Initial commit - WPinternals 2.6

2026-06-21 14:41:03 +10:00 · 2018-10-25 22:35:49 +02:00
commit 396ae57f05
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+//
+// Copyright (c) 2008-2011, Kenneth Bell
+//
+// 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 DiscUtils
+{
+    /// <summary>
+    /// Calculates CRC32 of buffers.
+    /// </summary>
+    internal sealed class Crc32LittleEndian : Crc32
+    {
+        private static readonly uint[][] Tables;
+
+        static Crc32LittleEndian()
+        {
+            Tables = new uint[4][];
+
+            Tables[(int)Crc32Algorithm.Common] = CalcTable(0xEDB88320);
+            Tables[(int)Crc32Algorithm.Castagnoli] = CalcTable(0x82F63B78);
+            Tables[(int)Crc32Algorithm.Koopman] = CalcTable(0xEB31D82E);
+            Tables[(int)Crc32Algorithm.Aeronautical] = CalcTable(0xD5828281);
+        }
+
+        public Crc32LittleEndian(Crc32Algorithm algorithm)
+            : base(Tables[(int)algorithm])
+        {
+        }
+
+        public static uint Compute(Crc32Algorithm algorithm, byte[] buffer, int offset, int count)
+        {
+            return Process(Tables[(int)algorithm], 0xFFFFFFFF, buffer, offset, count) ^ 0xFFFFFFFF;
+        }
+
+        public override void Process(byte[] buffer, int offset, int count)
+        {
+            _value = Process(Table, _value, buffer, offset, count);
+        }
+
+        private static uint[] CalcTable(uint polynomial)
+        {
+            uint[] table = new uint[256];
+
+            table[0] = 0;
+            for (uint i = 0; i <= 255; ++i)
+            {
+                uint crc = i;
+
+                for (int j = 8; j > 0; --j)
+                {
+                    if ((crc & 1) != 0)
+                    {
+                        crc = (crc >> 1) ^ polynomial;
+                    }
+                    else
+                    {
+                        crc >>= 1;
+                    }
+                }
+
+                table[i] = crc;
+            }
+
+            return table;
+        }
+
+        private static uint Process(uint[] table, uint accumulator, byte[] buffer, int offset, int count)
+        {
+            uint value = accumulator;
+
+            for (int i = 0; i < count; ++i)
+            {
+                byte b = buffer[offset + i];
+
+                uint temp1 = (value >> 8) & 0x00FFFFFF;
+                uint temp2 = table[(value ^ b) & 0xFF];
+                value = temp1 ^ temp2;
+            }
+
+            return value;
+        }
+    }
+}