forked from mirrors/gecko-dev
116 lines
4.3 KiB
C++
116 lines
4.3 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_dom_RefMessageBodyService_h
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#define mozilla_dom_RefMessageBodyService_h
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#include "mozilla/ErrorResult.h"
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#include "mozilla/dom/StructuredCloneHolder.h"
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#include "mozilla/Maybe.h"
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#include "mozilla/Mutex.h"
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#include "mozilla/StaticMutex.h"
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#include "nsRefPtrHashtable.h"
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namespace mozilla {
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namespace dom {
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/**
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* At the time a BroadcastChannel or MessagePort sends messages, we don't know
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* which process is going to receive it. Because of this, we need to check if
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* the message is able to cross the process boundary.
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* If the message contains objects such as SharedArrayBuffers, WASM modules or
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* ImageBitmaps, it can be delivered on the current process only.
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* Instead of sending the whole message via IPC, we send a unique ID, while the
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* message is kept alive by RefMessageBodyService, on the current process using
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* a ref-counted RefMessageBody object.
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* When the receiver obtains the message ID, it checks if the local
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* RefMessageBodyService knows that ID. If yes, the sender and the receiver are
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* on the same process and the delivery can be completed; if not, a
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* messageerror event has to be dispatched instead.
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*
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* For MessagePort communication is 1-to-1 and because of this, the
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* receiver takes ownership of the message (RefMessageBodyService::Steal()).
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* If the receiver port is on a different process, RefMessageBodyService will
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* return a nullptr and a messageerror event will be dispatched.
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* For BroadcastChannel, the life-time of a message is a bit different than for
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* MessagePort. It has a 1-to-many communication and we could have multiple
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* receivers. Each one needs to deliver the message without taking full
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* ownership of it.
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* In order to support this feature, BroadcastChannel needs to call
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* RefMessageBodyService::SetMaxCount() to inform how many ports are allowed to
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* retrieve the current message, on the current process. Receivers on other
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* processes are not kept in consideration because they will not be able to
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* retrieve the message from RefMessageBodyService. When the last allowed
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* port has called RefMessageBodyService::GetAndCount(), the message is
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* released.
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*/
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class RefMessageBody final {
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friend class RefMessageBodyService;
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public:
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NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RefMessageBody)
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RefMessageBody(const nsID& aPortID,
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UniquePtr<ipc::StructuredCloneData>&& aCloneData);
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const nsID& PortID() const { return mPortID; }
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void Read(JSContext* aCx, JS::MutableHandle<JS::Value> aValue,
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const JS::CloneDataPolicy& aCloneDataPolicy, ErrorResult& aRv);
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// This method can be called only if the RefMessageBody is not supposed to be
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// ref-counted (see mMaxCount).
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bool TakeTransferredPortsAsSequence(
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Sequence<OwningNonNull<mozilla::dom::MessagePort>>& aPorts);
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private:
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~RefMessageBody() = default;
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const nsID mPortID;
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// In case the RefMessageBody is shared and refcounted (see mCount/mMaxCount),
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// we must enforce that the reading does not happen simultaneously on
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// different threads.
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Mutex mMutex;
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UniquePtr<ipc::StructuredCloneData> mCloneData;
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// When mCount reaches mMaxCount, this object is released by the service.
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Maybe<uint32_t> mMaxCount;
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uint32_t mCount;
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};
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class RefMessageBodyService final {
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public:
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NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RefMessageBodyService)
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static already_AddRefed<RefMessageBodyService> GetOrCreate();
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void ForgetPort(const nsID& aPortID);
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const nsID Register(already_AddRefed<RefMessageBody> aBody, ErrorResult& aRv);
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already_AddRefed<RefMessageBody> Steal(const nsID& aID);
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already_AddRefed<RefMessageBody> GetAndCount(const nsID& aID);
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void SetMaxCount(const nsID& aID, uint32_t aMaxCount);
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private:
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RefMessageBodyService();
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~RefMessageBodyService();
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static RefMessageBodyService* GetOrCreateInternal(
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const StaticMutexAutoLock& aProofOfLock);
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nsRefPtrHashtable<nsIDHashKey, RefMessageBody> mMessages;
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};
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} // namespace dom
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} // namespace mozilla
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#endif // mozilla_dom_RefMessageBodyService_h
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