Added DBGuids.cs (static func DBGuid.FromDB()

This DBMS-independent function to be used converting UUIDs
from whatever format used in the DB (string/binary/Guid).
This is mostly needed for MySQL, as in MSSQL they are always
UNIQUEIDENTIFIERs and in SQLite always strings (but would look
better if we use it there anyway).

OpenSim/Data/DBGuids.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using OpenMetaverse;
+
+namespace OpenSim.Data
+{
+
+    public static class DBGuid
+    {
+        /// <summary>This function converts a value returned from the database in one of the
+        /// supported formats into a UUID.  This function is not actually DBMS-specific right
+        /// now
+        /// 
+        /// </summary>
+        /// <param name="id"></param>
+        /// <returns></returns>
+        public static UUID FromDB(object id)
+        {
+            if( (id == null) || (id == DBNull.Value))
+                return UUID.Zero;
+
+            if (id.GetType() == typeof(Guid))
+                return new UUID((Guid)id);
+
+            if (id.GetType() == typeof(byte[]))
+            {
+                if (((byte[])id).Length == 0)
+                    return UUID.Zero;
+                else if (((byte[])id).Length == 36)
+                    return new UUID((byte[])id, 0);
+            }
+            else if (id.GetType() == typeof(string))
+            {
+                if (((string)id).Length == 0)
+                    return UUID.Zero;
+                else if (((string)id).Length == 36)
+                    return new UUID((string)id);
+            }
+
+            throw new Exception("Failed to convert db value to UUID: " + id.ToString());
+        }
+    }
+}