1 files changed, 139 insertions, 0 deletions

diff --git a/OpenSim/Framework/Crc32.cs b/OpenSim/Framework/Crc32.cs
new file mode 100644
index 0000000..7ad1566
--- /dev/null
+++ b/OpenSim/Framework/Crc32.cs
@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) Contributors, http://opensimulator.org/
+ * See CONTRIBUTORS.TXT for a full list of copyright holders.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the OpenSimulator Project nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+using System;
+using System.Security.Cryptography;
+
+namespace OpenSim.Framework
+{
+    // this is more generic than openmetaverse CRC32
+
+    public class Crc32 : HashAlgorithm
+    {
+        public const UInt32 DefaultPolynomial = 0xedb88320;
+        public const UInt32 DefaultSeed = 0xffffffff;
+
+        private UInt32 hash;
+        private UInt32 seed;
+        private UInt32[] table;
+        private static UInt32[] defaultTable;
+
+        public Crc32()
+        {
+            table = InitializeTable(DefaultPolynomial);
+            seed = DefaultSeed;
+            Initialize();
+        }
+
+        public Crc32(UInt32 polynomial, UInt32 seed)
+        {
+            table = InitializeTable(polynomial);
+            this.seed = seed;
+            Initialize();
+        }
+
+        public override void Initialize()
+        {
+            hash = seed;
+        }
+
+        protected override void HashCore(byte[] buffer, int start, int length)
+        {
+            hash = CalculateHash(table, hash, buffer, start, length);
+        }
+
+        protected override byte[] HashFinal()
+        {
+            byte[] hashBuffer = UInt32ToBigEndianBytes(~hash);
+            this.HashValue = hashBuffer;
+            return hashBuffer;
+        }
+
+        public override int HashSize
+        {
+            get { return 32; }
+        }
+
+        public static UInt32 Compute(byte[] buffer)
+        {
+            return ~CalculateHash(InitializeTable(DefaultPolynomial), DefaultSeed, buffer, 0, buffer.Length);
+        }
+
+        public static UInt32 Compute(UInt32 seed, byte[] buffer)
+        {
+            return ~CalculateHash(InitializeTable(DefaultPolynomial), seed, buffer, 0, buffer.Length);
+        }
+
+        public static UInt32 Compute(UInt32 polynomial, UInt32 seed, byte[] buffer)
+        {
+            return ~CalculateHash(InitializeTable(polynomial), seed, buffer, 0, buffer.Length);
+        }
+
+        private static UInt32[] InitializeTable(UInt32 polynomial)
+        {
+            if (polynomial == DefaultPolynomial && defaultTable != null)
+                return defaultTable;
+
+            UInt32[] createTable = new UInt32[256];
+            for (int i = 0; i < 256; i++)
+            {
+                UInt32 entry = (UInt32)i;
+                for (int j = 0; j < 8; j++)
+                    if ((entry & 1) == 1)
+                        entry = (entry >> 1) ^ polynomial;
+                    else
+                        entry = entry >> 1;
+                createTable[i] = entry;
+            }
+
+            if (polynomial == DefaultPolynomial)
+                defaultTable = createTable;
+
+            return createTable;
+        }
+
+        private static UInt32 CalculateHash(UInt32[] table, UInt32 seed, byte[] buffer, int start, int size)
+        {
+            UInt32 crc = seed;
+            for (int i = start; i < size; i++)
+                unchecked
+                {
+                    crc = (crc >> 8) ^ table[buffer[i] ^ crc & 0xff];
+                }
+            return crc;
+        }
+
+        private byte[] UInt32ToBigEndianBytes(UInt32 x)
+        {
+            return new byte[] {
+                    (byte)((x >> 24) & 0xff),
+                    (byte)((x >> 16) & 0xff),
+                    (byte)((x >> 8) & 0xff),
+                    (byte)(x & 0xff) };
+        }
+    }
+}