//******************************************************************************************************//  CancellationToken.cs - Gbtc////  Copyright © 2016, Grid Protection Alliance.  All Rights Reserved.////  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See//  the NOTICE file distributed with this work for additional information regarding copyright ownership.//  The GPA licenses this file to you under the MIT License (MIT), the "License"; you may//  not use this file except in compliance with the License. You may obtain a copy of the License at:////      http://opensource.org/licenses/MIT////  Unless agreed to in writing, the subject software distributed under the License is distributed on an//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the//  License for the specific language governing permissions and limitations.////  Code Modification History://  ----------------------------------------------------------------------------------------------------//  01/29/2016 - Stephen C. Wills//       Generated original version of source code.//  09/13/2016 - J. Ritchie Carroll//       Updated to include cancellation event and implicit conversion to system cancellation tokens.////****************************************************************************************************** using System;using System.Threading; namespace GSF.Threading{    /// <summary>    /// Represents a token that can be used to cancel an asynchronous operation.    /// </summary>    public class CancellationToken : ICancellationToken    {        #region [ Members ]         // Events         /// <summary>        /// Event that will be raised when this <see cref="CancellationToken"/> is cancelled.        /// </summary>        public event EventHandler Cancelled;         // Fields        private int m_cancelled;                #endregion         #region [ Properties ]         /// <summary>        /// Gets a value that indicates whether the operation has been cancelled.        /// </summary>        public bool IsCancelled => Interlocked.CompareExchange(ref m_cancelled, 0, 0) != 0;         #endregion         #region [ Methods ]         /// <summary>        /// Cancels the operation.        /// </summary>        /// <returns><c>true</c> if the operation was cancelled; otherwise <c>false</c>.</returns>        public bool Cancel()        {            bool result = Interlocked.Exchange(ref m_cancelled, 1) == 0;             if (result && (object)Cancelled != null)                Cancelled(this, EventArgs.Empty);             return result;        }         #endregion         #region [ Operators ]         /// <summary>        /// Implicitly converts a GSF cancellation token to an associated <see cref="System.Threading.CancellationToken"/>.        /// </summary>        /// <param name="token">Existing GSF cancellation token that is converted to an associated <see cref="System.Threading.CancellationToken"/>.</param>        /// <returns>A <see cref="System.Threading.CancellationToken"/> based on an existing GSF cancellation token.</returns>        public static implicit operator System.Threading.CancellationToken(CancellationToken token)        {            return new CompatibleCancellationToken(token).GetToken();        }         /// <summary>        /// Implicitly converts a GSF cancellation token to an associated <see cref="CancellationTokenSource"/>.        /// </summary>        /// <param name="token">Existing GSF cancellation token that is converted to an associated <see cref="CancellationTokenSource"/>.</param>        /// <returns>A <see cref="CancellationToken"/> based on an existing GSF cancellation token.</returns>        public static implicit operator CancellationTokenSource(CancellationToken token)        {            return new CompatibleCancellationToken(token).GetTokenSource();        }         #endregion    }}