SubChannelDecoder/CRC16CCITTContext.cs

//
//  CRC16CCITTContext.cs
//
//  Author:
//       Natalia Portillo <claunia@claunia.com>
//
//  Copyright (c) 2015 © Claunia.com
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
using System;
using System.Text;
using System.IO;

namespace SubChannelDecoder
{
    /// <summary>
    /// Provides a UNIX similar API to calculate CRC16CCITT (x^16 + x^12 + x^5 + 1).
    /// </summary>
    public class CRC16CCITTContext
    {
        static UInt16[] table =
            {
            0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5,
            0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b,
            0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210,
            0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
            0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c,
            0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401,
            0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b,
            0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
            0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6,
            0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738,
            0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5,
            0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
            0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969,
            0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96,
            0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc,
            0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
            0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03,
            0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd,
            0xad2a, 0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6,
            0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
            0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a,
            0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb,
            0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1,
            0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
            0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c,
            0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2,
            0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb,
            0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
            0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447,
            0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8,
            0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2,
            0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
            0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9,
            0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827,
            0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c,
            0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
            0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0,
            0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d,
            0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07,
            0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
            0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba,
            0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74,
            0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
        };
        UInt16 hashInt;

        /// <summary>
        /// Initializes the CRC16CCITT table and seed
        /// </summary>
        public void Init()
        {
            hashInt = 0xFFFF;
        }

        /// <summary>
        /// Updates the hash with data.
        /// </summary>
        /// <param name="data">Data buffer.</param>
        /// <param name="len">Length of buffer to hash.</param>
        public void Update(byte[] data, uint len)
        {
            for (int i = 0; i < len; i++)
                hashInt = (ushort)((hashInt << 8) ^ table[data[i] ^ (hashInt>>8 & 0xFF)]);
        }

        /// <summary>
        /// Updates the hash with data.
        /// </summary>
        /// <param name="data">Data buffer.</param>
        public void Update(byte[] data)
        {
            Update(data, (uint)data.Length);
        }

        /// <summary>
        /// Returns a byte array of the hash value.
        /// </summary>
        public byte[] Final()
        {
            hashInt = (ushort)~hashInt;
            BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
            return BigEndianBitConverter.GetBytes(hashInt);
        }

        /// <summary>
        /// Returns a hexadecimal representation of the hash value.
        /// </summary>
        public string End()
        {
            hashInt = (ushort)~hashInt;

            StringBuilder crc16Output = new StringBuilder();

            BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
            for (int i = 0; i < BigEndianBitConverter.GetBytes(hashInt).Length; i++)
            {
                crc16Output.Append(BigEndianBitConverter.GetBytes(hashInt)[i].ToString("x2"));
            }

            return crc16Output.ToString();
        }

        /// <summary>
        /// Gets the hash of a file
        /// </summary>
        /// <param name="filename">File path.</param>
        public static byte[] File(string filename)
        {
            byte[] hash;
            File(filename, out hash);
            return hash;
        }

        /// <summary>
        /// Gets the hash of a file in hexadecimal and as a byte array.
        /// </summary>
        /// <param name="filename">File path.</param>
        /// <param name="hash">Byte array of the hash value.</param>
        public static string File(string filename, out byte[] hash)
        {
            FileStream fileStream = new FileStream(filename, FileMode.Open);
            UInt16 localhashInt;

            localhashInt = 0x0000;

            for (int i = 0; i < fileStream.Length; i++)
                localhashInt = (ushort)((localhashInt << 8) ^ table[fileStream.ReadByte() ^ (localhashInt>>8 & 0xFF)]);

            localhashInt = (ushort)~localhashInt;

            BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
            hash = BigEndianBitConverter.GetBytes(localhashInt);

            StringBuilder crc16Output = new StringBuilder();

            for (int i = 0; i < hash.Length; i++)
            {
                crc16Output.Append(hash[i].ToString("x2"));
            }

            return crc16Output.ToString();
        }

        /// <summary>
        /// Gets the hash of the specified data buffer.
        /// </summary>
        /// <param name="data">Data buffer.</param>
        /// <param name="len">Length of the data buffer to hash.</param>
        /// <param name="hash">Byte array of the hash value.</param>
        public static string Data(byte[] data, uint len, out byte[] hash)
        {
            UInt16 localhashInt;

            localhashInt = 0x0000;

            for (int i = 0; i < len; i++)
                localhashInt = (ushort)((localhashInt << 8) ^ table[data[i] ^ (localhashInt>>8 & 0xFF)]);

            localhashInt = (ushort)~localhashInt;

            BigEndianBitConverter.IsLittleEndian = BitConverter.IsLittleEndian;
            hash = BigEndianBitConverter.GetBytes(localhashInt);

            StringBuilder crc16Output = new StringBuilder();

            for (int i = 0; i < hash.Length; i++)
            {
                crc16Output.Append(hash[i].ToString("x2"));
            }

            return crc16Output.ToString();
        }

        /// <summary>
        /// Gets the hash of the specified data buffer.
        /// </summary>
        /// <param name="data">Data buffer.</param>
        /// <param name="hash">Byte array of the hash value.</param>
        public static string Data(byte[] data, out byte[] hash)
        {
            return Data(data, (uint)data.Length, out hash);
        }
    }}