зеркало из https://github.com/mozilla/gecko-dev.git
148 строки
4.6 KiB
C++
148 строки
4.6 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_ClearOnShutdown_h
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#define mozilla_ClearOnShutdown_h
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#include "mozilla/LinkedList.h"
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#include "mozilla/StaticPtr.h"
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#include "mozilla/Array.h"
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#include "ShutdownPhase.h"
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#include "MainThreadUtils.h"
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#include <functional>
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/*
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* This header exports two public methods in the mozilla namespace:
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*
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* template<class SmartPtr>
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* void ClearOnShutdown(SmartPtr *aPtr,
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* aPhase=ShutdownPhase::XPCOMShutdownFinal)
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*
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* This function takes a pointer to a smart pointer and nulls the smart pointer
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* on shutdown (and a particular phase of shutdown as needed). If a phase
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* is specified, the ptr will be cleared at the start of that phase. Also,
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* if a phase has already occurred when ClearOnShutdown() is called it will
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* cause a MOZ_ASSERT. In case a phase is not explicitly cleared we will
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* clear it on the next phase that occurs.
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*
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* This is useful if you have a global smart pointer object which you don't
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* want to "leak" on shutdown.
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*
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* Although ClearOnShutdown will work with any smart pointer (i.e., nsCOMPtr,
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* RefPtr, StaticRefPtr, and StaticAutoPtr), you probably want to
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* use it only with StaticRefPtr and StaticAutoPtr. There is no way to undo a
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* call to ClearOnShutdown, so you can call it only on smart pointers which you
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* know will live until the program shuts down. In practice, these are likely
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* global variables, which should be Static{Ref,Auto}Ptr.
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*
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* template <typename CallableT>
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* void RunOnShutdown(CallableT&& aCallable,
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* aPhase = ShutdownPhase::XPCOMShutdownFinal)
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*
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* This function takes a callable and executes it upon shutdown at the start of
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* the specified phase. If the phase has already occurred when RunOnShutdown()
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* is called, it will cause a MOZ_ASSERT. In case a phase is not explicitly
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* cleared, we will clear it on the next phase that occurs.
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*
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* ClearOnShutdown and RunOnShutdown are both currently main-thread only because
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* we don't want to accidentally free an object from a different thread than the
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* one it was created on.
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*/
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namespace mozilla {
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namespace ClearOnShutdown_Internal {
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class ShutdownObserver : public LinkedListElement<ShutdownObserver> {
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public:
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virtual void Shutdown() = 0;
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virtual ~ShutdownObserver() = default;
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};
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template <class SmartPtr>
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class PointerClearer : public ShutdownObserver {
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public:
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explicit PointerClearer(SmartPtr* aPtr) : mPtr(aPtr) {}
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virtual void Shutdown() override {
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if (mPtr) {
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*mPtr = nullptr;
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}
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}
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private:
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SmartPtr* mPtr;
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};
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class FunctionInvoker : public ShutdownObserver {
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public:
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template <typename CallableT>
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explicit FunctionInvoker(CallableT&& aCallable)
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: mCallable(std::forward<CallableT>(aCallable)) {}
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virtual void Shutdown() override {
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if (!mCallable) {
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return;
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}
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mCallable();
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}
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private:
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std::function<void()> mCallable;
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};
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void InsertIntoShutdownList(ShutdownObserver* aShutdownObserver,
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ShutdownPhase aPhase);
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typedef LinkedList<ShutdownObserver> ShutdownList;
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extern Array<StaticAutoPtr<ShutdownList>,
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static_cast<size_t>(ShutdownPhase::ShutdownPhase_Length)>
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sShutdownObservers;
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extern ShutdownPhase sCurrentClearOnShutdownPhase;
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} // namespace ClearOnShutdown_Internal
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template <class SmartPtr>
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inline void ClearOnShutdown(
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SmartPtr* aPtr, ShutdownPhase aPhase = ShutdownPhase::XPCOMShutdownFinal) {
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using namespace ClearOnShutdown_Internal;
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MOZ_ASSERT(NS_IsMainThread());
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MOZ_ASSERT(aPhase != ShutdownPhase::ShutdownPhase_Length);
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InsertIntoShutdownList(new PointerClearer<SmartPtr>(aPtr), aPhase);
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}
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template <typename CallableT>
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inline void RunOnShutdown(
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CallableT&& aCallable,
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ShutdownPhase aPhase = ShutdownPhase::XPCOMShutdownFinal) {
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using namespace ClearOnShutdown_Internal;
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MOZ_ASSERT(NS_IsMainThread());
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MOZ_ASSERT(aPhase != ShutdownPhase::ShutdownPhase_Length);
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InsertIntoShutdownList(
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new FunctionInvoker(std::forward<CallableT>(aCallable)), aPhase);
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}
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inline bool PastShutdownPhase(ShutdownPhase aPhase) {
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MOZ_ASSERT(NS_IsMainThread());
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return size_t(ClearOnShutdown_Internal::sCurrentClearOnShutdownPhase) >=
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size_t(aPhase);
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}
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// Called when XPCOM is shutting down, after all shutdown notifications have
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// been sent and after all threads' event loops have been purged.
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void KillClearOnShutdown(ShutdownPhase aPhase);
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} // namespace mozilla
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#endif
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