зеркало из https://github.com/mozilla/gecko-dev.git
96 строки
3.4 KiB
C++
96 строки
3.4 KiB
C++
/* -*- 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 http://mozilla.org/MPL/2.0/. */
|
|
|
|
#ifndef XPCOM_THREADS_EVENTTARGETCAPABILITY_H_
|
|
#define XPCOM_THREADS_EVENTTARGETCAPABILITY_H_
|
|
|
|
#include "mozilla/ThreadSafety.h"
|
|
#include "nsIEventTarget.h"
|
|
|
|
namespace mozilla {
|
|
|
|
// A helper to ensure that data access and function usage only take place on a
|
|
// specific nsIEventTarget.
|
|
//
|
|
// This class works with Clang's thread safety analysis so that static analysis
|
|
// can ensure AssertOnCurrentThread is called before using guarded data and
|
|
// functions.
|
|
//
|
|
// This means using the class is similar to calling
|
|
// `MOZ_ASSERT(mTarget->IsOnCurrentThread())`
|
|
// prior to accessing things we expect to be on `mTarget`. However, using this
|
|
// helper has the added benefit that static analysis will warn you if you
|
|
// fail to assert prior to usage.
|
|
//
|
|
// The following is a basic example of a class using this to ensure
|
|
// a data member is only accessed on a specific target.
|
|
//
|
|
// class SomeMediaHandlerThing {
|
|
// public:
|
|
// SomeMediaHandlerThing(nsIEventTarget* aTarget) : mTargetCapability(aTarget)
|
|
// {}
|
|
//
|
|
// void UpdateMediaState() {
|
|
// mTargetCapability.Dispatch(
|
|
// NS_NewRunnableFunction("UpdateMediaState", [this] {
|
|
// mTargetCapability.AssertOnCurrentThread();
|
|
// IncreaseMediaCount();
|
|
// }));
|
|
// }
|
|
//
|
|
// private:
|
|
// void IncreaseMediaCount() MOZ_REQUIRES(mTargetCapability) { mMediaCount +=
|
|
// 1; }
|
|
//
|
|
// uint32_t mMediaCount MOZ_GUARDED_BY(mTargetCapability) = 0;
|
|
// EventTargetCapability<nsIEventTarget> mTargetCapability;
|
|
// };
|
|
//
|
|
// NOTE: If you need a thread-safety capability for specifically the main
|
|
// thread, the static `mozilla::sMainThreadCapability` capability exists, and
|
|
// can be asserted using `AssertIsOnMainThread()`.
|
|
|
|
template <typename T>
|
|
class MOZ_CAPABILITY EventTargetCapability final {
|
|
static_assert(std::is_base_of_v<nsIEventTarget, T>,
|
|
"T must derive from nsIEventTarget");
|
|
|
|
public:
|
|
explicit EventTargetCapability(T* aTarget) : mTarget(aTarget) {
|
|
MOZ_ASSERT(mTarget, "mTarget should be non-null");
|
|
}
|
|
~EventTargetCapability() = default;
|
|
|
|
EventTargetCapability(const EventTargetCapability&) = default;
|
|
EventTargetCapability(EventTargetCapability&&) = default;
|
|
EventTargetCapability& operator=(const EventTargetCapability&) = default;
|
|
EventTargetCapability& operator=(EventTargetCapability&&) = default;
|
|
|
|
void AssertOnCurrentThread() const MOZ_ASSERT_CAPABILITY(this) {
|
|
MOZ_ASSERT(IsOnCurrentThread());
|
|
}
|
|
|
|
// Allow users to check if we're on the same thread as the event target.
|
|
bool IsOnCurrentThread() const { return mTarget->IsOnCurrentThread(); }
|
|
|
|
// Allow users to get the event target, so classes don't have to store the
|
|
// target as a separate member to use it.
|
|
T* GetEventTarget() const { return mTarget; }
|
|
|
|
// Helper to simplify dispatching to mTarget.
|
|
nsresult Dispatch(already_AddRefed<nsIRunnable> aRunnable,
|
|
uint32_t aFlags = NS_DISPATCH_NORMAL) const {
|
|
return mTarget->Dispatch(std::move(aRunnable), aFlags);
|
|
}
|
|
|
|
private:
|
|
RefPtr<T> mTarget;
|
|
};
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif // XPCOM_THREADS_EVENTTARGETCAPABILITY_H_
|