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

   1 //
   2 // LazyInitializer.cs
   3 //
   4 // Author:
   5 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   6 //
   7 // Copyright (c) 2009 Jérémie "Garuma" Laval
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining a copy
  10 // of this software and associated documentation files (the "Software"), to deal
  11 // in the Software without restriction, including without limitation the rights
  12 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13 // copies of the Software, and to permit persons to whom the Software is
  14 // furnished to do so, subject to the following conditions:
  15 //
  16 // The above copyright notice and this permission notice shall be included in
  17 // all copies or substantial portions of the Software.
  18 //
  19 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25 // THE SOFTWARE.
  26
  27 #if NET_4_0 || BOOTSTRAP_NET_4_0
  28
  29 using System;
  30
  31 namespace System.Threading
  32 {
  33         public static class LazyInitializer
  34         {
  35                 public static T EnsureInitialized<T> (ref T target) where T : class
  36                 {
  37                         return EnsureInitialized (ref target, GetDefaultCtorValue<T>);
  38                 }
  39
  40                 public static T EnsureInitialized<T> (ref T target, Func<T> initFunc) where T : class
  41                 {
  42                         if (target == null)
  43                                 Interlocked.CompareExchange (ref target, initFunc (), null);
  44
  45                         return target;
  46                 }
  47
  48                 public static T EnsureInitialized<T> (ref T target, ref bool initialized, ref object syncRoot)
  49                 {
  50                         return EnsureInitialized (ref target, ref initialized, ref syncRoot, GetDefaultCtorValue<T>);
  51                 }
  52
  53                 public static T EnsureInitialized<T> (ref T target, ref bool initialized, ref object syncRoot, Func<T> initFunc)
  54                 {
  55                         lock (syncRoot) {
  56                                 if (initialized)
  57                                         return target;
  58
  59                                 initialized = true;
  60                                 return target = initFunc ();
  61                         }
  62                 }
  63
  64                 internal static T GetDefaultCtorValue<T> ()
  65                 {
  66                         try {
  67                                 return Activator.CreateInstance<T> ();
  68                         } catch {
  69                                 throw new MissingMemberException ("The type being lazily initialized does not have a "
  70                                                                   + "public, parameterless constructor.");
  71                         }
  72                 }
  73         }
  74 }
  75 #endif