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85 lines
2.9 KiB
C++
85 lines
2.9 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_HoldDropJSObjects_h
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#define mozilla_HoldDropJSObjects_h
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#include <type_traits>
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#include "nsCycleCollectionNoteChild.h"
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class nsISupports;
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class nsScriptObjectTracer;
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class nsCycleCollectionParticipant;
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namespace JS {
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class Zone;
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}
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// Only HoldJSObjects and DropJSObjects should be called directly.
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namespace mozilla {
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namespace cyclecollector {
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void HoldJSObjectsImpl(void* aHolder, nsScriptObjectTracer* aTracer,
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JS::Zone* aZone = nullptr);
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void HoldJSObjectsImpl(nsISupports* aHolder);
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void DropJSObjectsImpl(void* aHolder);
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void DropJSObjectsImpl(nsISupports* aHolder);
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} // namespace cyclecollector
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template <class T, bool isISupports = std::is_base_of<nsISupports, T>::value,
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typename P = typename T::NS_CYCLE_COLLECTION_INNERCLASS>
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struct HoldDropJSObjectsHelper {
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static void Hold(T* aHolder) {
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cyclecollector::HoldJSObjectsImpl(aHolder,
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NS_CYCLE_COLLECTION_PARTICIPANT(T));
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}
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static void Drop(T* aHolder) { cyclecollector::DropJSObjectsImpl(aHolder); }
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};
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template <class T>
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struct HoldDropJSObjectsHelper<T, true> {
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static void Hold(T* aHolder) {
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cyclecollector::HoldJSObjectsImpl(ToSupports(aHolder));
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}
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static void Drop(T* aHolder) {
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cyclecollector::DropJSObjectsImpl(ToSupports(aHolder));
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}
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};
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/**
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Classes that hold strong references to JS GC things such as `JSObjects` and
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`JS::Values` (e.g. `JS::Heap<JSObject*> mFoo;`) must use these, generally by
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calling `HoldJSObjects(this)` and `DropJSObjects(this)` in the ctor and dtor
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respectively.
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For classes that are wrapper cached and hold no other strong references to JS
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GC things, there's no need to call these; it will be taken care of
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automatically by nsWrapperCache.
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**/
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template <class T>
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void HoldJSObjects(T* aHolder) {
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static_assert(!std::is_base_of<nsCycleCollectionParticipant, T>::value,
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"Don't call this on the CC participant but on the object that "
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"it's for (in an Unlink implementation it's usually stored in "
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"a variable named 'tmp').");
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HoldDropJSObjectsHelper<T>::Hold(aHolder);
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}
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template <class T>
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void DropJSObjects(T* aHolder) {
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static_assert(!std::is_base_of<nsCycleCollectionParticipant, T>::value,
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"Don't call this on the CC participant but on the object that "
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"it's for (in an Unlink implementation it's usually stored in "
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"a variable named 'tmp').");
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HoldDropJSObjectsHelper<T>::Drop(aHolder);
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}
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} // namespace mozilla
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#endif // mozilla_HoldDropJSObjects_h
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