diff options
| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
| commit | 26a029d407be480d791972afb5975cf62c9360a6 (patch) | |
| tree | f435a8308119effd964b339f76abb83a57c29483 /xpcom/threads/EventTargetCapability.h | |
| parent | Initial commit. (diff) | |
| download | firefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz firefox-26a029d407be480d791972afb5975cf62c9360a6.zip | |
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'xpcom/threads/EventTargetCapability.h')
| -rw-r--r-- | xpcom/threads/EventTargetCapability.h | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/xpcom/threads/EventTargetCapability.h b/xpcom/threads/EventTargetCapability.h new file mode 100644 index 0000000000..0cd85a7523 --- /dev/null +++ b/xpcom/threads/EventTargetCapability.h @@ -0,0 +1,95 @@ +/* -*- 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("event target") 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_ |