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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 mozilla_dom_ProxyHandlerUtils_h
#define mozilla_dom_ProxyHandlerUtils_h
#include "mozilla/Likely.h"
#include "mozilla/Maybe.h"
#include "mozilla/TextUtils.h"
#include "js/Id.h"
#include "js/Object.h" // JS::GetClass
#include "js/PropertyDescriptor.h"
#include "js/String.h" // JS::AtomToLinearString, JS::GetLinearString{CharAt,Length}
#include "js/TypeDecls.h"
#include "jsfriendapi.h" // js::StringIsArrayIndex
namespace mozilla::dom {
extern jsid s_length_id;
// A return value of UINT32_MAX indicates "not an array index". Note, in
// particular, that UINT32_MAX itself is not a valid array index in general.
inline uint32_t GetArrayIndexFromId(JS::Handle<jsid> id) {
// Much like js::IdIsIndex, except with a fast path for "length" and another
// fast path for starting with a lowercase ascii char. Is that second one
// really needed? I guess it is because StringIsArrayIndex is out of line...
// as of now, use id.get() instead of id otherwise operands mismatch error
// occurs.
if (MOZ_LIKELY(id.isInt())) {
return id.toInt();
if (MOZ_LIKELY(id.get() == s_length_id)) {
return UINT32_MAX;
if (MOZ_UNLIKELY(!id.isAtom())) {
return UINT32_MAX;
JSLinearString* str = JS::AtomToLinearString(id.toAtom());
if (MOZ_UNLIKELY(JS::GetLinearStringLength(str) == 0)) {
return UINT32_MAX;
char16_t firstChar = JS::GetLinearStringCharAt(str, 0);
if (MOZ_LIKELY(IsAsciiLowercaseAlpha(firstChar))) {
return UINT32_MAX;
uint32_t i;
return js::StringIsArrayIndex(str, &i) ? i : UINT32_MAX;
inline bool IsArrayIndex(uint32_t index) { return index < UINT32_MAX; }
} // namespace mozilla::dom
#endif /* mozilla_dom_ProxyHandlerUtils_h */