mcs/class/corlib/System.Threading/LazyInitializer.cs

   1 #if NET_4_0
   2 //
   3 // LazyInitializer.cs
   4 //
   5 // Author:
   6 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   7 //
   8 // Copyright (c) 2009 Jérémie "Garuma" Laval
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining a copy
  11 // of this software and associated documentation files (the "Software"), to deal
  12 // in the Software without restriction, including without limitation the rights
  13 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  14 // copies of the Software, and to permit persons to whom the Software is
  15 // furnished to do so, subject to the following conditions:
  16 //
  17 // The above copyright notice and this permission notice shall be included in
  18 // all copies or substantial portions of the Software.
  19 //
  20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  21 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  22 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  23 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  24 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  25 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  26 // THE SOFTWARE.
  27
  28 using System;
  29
  30 namespace System.Threading
  31 {
  32         public static class LazyInitializer
  33         {
  34                 public static T EnsureInitialized<T> (ref T target) where T : class
  35                 {
  36                         return EnsureInitialized (ref target, GetDefaultCtorValue<T>);
  37                 }
  38
  39                 public static T EnsureInitialized<T> (ref T target, Func<T> initFunc) where T : class
  40                 {
  41                         Interlocked.CompareExchange (ref target, initFunc (), null);
  42
  43                         return target;
  44                 }
  45
  46                 public static T EnsureInitialized<T> (ref T target, ref bool initialized, ref object syncRoot)
  47                 {
  48                         return EnsureInitialized (ref target, ref initialized, ref syncRoot, GetDefaultCtorValue<T>);
  49                 }
  50
  51                 public static T EnsureInitialized<T> (ref T target, ref bool initialized, ref object syncRoot, Func<T> initFunc)
  52                 {
  53                         lock (syncRoot) {
  54                                 if (initialized)
  55                                         return target;
  56
  57                                 initialized = true;
  58                                 return target = initFunc ();
  59                         }
  60                 }
  61
  62                 internal static T GetDefaultCtorValue<T> ()
  63                 {
  64                         try {
  65                                 return Activator.CreateInstance<T> ();
  66                         } catch {
  67                                 throw new MissingMemberException ("The type being lazily initialized does not have a "
  68                                                                   + "public, parameterless constructor.");
  69                         }
  70                 }
  71         }
  72 }
  73 #endif