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

   1 //
   2 // ThreadLocal.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
  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> : IDisposable
  38         {
  39                 readonly Func<T> initializer;
  40                 LocalDataStoreSlot localStore;
  41                 Exception cachedException;
  42
  43                 class DataSlotWrapper
  44                 {
  45                         public bool Creating;
  46                         public bool Init;
  47                         public Func<T> Getter;
  48                 }
  49
  50                 public ThreadLocal () : this (LazyInitializer.GetDefaultCtorValue<T>)
  51                 {
  52                 }
  53
  54                 public ThreadLocal (Func<T> initializer)
  55                 {
  56                         if (initializer == null)
  57                                 throw new ArgumentNullException ("initializer");
  58
  59                         localStore = Thread.AllocateDataSlot ();
  60                         this.initializer = initializer;
  61                 }
  62
  63                 public void Dispose ()
  64                 {
  65                         Dispose (true);
  66                 }
  67
  68                 protected virtual void Dispose (bool dispManagedRes)
  69                 {
  70
  71                 }
  72
  73                 public bool IsValueCreated {
  74                         get {
  75                                 ThrowIfNeeded ();
  76                                 return IsInitializedThreadLocal ();
  77                         }
  78                 }
  79
  80                 public T Value {
  81                         get {
  82                                 ThrowIfNeeded ();
  83                                 return GetValueThreadLocal ();
  84                         }
  85                         set {
  86                                 ThrowIfNeeded ();
  87
  88                                 DataSlotWrapper w = GetWrapper ();
  89                                 w.Init = true;
  90                                 w.Getter = () => value;
  91                         }
  92                 }
  93
  94                 public override string ToString ()
  95                 {
  96                         return string.Format ("[ThreadLocal: IsValueCreated={0}, Value={1}]", IsValueCreated, Value);
  97                 }
  98
  99
 100                 T GetValueThreadLocal ()
 101                 {
 102                         DataSlotWrapper myWrapper = GetWrapper ();
 103                         if (myWrapper.Creating)
 104                                 throw new InvalidOperationException ("The initialization function attempted to reference Value recursively");
 105
 106                         return myWrapper.Getter ();
 107                 }
 108
 109                 bool IsInitializedThreadLocal ()
 110                 {
 111                         DataSlotWrapper myWrapper = GetWrapper ();
 112
 113                         return myWrapper.Init;
 114                 }
 115
 116                 DataSlotWrapper GetWrapper ()
 117                 {
 118                         DataSlotWrapper myWrapper = (DataSlotWrapper)Thread.GetData (localStore);
 119                         if (myWrapper == null) {
 120                                 myWrapper = DataSlotCreator ();
 121                                 Thread.SetData (localStore, myWrapper);
 122                         }
 123
 124                         return myWrapper;
 125                 }
 126
 127                 void ThrowIfNeeded ()
 128                 {
 129                         if (cachedException != null)
 130                                 throw cachedException;
 131                 }
 132
 133                 DataSlotWrapper DataSlotCreator ()
 134                 {
 135                         DataSlotWrapper wrapper = new DataSlotWrapper ();
 136                         Func<T> valSelector = initializer;
 137
 138                         wrapper.Getter = delegate {
 139                                 wrapper.Creating = true;
 140                                 try {
 141                                         T val = valSelector ();
 142                                         wrapper.Creating = false;
 143                                         wrapper.Init = true;
 144                                         wrapper.Getter = () => val;
 145                                         return val;
 146                                 } catch (Exception e) {
 147                                         cachedException = e;
 148                                         throw e;
 149                                 }
 150                         };
 151
 152                         return wrapper;
 153                 }
 154         }
 155 }
 156 #endif