TpScheduler.cs

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//
// TpScheduler.cs
//
// Authors:
//    Jérémie Laval <jeremie dot laval at xamarin dot com>
//    Marek Safar  <marek.safar@gmail.com>
//
// Copyright (c) 2011 Jérémie "Garuma" Laval
// Copyright 2012 Xamarin Inc (http://www.xamarin.com).
//
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//

#if NET_4_0

using System.Collections.Generic;

namespace System.Threading.Tasks
{
    sealed class TpScheduler: TaskScheduler
    {
        static readonly WaitCallback callback = TaskExecuterCallback;

        protected internal override void QueueTask (Task task)
        {
            if ((task.CreationOptions & TaskCreationOptions.LongRunning) != 0) {
                var thread = new Thread (l => ((Task)l).Execute ()) {
                    IsBackground = true
                };

                thread.Start (task);
                return;
            }

            // Spicy Pixel: This seems to be working on AOT again. If not, use below.
            // The main difference is that the callstack is not propagated with the
            // unsafe method which allows for elevated security in the queued task
            // (which is desirable here).
            //
            // Switching back to QueueUserWorkItem as it works with 2.0 subset.
            // ThreadPool.UnsafeQueueUserWorkItem (callback, task);
            ThreadPool.QueueUserWorkItem (callback, task);
        }

        static void TaskExecuterCallback (object obj)
        {
            Task task = (Task)obj;
            task.Execute ();
        }

        protected override IEnumerable<Task> GetScheduledTasks ()
        {
            throw new NotImplementedException();
        }

        [MonoTODO ("Tasks cannot be dequeued")]
        protected internal override bool TryDequeue (Task task)
        {
            return false;
        }

        protected override bool TryExecuteTaskInline (Task task, bool taskWasPreviouslyQueued)
        {
            if (taskWasPreviouslyQueued && !TryDequeue (task))
                return false;

            return TryExecuteTask(task);
        }
    }
}
#endif