Hash and compress DAT file on import.

RomRepoMgr.Core/Checksums/SHA256Context.cs

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+// /***************************************************************************
+// Aaru Data Preservation Suite
+// ----------------------------------------------------------------------------
+//
+// Filename       : SHA256Context.cs
+// Author(s)      : Natalia Portillo <claunia@claunia.com>
+//
+// Component      : Checksums.
+//
+// --[ Description ] ----------------------------------------------------------
+//
+//     Wraps up .NET SHA256 implementation to a Init(), Update(), Final() context.
+//
+// --[ License ] --------------------------------------------------------------
+//
+//     This library is free software; you can redistribute it and/or modify
+//     it under the terms of the GNU Lesser General Public License as
+//     published by the Free Software Foundation; either version 2.1 of the
+//     License, or (at your option) any later version.
+//
+//     This library 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
+//     Lesser General Public License for more details.
+//
+//     You should have received a copy of the GNU Lesser General Public
+//     License along with this library; if not, see <http://www.gnu.org/licenses/>.
+//
+// ----------------------------------------------------------------------------
+// Copyright © 2011-2020 Natalia Portillo
+// ****************************************************************************/
+
+using System.IO;
+using System.Security.Cryptography;
+using System.Text;
+using Aaru.CommonTypes.Interfaces;
+
+namespace Aaru.Checksums
+{
+    /// <summary>Wraps up .NET SHA256 implementation to a Init(), Update(), Final() context.</summary>
+    public sealed class Sha256Context : IChecksum
+    {
+        readonly SHA256 _provider;
+
+        /// <summary>Initializes the SHA256 hash provider</summary>
+        public Sha256Context() => _provider = SHA256.Create();
+
+        /// <inheritdoc />
+        /// <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) => _provider.TransformBlock(data, 0, (int)len, data, 0);
+
+        /// <inheritdoc />
+        /// <summary>Updates the hash with data.</summary>
+        /// <param name="data">Data buffer.</param>
+        public void Update(byte[] data) => Update(data, (uint)data.Length);
+
+        /// <inheritdoc />
+        /// <summary>Returns a byte array of the hash value.</summary>
+        public byte[] Final()
+        {
+            _provider.TransformFinalBlock(new byte[0], 0, 0);
+
+            return _provider.Hash;
+        }
+
+        /// <inheritdoc />
+        /// <summary>Returns a hexadecimal representation of the hash value.</summary>
+        public string End()
+        {
+            _provider.TransformFinalBlock(new byte[0], 0, 0);
+            var sha256Output = new StringBuilder();
+
+            foreach(byte h in _provider.Hash)
+                sha256Output.Append(h.ToString("x2"));
+
+            return sha256Output.ToString();
+        }
+
+        /// <summary>Gets the hash of a file</summary>
+        /// <param name="filename">File path.</param>
+        public static byte[] File(string filename)
+        {
+            var    localSha256Provider = SHA256.Create();
+            var    fileStream          = new FileStream(filename, FileMode.Open);
+            byte[] result              = localSha256Provider.ComputeHash(fileStream);
+            fileStream.Close();
+
+            return result;
+        }
+
+        /// <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)
+        {
+            var localSha256Provider = SHA256.Create();
+            var fileStream          = new FileStream(filename, FileMode.Open);
+            hash = localSha256Provider.ComputeHash(fileStream);
+            var sha256Output = new StringBuilder();
+
+            foreach(byte h in hash)
+                sha256Output.Append(h.ToString("x2"));
+
+            fileStream.Close();
+
+            return sha256Output.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)
+        {
+            var localSha256Provider = SHA256.Create();
+            hash = localSha256Provider.ComputeHash(data, 0, (int)len);
+            var sha256Output = new StringBuilder();
+
+            foreach(byte h in hash)
+                sha256Output.Append(h.ToString("x2"));
+
+            return sha256Output.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) => Data(data, (uint)data.Length, out hash);
+    }
+}