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Hash and compress DAT file on import.
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233
RomRepoMgr.Core/Checksums/CRC32Context.cs
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233
RomRepoMgr.Core/Checksums/CRC32Context.cs
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// /***************************************************************************
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// Aaru Data Preservation Suite
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// ----------------------------------------------------------------------------
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//
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// Filename : CRC32Context.cs
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// Author(s) : Natalia Portillo <claunia@claunia.com>
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//
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// Component : Checksums.
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//
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// --[ Description ] ----------------------------------------------------------
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//
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// Implements a CRC32 algorithm.
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//
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// --[ License ] --------------------------------------------------------------
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//
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// This library is free software; you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 2.1 of the
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// License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, see <http://www.gnu.org/licenses/>.
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//
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// ----------------------------------------------------------------------------
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// Copyright © 2011-2020 Natalia Portillo
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// ****************************************************************************/
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using System.IO;
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using System.Text;
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using Aaru.CommonTypes.Interfaces;
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using Aaru.Helpers;
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namespace Aaru.Checksums
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{
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/// <summary>Implements a CRC32 algorithm</summary>
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public sealed class Crc32Context : IChecksum
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{
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const uint CRC32_ISO_POLY = 0xEDB88320;
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const uint CRC32_ISO_SEED = 0xFFFFFFFF;
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readonly uint _finalSeed;
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readonly uint[] _table;
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uint _hashInt;
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/// <summary>Initializes the CRC32 table and seed as CRC32-ISO</summary>
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public Crc32Context()
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{
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_hashInt = CRC32_ISO_SEED;
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_finalSeed = CRC32_ISO_SEED;
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_table = new uint[256];
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for(int i = 0; i < 256; i++)
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{
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uint entry = (uint)i;
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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) ^ CRC32_ISO_POLY;
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else
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entry = entry >> 1;
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_table[i] = entry;
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}
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}
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/// <summary>Initializes the CRC32 table with a custom polynomial and seed</summary>
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public Crc32Context(uint polynomial, uint seed)
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{
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_hashInt = seed;
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_finalSeed = seed;
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_table = new uint[256];
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for(int i = 0; i < 256; i++)
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{
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uint entry = (uint)i;
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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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_table[i] = entry;
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}
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}
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/// <inheritdoc />
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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++)
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_hashInt = (_hashInt >> 8) ^ _table[data[i] ^ (_hashInt & 0xff)];
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}
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/// <inheritdoc />
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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) => Update(data, (uint)data.Length);
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/// <inheritdoc />
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/// <summary>Returns a byte array of the hash value.</summary>
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public byte[] Final() => BigEndianBitConverter.GetBytes(_hashInt ^ _finalSeed);
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/// <inheritdoc />
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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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var crc32Output = new StringBuilder();
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for(int i = 0; i < BigEndianBitConverter.GetBytes(_hashInt ^ _finalSeed).Length; i++)
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crc32Output.Append(BigEndianBitConverter.GetBytes(_hashInt ^ _finalSeed)[i].ToString("x2"));
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return crc32Output.ToString();
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}
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/// <summary>Gets the hash of a file</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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{
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File(filename, out byte[] hash);
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return hash;
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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) =>
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File(filename, out hash, CRC32_ISO_POLY, CRC32_ISO_SEED);
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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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/// <param name="polynomial">CRC polynomial</param>
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/// <param name="seed">CRC seed</param>
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public static string File(string filename, out byte[] hash, uint polynomial, uint seed)
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{
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var fileStream = new FileStream(filename, FileMode.Open);
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uint localhashInt = seed;
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uint[] localTable = new uint[256];
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for(int i = 0; i < 256; i++)
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{
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uint entry = (uint)i;
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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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localTable[i] = entry;
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}
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for(int i = 0; i < fileStream.Length; i++)
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localhashInt = (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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var crc32Output = new StringBuilder();
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foreach(byte h in hash)
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crc32Output.Append(h.ToString("x2"));
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fileStream.Close();
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return crc32Output.ToString();
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}
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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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public static string Data(byte[] data, uint len, out byte[] hash) =>
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Data(data, len, out hash, CRC32_ISO_POLY, CRC32_ISO_SEED);
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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, uint polynomial, uint seed)
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{
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uint localhashInt = seed;
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uint[] localTable = new uint[256];
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for(int i = 0; i < 256; i++)
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{
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uint entry = (uint)i;
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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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localTable[i] = entry;
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}
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for(int i = 0; i < len; i++)
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localhashInt = (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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var crc32Output = new StringBuilder();
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foreach(byte h in hash)
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crc32Output.Append(h.ToString("x2"));
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return crc32Output.ToString();
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}
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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="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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}
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}
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