5 // Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
6 // Marek Safar (marek.safar@gmail.com)
8 // Copyright (c) 2009 Jérémie "Garuma" Laval
9 // Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
11 // Permission is hereby granted, free of charge, to any person obtaining a copy
12 // of this software and associated documentation files (the "Software"), to deal
13 // in the Software without restriction, including without limitation the rights
14 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
15 // copies of the Software, and to permit persons to whom the Software is
16 // furnished to do so, subject to the following conditions:
18 // The above copyright notice and this permission notice shall be included in
19 // all copies or substantial portions of the Software.
21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
22 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
23 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
24 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
25 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
26 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
31 namespace System.Threading
33 public static class LazyInitializer
35 public static T EnsureInitialized<T> (ref T target) where T : class
37 return target ?? EnsureInitialized (ref target, GetDefaultCtorValue<T>);
40 public static T EnsureInitialized<T> (ref T target, Func<T> valueFactory) where T : class
43 var value = valueFactory ();
45 throw new InvalidOperationException ();
47 Interlocked.CompareExchange (ref target, value, null);
53 public static T EnsureInitialized<T> (ref T target, ref bool initialized, ref object syncLock)
55 return EnsureInitialized (ref target, ref initialized, ref syncLock, GetDefaultCtorValue<T>);
58 public static T EnsureInitialized<T> (ref T target, ref bool initialized, ref object syncLock, Func<T> valueFactory)
64 Interlocked.CompareExchange (ref syncLock, new object (), null);
71 Thread.MemoryBarrier ();
72 target = valueFactory ();
78 static T GetDefaultCtorValue<T> ()
81 return Activator.CreateInstance<T> ();
83 throw new MissingMemberException ("The type being lazily initialized does not have a "
84 + "public, parameterless constructor.");