/* -*- 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 nsThreadSyncDispatch_h_

#define nsThreadSyncDispatch_h_

#include "mozilla/Atomics.h"

#include "mozilla/DebugOnly.h"

#include "nsThreadUtils.h"

#include "LeakRefPtr.h"

class nsThreadSyncDispatch : public mozilla::Runnable

{

public:

  nsThreadSyncDispatch(already_AddRefed<nsIEventTarget> aOrigin, already_AddRefed<nsIRunnable>&& aTask)

    : Runnable("nsThreadSyncDispatch")

    , mOrigin(aOrigin)

    , mSyncTask(std::move(aTask))

    , mIsPending(true)

  {

  }

  bool IsPending()

  {

    // This is an atomic acquire on the origin thread.

    return mIsPending;

  }

private:

  NS_IMETHOD Run() override

  {

    if (nsCOMPtr<nsIRunnable> task = mSyncTask.take()) {

      MOZ_ASSERT(!mSyncTask);

      mozilla::DebugOnly<nsresult> result = task->Run();

      MOZ_ASSERT(NS_SUCCEEDED(result),

                 "task in sync dispatch should not fail");

      // We must release the task here to ensure that when the original

      // thread is unblocked, this task has been released.

      task = nullptr;

      // This is an atomic release on the target thread.

      mIsPending = false;

      // unblock the origin thread

      mOrigin->Dispatch(this, NS_DISPATCH_NORMAL);

    }

    return NS_OK;

  }

  nsCOMPtr<nsIEventTarget> mOrigin;

  // The task is leaked by default when Run() is not called, because

  // otherwise we may release it in an incorrect thread.

  mozilla::LeakRefPtr<nsIRunnable> mSyncTask;

  mozilla::Atomic<bool, mozilla::ReleaseAcquire> mIsPending;

};

#endif // nsThreadSyncDispatch_h_