CancellationToken.cs

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//
// CancellationToken.cs
//
// Authors:
//       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
//       Marek Safar (marek.safar@gmail.com)
//
// Copyright (c) 2009 Jérémie "Garuma" Laval
// Copyright 2011 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;
using System.Threading;
using System.Diagnostics;

namespace System.Threading
{
    [DebuggerDisplay ("IsCancellationRequested = {IsCancellationRequested}")]
    public struct CancellationToken
    {
        readonly CancellationTokenSource source;

        public CancellationToken (bool canceled)
            : this (canceled ? CancellationTokenSource.CanceledSource : null)
        {
        }

        internal CancellationToken (CancellationTokenSource source)
        {
            this.source = source;
        }

        public static CancellationToken None {
            get {
                // simply return new struct value, it's the fastest option
                // and we don't have to bother with reseting source
                return new CancellationToken ();
            }
        }

        public CancellationTokenRegistration Register (Action callback)
        {
            return Register (callback, false);
        }

        public CancellationTokenRegistration Register (Action callback, bool useSynchronizationContext)
        {
            if (callback == null)
                throw new ArgumentNullException ("callback");

            return Source.Register (callback, useSynchronizationContext);
        }

        public CancellationTokenRegistration Register (Action<object> callback, object state)
        {
            return Register (callback, state, false);
        }

        public CancellationTokenRegistration Register (Action<object> callback, object state, bool useSynchronizationContext)
        {
            if (callback == null)
                throw new ArgumentNullException ("callback");

            return Register (() => callback (state), useSynchronizationContext);
        }

        public void ThrowIfCancellationRequested ()
        {
            if (Source.IsCancellationRequested)
                throw new Threading.OperationCanceledException (this);
        }

        public bool Equals (CancellationToken other)
        {
            return this.Source == other.Source;
        }

        public override bool Equals (object other)
        {
            return (other is CancellationToken) ? Equals ((CancellationToken)other) : false;
        }

        public override int GetHashCode ()
        {
            return Source.GetHashCode ();
        }

        public static bool operator == (CancellationToken left, CancellationToken right)
        {
            return left.Equals (right);
        }

        public static bool operator != (CancellationToken left, CancellationToken right)
        {
            return !left.Equals (right);
        }

        public bool CanBeCanceled {
            get {
                return source != null;
            }
        }

        public bool IsCancellationRequested {
            get {
                return Source.IsCancellationRequested;
            }
        }

        public WaitHandle WaitHandle {
            get {
                return Source.WaitHandle;
            }
        }

        CancellationTokenSource Source {
            get {
                return source ?? CancellationTokenSource.NoneSource;
            }
        }
    }
}
#endif