third_party/v8/include/v8.h

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

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

#ifndef INCLUDE_V8_H_
#define INCLUDE_V8_H_

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

#include <atomic>
#include <memory>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>

#include "cppgc/common.h"
#include "v8-internal.h"  // NOLINT(build/include_directory)
#include "v8-version.h"   // NOLINT(build/include_directory)
#include "v8config.h"     // NOLINT(build/include_directory)

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

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

class AccessorSignature;
class Array;
class ArrayBuffer;
class BigInt;
class BigIntObject;
class Boolean;
class BooleanObject;
class CFunction;
class Context;
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 MicrotaskQueue;
class Name;
class Number;
class NumberObject;
class Object;
class ObjectOperationDescriptor;
class ObjectTemplate;
class Platform;
class Primitive;
class Promise;
class PropertyDescriptor;
class Proxy;
class RawOperationDescriptor;
class Script;
class SharedArrayBuffer;
class Signature;
class StartupData;
class StackFrame;
class StackTrace;
class String;
class StringObject;
class Symbol;
class SymbolObject;
class TracedReferenceBase;
class PrimitiveArray;
class Private;
class Uint32;
class Utils;
class Value;
class WasmModuleObject;
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 T>
class TracedGlobal;
template <class T>
class TracedReference;
template <class T>
class BasicTracedReference;
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;
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 {
enum class ArgumentsType;
template <ArgumentsType>
class Arguments;
class BasicTracedReferenceExtractor;
template <typename T>
class CustomArguments;
class FunctionCallbackArguments;
class GlobalHandles;
class Heap;
class HeapObject;
class ExternalString;
class Isolate;
class LocalEmbedderHeapTracer;
class MicrotaskQueue;
class PropertyCallbackArguments;
class ReadOnlyHeap;
class ScopedExternalStringLock;
struct ScriptStreamingData;
class ThreadLocalTop;

namespace wasm {
class NativeModule;
class StreamingDecoder;
}  // namespace wasm

}  // namespace internal

namespace metrics {
class Recorder;
}  // namespace metrics

namespace debug {
class ConsoleCallArguments;
}  // namespace debug

// --- Handles ---

/**
 * 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. That means that a
 * HandleScope must exist on the stack when they are created and that they are
 * only valid inside of the HandleScope active during their creation.
 * For passing a local handle to an outer HandleScope, an EscapableHandleScope
 * and its Escape() method must be used.
 *
 * 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_(nullptr) {}
  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>.
     */
    static_assert(std::is_base_of<T, S>::value, "type check");
  }

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

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

  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.
   *
   * If both handles refer to JS objects, this is the same as strict equality.
   * For primitives, such as numbers or strings, a `false` return value does not
   * indicate that the values aren't equal in the JavaScript sense.
   * Use `Value::StrictEquals()` to check primitives for equality.
   */
  template <class S>
  V8_INLINE bool operator==(const Local<S>& that) const {
    internal::Address* a = reinterpret_cast<internal::Address*>(this->val_);
    internal::Address* b = reinterpret_cast<internal::Address*>(that.val_);
    if (a == nullptr) return b == nullptr;
    if (b == nullptr) return false;
    return *a == *b;
  }

  template <class S> V8_INLINE bool operator==(
      const PersistentBase<S>& that) const {
    internal::Address* a = reinterpret_cast<internal::Address*>(this->val_);
    internal::Address* b = reinterpret_cast<internal::Address*>(that.val_);
    if (a == nullptr) return b == nullptr;
    if (b == nullptr) 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.
   *
   * If both handles refer to JS objects, this is the same as strict
   * non-equality. For primitives, such as numbers or strings, a `true` return
   * value does not indicate that the values aren't equal in the JavaScript
   * sense. Use `Value::StrictEquals()` to check primitives for equality.
   */
  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);
  }

  /**
   * Cast a handle to a subclass, e.g. Local<Value> to Local<Object>.
   * This is only valid if the handle actually refers to a value of the
   * target type.
   */
  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));
  }

  /**
   * Calling this is equivalent to Local<S>::Cast().
   * In particular, this is only valid if the handle actually refers to a value
   * of the target type.
   */
  template <class S>
  V8_INLINE Local<S> As() const {
    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);
  V8_INLINE static Local<T> New(Isolate* isolate,
                                const BasicTracedReference<T>& that);

 private:
  friend class TracedReferenceBase;
  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;
  friend class Isolate;
  friend class Private;
  template<class F> friend class internal::CustomArguments;
  friend Local<Primitive> Undefined(Isolate* isolate);
  friend Local<Primitive> Null(Isolate* isolate);
  friend Local<Boolean> True(Isolate* isolate);
  friend Local<Boolean> False(Isolate* isolate);
  friend class HandleScope;
  friend class EscapableHandleScope;
  template <class F1, class F2, class F3>
  friend class PersistentValueMapBase;
  template<class F1, class F2> friend class PersistentValueVector;
  template <class F>
  friend class ReturnValue;
  template <class F>
  friend class Traced;
  template <class F>
  friend class TracedGlobal;
  template <class F>
  friend class BasicTracedReference;
  template <class F>
  friend class TracedReference;

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


#if !defined(V8_IMMINENT_DEPRECATION_WARNINGS)
// Handle 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)) {
    static_assert(std::is_base_of<T, S>::value, "type check");
  }

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

  /**
   * Converts this MaybeLocal<> to a Local<>. If this MaybeLocal<> is empty,
   * |false| is returned and |out| is left untouched.
   */
  template <class S>
  V8_WARN_UNUSED_RESULT V8_INLINE bool ToLocal(Local<S>* out) const {
    out->val_ = IsEmpty() ? nullptr : this->val_;
    return !IsEmpty();
  }

  /**
   * Converts this MaybeLocal<> to a Local<>. If this MaybeLocal<> is empty,
   * V8 will crash the process.
   */
  V8_INLINE Local<T> ToLocalChecked();

  /**
   * Converts this MaybeLocal<> to a Local<>, using a default value if this
   * MaybeLocal<> is empty.
   */
  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 lifetime of the
 * isolate.
 */
template <class T> class Eternal {
 public:
  V8_INLINE Eternal() : val_(nullptr) {}
  template <class S>
  V8_INLINE Eternal(Isolate* isolate, Local<S> handle) : val_(nullptr) {
    Set(isolate, handle);
  }
  // Can only be safely called if already set.
  V8_INLINE Local<T> Get(Isolate* isolate) const;
  V8_INLINE bool IsEmpty() const { return val_ == nullptr; }
  template<class S> V8_INLINE void Set(Isolate* isolate, Local<S> handle);

 private:
  T* val_;
};


static const int kInternalFieldsInWeakCallback = 2;
static const int kEmbedderFieldsInWeakCallback = 2;

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

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

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

  // 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* embedder_fields_[kEmbedderFieldsInWeakCallback];
};


// kParameter will pass a void* parameter back to the callback, kInternalFields
// will pass the first two internal fields back to the callback, kFinalizer
// will pass a void* parameter back, but is invoked before the object is
// actually collected, so it can be resurrected. In the last case, it is not
// possible to request a second pass callback.
enum class WeakCallbackType { kParameter, kInternalFields, kFinalizer };

/**
 * 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 using Reset().
 *
 * 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_ == nullptr; }
  V8_INLINE void Empty() { val_ = 0; }

  V8_INLINE Local<T> Get(Isolate* isolate) const {
    return Local<T>::New(isolate, *this);
  }

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

  template <class S>
  V8_INLINE bool operator==(const Local<S>& that) const {
    internal::Address* a = reinterpret_cast<internal::Address*>(this->val_);
    internal::Address* b = reinterpret_cast<internal::Address*>(that.val_);
    if (a == nullptr) return b == nullptr;
    if (b == nullptr) 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!
   *
   * The callback is supposed to reset the handle. No further V8 API may be
   * called in this callback. In case additional work involving V8 needs to be
   * done, a second callback can be scheduled using
   * WeakCallbackInfo<void>::SetSecondPassCallback.
   */
  template <typename P>
  V8_INLINE void SetWeak(P* parameter,
                         typename WeakCallbackInfo<P>::Callback callback,
                         WeakCallbackType type);

  /**
   * Turns this handle into a weak phantom handle without finalization callback.
   * The handle will be reset automatically when the garbage collector detects
   * that the object is no longer reachable.
   * A related function Isolate::NumberOfPhantomHandleResetsSinceLastCall
   * returns how many phantom handles were reset by the garbage collector.
   */
  V8_INLINE void SetWeak();

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

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

  /**
   * Annotates the strong handle with the given label, which is then used by the
   * heap snapshot generator as a name of the edge from the root to the handle.
   * The function does not take ownership of the label and assumes that the
   * label is valid as long as the handle is valid.
   */
  V8_INLINE void AnnotateStrongRetainer(const char* label);

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

  /**
   * Assigns a wrapper class ID to the handle.
   */
  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;

  PersistentBase(const PersistentBase& other) = delete;  // NOLINT
  void operator=(const PersistentBase&) = delete;

 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) {}
  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) {
    static_assert(sizeof(S) < 0,
                  "NonCopyablePersistentTraits::Copy is not instantiable");
  }
};


/**
 * 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 behavior 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>(nullptr) {}
  /**
   * 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)) {
    static_assert(std::is_base_of<T, S>::value, "type check");
  }
  /**
   * 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)) {
    static_assert(std::is_base_of<T, S>::value, "type check");
  }
  /**
   * 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>(nullptr) {
    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) {
    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(const 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>&>(const_cast<Persistent<S>&>(that));
  }

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

  explicit V8_INLINE Persistent(T* 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)) {
    static_assert(std::is_base_of<T, S>::value, "type check");
  }

  /**
   * 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_)) {
    static_assert(std::is_base_of<T, S>::value, "type check");
  }

  /**
   * Move constructor.
   */
  V8_INLINE Global(Global&& other);

  V8_INLINE ~Global() { this->Reset(); }

  /**
   * Move via assignment.
   */
  template <class S>
  V8_INLINE Global& operator=(Global<S>&& rhs);

  /**
   * Pass allows returning uniques from functions, etc.
   */
  Global Pass() { return static_cast<Global&&>(*this); }  // NOLINT

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

  Global(const Global&) = delete;
  void operator=(const Global&) = delete;

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


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

/**
 * Deprecated. Use |TracedReference<T>| instead.
 */
template <typename T>
struct TracedGlobalTrait {};

class TracedReferenceBase {
 public:
  /**
   * Returns true if the reference is empty, i.e., has not been assigned
   * object.
   */
  bool IsEmpty() const { return val_ == nullptr; }

  /**
   * If non-empty, destroy the underlying storage cell. |IsEmpty| will return
   * true after this call.
   */
  V8_INLINE void Reset();

  /**
   * Construct a Local<Value> from this handle.
   */
  V8_INLINE v8::Local<v8::Value> Get(v8::Isolate* isolate) const;

  /**
   * Returns true if this TracedReference is empty, i.e., has not been
   * assigned an object. This version of IsEmpty is thread-safe.
   */
  bool IsEmptyThreadSafe() const {
    return this->GetSlotThreadSafe() == nullptr;
  }

  /**
   * Assigns a wrapper class ID to the handle.
   */
  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;

 protected:
  /**
   * Update this reference in a thread-safe way.
   */
  void SetSlotThreadSafe(void* new_val) {
    reinterpret_cast<std::atomic<void*>*>(&val_)->store(
        new_val, std::memory_order_relaxed);
  }

  /**
   * Get this reference in a thread-safe way
   */
  const void* GetSlotThreadSafe() const {
    return reinterpret_cast<std::atomic<const void*> const*>(&val_)->load(
        std::memory_order_relaxed);
  }

  // val_ points to a GlobalHandles node.
  internal::Address* val_ = nullptr;

  friend class internal::BasicTracedReferenceExtractor;
  template <typename F>
  friend class Local;
  template <typename U>
  friend bool operator==(const TracedReferenceBase&, const Local<U>&);
  friend bool operator==(const TracedReferenceBase&,
                         const TracedReferenceBase&);
};

/**
 * A traced handle with copy and move semantics. The handle is to be used
 * together with |v8::EmbedderHeapTracer| or as part of GarbageCollected objects
 * (see v8-cppgc.h) and specifies edges from C++ objects to JavaScript.
 *
 * The exact semantics are:
 * - Tracing garbage collections use |v8::EmbedderHeapTracer| or cppgc.
 * - Non-tracing garbage collections refer to
 *   |v8::EmbedderHeapTracer::IsRootForNonTracingGC()| whether the handle should
 *   be treated as root or not.
 *
 * Note that the base class cannot be instantiated itself. Choose from
 * - TracedGlobal
 * - TracedReference
 */
template <typename T>
class BasicTracedReference : public TracedReferenceBase {
 public:
  /**
   * Construct a Local<T> from this handle.
   */
  Local<T> Get(Isolate* isolate) const { return Local<T>::New(isolate, *this); }

  template <class S>
  V8_INLINE BasicTracedReference<S>& As() const {
    return reinterpret_cast<BasicTracedReference<S>&>(
        const_cast<BasicTracedReference<T>&>(*this));
  }

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

 private:
  enum DestructionMode { kWithDestructor, kWithoutDestructor };

  /**
   * An empty BasicTracedReference without storage cell.
   */
  BasicTracedReference() = default;

  V8_INLINE static internal::Address* New(Isolate* isolate, T* that, void* slot,
                                          DestructionMode destruction_mode);

  friend class EmbedderHeapTracer;
  template <typename F>
  friend class Local;
  friend class Object;
  template <typename F>
  friend class TracedGlobal;
  template <typename F>
  friend class TracedReference;
  template <typename F>
  friend class BasicTracedReference;
  template <typename F>
  friend class ReturnValue;
};

/**
 * A traced handle with destructor that clears the handle. For more details see
 * BasicTracedReference.
 */
template <typename T>
class TracedGlobal : public BasicTracedReference<T> {
 public:
  using BasicTracedReference<T>::Reset;

  /**
   * Destructor resetting the handle.Is
   */
  ~TracedGlobal() { this->Reset(); }

  /**
   * An empty TracedGlobal without storage cell.
   */
  TracedGlobal() : BasicTracedReference<T>() {}

  /**
   * Construct a TracedGlobal from a Local.
   *
   * When the Local is non-empty, a new storage cell is created
   * pointing to the same object.
   */
  template <class S>
  TracedGlobal(Isolate* isolate, Local<S> that) : BasicTracedReference<T>() {
    this->val_ = this->New(isolate, that.val_, &this->val_,
                           BasicTracedReference<T>::kWithDestructor);
    static_assert(std::is_base_of<T, S>::value, "type check");
  }

  /**
   * Move constructor initializing TracedGlobal from an existing one.
   */
  V8_INLINE TracedGlobal(TracedGlobal&& other) {
    // Forward to operator=.
    *this = std::move(other);
  }

  /**
   * Move constructor initializing TracedGlobal from an existing one.
   */
  template <typename S>
  V8_INLINE TracedGlobal(TracedGlobal<S>&& other) {
    // Forward to operator=.
    *this = std::move(other);
  }

  /**
   * Copy constructor initializing TracedGlobal from an existing one.
   */
  V8_INLINE TracedGlobal(const TracedGlobal& other) {
    // Forward to operator=;
    *this = other;
  }

  /**
   * Copy constructor initializing TracedGlobal from an existing one.
   */
  template <typename S>
  V8_INLINE TracedGlobal(const TracedGlobal<S>& other) {
    // Forward to operator=;
    *this = other;
  }

  /**
   * Move assignment operator initializing TracedGlobal from an existing one.
   */
  V8_INLINE TracedGlobal& operator=(TracedGlobal&& rhs);

  /**
   * Move assignment operator initializing TracedGlobal from an existing one.
   */
  template <class S>
  V8_INLINE TracedGlobal& operator=(TracedGlobal<S>&& rhs);

  /**
   * Copy assignment operator initializing TracedGlobal from an existing one.
   *
   * Note: Prohibited when |other| has a finalization callback set through
   * |SetFinalizationCallback|.
   */
  V8_INLINE TracedGlobal& operator=(const TracedGlobal& rhs);

  /**
   * Copy assignment operator initializing TracedGlobal from an existing one.
   *
   * Note: Prohibited when |other| has a finalization callback set through
   * |SetFinalizationCallback|.
   */
  template <class S>
  V8_INLINE TracedGlobal& operator=(const TracedGlobal<S>& rhs);

  /**
   * 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);

  template <class S>
  V8_INLINE TracedGlobal<S>& As() const {
    return reinterpret_cast<TracedGlobal<S>&>(
        const_cast<TracedGlobal<T>&>(*this));
  }

  /**
   * Adds a finalization callback to the handle. The type of this callback is
   * similar to WeakCallbackType::kInternalFields, i.e., it will pass the
   * parameter and the first two internal fields of the object.
   *
   * The callback is then supposed to reset the handle in the callback. No
   * further V8 API may be called in this callback. In case additional work
   * involving V8 needs to be done, a second callback can be scheduled using
   * WeakCallbackInfo<void>::SetSecondPassCallback.
   */
  V8_INLINE void SetFinalizationCallback(
      void* parameter, WeakCallbackInfo<void>::Callback callback);
};

/**
 * A traced handle without destructor that clears the handle. The embedder needs
 * to ensure that the handle is not accessed once the V8 object has been
 * reclaimed. This can happen when the handle is not passed through the
 * EmbedderHeapTracer. For more details see BasicTracedReference.
 *
 * The reference assumes the embedder has precise knowledge about references at
 * all times. In case V8 needs to separately handle on-stack references, the
 * embedder is required to set the stack start through
 * |EmbedderHeapTracer::SetStackStart|.
 */
template <typename T>
class TracedReference : public BasicTracedReference<T> {
 public:
  using BasicTracedReference<T>::Reset;

  /**
   * An empty TracedReference without storage cell.
   */
  TracedReference() : BasicTracedReference<T>() {}

  /**
   * Construct a TracedReference from a Local.
   *
   * When the Local is non-empty, a new storage cell is created
   * pointing to the same object.
   */
  template <class S>
  TracedReference(Isolate* isolate, Local<S> that) : BasicTracedReference<T>() {
    this->val_ = this->New(isolate, that.val_, &this->val_,
                           BasicTracedReference<T>::kWithoutDestructor);
    static_assert(std::is_base_of<T, S>::value, "type check");
  }

  /**
   * Move constructor initializing TracedReference from an
   * existing one.
   */
  V8_INLINE TracedReference(TracedReference&& other) {
    // Forward to operator=.
    *this = std::move(other);
  }

  /**
   * Move constructor initializing TracedReference from an
   * existing one.
   */
  template <typename S>
  V8_INLINE TracedReference(TracedReference<S>&& other) {
    // Forward to operator=.
    *this = std::move(other);
  }

  /**
   * Copy constructor initializing TracedReference from an
   * existing one.
   */
  V8_INLINE TracedReference(const TracedReference& other) {
    // Forward to operator=;
    *this = other;
  }

  /**
   * Copy constructor initializing TracedReference from an
   * existing one.
   */
  template <typename S>
  V8_INLINE TracedReference(const TracedReference<S>& other) {
    // Forward to operator=;
    *this = other;
  }

  /**
   * Move assignment operator initializing TracedGlobal from an existing one.
   */
  V8_INLINE TracedReference& operator=(TracedReference&& rhs);

  /**
   * Move assignment operator initializing TracedGlobal from an existing one.
   */
  template <class S>
  V8_INLINE TracedReference& operator=(TracedReference<S>&& rhs);

  /**
   * Copy assignment operator initializing TracedGlobal from an existing one.
   */
  V8_INLINE TracedReference& operator=(const TracedReference& rhs);

  /**
   * Copy assignment operator initializing TracedGlobal from an existing one.
   */
  template <class S>
  V8_INLINE TracedReference& operator=(const TracedReference<S>& rhs);

  /**
   * 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);

  template <class S>
  V8_INLINE TracedReference<S>& As() const {
    return reinterpret_cast<TracedReference<S>&>(
        const_cast<TracedReference<T>&>(*this));
  }
};

 /**
 * 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:
  explicit 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_);
  }

  HandleScope(const HandleScope&) = delete;
  void operator=(const HandleScope&) = delete;

 protected:
  V8_INLINE HandleScope() = default;

  void Initialize(Isolate* isolate);

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

 private:
  // Declaring operator new and delete as deleted is not spec compliant.
  // Therefore declare them private instead to disable dynamic alloc
  void* operator new(size_t size);
  void* operator new[](size_t size);
  void operator delete(void*, size_t);
  void operator delete[](void*, size_t);

  internal::Isolate* isolate_;
  internal::Address* prev_next_;
  internal::Address* 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:
  explicit EscapableHandleScope(Isolate* isolate);
  V8_INLINE ~EscapableHandleScope() = default;

  /**
   * 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::Address* slot =
        Escape(reinterpret_cast<internal::Address*>(*value));
    return Local<T>(reinterpret_cast<T*>(slot));
  }

  template <class T>
  V8_INLINE MaybeLocal<T> EscapeMaybe(MaybeLocal<T> value) {
    return Escape(value.FromMaybe(Local<T>()));
  }

  EscapableHandleScope(const EscapableHandleScope&) = delete;
  void operator=(const EscapableHandleScope&) = delete;

 private:
  // Declaring operator new and delete as deleted is not spec compliant.
  // Therefore declare them private instead to disable dynamic alloc
  void* operator new(size_t size);
  void* operator new[](size_t size);
  void operator delete(void*, size_t);
  void operator delete[](void*, size_t);

  internal::Address* Escape(internal::Address* escape_value);
  internal::Address* escape_slot_;
};

/**
 * A SealHandleScope acts like a handle scope in which no handle allocations
 * are allowed. It can be useful for debugging handle leaks.
 * Handles can be allocated within inner normal HandleScopes.
 */
class V8_EXPORT SealHandleScope {
 public:
  explicit SealHandleScope(Isolate* isolate);
  ~SealHandleScope();

  SealHandleScope(const SealHandleScope&) = delete;
  void operator=(const SealHandleScope&) = delete;

 private:
  // Declaring operator new and delete as deleted is not spec compliant.
  // Therefore declare them private instead to disable dynamic alloc
  void* operator new(size_t size);
  void* operator new[](size_t size);
  void operator delete(void*, size_t);
  void operator delete[](void*, size_t);

  internal::Isolate* const isolate_;
  internal::Address* prev_limit_;
  int prev_sealed_level_;
};


// --- Special objects ---

/**
 * The superclass of objects that can reside on V8's heap.
 */
class V8_EXPORT Data {
 public:
  /**
   * Returns true if this data is a |v8::Value|.
   */
  bool IsValue() const;

  /**
   * Returns true if this data is a |v8::Module|.
   */
  bool IsModule() const;

  /**
   * Returns true if this data is a |v8::Private|.
   */
  bool IsPrivate() const;

  /**
   * Returns true if this data is a |v8::ObjectTemplate|.
   */
  bool IsObjectTemplate() const;

  /**
   * Returns true if this data is a |v8::FunctionTemplate|.
   */
  bool IsFunctionTemplate() const;

 private:
  Data();
};

/**
 * A container type that holds relevant metadata for module loading.
 *
 * This is passed back to the embedder as part of
 * HostImportModuleDynamicallyCallback for module loading.
 */
class V8_EXPORT ScriptOrModule {
 public:
  /**
   * The name that was passed by the embedder as ResourceName to the
   * ScriptOrigin. This can be either a v8::String or v8::Undefined.
   */
  Local<Value> GetResourceName();

  /**
   * The options that were passed by the embedder as HostDefinedOptions to
   * the ScriptOrigin.
   */
  Local<PrimitiveArray> GetHostDefinedOptions();
};

/**
 * An array to hold Primitive values. This is used by the embedder to
 * pass host defined options to the ScriptOptions during compilation.
 *
 * This is passed back to the embedder as part of
 * HostImportModuleDynamicallyCallback for module loading.
 *
 */
class V8_EXPORT PrimitiveArray {
 public:
  static Local<PrimitiveArray> New(Isolate* isolate, int length);
  int Length() const;
  void Set(Isolate* isolate, int index, Local<Primitive> item);
  Local<Primitive> Get(Isolate* isolate, int index);
};

/**
 * The optional attributes of ScriptOrigin.
 */
class ScriptOriginOptions {
 public:
  V8_INLINE ScriptOriginOptions(bool is_shared_cross_origin = false,
                                bool is_opaque = false, bool is_wasm = false,
                                bool is_module = false)
      : flags_((is_shared_cross_origin ? kIsSharedCrossOrigin : 0) |
               (is_wasm ? kIsWasm : 0) | (is_opaque ? kIsOpaque : 0) |
               (is_module ? kIsModule : 0)) {}
  V8_INLINE ScriptOriginOptions(int flags)
      : flags_(flags &
               (kIsSharedCrossOrigin | kIsOpaque | kIsWasm | kIsModule)) {}

  bool IsSharedCrossOrigin() const {
    return (flags_ & kIsSharedCrossOrigin) != 0;
  }
  bool IsOpaque() const { return (flags_ & kIsOpaque) != 0; }
  bool IsWasm() const { return (flags_ & kIsWasm) != 0; }
  bool IsModule() const { return (flags_ & kIsModule) != 0; }

  int Flags() const { return flags_; }

 private:
  enum {
    kIsSharedCrossOrigin = 1,
    kIsOpaque = 1 << 1,
    kIsWasm = 1 << 2,
    kIsModule = 1 << 3
  };
  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<Value> source_map_url = Local<Value>(),
      Local<Boolean> resource_is_opaque = Local<Boolean>(),
      Local<Boolean> is_wasm = Local<Boolean>(),
      Local<Boolean> is_module = Local<Boolean>(),
      Local<PrimitiveArray> host_defined_options = Local<PrimitiveArray>());

  V8_INLINE Local<Value> ResourceName() const;
  V8_INLINE Local<Integer> ResourceLineOffset() const;
  V8_INLINE Local<Integer> ResourceColumnOffset() const;
  V8_INLINE Local<Integer> ScriptID() const;
  V8_INLINE Local<Value> SourceMapUrl() const;
  V8_INLINE Local<PrimitiveArray> HostDefinedOptions() 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_;
  Local<PrimitiveArray> host_defined_options_;
};

/**
 * 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 module, not yet tied to a Context.
 */
class V8_EXPORT UnboundModuleScript : public Data {
  // Only used as a container for code caching.
};

/**
 * A location in JavaScript source.
 */
class V8_EXPORT Location {
 public:
  int GetLineNumber() { return line_number_; }
  int GetColumnNumber() { return column_number_; }

  Location(int line_number, int column_number)
      : line_number_(line_number), column_number_(column_number) {}

 private:
  int line_number_;
  int column_number_;
};

/**
 * A compiled JavaScript module.
 */
class V8_EXPORT Module : public Data {
 public:
  /**
   * The different states a module can be in.
   *
   * This corresponds to the states used in ECMAScript except that "evaluated"
   * is split into kEvaluated and kErrored, indicating success and failure,
   * respectively.
   */
  enum Status {
    kUninstantiated,
    kInstantiating,
    kInstantiated,
    kEvaluating,
    kEvaluated,
    kErrored
  };

  /**
   * Returns the module's current status.
   */
  Status GetStatus() const;

  /**
   * For a module in kErrored status, this returns the corresponding exception.
   */
  Local<Value> GetException() const;

  /**
   * Returns the number of modules requested by this module.
   */
  int GetModuleRequestsLength() const;

  /**
   * Returns the ith module specifier in this module.
   * i must be < GetModuleRequestsLength() and >= 0.
   */
  Local<String> GetModuleRequest(int i) const;

  /**
   * Returns the source location (line number and column number) of the ith
   * module specifier's first occurrence in this module.
   */
  Location GetModuleRequestLocation(int i) const;

  /**
   * Returns the identity hash for this object.
   */
  int GetIdentityHash() const;

  typedef MaybeLocal<Module> (*ResolveCallback)(Local<Context> context,
                                                Local<String> specifier,
                                                Local<Module> referrer);

  /**
   * Instantiates the module and its dependencies.
   *
   * Returns an empty Maybe<bool> if an exception occurred during
   * instantiation. (In the case where the callback throws an exception, that
   * exception is propagated.)
   */
  V8_WARN_UNUSED_RESULT Maybe<bool> InstantiateModule(Local<Context> context,
                                                      ResolveCallback callback);

  /**
   * Evaluates the module and its dependencies.
   *
   * If status is kInstantiated, run the module's code. On success, set status
   * to kEvaluated and return the completion value; on failure, set status to
   * kErrored and propagate the thrown exception (which is then also available
   * via |GetException|).
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> Evaluate(Local<Context> context);

  /**
   * Returns the namespace object of this module.
   *
   * The module's status must be at least kInstantiated.
   */
  Local<Value> GetModuleNamespace();

  /**
   * Returns the corresponding context-unbound module script.
   *
   * The module must be unevaluated, i.e. its status must not be kEvaluating,
   * kEvaluated or kErrored.
   */
  Local<UnboundModuleScript> GetUnboundModuleScript();

  /**
   * Returns the underlying script's id.
   *
   * The module must be a SourceTextModule and must not have a kErrored status.
   */
  int ScriptId();

  /**
   * Returns whether this module or any of its requested modules is async,
   * i.e. contains top-level await.
   *
   * The module's status must be at least kInstantiated.
   */
  bool IsGraphAsync() const;

  /**
   * Returns whether the module is a SourceTextModule.
   */
  bool IsSourceTextModule() const;

  /**
   * Returns whether the module is a SyntheticModule.
   */
  bool IsSyntheticModule() const;

  /*
   * Callback defined in the embedder.  This is responsible for setting
   * the module's exported values with calls to SetSyntheticModuleExport().
   * The callback must return a Value to indicate success (where no
   * exception was thrown) and return an empy MaybeLocal to indicate falure
   * (where an exception was thrown).
   */
  typedef MaybeLocal<Value> (*SyntheticModuleEvaluationSteps)(
      Local<Context> context, Local<Module> module);

  /**
   * Creates a new SyntheticModule with the specified export names, where
   * evaluation_steps will be executed upon module evaluation.
   * export_names must not contain duplicates.
   * module_name is used solely for logging/debugging and doesn't affect module
   * behavior.
   */
  static Local<Module> CreateSyntheticModule(
      Isolate* isolate, Local<String> module_name,
      const std::vector<Local<String>>& export_names,
      SyntheticModuleEvaluationSteps evaluation_steps);

  /**
   * Set this module's exported value for the name export_name to the specified
   * export_value. This method must be called only on Modules created via
   * CreateSyntheticModule.  An error will be thrown if export_name is not one
   * of the export_names that were passed in that CreateSyntheticModule call.
   * Returns Just(true) on success, Nothing<bool>() if an error was thrown.
   */
  V8_WARN_UNUSED_RESULT Maybe<bool> SetSyntheticModuleExport(
      Isolate* isolate, Local<String> export_name, Local<Value> export_value);
  V8_DEPRECATE_SOON(
      "Use the preceding SetSyntheticModuleExport with an Isolate parameter, "
      "instead of the one that follows.  The former will throw a runtime "
      "error if called for an export that doesn't exist (as per spec); "
      "the latter will crash with a failed CHECK().")
  void SetSyntheticModuleExport(Local<String> export_name,
                                Local<Value> export_value);

  V8_INLINE static Module* Cast(Data* data);

 private:
  static void CheckCast(Data* obj);
};

/**
 * 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_WARN_UNUSED_RESULT MaybeLocal<Script> Compile(
      Local<Context> context, Local<String> source,
      ScriptOrigin* origin = nullptr);

  /**
   * 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_WARN_UNUSED_RESULT MaybeLocal<Value> Run(Local<Context> context);

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


/**
 * 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(nullptr),
          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;

    // Prevent copying.
    CachedData(const CachedData&) = delete;
    CachedData& operator=(const CachedData&) = delete;
  };

  /**
   * 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 = nullptr);
    V8_INLINE Source(Local<String> source_string,
                     CachedData* cached_data = nullptr);
    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;

    V8_INLINE const ScriptOriginOptions& GetResourceOptions() const;

    // Prevent copying.
    Source(const Source&) = delete;
    Source& operator=(const Source&) = delete;

   private:
    friend class ScriptCompiler;

    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;
    Local<PrimitiveArray> host_defined_options;

    // 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() = default;

    /**
     * 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.
     *
     * When streaming UTF-16 data, V8 does not handle characters split between
     * two data chunks. The embedder has to make sure that chunks have an even
     * length.
     *
     * 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 and compiled after parsing has completed. StreamedSource
   * must be kept alive while the streaming task is run (see ScriptStreamingTask
   * below).
   */
  class V8_EXPORT StreamedSource {
   public:
    enum Encoding { ONE_BYTE, TWO_BYTE, UTF8 };

    V8_DEPRECATE_SOON(
        "This class takes ownership of source_stream, so use the constructor "
        "taking a unique_ptr to make these semantics clearer")
    StreamedSource(ExternalSourceStream* source_stream, Encoding encoding);
    StreamedSource(std::unique_ptr<ExternalSourceStream> source_stream,
                   Encoding encoding);
    ~StreamedSource();

    internal::ScriptStreamingData* impl() const { return impl_.get(); }

    // Prevent copying.
    StreamedSource(const StreamedSource&) = delete;
    StreamedSource& operator=(const StreamedSource&) = delete;

   private:
    std::unique_ptr<internal::ScriptStreamingData> impl_;
  };

  /**
   * A streaming task which the embedder must run on a background thread to
   * stream scripts into V8. Returned by ScriptCompiler::StartStreaming.
   */
  class V8_EXPORT ScriptStreamingTask final {
   public:
    void Run();

   private:
    friend class ScriptCompiler;

    explicit ScriptStreamingTask(internal::ScriptStreamingData* data)
        : data_(data) {}

    internal::ScriptStreamingData* data_;
  };

  enum CompileOptions {
    kNoCompileOptions = 0,
    kConsumeCodeCache,
    kEagerCompile
  };

  /**
   * The reason for which we are not requesting or providing a code cache.
   */
  enum NoCacheReason {
    kNoCacheNoReason = 0,
    kNoCacheBecauseCachingDisabled,
    kNoCacheBecauseNoResource,
    kNoCacheBecauseInlineScript,
    kNoCacheBecauseModule,
    kNoCacheBecauseStreamingSource,
    kNoCacheBecauseInspector,
    kNoCacheBecauseScriptTooSmall,
    kNoCacheBecauseCacheTooCold,
    kNoCacheBecauseV8Extension,
    kNoCacheBecauseExtensionModule,
    kNoCacheBecausePacScript,
    kNoCacheBecauseInDocumentWrite,
    kNoCacheBecauseResourceWithNoCacheHandler,
    kNoCacheBecauseDeferredProduceCodeCache
  };

  /**
   * 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_WARN_UNUSED_RESULT MaybeLocal<UnboundScript> CompileUnboundScript(
      Isolate* isolate, Source* source,
      CompileOptions options = kNoCompileOptions,
      NoCacheReason no_cache_reason = kNoCacheNoReason);

  /**
   * 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_WARN_UNUSED_RESULT MaybeLocal<Script> Compile(
      Local<Context> context, Source* source,
      CompileOptions options = kNoCompileOptions,
      NoCacheReason no_cache_reason = kNoCacheNoReason);

  /**
   * 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.
   */
  V8_DEPRECATE_SOON("Use ScriptCompiler::StartStreamingScript instead.")
  static ScriptStreamingTask* StartStreamingScript(
      Isolate* isolate, StreamedSource* source,
      CompileOptions options = kNoCompileOptions);
  static ScriptStreamingTask* StartStreaming(Isolate* isolate,
                                             StreamedSource* source);

  /**
   * 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_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 current compiler flags. This means that 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 ES module, returning a Module that encapsulates
   * the compiled code.
   *
   * Corresponds to the ParseModule abstract operation in the
   * ECMAScript specification.
   */
  static V8_WARN_UNUSED_RESULT MaybeLocal<Module> CompileModule(
      Isolate* isolate, Source* source,
      CompileOptions options = kNoCompileOptions,
      NoCacheReason no_cache_reason = kNoCacheNoReason);

  /**
   * 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_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[],
      CompileOptions options = kNoCompileOptions,
      NoCacheReason no_cache_reason = kNoCacheNoReason,
      Local<ScriptOrModule>* script_or_module_out = nullptr);

  /**
   * Creates and returns code cache for the specified unbound_script.
   * This will return nullptr if the script cannot be serialized. The
   * CachedData returned by this function should be owned by the caller.
   */
  static CachedData* CreateCodeCache(Local<UnboundScript> unbound_script);

  /**
   * Creates and returns code cache for the specified unbound_module_script.
   * This will return nullptr if the script cannot be serialized. The
   * CachedData returned by this function should be owned by the caller.
   */
  static CachedData* CreateCodeCache(
      Local<UnboundModuleScript> unbound_module_script);

  /**
   * Creates and returns code cache for the specified function that was
   * previously produced by CompileFunctionInContext.
   * This will return nullptr if the script cannot be serialized. The
   * CachedData returned by this function should be owned by the caller.
   */
  static CachedData* CreateCodeCacheForFunction(Local<Function> function);

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


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

  /**
   * Return the isolate to which the Message belongs.
   */
  Isolate* GetIsolate() 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_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 Wasm function index where the error occurred. Returns -1 if
   * message is not from a Wasm script.
   */
  int GetWasmFunctionIndex() const;

  /**
   * Returns the error level of the message.
   */
  int ErrorLevel() const;

  /**
   * Returns the index within the line of the first character where
   * the error occurred.
   */
  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.
   */
  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;
  static const int kNoWasmFunctionIndexInfo = -1;
};


/**
 * 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.
   * Note: these options are deprecated and we always collect all available
   * information (kDetailed).
   */
  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(Isolate* isolate, uint32_t index) const;

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

  /**
   * 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 = kDetailed);
};


/**
 * 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;

  /**
   * Returns whether or not the associated functions is defined in wasm.
   */
  bool IsWasm() const;

  /**
   * Returns whether or not the associated function is defined by the user.
   */
  bool IsUserJavaScript() const;
};


// A StateTag represents a possible state of the VM.
enum StateTag {
  JS,
  GC,
  PARSER,
  BYTECODE_COMPILER,
  COMPILER,
  OTHER,
  EXTERNAL,
  ATOMICS_WAIT,
  IDLE
};

// Holds the callee saved registers needed for the stack unwinder. It is the
// empty struct if no registers are required. Implemented in
// include/v8-unwinder-state.h.
struct CalleeSavedRegisters;

// A RegisterState represents the current state of registers used
// by the sampling profiler API.
struct V8_EXPORT RegisterState {
  RegisterState();
  ~RegisterState();
  RegisterState(const RegisterState& other);
  RegisterState& operator=(const RegisterState& other);

  void* pc;  // Instruction pointer.
  void* sp;  // Stack pointer.
  void* fp;  // Frame pointer.
  void* lr;  // Link register (or nullptr on platforms without a link register).
  // Callee saved registers (or null if no callee saved registers were stored)
  std::unique_ptr<CalleeSavedRegisters> callee_saved;
};

// The output structure filled up by GetStackSample API function.
struct SampleInfo {
  size_t frames_count;            // Number of frames collected.
  StateTag vm_state;              // Current VM state.
  void* external_callback_entry;  // External callback address if VM is
                                  // executing an external callback.
  void* top_context;              // Incumbent native context address.
};

struct MemoryRange {
  const void* start = nullptr;
  size_t length_in_bytes = 0;
};

struct JSEntryStub {
  MemoryRange code;
};

struct JSEntryStubs {
  JSEntryStub js_entry_stub;
  JSEntryStub js_construct_entry_stub;
  JSEntryStub js_run_microtasks_entry_stub;
};

/**
 * A JSON Parser and Stringifier.
 */
class V8_EXPORT JSON {
 public:
  /**
   * Tries to parse the string |json_string| and returns it as value if
   * successful.
   *
   * \param the context in which to parse and create the value.
   * \param json_string The string to parse.
   * \return The corresponding value if successfully parsed.
   */
  static V8_WARN_UNUSED_RESULT MaybeLocal<Value> Parse(
      Local<Context> context, Local<String> json_string);

  /**
   * Tries to stringify the JSON-serializable object |json_object| and returns
   * it as string if successful.
   *
   * \param json_object The JSON-serializable object to stringify.
   * \return The corresponding string if successfully stringified.
   */
  static V8_WARN_UNUSED_RESULT MaybeLocal<String> Stringify(
      Local<Context> context, Local<Value> json_object,
      Local<String> gap = Local<String>());
};

/**
 * Value serialization compatible with the HTML structured clone algorithm.
 * The format is backward-compatible (i.e. safe to store to disk).
 */
class V8_EXPORT ValueSerializer {
 public:
  class V8_EXPORT Delegate {
   public:
    virtual ~Delegate() = default;

    /**
     * Handles the case where a DataCloneError would be thrown in the structured
     * clone spec. Other V8 embedders may throw some other appropriate exception
     * type.
     */
    virtual void ThrowDataCloneError(Local<String> message) = 0;

    /**
     * The embedder overrides this method to write some kind of host object, if
     * possible. If not, a suitable exception should be thrown and
     * Nothing<bool>() returned.
     */
    virtual Maybe<bool> WriteHostObject(Isolate* isolate, Local<Object> object);

    /**
     * Called when the ValueSerializer is going to serialize a
     * SharedArrayBuffer object. The embedder must return an ID for the
     * object, using the same ID if this SharedArrayBuffer has already been
     * serialized in this buffer. When deserializing, this ID will be passed to
     * ValueDeserializer::GetSharedArrayBufferFromId as |clone_id|.
     *
     * If the object cannot be serialized, an
     * exception should be thrown and Nothing<uint32_t>() returned.
     */
    virtual Maybe<uint32_t> GetSharedArrayBufferId(
        Isolate* isolate, Local<SharedArrayBuffer> shared_array_buffer);

    virtual Maybe<uint32_t> GetWasmModuleTransferId(
        Isolate* isolate, Local<WasmModuleObject> module);
    /**
     * Allocates memory for the buffer of at least the size provided. The actual
     * size (which may be greater or equal) is written to |actual_size|. If no
     * buffer has been allocated yet, nullptr will be provided.
     *
     * If the memory cannot be allocated, nullptr should be returned.
     * |actual_size| will be ignored. It is assumed that |old_buffer| is still
     * valid in this case and has not been modified.
     *
     * The default implementation uses the stdlib's `realloc()` function.
     */
    virtual void* ReallocateBufferMemory(void* old_buffer, size_t size,
                                         size_t* actual_size);

    /**
     * Frees a buffer allocated with |ReallocateBufferMemory|.
     *
     * The default implementation uses the stdlib's `free()` function.
     */
    virtual void FreeBufferMemory(void* buffer);
  };

  explicit ValueSerializer(Isolate* isolate);
  ValueSerializer(Isolate* isolate, Delegate* delegate);
  ~ValueSerializer();

  /**
   * Writes out a header, which includes the format version.
   */
  void WriteHeader();

  /**
   * Serializes a JavaScript value into the buffer.
   */
  V8_WARN_UNUSED_RESULT Maybe<bool> WriteValue(Local<Context> context,
                                               Local<Value> value);

  /**
   * Returns the stored data (allocated using the delegate's
   * ReallocateBufferMemory) and its size. This serializer should not be used
   * once the buffer is released. The contents are undefined if a previous write
   * has failed. Ownership of the buffer is transferred to the caller.
   */
  V8_WARN_UNUSED_RESULT std::pair<uint8_t*, size_t> Release();

  /**
   * Marks an ArrayBuffer as havings its contents transferred out of band.
   * Pass the corresponding ArrayBuffer in the deserializing context to
   * ValueDeserializer::TransferArrayBuffer.
   */
  void TransferArrayBuffer(uint32_t transfer_id,
                           Local<ArrayBuffer> array_buffer);


  /**
   * Indicate whether to treat ArrayBufferView objects as host objects,
   * i.e. pass them to Delegate::WriteHostObject. This should not be
   * called when no Delegate was passed.
   *
   * The default is not to treat ArrayBufferViews as host objects.
   */
  void SetTreatArrayBufferViewsAsHostObjects(bool mode);

  /**
   * Write raw data in various common formats to the buffer.
   * Note that integer types are written in base-128 varint format, not with a
   * binary copy. For use during an override of Delegate::WriteHostObject.
   */
  void WriteUint32(uint32_t value);
  void WriteUint64(uint64_t value);
  void WriteDouble(double value);
  void WriteRawBytes(const void* source, size_t length);

  ValueSerializer(const ValueSerializer&) = delete;
  void operator=(const ValueSerializer&) = delete;

 private:
  struct PrivateData;
  PrivateData* private_;
};

/**
 * Deserializes values from data written with ValueSerializer, or a compatible
 * implementation.
 */
class V8_EXPORT ValueDeserializer {
 public:
  class V8_EXPORT Delegate {
   public:
    virtual ~Delegate() = default;

    /**
     * The embedder overrides this method to read some kind of host object, if
     * possible. If not, a suitable exception should be thrown and
     * MaybeLocal<Object>() returned.
     */
    virtual MaybeLocal<Object> ReadHostObject(Isolate* isolate);

    /**
     * Get a WasmModuleObject given a transfer_id previously provided
     * by ValueSerializer::GetWasmModuleTransferId
     */
    virtual MaybeLocal<WasmModuleObject> GetWasmModuleFromId(
        Isolate* isolate, uint32_t transfer_id);

    /**
     * Get a SharedArrayBuffer given a clone_id previously provided
     * by ValueSerializer::GetSharedArrayBufferId
     */
    virtual MaybeLocal<SharedArrayBuffer> GetSharedArrayBufferFromId(
        Isolate* isolate, uint32_t clone_id);
  };

  ValueDeserializer(Isolate* isolate, const uint8_t* data, size_t size);
  ValueDeserializer(Isolate* isolate, const uint8_t* data, size_t size,
                    Delegate* delegate);
  ~ValueDeserializer();

  /**
   * Reads and validates a header (including the format version).
   * May, for example, reject an invalid or unsupported wire format.
   */
  V8_WARN_UNUSED_RESULT Maybe<bool> ReadHeader(Local<Context> context);

  /**
   * Deserializes a JavaScript value from the buffer.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<Value> ReadValue(Local<Context> context);

  /**
   * Accepts the array buffer corresponding to the one passed previously to
   * ValueSerializer::TransferArrayBuffer.
   */
  void TransferArrayBuffer(uint32_t transfer_id,
                           Local<ArrayBuffer> array_buffer);

  /**
   * Similar to TransferArrayBuffer, but for SharedArrayBuffer.
   * The id is not necessarily in the same namespace as unshared ArrayBuffer
   * objects.
   */
  void TransferSharedArrayBuffer(uint32_t id,
                                 Local<SharedArrayBuffer> shared_array_buffer);

  /**
   * Must be called before ReadHeader to enable support for reading the legacy
   * wire format (i.e., which predates this being shipped).
   *
   * Don't use this unless you need to read data written by previous versions of
   * blink::ScriptValueSerializer.
   */
  void SetSupportsLegacyWireFormat(bool supports_legacy_wire_format);

  /**
   * Reads the underlying wire format version. Likely mostly to be useful to
   * legacy code reading old wire format versions. Must be called after
   * ReadHeader.
   */
  uint32_t GetWireFormatVersion() const;

  /**
   * Reads raw data in various common formats to the buffer.
   * Note that integer types are read in base-128 varint format, not with a
   * binary copy. For use during an override of Delegate::ReadHostObject.
   */
  V8_WARN_UNUSED_RESULT bool ReadUint32(uint32_t* value);
  V8_WARN_UNUSED_RESULT bool ReadUint64(uint64_t* value);
  V8_WARN_UNUSED_RESULT bool ReadDouble(double* value);
  V8_WARN_UNUSED_RESULT bool ReadRawBytes(size_t length, const void** data);

  ValueDeserializer(const ValueDeserializer&) = delete;
  void operator=(const ValueDeserializer&) = delete;

 private:
  struct PrivateData;
  PrivateData* private_;
};


// --- 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.
   *
   * This is equivalent to `value === undefined` in JS.
   */
  V8_INLINE bool IsUndefined() const;

  /**
   * Returns true if this value is the null value.  See ECMA-262
   * 4.3.11.
   *
   * This is equivalent to `value === null` in JS.
   */
  V8_INLINE bool IsNull() const;

  /**
   * Returns true if this value is either the null or the undefined value.
   * See ECMA-262
   * 4.3.11. and 4.3.12
   *
   * This is equivalent to `value == null` in JS.
   */
  V8_INLINE bool IsNullOrUndefined() const;

  /**
   * Returns true if this value is true.
   *
   * This is not the same as `BooleanValue()`. The latter performs a
   * conversion to boolean, i.e. the result of `Boolean(value)` in JS, whereas
   * this checks `value === true`.
   */
  bool IsTrue() const;

  /**
   * Returns true if this value is false.
   *
   * This is not the same as `!BooleanValue()`. The latter performs a
   * conversion to boolean, i.e. the result of `!Boolean(value)` in JS, whereas
   * this checks `value === false`.
   */
  bool IsFalse() const;

  /**
   * Returns true if this value is a symbol or a string.
   *
   * This is equivalent to
   * `typeof value === 'string' || typeof value === 'symbol'` in JS.
   */
  bool IsName() const;

  /**
   * Returns true if this value is an instance of the String type.
   * See ECMA-262 8.4.
   *
   * This is equivalent to `typeof value === 'string'` in JS.
   */
  V8_INLINE bool IsString() const;

  /**
   * Returns true if this value is a symbol.
   *
   * This is equivalent to `typeof value === 'symbol'` in JS.
   */
  bool IsSymbol() const;

  /**
   * Returns true if this value is a function.
   *
   * This is equivalent to `typeof value === 'function'` in JS.
   */
  bool IsFunction() const;

  /**
   * Returns true if this value is an array. Note that it will return false for
   * an Proxy for an array.
   */
  bool IsArray() const;

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

  /**
   * Returns true if this value is a bigint.
   *
   * This is equivalent to `typeof value === 'bigint'` in JS.
   */
  bool IsBigInt() const;

  /**
   * Returns true if this value is boolean.
   *
   * This is equivalent to `typeof value === 'boolean'` in JS.
   */
  bool IsBoolean() const;

  /**
   * Returns true if this value is a number.
   *
   * This is equivalent to `typeof value === 'number'` in JS.
   */
  bool IsNumber() const;

  /**
   * Returns true if this value is an `External` object.
   */
  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 BigInt object.
   */
  bool IsBigIntObject() 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.
   */
  bool IsSymbolObject() const;

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

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

  /**
   * Returns true if this value is an async function.
   */
  bool IsAsyncFunction() const;

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

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

  /**
   * Returns true if this value is a Promise.
   */
  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.
   */
  bool IsArrayBuffer() const;

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

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

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

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

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

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

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

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

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

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

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

  /**
   * Returns true if this value is a BigInt64Array.
   */
  bool IsBigInt64Array() const;

  /**
   * Returns true if this value is a BigUint64Array.
   */
  bool IsBigUint64Array() const;

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

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

  /**
   * Returns true if this value is a JavaScript Proxy.
   */
  bool IsProxy() const;

  /**
   * Returns true if this value is a WasmModuleObject.
   */
  bool IsWasmModuleObject() const;

  /**
   * Returns true if the value is a Module Namespace Object.
   */
  bool IsModuleNamespaceObject() const;

  /**
   * Perform the equivalent of `BigInt(value)` in JS.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<BigInt> ToBigInt(
      Local<Context> context) const;
  /**
   * Perform the equivalent of `Number(value)` in JS.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<Number> ToNumber(
      Local<Context> context) const;
  /**
   * Perform the equivalent of `String(value)` in JS.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<String> ToString(
      Local<Context> context) const;
  /**
   * Provide a string representation of this value usable for debugging.
   * This operation has no observable side effects and will succeed
   * unless e.g. execution is being terminated.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<String> ToDetailString(
      Local<Context> context) const;
  /**
   * Perform the equivalent of `Object(value)` in JS.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<Object> ToObject(
      Local<Context> context) const;
  /**
   * Perform the equivalent of `Number(value)` in JS and convert the result
   * to an integer. Negative values are rounded up, positive values are rounded
   * down. NaN is converted to 0. Infinite values yield undefined results.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<Integer> ToInteger(
      Local<Context> context) const;
  /**
   * Perform the equivalent of `Number(value)` in JS and convert the result
   * to an unsigned 32-bit integer by performing the steps in
   * https://tc39.es/ecma262/#sec-touint32.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<Uint32> ToUint32(
      Local<Context> context) const;
  /**
   * Perform the equivalent of `Number(value)` in JS and convert the result
   * to a signed 32-bit integer by performing the steps in
   * https://tc39.es/ecma262/#sec-toint32.
   */
  V8_WARN_UNUSED_RESULT MaybeLocal<Int32> ToInt32(Local<Context> context) const;

  /**
   * Perform the equivalent of `Boolean(value)` in JS. This can never fail.
   */
  Local<Boolean> ToBoolean(Isolate* isolate) const;

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

  /** Returns the equivalent of `ToBoolean()->Value()`. */
  bool BooleanValue(Isolate* isolate) const;

  /** Returns the equivalent of `ToNumber()->Value()`. */
  V8_WARN_UNUSED_RESULT Maybe<double> NumberValue(Local<Context> context) const;
  /** Returns the equivalent of `ToInteger()->Value()`. */
  V8_WARN_UNUSED_RESULT Maybe<int64_t> IntegerValue(
      Local<Context> context) const;
  /** Returns the equivalent of `ToUint32()->Value()`. */
  V8_WARN_UNUSED_RESULT Maybe<uint32_t> Uint32Value(
      Local<Context> context) const;
  /** Returns the equivalent of `ToInt32()->Value()`. */
  V8_WARN_UNUSED_RESULT Maybe<int32_t> Int32Value(Local<Context> context) const;

  /** JS == */
  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);

  Local<String> TypeOf(Isolate*);

  Maybe<bool> InstanceOf(Local<Context> context, Local<Object> object);

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

  static void CheckCast(Data* that);
};


/**
 * 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(Value* obj);

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

/**
 * A flag describing different modes of string creation.
 *
 * Aside from performance implications there are no differences between the two
 * creation modes.
 */
enum class NewStringType {
  /**
   * Create a new string, always allocating new storage memory.
   */
  kNormal,

  /**
   * Acts as a hint that the string should be created in the
   * old generation heap space and be deduplicated if an identical string
   * already exists.
   */
  kInternalized
};

/**
 * A JavaScript string value (ECMA-262, 4.3.17).
 */
class V8_EXPORT String : public Name {
 public:
  static constexpr int kMaxLength =
      internal::kApiSystemPointerSize == 4 ? (1 << 28) - 16 : (1 << 29) - 24;

  enum Encoding {
    UNKNOWN_ENCODING = 0x1,
    TWO_BYTE_ENCODING = 0x0,
    ONE_BYTE_ENCODING = 0x8
  };
  /**
   * Returns the number of characters (UTF-16 code units) in this string.
   */
  int Length() const;

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

  /**
   * Returns whether this string is known to contain only one byte data,
   * i.e. ISO-8859-1 code points.
   * Does not read the string.
   * False negatives are possible.
   */
  bool IsOneByte() const;

  /**
   * Returns whether this string contain only one byte data,
   * i.e. ISO-8859-1 code points.
   * 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(Isolate* isolate, uint16_t* buffer, int start = 0, int length = -1,
            int options = NO_OPTIONS) const;
  // One byte characters.
  int WriteOneByte(Isolate* isolate, uint8_t* buffer, int start = 0,
                   int length = -1, int options = NO_OPTIONS) const;
  // UTF-8 encoded characters.
  int WriteUtf8(Isolate* isolate, char* buffer, int length = -1,
                int* nchars_ref = nullptr, int options = NO_OPTIONS) const;

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

  /**
   * Returns true if the string is external two-byte.
   *
   */
  V8_DEPRECATED(
      "Use String::IsExternalTwoByte() or String::IsExternalOneByte()")
  bool IsExternal() const;

  /**
   * Returns true if the string is both external and two-byte.
   */
  bool IsExternalTwoByte() const;

  /**
   * Returns true if the string is both external and one-byte.
   */
  bool IsExternalOneByte() const;

  class V8_EXPORT ExternalStringResourceBase {  // NOLINT
   public:
    virtual ~ExternalStringResourceBase() = default;

    /**
     * If a string is cacheable, the value returned by
     * ExternalStringResource::data() may be cached, otherwise it is not
     * expected to be stable beyond the current top-level task.
     */
    virtual bool IsCacheable() const { return true; }

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

   protected:
    ExternalStringResourceBase() = default;

    /**
     * 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; }

    /**
     * For a non-cacheable string, the value returned by
     * |ExternalStringResource::data()| has to be stable between |Lock()| and
     * |Unlock()|, that is the string must behave as is |IsCacheable()| returned
     * true.
     *
     * These two functions must be thread-safe, and can be called from anywhere.
     * They also must handle lock depth, in the sense that each can be called
     * several times, from different threads, and unlocking should only happen
     * when the balance of Lock() and Unlock() calls is 0.
     */
    virtual void Lock() const {}

    /**
     * Unlocks the string.
     */
    virtual void Unlock() const {}

   private:
    friend class internal::ExternalString;
    friend class v8::String;
    friend class internal::ScopedExternalStringLock;
  };

  /**
   * 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.
     */
    ~ExternalStringResource() override = default;

    /**
     * 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() = default;
  };

  /**
   * 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.
     */
    ~ExternalOneByteStringResource() override = default;
    /** 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() = default;
  };

  /**
   * 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);

  /**
   * Allocates a new string from a UTF-8 literal. This is equivalent to calling
   * String::NewFromUtf(isolate, "...").ToLocalChecked(), but without the check
   * overhead.
   *
   * When called on a string literal containing '\0', the inferred length is the
   * length of the input array minus 1 (for the final '\0') and not the value
   * returned by strlen.
   **/
  template <int N>
  static V8_WARN_UNUSED_RESULT Local<String> NewFromUtf8Literal(
      Isolate* isolate, const char (&literal)[N],
      NewStringType type = NewStringType::kNormal) {
    static_assert(N <= kMaxLength, "String is too long");
    return NewFromUtf8Literal(isolate, literal, type, N - 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,
      NewStringType type = NewStringType::kNormal, 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,
      NewStringType type = NewStringType::kNormal, int length = -1);