CRC-64 implementation.

ArcFormats/Crc64.cs

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+//! \file       Crc64.cs
+//! \date       Sun Apr 24 22:07:30 2016
+//! \brief      Crc-64 implementation.
+//
+// Copyright (C) 2016 by morkt
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+//
+
+namespace GameRes.Utility
+{
+    public sealed class Crc64
+    {
+        const ulong Polynomial = 0x42F0E1EBA9EA3693ul;
+
+        private static readonly ulong[] crc_table = InitializeTable (Polynomial);
+
+        public static ulong[] Table { get { return crc_table; } }
+
+        private static ulong[] InitializeTable (ulong poly)
+        {
+            var table = new ulong[256];
+            for (uint i = 0; i < 256; ++i)
+            {
+                ulong crc = (ulong)i << 56;
+                for (int j = 0; j < 8; ++j)
+                {
+                    if ((crc >> 63) != 0)
+                        crc = (crc << 1) ^ poly;
+                    else
+                        crc <<= 1;
+                }
+                table[i] = crc;
+            }
+            return table;
+        }
+   
+        public static ulong UpdateCrc (ulong crc, byte[] buf, int pos, int len)
+        {
+            for (int n = 0; n < len; n++)
+                crc = crc_table[((crc >> 56) ^ buf[pos+n]) & 0xFF] ^ (crc << 8);
+            return crc;
+        }
+   
+        public static ulong Compute (byte[] buf, int pos, int len)
+        {
+            return ~UpdateCrc (~0ul, buf, pos, len);
+        }
+
+        private ulong m_crc = ~0ul;
+        public  ulong Value { get { return ~m_crc; } }
+
+        public void Update (byte[] buf, int pos, int len)
+        {
+            m_crc = UpdateCrc (m_crc, buf, pos, len);
+        }
+    }
+}