Create MurmurHash2.cs

Author: mythz

src/ServiceStack.Text/MurmurHash2.cs

@@ -0,0 +1,65 @@
+using System;
+
+namespace ServiceStack.Text
+{
+    // https://softwareengineering.stackexchange.com/questions/49550/which-hashing-algorithm-is-best-for-uniqueness-and-speed#answer-145633
+    // https://github.com/jitbit/MurmurHash.net
+    public class MurmurHash2
+    {
+        public static uint Hash(string data)
+        {
+            return Hash(System.Text.Encoding.UTF8.GetBytes(data));
+        }
+
+        public static uint Hash(byte[] data)
+        {
+            return Hash(data, 0xc58f1a7a);
+        }
+        const uint m = 0x5bd1e995;
+        const int r = 24;
+
+        public static uint Hash(byte[] data, uint seed)
+        {
+            int length = data.Length;
+            if (length == 0)
+                return 0;
+            uint h = seed ^ (uint)length;
+            int currentIndex = 0;
+            while (length >= 4)
+            {
+                uint k = (uint)(data[currentIndex++] | data[currentIndex++] << 8 | data[currentIndex++] << 16 | data[currentIndex++] << 24);
+                k *= m;
+                k ^= k >> r;
+                k *= m;
+
+                h *= m;
+                h ^= k;
+                length -= 4;
+            }
+            switch (length)
+            {
+                case 3:
+                    h ^= (UInt16)(data[currentIndex++] | data[currentIndex++] << 8);
+                    h ^= (uint)(data[currentIndex] << 16);
+                    h *= m;
+                    break;
+                case 2:
+                    h ^= (UInt16)(data[currentIndex++] | data[currentIndex] << 8);
+                    h *= m;
+                    break;
+                case 1:
+                    h ^= data[currentIndex];
+                    h *= m;
+                    break;
+                default:
+                    break;
+            }
+
+            h ^= h >> 13;
+            h *= m;
+            h ^= h >> 15;
+
+            return h;
+        }
+    }
+}