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

   1 //
   2 // CancellationTokenSource.cs
   3 //
   4 // Authors:
   5 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   6 //       Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Copyright (c) 2009 Jérémie "Garuma" Laval
   9 // Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining a copy
  12 // of this software and associated documentation files (the "Software"), to deal
  13 // in the Software without restriction, including without limitation the rights
  14 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15 // copies of the Software, and to permit persons to whom the Software is
  16 // furnished to do so, subject to the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be included in
  19 // all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  22 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  23 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  24 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  25 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  26 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  27 // THE SOFTWARE.
  28
  29 #if NET_4_0
  30 using System.Collections.Generic;
  31 using System.Collections.Concurrent;
  32
  33 namespace System.Threading
  34 {
  35 #if !NET_4_5
  36         sealed
  37 #endif
  38         public class CancellationTokenSource : IDisposable
  39         {
  40                 bool canceled;
  41                 bool disposed;
  42
  43                 int currId = int.MinValue;
  44                 ConcurrentDictionary<CancellationTokenRegistration, Action> callbacks;
  45                 CancellationTokenRegistration[] linkedTokens;
  46
  47                 ManualResetEvent handle;
  48
  49                 internal static readonly CancellationTokenSource NoneSource = new CancellationTokenSource ();
  50                 internal static readonly CancellationTokenSource CanceledSource = new CancellationTokenSource ();
  51
  52 #if NET_4_5
  53                 static readonly TimerCallback timer_callback;
  54                 Timer timer;
  55 #endif
  56
  57                 static CancellationTokenSource ()
  58                 {
  59                         CanceledSource.canceled = true;
  60
  61 #if NET_4_5
  62                         timer_callback = token => {
  63                                 var cts = (CancellationTokenSource) token;
  64                                 cts.Cancel ();
  65                         };
  66 #endif
  67                 }
  68
  69                 public CancellationTokenSource ()
  70                 {
  71                         callbacks = new ConcurrentDictionary<CancellationTokenRegistration, Action> ();
  72                         handle = new ManualResetEvent (false);
  73                 }
  74
  75 #if NET_4_5
  76                 public CancellationTokenSource (int millisecondsDelay)
  77                         : this ()
  78                 {
  79                         if (millisecondsDelay < -1)
  80                                 throw new ArgumentOutOfRangeException ("millisecondsDelay");
  81
  82                         if (millisecondsDelay != Timeout.Infinite)
  83                                 timer = new Timer (timer_callback, this, millisecondsDelay, Timeout.Infinite);
  84                 }
  85
  86                 public CancellationTokenSource (TimeSpan delay)
  87                         : this (CheckTimeout (delay))
  88                 {
  89                 }
  90 #endif
  91
  92                 public CancellationToken Token {
  93                         get {
  94                                 CheckDisposed ();
  95                                 return new CancellationToken (this);
  96                         }
  97                 }
  98
  99                 public bool IsCancellationRequested {
 100                         get {
 101                                 return canceled;
 102                         }
 103                 }
 104
 105                 internal WaitHandle WaitHandle {
 106                         get {
 107                                 CheckDisposed ();
 108                                 return handle;
 109                         }
 110                 }
 111
 112                 public void Cancel ()
 113                 {
 114                         Cancel (false);
 115                 }
 116
 117                 // If parameter is true we throw exception as soon as they appear otherwise we aggregate them
 118                 public void Cancel (bool throwOnFirstException)
 119                 {
 120                         CheckDisposed ();
 121
 122                         if (canceled)
 123                                 return;
 124
 125                         Thread.MemoryBarrier ();
 126                         canceled = true;
 127
 128                         handle.Set ();
 129                         if (linkedTokens != null)
 130                                 UnregisterLinkedTokens ();
 131
 132                         List<Exception> exceptions = null;
 133
 134                         try {
 135                                 Action cb;
 136                                 for (int id = int.MinValue + 1; id <= currId; id++) {
 137                                         if (!callbacks.TryRemove (new CancellationTokenRegistration (id, this), out cb))
 138                                                 continue;
 139                                         if (cb == null)
 140                                                 continue;
 141
 142                                         if (throwOnFirstException) {
 143                                                 cb ();
 144                                         } else {
 145                                                 try {
 146                                                         cb ();
 147                                                 } catch (Exception e) {
 148                                                         if (exceptions == null)
 149                                                                 exceptions = new List<Exception> ();
 150
 151                                                         exceptions.Add (e);
 152                                                 }
 153                                         }
 154                                 }
 155                         } finally {
 156                                 callbacks.Clear ();
 157                         }
 158
 159                         if (exceptions != null)
 160                                 throw new AggregateException (exceptions);
 161                 }
 162
 163                 /* This is the callback registered on linked tokens
 164                  * so that they don't throw an ODE if the callback
 165                  * is called concurrently with a Dispose
 166                  */
 167                 void SafeLinkedCancel ()
 168                 {
 169                         try {
 170                                 Cancel ();
 171                         } catch (ObjectDisposedException) {}
 172                 }
 173
 174 #if NET_4_5
 175                 public void CancelAfter (TimeSpan delay)
 176                 {
 177                         CancelAfter (CheckTimeout (delay));
 178                 }
 179
 180                 public void CancelAfter (int millisecondsDelay)
 181                 {
 182                         if (millisecondsDelay < -1)
 183                                 throw new ArgumentOutOfRangeException ("millisecondsDelay");
 184
 185                         CheckDisposed ();
 186
 187                         if (canceled || millisecondsDelay == Timeout.Infinite)
 188                                 return;
 189
 190                         if (timer == null) {
 191                                 // Have to be carefull not to create secondary background timer
 192                                 var t = new Timer (timer_callback, this, Timeout.Infinite, Timeout.Infinite);
 193                                 if (Interlocked.CompareExchange (ref timer, t, null) != null)
 194                                         t.Dispose ();
 195                         }
 196
 197                         timer.Change (millisecondsDelay, Timeout.Infinite);
 198                 }
 199 #endif
 200
 201                 public static CancellationTokenSource CreateLinkedTokenSource (CancellationToken token1, CancellationToken token2)
 202                 {
 203                         return CreateLinkedTokenSource (new [] { token1, token2 });
 204                 }
 205
 206                 public static CancellationTokenSource CreateLinkedTokenSource (params CancellationToken[] tokens)
 207                 {
 208                         if (tokens == null)
 209                                 throw new ArgumentNullException ("tokens");
 210
 211                         if (tokens.Length == 0)
 212                                 throw new ArgumentException ("Empty tokens array");
 213
 214                         CancellationTokenSource src = new CancellationTokenSource ();
 215                         Action action = src.SafeLinkedCancel;
 216                         var registrations = new List<CancellationTokenRegistration> (tokens.Length);
 217
 218                         foreach (CancellationToken token in tokens) {
 219                                 if (token.CanBeCanceled)
 220                                         registrations.Add (token.Register (action));
 221                         }
 222                         src.linkedTokens = registrations.ToArray ();
 223
 224                         return src;
 225                 }
 226
 227                 static int CheckTimeout (TimeSpan delay)
 228                 {
 229                         try {
 230                                 return checked ((int) delay.TotalMilliseconds);
 231                         } catch (OverflowException) {
 232                                 throw new ArgumentOutOfRangeException ("delay");
 233                         }
 234                 }
 235
 236                 void CheckDisposed ()
 237                 {
 238                         if (disposed)
 239                                 throw new ObjectDisposedException (GetType ().Name);
 240                 }
 241
 242                 public void Dispose ()
 243                 {
 244                         Dispose (true);
 245                 }
 246
 247 #if NET_4_5
 248                 protected virtual
 249 #endif
 250                 void Dispose (bool disposing)
 251                 {
 252                         if (disposing && !disposed) {
 253                                 Thread.MemoryBarrier ();
 254                                 disposed = true;
 255
 256                                 if (!canceled) {
 257                                         Thread.MemoryBarrier ();
 258                                         UnregisterLinkedTokens ();
 259                                         callbacks = null;
 260                                 }
 261 #if NET_4_5
 262                                 if (timer != null)
 263                                         timer.Dispose ();
 264 #endif
 265                                 handle.Dispose ();
 266                         }
 267                 }
 268
 269                 void UnregisterLinkedTokens ()
 270                 {
 271                         var registrations = Interlocked.Exchange (ref linkedTokens, null);
 272                         if (registrations == null)
 273                                 return;
 274                         foreach (var linked in registrations)
 275                                 linked.Dispose ();
 276                 }
 277
 278                 internal CancellationTokenRegistration Register (Action callback, bool useSynchronizationContext)
 279                 {
 280                         CheckDisposed ();
 281
 282                         var tokenReg = new CancellationTokenRegistration (Interlocked.Increment (ref currId), this);
 283
 284                         /* If the source is already canceled we execute the callback immediately
 285                          * if not, we try to add it to the queue and if it is currently being processed
 286                          * we try to execute it back ourselves to be sure the callback is ran
 287                          */
 288                         if (canceled)
 289                                 callback ();
 290                         else {
 291                                 callbacks.TryAdd (tokenReg, callback);
 292                                 if (canceled && callbacks.TryRemove (tokenReg, out callback))
 293                                         callback ();
 294                         }
 295
 296                         return tokenReg;
 297                 }
 298
 299                 internal void RemoveCallback (CancellationTokenRegistration reg)
 300                 {
 301                         // Ignore call if the source has been disposed
 302                         if (disposed)
 303                                 return;
 304                         Action dummy;
 305                         var cbs = callbacks;
 306                         if (cbs != null)
 307                                 cbs.TryRemove (reg, out dummy);
 308                 }
 309         }
 310 }
 311 #endif