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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_List_h
#define vm_List_h
#include "NamespaceImports.h"
#include "js/Value.h"
#include "vm/NativeObject.h"
namespace js {
* The List specification type, ECMA-262 6.2.1.
* Lists are simple mutable sequences of values. Many standards use them.
* Abstractly, they're not objects; they don't have properties or prototypes;
* they're for internal specification use only. ListObject is our most direct
* implementation of a List: store the values in the slots of a JSObject.
* We often implement Lists in other ways. For example, builtin/Utilities.js
* contains a completely unrelated List constructor that's used in self-hosted
* code. And AsyncGeneratorObject optimizes away the ListObject in the common
* case where its internal queue never holds more than one element.
* ListObjects must not be exposed to content scripts.
class ListObject : public NativeObject {
static const JSClass class_;
[[nodiscard]] inline static ListObject* create(JSContext* cx);
uint32_t length() const { return getDenseInitializedLength(); }
bool isEmpty() const { return length() == 0; }
const Value& get(uint32_t index) const { return getDenseElement(index); }
template <class T>
T& getAs(uint32_t index) const {
return get(index).toObject().as<T>();
* Add an element to the end of the list. Returns false on OOM.
[[nodiscard]] inline bool append(JSContext* cx, HandleValue value);
* Adds |value| and |size| elements to a list consisting of (value, size)
* pairs stored in successive elements.
* This function is intended for use by streams code's queue-with-sizes data
* structure and related operations. See builtin/streams/QueueWithSizes*.
* (You *could* use this on any list of even length without issue, but it's
* hard to imagine realistic situations where you'd want to...)
[[nodiscard]] inline bool appendValueAndSize(JSContext* cx, HandleValue value,
double size);
* Remove and return the first element of the list.
* Precondition: This list is not empty.
inline JS::Value popFirst(JSContext* cx);
* Remove the first two elements from a nonempty list of (value, size) pairs
* of elements.
inline void popFirstPair(JSContext* cx);
* Remove and return the first element of the list.
* Precondition: This list is not empty, and the first element
* is an object of class T.
template <class T>
inline T& popFirstAs(JSContext* cx);
} // namespace js
#endif // vm_List_h