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

   1 #if NET_4_0
   2 //
   3 // ThreadLocal.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 using System.Runtime.Serialization;
  30 using System.Runtime.InteropServices;
  31 using System.Security.Permissions;
  32
  33 namespace System.Threading
  34 {
  35         [HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true,
  36                                  ExternalThreading = true)]
  37         public class ThreadLocal<T>
  38         {
  39                 readonly Func<T> initializer;
  40                 LocalDataStoreSlot localStore;
  41
  42                 class DataSlotWrapper
  43                 {
  44                         public bool Init;
  45                         public Func<T> Getter;
  46                 }
  47
  48                 public ThreadLocal () : this (LazyInitializer.GetDefaultCtorValue<T>)
  49                 {
  50                 }
  51
  52                 public ThreadLocal (Func<T> initializer)
  53                 {
  54                         if (initializer == null)
  55                                 throw new ArgumentNullException ("initializer");
  56
  57                         localStore = Thread.AllocateDataSlot ();
  58                         this.initializer = initializer;
  59                 }
  60
  61                 public bool IsValueCreated {
  62                         get {
  63                                 return IsInitializedThreadLocal ();
  64                         }
  65                 }
  66
  67                 public T Value {
  68                         get {
  69                                 return GetValueThreadLocal ();
  70                         }
  71                 }
  72
  73                 public override string ToString ()
  74                 {
  75                         return string.Format("[ThreadLocal: IsValueCreated={0}, Value={1}]", IsValueCreated, Value);
  76                 }
  77
  78
  79                 T GetValueThreadLocal ()
  80                 {
  81                         DataSlotWrapper myWrapper = Thread.GetData (localStore) as DataSlotWrapper;
  82                         // In case it's the first time the Thread access its data
  83                         if (myWrapper == null) {
  84                                 myWrapper = DataSlotCreator ();
  85                                 Thread.SetData (localStore, myWrapper);
  86                         }
  87
  88                         return myWrapper.Getter();
  89                 }
  90
  91                 bool IsInitializedThreadLocal ()
  92                 {
  93                         DataSlotWrapper myWrapper = (DataSlotWrapper)Thread.GetData (localStore);
  94                         if (myWrapper == null) {
  95                                 myWrapper = DataSlotCreator ();
  96                                 Thread.SetData (localStore, myWrapper);
  97                         }
  98
  99                         return myWrapper.Init;
 100                 }
 101
 102                 DataSlotWrapper DataSlotCreator ()
 103                 {
 104                         DataSlotWrapper wrapper = new DataSlotWrapper ();
 105                         Func<T> valSelector = initializer;
 106
 107                         wrapper.Getter = delegate {
 108                                 T val = valSelector ();
 109                                 wrapper.Init = true;
 110                                 wrapper.Getter = delegate { return val; };
 111                                 return val;
 112                         };
 113
 114                         return wrapper;
 115                 }
 116         }
 117 }
 118 #endif