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

   1 //
   2 // ThreadLocal.cs
   3 //
   4 // Author:
   5 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   6 //       Rewritten by Paolo Molaro (lupus@ximian.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 #if NET_4_0
  29 using System;
  30 using System.Collections.Generic;
  31 using System.Runtime.Serialization;
  32 using System.Runtime.InteropServices;
  33 using System.Security.Permissions;
  34
  35 namespace System.Threading
  36 {
  37         [HostProtection (SecurityAction.LinkDemand, Synchronization = true, ExternalThreading = true)]
  38         [System.Diagnostics.DebuggerDisplay ("IsValueCreated={IsValueCreated}, Value={ValueForDebugDisplay}")]
  39         [System.Diagnostics.DebuggerTypeProxy ("System.Threading.SystemThreading_ThreadLocalDebugView`1")]
  40         public class ThreadLocal<T> : IDisposable
  41         {
  42                 struct TlsDatum {
  43                         internal sbyte state; /* 0 uninitialized, < 0 initializing, > 0 inited */
  44                         internal Exception cachedException; /* this is per-thread */
  45                         internal T data;
  46                 }
  47
  48                 Func<T> valueFactory;
  49                 /* The tlsdata field is handled magically by the JIT
  50                  * It must be a struct and it is always accessed by ldflda: the JIT, instead of
  51                  * computing the address inside the instance, will return the address of the variable
  52                  * for the current thread (based on tls_offset). This magic wouldn't be needed if C#
  53                  * let us declare an icall with a TlsDatum& return type...
  54                  * For this same reason, we must check tls_offset for != 0 to make sure it's valid before accessing tlsdata
  55                  * The address of the tls var is cached per method at the first IL ldflda instruction, so care must be taken
  56                  * not to cause it to be conditionally executed.
  57                  */
  58                 uint tls_offset;
  59                 TlsDatum tlsdata;
  60
  61                 public ThreadLocal ()
  62                 {
  63                         tls_offset = Thread.AllocTlsData (typeof (TlsDatum));
  64                 }
  65
  66                 public ThreadLocal (Func<T> valueFactory) : this ()
  67                 {
  68                         if (valueFactory == null)
  69                                 throw new ArgumentNullException ("valueFactory");
  70                         this.valueFactory = valueFactory;
  71                 }
  72
  73 #if NET_4_5
  74                 public ThreadLocal (bool trackAllValues) : this () {
  75                         if (trackAllValues)
  76                                 throw new NotImplementedException ();
  77                 }
  78
  79                 public ThreadLocal (Func<T> valueFactory, bool trackAllValues) : this (valueFactory) {
  80                         if (trackAllValues)
  81                                 throw new NotImplementedException ();
  82                 }
  83 #endif
  84
  85                 public void Dispose ()
  86                 {
  87                         Dispose (true);
  88                 }
  89
  90                 protected virtual void Dispose (bool disposing)
  91                 {
  92                         if (tls_offset != 0) {
  93                                 uint o = tls_offset;
  94                                 tls_offset = 0;
  95                                 if (disposing)
  96                                         valueFactory = null;
  97                                 Thread.DestroyTlsData (o);
  98                                 GC.SuppressFinalize (this);
  99                         }
 100                 }
 101
 102                 ~ThreadLocal ()
 103                 {
 104                         Dispose (false);
 105                 }
 106
 107                 public bool IsValueCreated {
 108                         get {
 109                                 if (tls_offset == 0)
 110                                         throw new ObjectDisposedException ("ThreadLocal object");
 111                                 /* ALERT! magic tlsdata JIT access redirects to TLS value instead of instance field */
 112                                 return tlsdata.state > 0;
 113                         }
 114                 }
 115
 116                 T GetSlowPath () {
 117                         /* ALERT! magic tlsdata JIT access redirects to TLS value instead of instance field */
 118                         if (tlsdata.cachedException != null)
 119                                 throw tlsdata.cachedException;
 120                         if (tlsdata.state < 0)
 121                                 throw new InvalidOperationException ("The initialization function attempted to reference Value recursively");
 122                         tlsdata.state = -1;
 123                         if (valueFactory != null) {
 124                                 try {
 125                                         tlsdata.data = valueFactory ();
 126                                 } catch (Exception ex) {
 127                                         tlsdata.cachedException = ex;
 128                                         throw ex;
 129                                 }
 130                         } else {
 131                                 tlsdata.data = default (T);
 132                         }
 133                         tlsdata.state = 1;
 134                         return tlsdata.data;
 135                 }
 136
 137                 [System.Diagnostics.DebuggerBrowsableAttribute (System.Diagnostics.DebuggerBrowsableState.Never)]
 138                 public T Value {
 139                         get {
 140                                 if (tls_offset == 0)
 141                                         throw new ObjectDisposedException ("ThreadLocal object");
 142                                 /* ALERT! magic tlsdata JIT access redirects to TLS value instead of instance field */
 143                                 if (tlsdata.state > 0)
 144                                         return tlsdata.data;
 145                                 return GetSlowPath ();
 146                         }
 147                         set {
 148                                 if (tls_offset == 0)
 149                                         throw new ObjectDisposedException ("ThreadLocal object");
 150                                 /* ALERT! magic tlsdata JIT access redirects to TLS value instead of instance field */
 151                                 tlsdata.state = 1;
 152                                 tlsdata.data = value;
 153                         }
 154                 }
 155
 156 #if NET_4_5
 157                 public IList<T> Values {
 158                         get {
 159                                 if (tls_offset == 0)
 160                                         throw new ObjectDisposedException ("ThreadLocal object");
 161                                 throw new NotImplementedException ();
 162                         }
 163                 }
 164 #endif
 165
 166                 public override string ToString ()
 167                 {
 168                         return string.Format ("[ThreadLocal: IsValueCreated={0}, Value={1}]", IsValueCreated, Value);
 169                 }
 170
 171         }
 172 }
 173 #endif