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Separate CRC16 IBM and CRC16 CCITT contexts, use cached tables.
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@@ -31,208 +31,196 @@
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// ****************************************************************************/
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using System.IO;
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using System.Linq;
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using System.Text;
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using DiscImageChef.CommonTypes.Interfaces;
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namespace DiscImageChef.Checksums
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{
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/// <summary>
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/// Implements a CRC16 algorithm
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/// </summary>
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/// <summary>Implements a CRC16 algorithm</summary>
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public class Crc16Context : IChecksum
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{
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public const ushort CRC16_IBM_POLY = 0xA001;
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public const ushort CRC16_IBM_SEED = 0x0000;
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public const ushort CRC16_CCITT_POLY = 0x8408;
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public const ushort CRC16_CCITT_SEED = 0x0000;
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protected ushort _finalSeed;
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protected ushort _hashInt;
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protected bool _inverse;
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readonly ushort finalSeed;
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readonly ushort[] table;
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ushort hashInt;
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protected ushort[] _table;
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/// <summary>
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/// Initializes the CRC16 table and seed as CRC16-IBM
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/// </summary>
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public Crc16Context()
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/// <summary>Initializes the CRC16 table with a custom polynomial and seed</summary>
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public Crc16Context(ushort polynomial, ushort seed, ushort[] table, bool inverse)
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{
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hashInt = CRC16_IBM_SEED;
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finalSeed = CRC16_IBM_SEED;
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_hashInt = seed;
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_finalSeed = seed;
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_inverse = inverse;
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table = new ushort[256];
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for(int i = 0; i < 256; i++)
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{
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ushort entry = (ushort)i;
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for(int j = 0; j < 8; j++)
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if((entry & 1) == 1) entry = (ushort)((entry >> 1) ^ CRC16_IBM_POLY);
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else entry = (ushort)(entry >> 1);
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table[i] = entry;
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}
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_table = table ?? GenerateTable(polynomial, inverse);
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}
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/// <summary>
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/// Initializes the CRC16 table with a custom polynomial and seed
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/// </summary>
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public Crc16Context(ushort polynomial, ushort seed)
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{
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hashInt = seed;
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finalSeed = seed;
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table = new ushort[256];
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for(int i = 0; i < 256; i++)
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{
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ushort entry = (ushort)i;
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for(int j = 0; j < 8; j++)
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if((entry & 1) == 1) entry = (ushort)((entry >> 1) ^ polynomial);
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else entry = (ushort)(entry >> 1);
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table[i] = entry;
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}
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}
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/// <summary>
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/// Updates the hash with data.
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/// </summary>
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/// <summary>Updates the hash with data.</summary>
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/// <param name="data">Data buffer.</param>
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/// <param name="len">Length of buffer to hash.</param>
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public void Update(byte[] data, uint len)
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{
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for(int i = 0; i < len; i++) hashInt = (ushort)((hashInt >> 8) ^ table[data[i] ^ (hashInt & 0xFF)]);
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for(int i = 0; i < len; i++)
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{
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if(_inverse)
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_hashInt = (ushort)(_table[(_hashInt >> 8) ^ data[i]] ^ (_hashInt << 8));
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else
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_hashInt = (ushort)((_hashInt >> 8) ^ _table[data[i] ^ (_hashInt & 0xFF)]);
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}
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}
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/// <summary>
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/// Updates the hash with data.
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/// </summary>
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/// <summary>Updates the hash with data.</summary>
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/// <param name="data">Data buffer.</param>
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public void Update(byte[] data)
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{
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Update(data, (uint)data.Length);
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}
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public void Update(byte[] data) => Update(data, (uint)data.Length);
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/// <summary>
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/// Returns a byte array of the hash value.
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/// </summary>
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public byte[] Final() => BigEndianBitConverter.GetBytes((ushort)(hashInt ^ finalSeed));
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/// <summary>Returns a byte array of the hash value.</summary>
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public byte[] Final() => BigEndianBitConverter.GetBytes((ushort)(_hashInt ^ _finalSeed));
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/// <summary>
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/// Returns a hexadecimal representation of the hash value.
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/// </summary>
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/// <summary>Returns a hexadecimal representation of the hash value.</summary>
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public string End()
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{
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StringBuilder crc16Output = new StringBuilder();
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var crc16Output = new StringBuilder();
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for(int i = 0; i < BigEndianBitConverter.GetBytes((ushort)(hashInt ^ finalSeed)).Length; i++)
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crc16Output.Append(BigEndianBitConverter.GetBytes((ushort)(hashInt ^ finalSeed))[i].ToString("x2"));
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ushort final = (ushort)(_hashInt ^ _finalSeed);
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if(_inverse)
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final = (ushort)~final;
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byte[] finalBytes = BigEndianBitConverter.GetBytes(final);
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for(int i = 0; i < finalBytes.Length; i++)
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crc16Output.Append(finalBytes[i].ToString("x2"));
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return crc16Output.ToString();
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}
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/// <summary>
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/// Gets the hash of a file
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/// </summary>
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/// <param name="filename">File path.</param>
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public static byte[] File(string filename)
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static ushort[] GenerateTable(ushort polynomial, bool inverseTable)
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{
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File(filename, out byte[] hash);
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return hash;
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}
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ushort[] table = new ushort[256];
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/// <summary>
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/// Gets the hash of a file in hexadecimal and as a byte array.
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/// </summary>
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/// <param name="filename">File path.</param>
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/// <param name="hash">Byte array of the hash value.</param>
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public static string File(string filename, out byte[] hash) =>
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File(filename, out hash, CRC16_IBM_POLY, CRC16_IBM_SEED);
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if(!inverseTable)
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for(uint i = 0; i < 256; i++)
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{
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uint entry = i;
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/// <summary>
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/// Gets the hash of a file in hexadecimal and as a byte array.
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/// </summary>
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/// <param name="filename">File path.</param>
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/// <param name="hash">Byte array of the hash value.</param>
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public static string File(string filename, out byte[] hash, ushort polynomial, ushort seed)
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{
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FileStream fileStream = new FileStream(filename, FileMode.Open);
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for(int j = 0; j < 8; j++)
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if((entry & 1) == 1)
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entry = (entry >> 1) ^ polynomial;
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else
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entry = entry >> 1;
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ushort localhashInt = seed;
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ushort[] localTable = new ushort[256];
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for(int i = 0; i < 256; i++)
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table[i] = (ushort)entry;
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}
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else
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{
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ushort entry = (ushort)i;
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for(int j = 0; j < 8; j++)
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if((entry & 1) == 1) entry = (ushort)((entry >> 1) ^ polynomial);
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else entry = (ushort)(entry >> 1);
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for(uint i = 0; i < 256; i++)
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{
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uint entry = i << 8;
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localTable[i] = entry;
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for(uint j = 0; j < 8; j++)
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{
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if((entry & 0x8000) > 0)
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entry = (entry << 1) ^ polynomial;
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else
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entry <<= 1;
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table[i] = (ushort)entry;
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}
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}
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}
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return table;
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}
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/// <summary>Gets the hash of a file in hexadecimal and as a byte array.</summary>
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/// <param name="filename">File path.</param>
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/// <param name="hash">Byte array of the hash value.</param>
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public static string File(string filename, out byte[] hash, ushort polynomial, ushort seed, ushort[] table,
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bool inverse)
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{
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var fileStream = new FileStream(filename, FileMode.Open);
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ushort localHashInt = seed;
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ushort[] localTable = table ?? GenerateTable(polynomial, inverse);
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for(int i = 0; i < fileStream.Length; i++)
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localhashInt =
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(ushort)((localhashInt >> 8) ^ localTable[fileStream.ReadByte() ^ (localhashInt & 0xff)]);
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if(inverse)
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localHashInt =
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(ushort)(localTable[(localHashInt >> 8) ^ fileStream.ReadByte()] ^ (localHashInt << 8));
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else
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localHashInt =
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(ushort)((localHashInt >> 8) ^ localTable[fileStream.ReadByte() ^ (localHashInt & 0xff)]);
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localhashInt ^= seed;
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hash = BigEndianBitConverter.GetBytes(localhashInt);
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localHashInt ^= seed;
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StringBuilder crc16Output = new StringBuilder();
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if(inverse)
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localHashInt = (ushort)~localHashInt;
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foreach(byte h in hash) crc16Output.Append(h.ToString("x2"));
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hash = BigEndianBitConverter.GetBytes(localHashInt);
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var crc16Output = new StringBuilder();
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foreach(byte h in hash)
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crc16Output.Append(h.ToString("x2"));
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fileStream.Close();
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return crc16Output.ToString();
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}
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/// <summary>
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/// Gets the hash of the specified data buffer.
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/// </summary>
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/// <param name="data">Data buffer.</param>
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/// <param name="len">Length of the data buffer to hash.</param>
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/// <param name="hash">Byte array of the hash value.</param>
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public static string Data(byte[] data, uint len, out byte[] hash) =>
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Data(data, len, out hash, CRC16_IBM_POLY, CRC16_IBM_SEED);
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/// <summary>
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/// Gets the hash of the specified data buffer.
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/// </summary>
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/// <summary>Gets the hash of the specified data buffer.</summary>
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/// <param name="data">Data buffer.</param>
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/// <param name="len">Length of the data buffer to hash.</param>
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/// <param name="hash">Byte array of the hash value.</param>
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/// <param name="polynomial">CRC polynomial</param>
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/// <param name="seed">CRC seed</param>
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public static string Data(byte[] data, uint len, out byte[] hash, ushort polynomial, ushort seed)
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public static string Data(byte[] data, uint len, out byte[] hash, ushort polynomial, ushort seed,
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ushort[] table, bool inverse)
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{
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ushort localhashInt = seed;
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ushort localHashInt = seed;
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ushort[] localTable = new ushort[256];
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for(int i = 0; i < 256; i++)
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{
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ushort entry = (ushort)i;
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for(int j = 0; j < 8; j++)
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if((entry & 1) == 1) entry = (ushort)((entry >> 1) ^ polynomial);
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else entry = (ushort)(entry >> 1);
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localTable[i] = entry;
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}
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ushort[] localTable = table ?? GenerateTable(polynomial, inverse);
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for(int i = 0; i < len; i++)
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localhashInt = (ushort)((localhashInt >> 8) ^ localTable[data[i] ^ (localhashInt & 0xff)]);
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if(inverse)
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localHashInt = (ushort)(localTable[(localHashInt >> 8) ^ data[i]] ^ (localHashInt << 8));
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else
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localHashInt = (ushort)((localHashInt >> 8) ^ localTable[data[i] ^ (localHashInt & 0xff)]);
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localhashInt ^= seed;
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hash = BigEndianBitConverter.GetBytes(localhashInt);
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localHashInt ^= seed;
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StringBuilder crc16Output = new StringBuilder();
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if(inverse)
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localHashInt = (ushort)~localHashInt;
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foreach(byte h in hash) crc16Output.Append(h.ToString("x2"));
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hash = BigEndianBitConverter.GetBytes(localHashInt);
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var crc16Output = new StringBuilder();
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foreach(byte h in hash)
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crc16Output.Append(h.ToString("x2"));
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return crc16Output.ToString();
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}
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/// <summary>
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/// Gets the hash of the specified data buffer.
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/// </summary>
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/// <param name="data">Data buffer.</param>
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/// <param name="hash">Byte array of the hash value.</param>
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public static string Data(byte[] data, out byte[] hash) => Data(data, (uint)data.Length, out hash);
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public static ushort Calculate(byte[] buffer, ushort polynomial, ushort seed, ushort[] table, bool inverse)
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{
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ushort[] localTable = table ?? GenerateTable(polynomial, inverse);
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ushort crc16 =
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buffer.Aggregate<byte, ushort>(0,
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(current, b) =>
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inverse ? (ushort)(localTable[(current >> 8) ^ b] ^ (current << 8))
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: (ushort)((current >> 8) ^
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localTable[b ^ (current & 0xff)]));
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crc16 ^= seed;
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if(inverse)
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crc16 = (ushort)~crc16;
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return crc16;
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}
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}
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}
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