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.CancelSafe ();
  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                         Cancellation (throwOnFirstException);
 122                 }
 123
 124                 //
 125                 // Don't throw ObjectDisposedException if the callback
 126                 // is called concurrently with a Dispose
 127                 //
 128                 public void CancelSafe ()
 129                 {
 130                         if (!disposed)
 131                                 Cancellation (true);
 132                 }
 133
 134                 void Cancellation (bool throwOnFirstException)
 135                 {
 136                         if (canceled)
 137                                 return;
 138
 139                         Thread.MemoryBarrier ();
 140                         canceled = true;
 141
 142                         Thread.MemoryBarrier ();
 143
 144                         // Dispose might be running at same time
 145                         if (!disposed)
 146                                 handle.Set ();
 147
 148                         if (linkedTokens != null)
 149                                 UnregisterLinkedTokens ();
 150
 151                         var cbs = callbacks;
 152                         if (cbs == null)
 153                                 return;
 154
 155                         List<Exception> exceptions = null;
 156
 157                         try {
 158                                 Action cb;
 159                                 for (int id = currId; id != int.MinValue; id--) {
 160                                         if (!cbs.TryRemove (new CancellationTokenRegistration (id, this), out cb))
 161                                                 continue;
 162                                         if (cb == null)
 163                                                 continue;
 164
 165                                         if (throwOnFirstException) {
 166                                                 cb ();
 167                                         } else {
 168                                                 try {
 169                                                         cb ();
 170                                                 } catch (Exception e) {
 171                                                         if (exceptions == null)
 172                                                                 exceptions = new List<Exception> ();
 173
 174                                                         exceptions.Add (e);
 175                                                 }
 176                                         }
 177                                 }
 178                         } finally {
 179                                 cbs.Clear ();
 180                         }
 181
 182                         if (exceptions != null)
 183                                 throw new AggregateException (exceptions);
 184                 }
 185
 186 #if NET_4_5
 187                 public void CancelAfter (TimeSpan delay)
 188                 {
 189                         CancelAfter (CheckTimeout (delay));
 190                 }
 191
 192                 public void CancelAfter (int millisecondsDelay)
 193                 {
 194                         if (millisecondsDelay < -1)
 195                                 throw new ArgumentOutOfRangeException ("millisecondsDelay");
 196
 197                         CheckDisposed ();
 198
 199                         if (canceled || millisecondsDelay == Timeout.Infinite)
 200                                 return;
 201
 202                         if (timer == null) {
 203                                 // Have to be carefull not to create secondary background timer
 204                                 var t = new Timer (timer_callback, this, Timeout.Infinite, Timeout.Infinite);
 205                                 if (Interlocked.CompareExchange (ref timer, t, null) != null)
 206                                         t.Dispose ();
 207                         }
 208
 209                         timer.Change (millisecondsDelay, Timeout.Infinite);
 210                 }
 211 #endif
 212
 213                 public static CancellationTokenSource CreateLinkedTokenSource (CancellationToken token1, CancellationToken token2)
 214                 {
 215                         return CreateLinkedTokenSource (new [] { token1, token2 });
 216                 }
 217
 218                 public static CancellationTokenSource CreateLinkedTokenSource (params CancellationToken[] tokens)
 219                 {
 220                         if (tokens == null)
 221                                 throw new ArgumentNullException ("tokens");
 222
 223                         if (tokens.Length == 0)
 224                                 throw new ArgumentException ("Empty tokens array");
 225
 226                         CancellationTokenSource src = new CancellationTokenSource ();
 227                         Action action = src.CancelSafe;
 228                         var registrations = new List<CancellationTokenRegistration> (tokens.Length);
 229
 230                         foreach (CancellationToken token in tokens) {
 231                                 if (token.CanBeCanceled)
 232                                         registrations.Add (token.Register (action));
 233                         }
 234                         src.linkedTokens = registrations.ToArray ();
 235
 236                         return src;
 237                 }
 238
 239                 static int CheckTimeout (TimeSpan delay)
 240                 {
 241                         try {
 242                                 return checked ((int) delay.TotalMilliseconds);
 243                         } catch (OverflowException) {
 244                                 throw new ArgumentOutOfRangeException ("delay");
 245                         }
 246                 }
 247
 248                 void CheckDisposed ()
 249                 {
 250                         if (disposed)
 251                                 throw new ObjectDisposedException (GetType ().Name);
 252                 }
 253
 254                 public void Dispose ()
 255                 {
 256                         Dispose (true);
 257                 }
 258
 259 #if NET_4_5
 260                 protected virtual
 261 #endif
 262                 void Dispose (bool disposing)
 263                 {
 264                         if (disposing && !disposed) {
 265                                 disposed = true;
 266                                 Thread.MemoryBarrier ();
 267
 268                                 if (!canceled) {
 269                                         UnregisterLinkedTokens ();
 270                                         callbacks = null;
 271                                 } else {
 272                                         handle.WaitOne ();
 273                                 }
 274 #if NET_4_5
 275                                 if (timer != null)
 276                                         timer.Dispose ();
 277 #endif
 278
 279                                 handle.Dispose ();
 280                         }
 281                 }
 282
 283                 void UnregisterLinkedTokens ()
 284                 {
 285                         var registrations = Interlocked.Exchange (ref linkedTokens, null);
 286                         if (registrations == null)
 287                                 return;
 288                         foreach (var linked in registrations)
 289                                 linked.Dispose ();
 290                 }
 291
 292                 internal CancellationTokenRegistration Register (Action callback, bool useSynchronizationContext)
 293                 {
 294                         CheckDisposed ();
 295
 296                         var tokenReg = new CancellationTokenRegistration (Interlocked.Increment (ref currId), this);
 297
 298                         /* If the source is already canceled we execute the callback immediately
 299                          * if not, we try to add it to the queue and if it is currently being processed
 300                          * we try to execute it back ourselves to be sure the callback is ran
 301                          */
 302                         if (canceled)
 303                                 callback ();
 304                         else {
 305                                 callbacks.TryAdd (tokenReg, callback);
 306                                 if (canceled && callbacks.TryRemove (tokenReg, out callback))
 307                                         callback ();
 308                         }
 309
 310                         return tokenReg;
 311                 }
 312
 313                 internal void RemoveCallback (CancellationTokenRegistration reg)
 314                 {
 315                         // Ignore call if the source has been disposed
 316                         if (disposed)
 317                                 return;
 318                         Action dummy;
 319                         var cbs = callbacks;
 320                         if (cbs != null)
 321                                 cbs.TryRemove (reg, out dummy);
 322                 }
 323         }
 324 }
 325 #endif