tenfourfox/gfx/layers/IPDLActor.h
Cameron Kaiser c9b2922b70 hello FPR
2017-04-19 00:56:45 -07:00

140 lines
3.7 KiB
C++

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