140 lines
3.7 KiB
C++
140 lines
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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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_LAYERS_IPDLACTOR_H
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#define MOZILLA_LAYERS_IPDLACTOR_H
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#include "mozilla/ipc/ProtocolUtils.h"
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#include "mozilla/unused.h"
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namespace mozilla {
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namespace layers {
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/// A base class to facilitate the deallocation of IPDL actors.
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///
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/// This class implements a simple deallocation protocol that avoids races
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/// between async messages and actor destruction. The priniple is that the
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/// child side is always the one that tells the parent that the actor pair is
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/// going to be destroyed through the async Destroy message, and the parent
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/// side always sends the __delete__ message.
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/// Once ChildActor::Destroy has been called it is invalid to send any other
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/// IPDL message from the child, although the child might receive messages
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/// from the parent that were sent before the parent received the Destroy
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/// message. Always check the result of ChildActor::Destroy before sending
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/// anything.
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///
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/// The actual IPDL protocol must have the following messages:
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///
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/// child:
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/// async __delete__();
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/// parent:
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/// async Destroy();
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/// sync DestroySynchronously();
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///
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template<typename Protocol>
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class ChildActor : public Protocol
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{
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public:
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ChildActor() : mDestroyed(false) {}
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~ChildActor() { MOZ_ASSERT(mDestroyed); }
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/// Check the return of CanSend before sending any message!
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bool CanSend() const { return !mDestroyed; }
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/// The normal way to destroy the actor.
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///
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/// This will asynchronously send a Destroy message to the parent actor, whom
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/// will send the delete message.
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void Destroy()
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{
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MOZ_ASSERT(!mDestroyed);
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if (!mDestroyed) {
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mDestroyed = true;
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DestroyManagees();
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this->SendDestroy();
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}
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}
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/// The ugly and slow way to destroy the actor.
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///
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/// This will block until the Parent actor has handled the Destroy message,
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/// and then start the asynchronous handshake (and destruction will already
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/// be done on the parent side, when the async part happens).
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void DestroySynchronously()
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{
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MOZ_PERFORMANCE_WARNING("gfx", "IPDL actor requires synchronous deallocation");
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MOZ_ASSERT(!mDestroyed);
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if (!mDestroyed) {
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DestroyManagees();
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mDestroyed = true;
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this->SendDestroySync();
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this->SendDestroy();
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}
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}
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/// Override this if the protocol manages other protocols, and destroy the
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/// managees from there
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virtual void DestroyManagees() {}
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private:
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bool mDestroyed;
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};
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/// A base class to facilitate the deallocation of IPDL actors.
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///
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/// Implements the parent side of the simple deallocation handshake.
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/// Override the Destroy method rather than the ActorDestroy method.
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template<typename Protocol>
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class ParentActor : public Protocol
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{
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public:
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ParentActor() : mDestroyed(false) {}
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~ParentActor() { MOZ_ASSERT(mDestroyed); }
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bool CanSend() const { return !mDestroyed; }
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// Override this rather than ActorDestroy
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virtual void Destroy() {}
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virtual bool RecvDestroy() override
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{
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if (!mDestroyed) {
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Destroy();
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mDestroyed = true;
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}
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Unused << Protocol::Send__delete__(this);
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return true;
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}
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virtual bool RecvDestroySync() override
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{
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if (!mDestroyed) {
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Destroy();
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mDestroyed = true;
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}
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return true;
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}
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typedef ipc::IProtocolManager<ipc::IProtocol>::ActorDestroyReason Why;
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virtual void ActorDestroy(Why) override
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{
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if (!mDestroyed) {
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Destroy();
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mDestroyed = true;
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}
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}
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private:
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bool mDestroyed;
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};
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} // namespace
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} // namespace
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#endif
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