo<void>& info);
typedef void (*AccessorNameSetterCallback)(
    Local<Name> 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.
 *
 * TODO(dcarney): Remove PROHIBITS_OVERWRITING as it is now unused.
 */
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:
  V8_DEPRECATE_SOON("Use maybe version",
                    bool Set(Local<Value> key, Local<Value> value));
  V8_WARN_UNUSED_RESULT Maybe<bool> Set(Local<Context> context,
                                        Local<Value> key, Local<Value> value);

  V8_DEPRECATE_SOON("Use maybe version",
                    bool Set(uint32_t index, Local<Value> value));
  V8_WARN_UNUSED_RESULT Maybe<bool> Set(Local<Context> context, uint32_t index,
                                        Local<Value> value);

  // Implements CreateDataProperty (ECMA-262, 7.3.4).
  //
  // Defines a configurable, writable, enumerable property with the given value
  // on the object unless the property already exists and is not configurable
  // or the object is not extensible.
  //
  // Returns true on success.
  V8_WARN_UNUSED_RESULT Maybe<bool> CreateDataProperty(Local<Context> context,
                                                       Local<Name> key,
                                                       Local<Value> value);
  V8_WARN_UNUSED_RESULT Maybe<bool> CreateDataProperty(Local<Context> context,
                                                       uint32_t index,
                                                       Local<Value> value);

  // Implements DefineOwnProperty.
  //
  // In general, CreateDataProperty will be faster, however, does not allow
  // for specifying attributes.
  //
  // Returns true on success.
  V8_WARN_UNUSED_RESULT Maybe<bool> DefineOwnProperty(
      Local<Context> context, Local<Name> key, Local<Value> value,
      PropertyAttribute attributes = None);

  // Sets an own 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.
  V8_DEPRECATE_SOON("Use CreateDataProperty",
                    bool ForceSet(Local<Value> key, Local<Value> value,
                                  PropertyAttribute attribs = None));
  V8_DEPRECATE_SOON("Use CreateDataProperty",
                    Maybe<bool> ForceSet(Local<Context> context,
                                         Local<Value> key, Local<Value> value,
                                         PropertyAttribute attribs = None));

  V8_DEPRECATE_SOON("Use maybe version", Local<Value> Get(Local<Value> key));
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> Get(Local<Context> context,
                                              Local<Value> key);

  V8_DEPRECATE_SOON("Use maybe version", Local<Value> Get(uint32_t index));
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> Get(Local<Context> context,
                                              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.
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    PropertyAttribute GetPropertyAttributes(Local<Value> key));
  V8_WARN_UNUSED_RESULT Maybe<PropertyAttribute> GetPropertyAttributes(
      Local<Context> context, Local<Value> key);

  /**
   * Returns Object.getOwnPropertyDescriptor as per ES5 section 15.2.3.3.
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Value> GetOwnPropertyDescriptor(Local<String> key));
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> GetOwnPropertyDescriptor(
      Local<Context> context, Local<String> key);

  V8_DEPRECATE_SOON("Use maybe version", bool Has(Local<Value> key));
  V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context,
                                        Local<Value> key);

  V8_DEPRECATE_SOON("Use maybe version", bool Delete(Local<Value> key));
  // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
  Maybe<bool> Delete(Local<Context> context, Local<Value> key);

  V8_DEPRECATE_SOON("Use maybe version", bool Has(uint32_t index));
  V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context, uint32_t index);

  V8_DEPRECATE_SOON("Use maybe version", bool Delete(uint32_t index));
  // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
  Maybe<bool> Delete(Local<Context> context, uint32_t index);

  V8_DEPRECATE_SOON("Use maybe version",
                    bool SetAccessor(Local<String> name,
                                     AccessorGetterCallback getter,
                                     AccessorSetterCallback setter = 0,
                                     Local<Value> data = Local<Value>(),
                                     AccessControl settings = DEFAULT,
                                     PropertyAttribute attribute = None));
  V8_DEPRECATE_SOON("Use maybe version",
                    bool SetAccessor(Local<Name> name,
                                     AccessorNameGetterCallback getter,
                                     AccessorNameSetterCallback setter = 0,
                                     Local<Value> data = Local<Value>(),
                                     AccessControl settings = DEFAULT,
                                     PropertyAttribute attribute = None));
  // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
  Maybe<bool> SetAccessor(Local<Context> context, Local<Name> name,
                          AccessorNameGetterCallback getter,
                          AccessorNameSetterCallback setter = 0,
                          MaybeLocal<Value> data = MaybeLocal<Value>(),
                          AccessControl settings = DEFAULT,
                          PropertyAttribute attribute = None);

  void SetAccessorProperty(Local<Name> name, Local<Function> getter,
                           Local<Function> setter = Local<Function>(),
                           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.
   */
  V8_DEPRECATE_SOON("Use maybe version", Local<Array> GetPropertyNames());
  V8_WARN_UNUSED_RESULT MaybeLocal<Array> GetPropertyNames(
      Local<Context> context);

  /**
   * This function has the same functionality as GetPropertyNames but
   * the returned array doesn't contain the names of properties from
   * prototype objects.
   */
  V8_DEPRECATE_SOON("Use maybe version", Local<Array> GetOwnPropertyNames());
  V8_WARN_UNUSED_RESULT MaybeLocal<Array> GetOwnPropertyNames(
      Local<Context> context);

  /**
   * 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.
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    bool SetPrototype(Local<Value> prototype));
  V8_WARN_UNUSED_RESULT Maybe<bool> SetPrototype(Local<Context> context,
                                                 Local<Value> prototype);

  /**
   * Finds an instance of the given function template in the prototype
   * chain.
   */
  Local<Object> FindInstanceInPrototypeChain(Local<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.
   */
  V8_DEPRECATE_SOON("Use maybe version", Local<String> ObjectProtoToString());
  V8_WARN_UNUSED_RESULT MaybeLocal<String> ObjectProtoToString(
      Local<Context> context);

  /**
   * 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();

  /** Same as above, but works for Persistents */
  V8_INLINE static int InternalFieldCount(
      const PersistentBase<Object>& object) {
    return object.val_->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, Local<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);

  /** Same as above, but works for Persistents */
  V8_INLINE static void* GetAlignedPointerFromInternalField(
      const PersistentBase<Object>& object, int index) {
    return object.val_->GetAlignedPointerFromInternalField(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.
  V8_DEPRECATE_SOON("Use maybe version",
                    bool HasOwnProperty(Local<String> key));
  V8_WARN_UNUSED_RESULT Maybe<bool> HasOwnProperty(Local<Context> context,
                                                   Local<Name> key);
  V8_DEPRECATE_SOON("Use maybe version",
                    bool HasRealNamedProperty(Local<String> key));
  V8_WARN_UNUSED_RESULT Maybe<bool> HasRealNamedProperty(Local<Context> context,
                                                         Local<Name> key);
  V8_DEPRECATE_SOON("Use maybe version",
                    bool HasRealIndexedProperty(uint32_t index));
  V8_WARN_UNUSED_RESULT Maybe<bool> HasRealIndexedProperty(
      Local<Context> context, uint32_t index);
  V8_DEPRECATE_SOON("Use maybe version",
                    bool HasRealNamedCallbackProperty(Local<String> key));
  V8_WARN_UNUSED_RESULT Maybe<bool> HasRealNamedCallbackProperty(
      Local<Context> context, Local<Name> key);

  /**
   * If result.IsEmpty() no real property was located in the prototype chain.
   * This means interceptors in the prototype chain are not called.
   */
  V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<Value> GetRealNamedPropertyInPrototypeChain(Local<String> key));
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> GetRealNamedPropertyInPrototypeChain(
      Local<Context> context, Local<Name> key);

  /**
   * Gets the property attributes of a real property in the prototype chain,
   * which can be None or any combination of ReadOnly, DontEnum and DontDelete.
   * Interceptors in the prototype chain are not called.
   */
  V8_DEPRECATE_SOON(
      "Use maybe version",
      Maybe<PropertyAttribute> GetRealNamedPropertyAttributesInPrototypeChain(
          Local<String> key));
  V8_WARN_UNUSED_RESULT Maybe<PropertyAttribute>
  GetRealNamedPropertyAttributesInPrototypeChain(Local<Context> context,
                                                 Local<Name> 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.
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Value> GetRealNamedProperty(Local<String> key));
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> GetRealNamedProperty(
      Local<Context> context, Local<Name> key);

  /**
   * Gets the property attributes of a real property which can be
   * None or any combination of ReadOnly, DontEnum and DontDelete.
   * Interceptors in the prototype chain are not called.
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    Maybe<PropertyAttribute> GetRealNamedPropertyAttributes(
                        Local<String> key));
  V8_WARN_UNUSED_RESULT Maybe<PropertyAttribute> GetRealNamedPropertyAttributes(
      Local<Context> context, Local<Name> key);

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

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

  /**
   * 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::".
   */
  // TODO(dcarney): convert these to take a isolate and optionally bailout?
  bool SetHiddenValue(Local<String> key, Local<Value> value);
  Local<Value> GetHiddenValue(Local<String> key);
  bool DeleteHiddenValue(Local<String> key);

  /**
   * Clone this object with a fast but shallow copy.  Values will point
   * to the same values as the original object.
   */
  // TODO(dcarney): take an isolate and optionally bail out?
  Local<Object> Clone();

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

  /**
   * 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.
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Value> CallAsFunction(Local<Value> recv, int argc,
                                                Local<Value> argv[]));
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> CallAsFunction(Local<Context> context,
                                                         Local<Value> recv,
                                                         int argc,
                                                         Local<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.
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Value> CallAsConstructor(int argc,
                                                   Local<Value> argv[]));
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> CallAsConstructor(
      Local<Context> context, int argc, Local<Value> argv[]);

  /**
   * Return the isolate to which the Object belongs to.
   */
  V8_DEPRECATE_SOON("Keep track of isolate correctly", Isolate* GetIsolate());

  static Local<Object> New(Isolate* isolate);

  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).
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Object> CloneElementAt(uint32_t index));
  V8_WARN_UNUSED_RESULT MaybeLocal<Object> CloneElementAt(
      Local<Context> context, 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(Isolate* isolate, int length = 0);

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


/**
 * An instance of the built-in Map constructor (ECMA-262, 6th Edition, 23.1.1).
 */
class V8_EXPORT Map : public Object {
 public:
  size_t Size() const;
  void Clear();
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> Get(Local<Context> context,
                                              Local<Value> key);
  V8_WARN_UNUSED_RESULT MaybeLocal<Map> Set(Local<Context> context,
                                            Local<Value> key,
                                            Local<Value> value);
  V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context,
                                        Local<Value> key);
  V8_WARN_UNUSED_RESULT Maybe<bool> Delete(Local<Context> context,
                                           Local<Value> key);

  /**
   * Returns an array of length Size() * 2, where index N is the Nth key and
   * index N + 1 is the Nth value.
   */
  Local<Array> AsArray() const;

  /**
   * Creates a new empty Map.
   */
  static Local<Map> New(Isolate* isolate);

  /**
   * Creates a new Map containing the elements of array, which must be formatted
   * in the same manner as the array returned from AsArray().
   * Guaranteed to be side-effect free if the array contains no holes.
   */
  static V8_WARN_UNUSED_RESULT MaybeLocal<Map> FromArray(Local<Context> context,
                                                         Local<Array> array);

  V8_INLINE static Map* Cast(Value* obj);

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


/**
 * An instance of the built-in Set constructor (ECMA-262, 6th Edition, 23.2.1).
 */
class V8_EXPORT Set : public Object {
 public:
  size_t Size() const;
  void Clear();
  V8_WARN_UNUSED_RESULT MaybeLocal<Set> Add(Local<Context> context,
                                            Local<Value> key);
  V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context,
                                        Local<Value> key);
  V8_WARN_UNUSED_RESULT Maybe<bool> Delete(Local<Context> context,
                                           Local<Value> key);

  /**
   * Returns an array of the keys in this Set.
   */
  Local<Array> AsArray() const;

  /**
   * Creates a new empty Set.
   */
  static Local<Set> New(Isolate* isolate);

  /**
   * Creates a new Set containing the items in array.
   * Guaranteed to be side-effect free if the array contains no holes.
   */
  static V8_WARN_UNUSED_RESULT MaybeLocal<Set> FromArray(Local<Context> context,
                                                         Local<Array> array);

  V8_INLINE static Set* Cast(Value* obj);

 private:
  Set();
  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);
  }
  // Local setters
  template <typename S>
  V8_INLINE V8_DEPRECATE_SOON("Use Global<> instead",
                              void Set(const Persistent<S>& handle));
  template <typename S>
  V8_INLINE void Set(const Global<S>& handle);
  template <typename S>
  V8_INLINE void Set(const Local<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();

  // Pointer setter: Uncompilable to prevent inadvertent misuse.
  template <typename S>
  V8_INLINE void Set(S* whatever);

 private:
  template<class F> friend class ReturnValue;
  template<class F> friend class FunctionCallbackInfo;
  template<class F> friend class PropertyCallbackInfo;
  template <class F, class G, class H>
  friend class PersistentValueMapBase;
  V8_INLINE void SetInternal(internal::Object* value) { *value_ = value; }
  V8_INLINE internal::Object* GetDefaultValue();
  V8_INLINE explicit ReturnValue(internal::Object** slot);
  internal::Object** value_;
};


/**
 * 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 kHolderIndex = 0;
  static const int kIsolateIndex = 1;
  static const int kReturnValueDefaultValueIndex = 2;
  static const int kReturnValueIndex = 3;
  static const int kDataIndex = 4;
  static const int kCalleeIndex = 5;
  static const int kContextSaveIndex = 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_;
  int 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 kHolderIndex = 0;
  static const int kIsolateIndex = 1;
  static const int kReturnValueDefaultValueIndex = 2;
  static const int kReturnValueIndex = 3;
  static const int kDataIndex = 4;
  static const int kThisIndex = 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 MaybeLocal<Function> New(Local<Context> context,
                                  FunctionCallback callback,
                                  Local<Value> data = Local<Value>(),
                                  int length = 0);
  static V8_DEPRECATE_SOON(
      "Use maybe version",
      Local<Function> New(Isolate* isolate, FunctionCallback callback,
                          Local<Value> data = Local<Value>(), int length = 0));

  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Object> NewInstance(int argc, Local<Value> argv[])
                        const);
  V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewInstance(
      Local<Context> context, int argc, Local<Value> argv[]) const;

  V8_DEPRECATE_SOON("Use maybe version", Local<Object> NewInstance() const);
  V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewInstance(
      Local<Context> context) const {
    return NewInstance(context, 0, nullptr);
  }

  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Value> Call(Local<Value> recv, int argc,
                                      Local<Value> argv[]));
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> Call(Local<Context> context,
                                               Local<Value> recv, int argc,
                                               Local<Value> argv[]);

  void SetName(Local<String> name);
  Local<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.
   */
  Local<Value> GetInferredName() const;

  /**
   * User-defined name assigned to the "displayName" property of this function.
   * Used to facilitate debugging and profiling of JavaScript code.
   */
  Local<Value> GetDisplayName() 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;

  /**
   * Tells whether this function is builtin.
   */
  bool IsBuiltin() const;

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

  /**
   * Returns the original function if this function is bound, else returns
   * v8::Undefined.
   */
  Local<Value> GetBoundFunction() const;

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

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


/**
 * An instance of the built-in Promise constructor (ES6 draft).
 * This API is experimental. Only works with --harmony flag.
 */
class V8_EXPORT Promise : public Object {
 public:
  class V8_EXPORT Resolver : public Object {
   public:
    /**
     * Create a new resolver, along with an associated promise in pending state.
     */
    static V8_DEPRECATE_SOON("Use maybe version",
                             Local<Resolver> New(Isolate* isolate));
    static V8_WARN_UNUSED_RESULT MaybeLocal<Resolver> New(
        Local<Context> context);

    /**
     * Extract the associated promise.
     */
    Local<Promise> GetPromise();

    /**
     * Resolve/reject the associated promise with a given value.
     * Ignored if the promise is no longer pending.
     */
    V8_DEPRECATE_SOON("Use maybe version", void Resolve(Local<Value> value));
    // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
    Maybe<bool> Resolve(Local<Context> context, Local<Value> value);

    V8_DEPRECATE_SOON("Use maybe version", void Reject(Local<Value> value));
    // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
    Maybe<bool> Reject(Local<Context> context, Local<Value> value);

    V8_INLINE static Resolver* Cast(Value* obj);

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

  /**
   * Register a resolution/rejection handler with a promise.
   * The handler is given the respective resolution/rejection value as
   * an argument. If the promise is already resolved/rejected, the handler is
   * invoked at the end of turn.
   */
  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Promise> Chain(Local<Function> handler));
  V8_WARN_UNUSED_RESULT MaybeLocal<Promise> Chain(Local<Context> context,
                                                  Local<Function> handler);

  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Promise> Catch(Local<Function> handler));
  V8_WARN_UNUSED_RESULT MaybeLocal<Promise> Catch(Local<Context> context,
                                                  Local<Function> handler);

  V8_DEPRECATE_SOON("Use maybe version",
                    Local<Promise> Then(Local<Function> handler));
  V8_WARN_UNUSED_RESULT MaybeLocal<Promise> Then(Local<Context> context,
                                                 Local<Function> handler);

  /**
   * Returns true if the promise has at least one derived promise, and
   * therefore resolve/reject handlers (including default handler).
   */
  bool HasHandler();

  V8_INLINE static Promise* Cast(Value* obj);

 private:
  Promise();
  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


enum class ArrayBufferCreationMode { kInternalized, kExternalized };


/**
 * 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 has to be set via
   * Isolate::CreateParams.
   *
   * 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 via Isolate::CreateParams.
   *
   * 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(Isolate* isolate, size_t byte_length);

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

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

  /**
   * Returns true if this ArrayBuffer may be neutered.
   */
  bool IsNeuterable() 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 and must be neuterable.
   */
  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 via Isolate::CreateParams.
   */
  Contents Externalize();

  /**
   * Get a pointer to the ArrayBuffer's underlying memory block without
   * externalizing it. If the ArrayBuffer is not externalized, this pointer
   * will become invalid as soon as the ArrayBuffer became garbage collected.
   *
   * The embedder should make sure to hold a strong reference to the
   * ArrayBuffer while accessing this pointer.
   *
   * The memory block is guaranteed to be allocated with |Allocator::Allocate|.
   */
  Contents GetContents();

  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();

  /**
   * Copy the contents of the ArrayBufferView's buffer to an embedder defined
   * memory without additional overhead that calling ArrayBufferView::Buffer
   * might incur.
   *
   * Will write at most min(|byte_length|, ByteLength) bytes starting at
   * ByteOffset of the underling buffer to the memory starting at |dest|.
   * Returns the number of bytes actually written.
   */
  size_t CopyContents(void* dest, size_t byte_length);

  /**
   * Returns true if ArrayBufferView's backing ArrayBuffer has already been
   * allocated.
   */
  bool HasBuffer() const;

  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(Local<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  static Local<Uint8Array> New(Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                                      size_t byte_offset, size_t length);
  static Local<Uint8ClampedArray> New(
      Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                              size_t byte_offset, size_t length);
  static Local<Int8Array> New(Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                                size_t byte_offset, size_t length);
  static Local<Uint16Array> New(Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  static Local<Int16Array> New(Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                                size_t byte_offset, size_t length);
  static Local<Uint32Array> New(Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                               size_t byte_offset, size_t length);
  static Local<Int32Array> New(Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                                 size_t byte_offset, size_t length);
  static Local<Float32Array> New(Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                                 size_t byte_offset, size_t length);
  static Local<Float64Array> New(Local<SharedArrayBuffer> shared_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(Local<ArrayBuffer> array_buffer,
                             size_t byte_offset, size_t length);
  static Local<DataView> New(Local<SharedArrayBuffer> shared_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 SharedArrayBuffer constructor.
 * This API is experimental and may change significantly.
 */
class V8_EXPORT SharedArrayBuffer : public Object {
 public:
  /**
   * The contents of an |SharedArrayBuffer|. Externalization of
   * |SharedArrayBuffer| returns an instance of this class, populated, with a
   * pointer to data and byte length.
   *
   * The Data pointer of SharedArrayBuffer::Contents is always allocated with
   * |ArrayBuffer::Allocator::Allocate| by the allocator specified in
   * v8::Isolate::CreateParams::array_buffer_allocator.
   *
   * 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 SharedArrayBuffer;
  };


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

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

  /**
   * Create a new SharedArrayBuffer over an existing memory block.  The created
   * array buffer is immediately in externalized state unless otherwise
   * specified. The memory block will not be reclaimed when a created
   * SharedArrayBuffer is garbage-collected.
   */
  static Local<SharedArrayBuffer> New(
      Isolate* isolate, void* data, size_t byte_length,
      ArrayBufferCreationMode mode = ArrayBufferCreationMode::kExternalized);

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

  /**
   * Make this SharedArrayBuffer external. The pointer to underlying memory
   * block and byte length are returned as |Contents| structure. After
   * SharedArrayBuffer 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|
   * by the allocator specified in
   * v8::Isolate::CreateParams::array_buffer_allocator.
   *
   */
  Contents Externalize();

  /**
   * Get a pointer to the ArrayBuffer's underlying memory block without
   * externalizing it. If the ArrayBuffer is not externalized, this pointer
   * will become invalid as soon as the ArrayBuffer became garbage collected.
   *
   * The embedder should make sure to hold a strong reference to the
   * ArrayBuffer while accessing this pointer.
   *
   * The memory block is guaranteed to be allocated with |Allocator::Allocate|
   * by the allocator specified in
   * v8::Isolate::CreateParams::array_buffer_allocator.
   */
  Contents GetContents();

  V8_INLINE static SharedArrayBuffer* Cast(Value* obj);

  static const int kInternalFieldCount = V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT;

 private:
  SharedArrayBuffer();
  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 V8_DEPRECATE_SOON("Use maybe version.",
                           Local<Value> New(Isolate* isolate, double time));
  static V8_WARN_UNUSED_RESULT MaybeLocal<Value> New(Local<Context> context,
                                                     double time);

  /**
   * 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(Isolate* isolate);

 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(Isolate* isolate, double value);

  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);

  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(Local<String> value);

  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, Local<Symbol> value);

  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 V8_DEPRECATE_SOON("Use maybe version",
                           Local<RegExp> New(Local<String> pattern,
                                             Flags flags));
  static V8_WARN_UNUSED_RESULT MaybeLocal<RegExp> New(Local<Context> context,
                                                      Local<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(Isolate* isolate, 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(Local<Name> name, Local<Data> value,
           PropertyAttribute attributes = None);
  V8_INLINE void Set(Isolate* isolate, const char* name, Local<Data> value);

  void SetAccessorProperty(
     Local<Name> 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
      Local<Value> data = Local<Value>(), PropertyAttribute attribute = None,
      Local<AccessorSignature> signature = Local<AccessorSignature>(),
      AccessControl settings = DEFAULT);
  void SetNativeDataProperty(
      Local<Name> name, AccessorNameGetterCallback getter,
      AccessorNameSetterCallback setter = 0,
      // TODO(dcarney): gcc can't handle Local below
      Local<Value> data = Local<Value>(), 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);


// TODO(dcarney): Deprecate and remove previous typedefs, and replace
// GenericNamedPropertyFooCallback with just NamedPropertyFooCallback.
/**
 * GenericNamedProperty[Getter|Setter] are used as interceptors on object.
 * See ObjectTemplate::SetNamedPropertyHandler.
 */
typedef void (*GenericNamedPropertyGetterCallback)(
    Local<Name> property, const PropertyCallbackInfo<Value>& info);


/**
 * Returns the value if the setter intercepts the request.
 * Otherwise, returns an empty handle.
 */
typedef void (*GenericNamedPropertySetterCallback)(
    Local<Name> 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 (*GenericNamedPropertyQueryCallback)(
    Local<Name> 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 (*GenericNamedPropertyDeleterCallback)(
    Local<Name> property, const PropertyCallbackInfo<Boolean>& info);


/**
 * Returns an array containing the names of the properties the named
 * property getter intercepts.
 */
typedef void (*GenericNamedPropertyEnumeratorCallback)(
    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.
 *
 * Any modification of a FunctionTemplate after first instantiation will trigger
 *a crash.
 *
 * 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(
      Isolate* isolate, FunctionCallback callback = 0,
      Local<Value> data = Local<Value>(),
      Local<Signature> signature = Local<Signature>(), int length = 0);

  /** Returns the unique function instance in the current execution context.*/
  V8_DEPRECATE_SOON("Use maybe version", Local<Function> GetFunction());
  V8_WARN_UNUSED_RESULT MaybeLocal<Function> GetFunction(
      Local<Context> context);

  /**
   * 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,
                      Local<Value> data = Local<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(Local<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(Local<String> name);


  /**
   * When set to true, no access check will be performed on the receiver of a
   * function call.  Currently defaults to true, but this is subject to change.
   */
  void SetAcceptAnyReceiver(bool value);

  /**
   * 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(Local<Value> object);

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


enum class PropertyHandlerFlags {
  kNone = 0,
  // See ALL_CAN_READ above.
  kAllCanRead = 1,
  // Will not call into interceptor for properties on the receiver or prototype
  // chain.  Currently only valid for named interceptors.
  kNonMasking = 1 << 1,
  // Will not call into interceptor for symbol lookup.  Only meaningful for
  // named interceptors.
  kOnlyInterceptStrings = 1 << 2,
};


struct NamedPropertyHandlerConfiguration {
  NamedPropertyHandlerConfiguration(
      /** Note: getter is required **/
      GenericNamedPropertyGetterCallback getter = 0,
      GenericNamedPropertySetterCallback setter = 0,
      GenericNamedPropertyQueryCallback query = 0,
      GenericNamedPropertyDeleterCallback deleter = 0,
      GenericNamedPropertyEnumeratorCallback enumerator = 0,
      Local<Value> data = Local<Value>(),
      PropertyHandlerFlags flags = PropertyHandlerFlags::kNone)
      : getter(getter),
        setter(setter),
        query(query),
        deleter(deleter),
        enumerator(enumerator),
        data(data),
        flags(flags) {}

  GenericNamedPropertyGetterCallback getter;
  GenericNamedPropertySetterCallback setter;
  GenericNamedPropertyQueryCallback query;
  GenericNamedPropertyDeleterCallback deleter;
  GenericNamedPropertyEnumeratorCallback enumerator;
  Local<Value> data;
  PropertyHandlerFlags flags;
};


struct IndexedPropertyHandlerConfiguration {
  IndexedPropertyHandlerConfiguration(
      /** Note: getter is required **/
      IndexedPropertyGetterCallback getter = 0,
      IndexedPropertySetterCallback setter = 0,
      IndexedPropertyQueryCallback query = 0,
      IndexedPropertyDeleterCallback deleter = 0,
      IndexedPropertyEnumeratorCallback enumerator = 0,
      Local<Value> data = Local<Value>(),
      PropertyHandlerFlags flags = PropertyHandlerFlags::kNone)
      : getter(getter),
        setter(setter),
        query(query),
        deleter(deleter),
        enumerator(enumerator),
        data(data),
        flags(flags) {}

  IndexedPropertyGetterCallback getter;
  IndexedPropertySetterCallback setter;
  IndexedPropertyQueryCallback query;
  IndexedPropertyDeleterCallback deleter;
  IndexedPropertyEnumeratorCallback enumerator;
  Local<Value> data;
  PropertyHandlerFlags flags;
};


/**
 * 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(
      Isolate* isolate,
      Local<FunctionTemplate> constructor = Local<FunctionTemplate>());
  static V8_DEPRECATE_SOON("Use isolate version", Local<ObjectTemplate> New());

  /** Creates a new instance of this template.*/
  V8_DEPRECATE_SOON("Use maybe version", Local<Object> NewInstance());
  V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewInstance(Local<Context> context);

  /**
   * 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(
      Local<String> name, AccessorGetterCallback getter,
      AccessorSetterCallback setter = 0, Local<Value> data = Local<Value>(),
      AccessControl settings = DEFAULT, PropertyAttribute attribute = None,
      Local<AccessorSignature> signature = Local<AccessorSignature>());
  void SetAccessor(
      Local<Name> name, AccessorNameGetterCallback getter,
      AccessorNameSetterCallback setter = 0, Local<Value> data = Local<Value>(),
      AccessControl settings = DEFAULT, PropertyAttribute attribute = None,
      Local<AccessorSignature> signature = Local<AccessorSignature>());

  /**
   * Sets a named property handler on the object template.
   *
   * Whenever a property whose name is a string is accessed on objects created
   * from this object template, the provided callback is invoked instead of
   * accessing the property directly on the JavaScript object.
   *
   * Note that new code should use the second version that can intercept
   * symbol-named properties as well as string-named properties.
   *
   * \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.
   */
  // TODO(dcarney): deprecate
  void SetNamedPropertyHandler(NamedPropertyGetterCallback getter,
                               NamedPropertySetterCallback setter = 0,
                               NamedPropertyQueryCallback query = 0,
                               NamedPropertyDeleterCallback deleter = 0,
                               NamedPropertyEnumeratorCallback enumerator = 0,
                               Local<Value> data = Local<Value>());
  void SetHandler(const NamedPropertyHandlerConfiguration& configuration);

  /**
   * 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 SetHandler(const IndexedPropertyHandlerConfiguration& configuration);
  // TODO(dcarney): deprecate
  void SetIndexedPropertyHandler(
      IndexedPropertyGetterCallback getter,
      IndexedPropertySetterCallback setter = 0,
      IndexedPropertyQueryCallback query = 0,
      IndexedPropertyDeleterCallback deleter = 0,
      IndexedPropertyEnumeratorCallback enumerator = 0,
      Local<Value> data = Local<Value>()) {
    SetHandler(IndexedPropertyHandlerConfiguration(getter, setter, query,
                                                   deleter, enumerator, data));
  }
  /**
   * 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,
                                Local<Value> data = Local<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 and enables
   * access checks.
   *
   * 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.
   */
  void SetAccessCheckCallbacks(NamedSecurityCallback named_handler,
                               IndexedSecurityCallback indexed_handler,
                               Local<Value> data = Local<Value>());

  /**
   * 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(internal::Isolate* isolate,
                                   Local<FunctionTemplate> constructor);
  friend class FunctionTemplate;
};


/**
 * A Signature specifies which receiver is valid for a function.
 */
class V8_EXPORT Signature : public Data {
 public:
  static Local<Signature> New(
      Isolate* isolate,
      Local<FunctionTemplate> receiver = Local<FunctionTemplate>());

 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(
      Isolate* isolate,
      Local<FunctionTemplate> receiver = Local<FunctionTemplate>());

 private:
  AccessorSignature();
};


/**
 * 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(Local<FunctionTemplate> type);
  static Local<TypeSwitch> New(int argc, Local<FunctionTemplate> types[]);
  int match(Local<Value> value);

 private:
  TypeSwitch();
};


// --- Extensions ---

class V8_EXPORT ExternalOneByteStringResourceImpl
    : public String::ExternalOneByteStringResource {
 public:
  ExternalOneByteStringResourceImpl() : data_(0), length_(0) {}
  ExternalOneByteStringResourceImpl(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::Local<v8::FunctionTemplate> GetNativeFunctionTemplate(
      v8::Isolate* isolate, v8::Local<v8::String> name) {
    return v8::Local<v8::FunctionTemplate>();
  }

  const char* name() const { return name_; }
  size_t source_length() const { return source_length_; }
  const String::ExternalOneByteStringResource* 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_
  ExternalOneByteStringResourceImpl 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);


// --- Statics ---

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

  /**
   * Configures the constraints with reasonable default values based on the
   * capabilities of the current device the VM is running on.
   *
   * \param physical_memory The total amount of physical memory on the current
   *   device, in bytes.
   * \param virtual_memory_limit The amount of virtual memory on the current
   *   device, in bytes, or zero, if there is no limit.
   */
  void ConfigureDefaults(uint64_t physical_memory,
                         uint64_t virtual_memory_limit);

  // Deprecated, will be removed soon.
  V8_DEPRECATED("Use two-args version instead",
                void ConfigureDefaults(uint64_t physical_memory,
                                       uint64_t virtual_memory_limit,
                                       uint32_t number_of_processors));

  int max_semi_space_size() const { return max_semi_space_size_; }
  void set_max_semi_space_size(int value) { max_semi_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() const { 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; }
  V8_DEPRECATED("Unused, will be removed", int max_available_threads() const) {
    return max_available_threads_;
  }
  // Set the number of threads available to V8, assuming at least 1.
  V8_DEPRECATED("Unused, will be removed",
                void set_max_available_threads(int value)) {
    max_available_threads_ = value;
  }
  size_t code_range_size() const { return code_range_size_; }
  void set_code_range_size(size_t value) {
    code_range_size_ = value;
  }

 private:
  int max_semi_space_size_;
  int max_old_space_size_;
  int max_executable_size_;
  uint32_t* stack_limit_;
  int max_available_threads_;
  size_t code_range_size_;
};


// --- Exceptions ---


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


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

// --- Tracing ---

typedef void (*LogEventCallback)(const char* name, int event);

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

  /**
   * Creates an error message for the given exception.
   * Will try to reconstruct the original stack trace from the exception value,
   * or capture the current stack trace if not available.
   */
  static Local<Message> CreateMessage(Local<Value> exception);

  /**
   * Returns the original stack trace that was captured at the creation time
   * of a given exception, or an empty handle if not available.
   */
  static Local<StackTrace> GetStackTrace(Local<Value> exception);
};


// --- 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,
  kObjectSpaceOldSpace = 1 << 1,
  kObjectSpaceCodeSpace = 1 << 2,
  kObjectSpaceMapSpace = 1 << 3,
  kObjectSpaceLoSpace = 1 << 4,
  kObjectSpaceAll = kObjectSpaceNewSpace | kObjectSpaceOldSpace |
                    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)();

// --- Promise Reject Callback ---
enum PromiseRejectEvent {
  kPromiseRejectWithNoHandler = 0,
  kPromiseHandlerAddedAfterReject = 1
};

class PromiseRejectMessage {
 public:
  PromiseRejectMessage(Local<Promise> promise, PromiseRejectEvent event,
                       Local<Value> value, Local<StackTrace> stack_trace)
      : promise_(promise),
        event_(event),
        value_(value),
        stack_trace_(stack_trace) {}

  V8_INLINE Local<Promise> GetPromise() const { return promise_; }
  V8_INLINE PromiseRejectEvent GetEvent() const { return event_; }
  V8_INLINE Local<Value> GetValue() const { return value_; }

  // DEPRECATED. Use v8::Exception::CreateMessage(GetValue())->GetStackTrace()
  V8_INLINE Local<StackTrace> GetStackTrace() const { return stack_trace_; }

 private:
  Local<Promise> promise_;
  PromiseRejectEvent event_;
  Local<Value> value_;
  Local<StackTrace> stack_trace_;
};

typedef void (*PromiseRejectCallback)(PromiseRejectMessage message);

// --- Microtask Callback ---
typedef void (*MicrotaskCallback)(void* data);

// --- 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,
  kGCCallbackFlagForced = 1 << 2
};

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

typedef void (*InterruptCallback)(Isolate* isolate, void* data);


/**
 * 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 total_available_size() { return total_available_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 total_available_size_;
  size_t used_heap_size_;
  size_t heap_size_limit_;

  friend class V8;
  friend class Isolate;
};


class V8_EXPORT HeapSpaceStatistics {
 public:
  HeapSpaceStatistics();
  const char* space_name() { return space_name_; }
  size_t space_size() { return space_size_; }
  size_t space_used_size() { return space_used_size_; }
  size_t space_available_size() { return space_available_size_; }
  size_t physical_space_size() { return physical_space_size_; }

 private:
  const char* space_name_;
  size_t space_size_;
  size_t space_used_size_;
  size_t space_available_size_;
  size_t physical_space_size_;

  friend class Isolate;
};


class V8_EXPORT HeapObjectStatistics {
 public:
  HeapObjectStatistics();
  const char* object_type() { return object_type_; }
  const char* object_sub_type() { return object_sub_type_; }
  size_t object_count() { return object_count_; }
  size_t object_size() { return object_size_; }

 private:
  const char* object_type_;
  const char* object_sub_type_;
  size_t object_count_;
  size_t object_size_;

  friend class Isolate;
};