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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef vm_PromiseLookup_h
#define vm_PromiseLookup_h
#include "mozilla/Attributes.h" // MOZ_NON_TEMPORARY_CLASS, MOZ_INIT_OUTSIDE_CTOR
#include <stdint.h> // uint8_t, uint32_t
#include "js/CallArgs.h" // JSNative
struct JS_PUBLIC_API JSContext;
class JSFunction;
namespace js {
class NativeObject;
class PromiseObject;
class Shape;
class MOZ_NON_TEMPORARY_CLASS PromiseLookup final {
// clang-format off
* A PromiseLookup holds the following:
* Promise's shape (promiseConstructorShape_)
* To ensure that Promise has not been modified.
* Promise.prototype's shape (promiseProtoShape_)
* To ensure that Promise.prototype has not been modified.
* Promise's slot number for the @@species getter
* (promiseSpeciesGetterSlot_)
* To quickly retrieve the @@species getter for Promise.
* Promise's slot number for resolve (promiseResolveSlot_)
* To quickly retrieve the Promise.resolve function.
* Promise.prototype's slot number for constructor (promiseProtoConstructorSlot_)
* To quickly retrieve the Promise.prototype.constructor property.
* Promise.prototype's slot number for then (promiseProtoThenSlot_)
* To quickly retrieve the Promise.prototype.then function.
* MOZ_INIT_OUTSIDE_CTOR fields below are set in |initialize()|. The
* constructor only initializes a |state_| field, that defines whether the
* other fields are accessible.
// clang-format on
// Shape of matching Promise object.
MOZ_INIT_OUTSIDE_CTOR Shape* promiseConstructorShape_;
// Shape of matching Promise.prototype object.
MOZ_INIT_OUTSIDE_CTOR Shape* promiseProtoShape_;
// Slot number for the @@species property on the Promise constructor.
MOZ_INIT_OUTSIDE_CTOR uint32_t promiseSpeciesGetterSlot_;
// Slots Promise.resolve, Promise.prototype.constructor, and
// Promise.prototype.then.
MOZ_INIT_OUTSIDE_CTOR uint32_t promiseResolveSlot_;
MOZ_INIT_OUTSIDE_CTOR uint32_t promiseProtoConstructorSlot_;
MOZ_INIT_OUTSIDE_CTOR uint32_t promiseProtoThenSlot_;
enum class State : uint8_t {
// Flags marking the lazy initialization of the above fields.
// The disabled flag is set when we don't want to try optimizing
// anymore because core objects were changed.
State state_ = State::Uninitialized;
// Initialize the internal fields.
// The cache is successfully initialized iff
// 1. Promise and Promise.prototype classes are initialized.
// 2. Promise.prototype.constructor is equal to Promise.
// 3. Promise.prototype.then is the original `then` function.
// 4. Promise[@@species] is the original @@species getter.
// 5. Promise.resolve is the original `resolve` function.
void initialize(JSContext* cx);
// Reset the cache.
void reset();
// Check if the global promise-related objects have not been messed with
// in a way that would disable this cache.
bool isPromiseStateStillSane(JSContext* cx);
// Flags to control whether or not ensureInitialized() is allowed to
// reinitialize the cache when the Promise state is no longer sane.
enum class Reinitialize : bool { Allowed, Disallowed };
// Return true if the lookup cache is properly initialized for usage.
bool ensureInitialized(JSContext* cx, Reinitialize reinitialize);
// Return true if the prototype of the given Promise object is
// Promise.prototype and the object doesn't shadow properties from
// Promise.prototype.
bool hasDefaultProtoAndNoShadowedProperties(JSContext* cx,
PromiseObject* promise);
// Return true if the given Promise object uses the default @@species,
// "constructor", and "then" properties.
bool isDefaultInstance(JSContext* cx, PromiseObject* promise,
Reinitialize reinitialize);
// Return the built-in Promise constructor or null if not yet initialized.
static JSFunction* getPromiseConstructor(JSContext* cx);
// Return the built-in Promise prototype or null if not yet initialized.
static NativeObject* getPromisePrototype(JSContext* cx);
// Return true if the slot contains the given native.
static bool isDataPropertyNative(JSContext* cx, NativeObject* obj,
uint32_t slot, JSNative native);
// Return true if the accessor shape contains the given native.
static bool isAccessorPropertyNative(JSContext* cx, NativeObject* holder,
uint32_t getterSlot, JSNative native);
/** Construct a |PromiseSpeciesLookup| in the uninitialized state. */
PromiseLookup() { reset(); }
// Return true if the Promise constructor and Promise.prototype still use
// the default built-in functions.
bool isDefaultPromiseState(JSContext* cx);
// Return true if the given Promise object uses the default @@species,
// "constructor", and "then" properties.
bool isDefaultInstance(JSContext* cx, PromiseObject* promise) {
return isDefaultInstance(cx, promise, Reinitialize::Allowed);
// Return true if the given Promise object uses the default @@species,
// "constructor", and "then" properties.
bool isDefaultInstanceWhenPromiseStateIsSane(JSContext* cx,
PromiseObject* promise) {
return isDefaultInstance(cx, promise, Reinitialize::Disallowed);
// Purge the cache and all info associated with it.
void purge() {
if (state_ == State::Initialized) {
} // namespace js
#endif // vm_PromiseLookup_h