//******************************************************************************************************//  Xor16.cs - Gbtc////  Copyright © 2012, 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://www.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://  ----------------------------------------------------------------------------------------------------//  09/24/2008 - J. Ritchie Carroll//       Generated original version of source code.//  08/05/2009 - Josh L. Patterson//       Edited Comments.//  09/14/2009 - Stephen C. Wills//       Added new header and license agreement.//  12/14/2012 - Starlynn Danyelle Gilliam//       Modified Header.////****************************************************************************************************** using System; namespace GSF.IO.Checksums{    /// <summary>Calculates word length (16-bit) XOR-based check-sum on specified portion of a buffer.</summary>    public sealed class Xor16    {        #region [ Members ]         // Fields        private ushort m_checksum;         #endregion         #region [ Constructors ]         /// <summary>        /// Creates a new instance of the Xor16Bit class.        /// The checksum starts off with a value of 0.        /// </summary>        public Xor16()        {            Reset();        }         #endregion         #region [ Properties ]         /// <summary>        /// Returns the Xor 16-bit checksum computed so far.        /// </summary>        public ushort Value        {            get            {                return m_checksum;            }        }         #endregion         #region [ Methods ]         /// <summary>        /// Resets the checksum to the initial value.        /// </summary>        public void Reset()        {            m_checksum = 0;        }         /// <summary>        /// Updates the checksum with a ushort value.        /// </summary>        /// <param name="value">The <see cref="ushort"/> value to use for the update.</param>        public void Update(ushort value)        {            m_checksum ^= value;        }         /// <summary>        /// Updates the checksum with an array of bytes.        /// </summary>        /// <param name="buffer">        /// The source of the data to update with.        /// </param>        public void Update(byte[] buffer)        {            if ((object)buffer == null)                throw new ArgumentNullException(nameof(buffer));             Update(buffer, 0, buffer.Length);        }         /// <summary>        /// Updates the checksum with the bytes taken from the array.        /// </summary>        /// <param name="buffer">        /// an array of bytes        /// </param>        /// <param name="offset">        /// the start of the data used for this update        /// </param>        /// <param name="count">        /// the number of bytes to use for this update        /// </param>        public void Update(byte[] buffer, int offset, int count)        {            if ((object)buffer == null)                throw new ArgumentNullException(nameof(buffer));             if (offset < 0)                throw new ArgumentOutOfRangeException(nameof(offset), "cannot be negative");             if (count < 0)                throw new ArgumentOutOfRangeException(nameof(count), "cannot be negative");             if (offset >= buffer.Length)                throw new ArgumentOutOfRangeException(nameof(offset), "not a valid index into buffer");             if (offset + count > buffer.Length)                throw new ArgumentOutOfRangeException(nameof(count), "exceeds buffer size");             for (int x = 0; x < count; x += 2)            {                m_checksum ^= BitConverter.ToUInt16(buffer, offset + x);            }        }         #endregion    }}