1 files changed, 236 insertions, 0 deletions

diff --git a/OpenSim/Framework/Lazy.cs b/OpenSim/Framework/Lazy.cs
new file mode 100644
index 0000000..91de4bd
--- /dev/null
+++ b/OpenSim/Framework/Lazy.cs
@@ -0,0 +1,236 @@
+//
+// Lazy.cs
+//
+// Authors:
+//  Zoltan Varga (vargaz@gmail.com)
+//  Marek Safar (marek.safar@gmail.com)
+//
+// Copyright (C) 2009 Novell
+//
+// 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.
+//
+
+using System;
+using System.Runtime.Serialization;
+using System.Runtime.InteropServices;
+using System.Security.Permissions;
+using System.Threading;
+using System.Diagnostics;
+
+namespace OpenSim.Framework
+{
+    public enum LazyThreadSafetyMode
+    {
+        None,
+        PublicationOnly,
+        ExecutionAndPublication
+    }
+
+    [SerializableAttribute]
+    [ComVisibleAttribute(false)]
+    [HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, ExternalThreading = true)]
+    public class Lazy<T>
+    {
+        T value;
+        bool inited;
+        LazyThreadSafetyMode mode;
+        Func<T> factory;
+        object monitor;
+        Exception exception;
+
+        public Lazy()
+            : this(LazyThreadSafetyMode.ExecutionAndPublication)
+        {
+        }
+
+        public Lazy(Func<T> valueFactory)
+            : this(valueFactory, LazyThreadSafetyMode.ExecutionAndPublication)
+        {
+        }
+
+        public Lazy(bool isThreadSafe)
+            : this(() => Activator.CreateInstance<T>(), isThreadSafe ? LazyThreadSafetyMode.ExecutionAndPublication : LazyThreadSafetyMode.None)
+        {
+        }
+
+        public Lazy(Func<T> valueFactory, bool isThreadSafe)
+            : this(valueFactory, isThreadSafe ? LazyThreadSafetyMode.ExecutionAndPublication : LazyThreadSafetyMode.None)
+        {
+        }
+
+        public Lazy(LazyThreadSafetyMode mode)
+            : this(() => Activator.CreateInstance<T>(), mode)
+        {
+        }
+
+        public Lazy(Func<T> valueFactory, LazyThreadSafetyMode mode)
+        {
+            if (valueFactory == null)
+                throw new ArgumentNullException("valueFactory");
+            this.factory = valueFactory;
+            if (mode != LazyThreadSafetyMode.None)
+                monitor = new object();
+            this.mode = mode;
+        }
+
+        // Don't trigger expensive initialization
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        public T Value
+        {
+            get
+            {
+                if (inited)
+                    return value;
+                if (exception != null)
+                    throw exception;
+
+                return InitValue();
+            }
+        }
+
+        T InitValue()
+        {
+            switch (mode)
+            {
+                case LazyThreadSafetyMode.None:
+                    {
+                        var init_factory = factory;
+                        if (init_factory == null)
+                            throw exception = new InvalidOperationException("The initialization function tries to access Value on this instance");
+                        try
+                        {
+                            factory = null;
+                            T v = init_factory();
+                            value = v;
+                            Thread.MemoryBarrier();
+                            inited = true;
+                        }
+                        catch (Exception ex)
+                        {
+                            exception = ex;
+                            throw;
+                        }
+                        break;
+                    }
+                case LazyThreadSafetyMode.PublicationOnly:
+                    {
+                        var init_factory = factory;
+                        T v;
+
+                        //exceptions are ignored
+                        if (init_factory != null)
+                            v = init_factory();
+                        else
+                            v = default(T);
+
+                        lock (monitor)
+                        {
+                            if (inited)
+                                return value;
+                            value = v;
+                            Thread.MemoryBarrier();
+                            inited = true;
+                            factory = null;
+                        }
+                        break;
+                    }
+                case LazyThreadSafetyMode.ExecutionAndPublication:
+                    {
+                        lock (monitor)
+                        {
+                            if (inited)
+                                return value;
+
+                            if (factory == null)
+                                throw exception = new InvalidOperationException("The initialization function tries to access Value on this instance");
+
+                            var init_factory = factory;
+                            try
+                            {
+                                factory = null;
+                                T v = init_factory();
+                                value = v;
+                                Thread.MemoryBarrier();
+                                inited = true;
+                            }
+                            catch (Exception ex)
+                            {
+                                exception = ex;
+                                throw;
+                            }
+                        }
+                        break;
+                    }
+                default:
+                    throw new InvalidOperationException("Invalid LazyThreadSafetyMode " + mode);
+            }
+
+            if (monitor == null)
+            {
+                value = factory();
+                inited = true;
+            }
+            else
+            {
+                lock (monitor)
+                {
+                    if (inited)
+                        return value;
+
+                    if (factory == null)
+                        throw new InvalidOperationException("The initialization function tries to access Value on this instance");
+
+                    var init_factory = factory;
+                    try
+                    {
+                        factory = null;
+                        T v = init_factory();
+                        value = v;
+                        Thread.MemoryBarrier();
+                        inited = true;
+                    }
+                    catch
+                    {
+                        factory = init_factory;
+                        throw;
+                    }
+                }
+            }
+
+            return value;
+        }
+
+        public bool IsValueCreated
+        {
+            get
+            {
+                return inited;
+            }
+        }
+
+        public override string ToString()
+        {
+            if (inited)
+                return value.ToString();
+            else
+                return "Value is not created";
+        }
+    }
+}