gecko-dev/dom/workers/WorkerRef.cpp

/* -*- 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/. */

#include "WorkerRef.h"

#include "mozilla/Unused.h"
#include "WorkerHolder.h"
#include "WorkerRunnable.h"
#include "WorkerPrivate.h"

namespace mozilla {
namespace dom {

namespace {

// This runnable is used to release the StrongWorkerRef on the worker thread
// when a ThreadSafeWorkerRef is released.
class ReleaseRefControlRunnable final : public WorkerControlRunnable
{
public:
  ReleaseRefControlRunnable(WorkerPrivate* aWorkerPrivate,
                            already_AddRefed<StrongWorkerRef> aRef)
    : WorkerControlRunnable(aWorkerPrivate, WorkerThreadUnchangedBusyCount)
    , mRef(std::move(aRef))
  {
    MOZ_ASSERT(mRef);
  }

  bool
  PreDispatch(WorkerPrivate* aWorkerPrivate) override
  {
    return true;
  }

  void
  PostDispatch(WorkerPrivate* aWorkerPrivate,
               bool aDispatchResult) override
  {
  }

  bool
  WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate) override
  {
    mRef = nullptr;
    return true;
  }

private:
  RefPtr<StrongWorkerRef> mRef;
};

} // anonymous

// ----------------------------------------------------------------------------
// WorkerRef::Holder

class WorkerRef::Holder final : public mozilla::dom::WorkerHolder
{
public:
  Holder(const char* aName, WorkerRef* aWorkerRef, Behavior aBehavior)
    : mozilla::dom::WorkerHolder(aName, aBehavior)
    , mWorkerRef(aWorkerRef)
  {}

  bool
  Notify(WorkerStatus aStatus) override
  {
    MOZ_ASSERT(mWorkerRef);

    if (aStatus < Canceling) {
      return true;
    }

    // Let's keep this object alive for the whole Notify() execution.
    RefPtr<WorkerRef> workerRef;
    workerRef = mWorkerRef;

    workerRef->Notify();
    return true;
  }

public:
  WorkerRef* mWorkerRef;
};

// ----------------------------------------------------------------------------
// WorkerRef

WorkerRef::WorkerRef(WorkerPrivate* aWorkerPrivate)
  : mWorkerPrivate(aWorkerPrivate)
{
  MOZ_ASSERT(aWorkerPrivate);
  aWorkerPrivate->AssertIsOnWorkerThread();
}

WorkerRef::~WorkerRef()
{
  NS_ASSERT_OWNINGTHREAD(WorkerRef);
}

void
WorkerRef::Notify()
{
  MOZ_ASSERT(mHolder);
  NS_ASSERT_OWNINGTHREAD(WorkerRef);

  if (!mCallback) {
    return;
  }

  std::function<void()> callback = mCallback;
  mCallback = nullptr;

  callback();
}

// ----------------------------------------------------------------------------
// WeakWorkerRef

/* static */ already_AddRefed<WeakWorkerRef>
WeakWorkerRef::Create(WorkerPrivate* aWorkerPrivate,
                      const std::function<void()>& aCallback)
{
  MOZ_ASSERT(aWorkerPrivate);
  aWorkerPrivate->AssertIsOnWorkerThread();

  RefPtr<WeakWorkerRef> ref = new WeakWorkerRef(aWorkerPrivate);

  // This holder doesn't keep the worker alive.
  UniquePtr<Holder> holder(new Holder("WeakWorkerRef::Holder", ref,
                                      WorkerHolder::AllowIdleShutdownStart));
  if (NS_WARN_IF(!holder->HoldWorker(aWorkerPrivate, Canceling))) {
    return nullptr;
  }

  ref->mHolder = std::move(holder);
  ref->mCallback = aCallback;

  return ref.forget();
}

WeakWorkerRef::WeakWorkerRef(WorkerPrivate* aWorkerPrivate)
  : WorkerRef(aWorkerPrivate)
{}

WeakWorkerRef::~WeakWorkerRef() = default;

void
WeakWorkerRef::Notify()
{
  WorkerRef::Notify();

  mHolder = nullptr;
  mWorkerPrivate = nullptr;
}

WorkerPrivate*
WeakWorkerRef::GetPrivate() const
{
  NS_ASSERT_OWNINGTHREAD(WeakWorkerRef);
  return mWorkerPrivate;
}

WorkerPrivate*
WeakWorkerRef::GetUnsafePrivate() const
{
  return mWorkerPrivate;
}

// ----------------------------------------------------------------------------
// StrongWorkerRef

/* static */ already_AddRefed<StrongWorkerRef>
StrongWorkerRef::Create(WorkerPrivate* aWorkerPrivate,
                        const char* aName,
                        const std::function<void()>& aCallback)
{
  MOZ_ASSERT(aWorkerPrivate);
  MOZ_ASSERT(aName);

  RefPtr<StrongWorkerRef> ref = new StrongWorkerRef(aWorkerPrivate);

  // The worker is kept alive by this holder.
  UniquePtr<Holder> holder(new Holder(aName, ref,
                                      WorkerHolder::PreventIdleShutdownStart));
  if (NS_WARN_IF(!holder->HoldWorker(aWorkerPrivate, Canceling))) {
    return nullptr;
  }

  ref->mHolder = std::move(holder);
  ref->mCallback = aCallback;

  return ref.forget();
}

StrongWorkerRef::StrongWorkerRef(WorkerPrivate* aWorkerPrivate)
  : WorkerRef(aWorkerPrivate)
{}

StrongWorkerRef::~StrongWorkerRef()
{
  NS_ASSERT_OWNINGTHREAD(StrongWorkerRef);
}

WorkerPrivate*
StrongWorkerRef::Private() const
{
  MOZ_ASSERT(mHolder);
  NS_ASSERT_OWNINGTHREAD(StrongWorkerRef);
  return mWorkerPrivate;
}

// ----------------------------------------------------------------------------
// ThreadSafeWorkerRef

ThreadSafeWorkerRef::ThreadSafeWorkerRef(StrongWorkerRef* aRef)
  : mRef(aRef)
{
  MOZ_ASSERT(aRef);
  aRef->Private()->AssertIsOnWorkerThread();
}

ThreadSafeWorkerRef::~ThreadSafeWorkerRef()
{
  // Let's release the StrongWorkerRef on the correct thread.
  if (!mRef->mWorkerPrivate->IsOnWorkerThread()) {
    WorkerPrivate* workerPrivate = mRef->mWorkerPrivate;
    RefPtr<ReleaseRefControlRunnable> r =
      new ReleaseRefControlRunnable(workerPrivate, mRef.forget());
    r->Dispatch();
    return;
  }
}

WorkerPrivate*
ThreadSafeWorkerRef::Private() const
{
  return mRef->mWorkerPrivate;
}

} // dom namespace
} // mozilla namespace