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 || MOBILE
  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
  46                 ManualResetEvent handle;
  47
  48                 internal static readonly CancellationTokenSource NoneSource = new CancellationTokenSource ();
  49                 internal static readonly CancellationTokenSource CanceledSource = new CancellationTokenSource ();
  50
  51 #if NET_4_5
  52                 static readonly TimerCallback timer_callback;
  53                 Timer timer;
  54 #endif
  55
  56                 static CancellationTokenSource ()
  57                 {
  58                         CanceledSource.canceled = true;
  59
  60 #if NET_4_5
  61                         timer_callback = token => {
  62                                 var cts = (CancellationTokenSource) token;
  63                                 cts.Cancel ();
  64                         };
  65 #endif
  66                 }
  67
  68                 public CancellationTokenSource ()
  69                 {
  70                         callbacks = new ConcurrentDictionary<CancellationTokenRegistration, Action> ();
  71                         handle = new ManualResetEvent (false);
  72                 }
  73
  74 #if NET_4_5
  75                 public CancellationTokenSource (int millisecondsDelay)
  76                         : this ()
  77                 {
  78                         if (millisecondsDelay < -1)
  79                                 throw new ArgumentOutOfRangeException ("millisecondsDelay");
  80
  81                         if (millisecondsDelay != Timeout.Infinite)
  82                                 timer = new Timer (timer_callback, this, millisecondsDelay, Timeout.Infinite);
  83                 }
  84
  85                 public CancellationTokenSource (TimeSpan delay)
  86                         : this (CheckTimeout (delay))
  87                 {
  88                 }
  89 #endif
  90
  91                 public CancellationToken Token {
  92                         get {
  93                                 CheckDisposed ();
  94                                 return new CancellationToken (this);
  95                         }
  96                 }
  97
  98                 public bool IsCancellationRequested {
  99                         get {
 100                                 return canceled;
 101                         }
 102                 }
 103
 104                 internal WaitHandle WaitHandle {
 105                         get {
 106                                 CheckDisposed ();
 107                                 return handle;
 108                         }
 109                 }
 110
 111                 public void Cancel ()
 112                 {
 113                         Cancel (false);
 114                 }
 115
 116                 // If parameter is true we throw exception as soon as they appear otherwise we aggregate them
 117                 public void Cancel (bool throwOnFirstException)
 118                 {
 119                         CheckDisposed ();
 120
 121                         canceled = true;
 122                         handle.Set ();
 123
 124                         List<Exception> exceptions = null;
 125
 126                         try {
 127                                 Action cb;
 128                                 for (int id = int.MinValue + 1; id <= currId; id++) {
 129                                         if (!callbacks.TryRemove (new CancellationTokenRegistration (id, this), out cb))
 130                                                 continue;
 131                                         if (cb == null)
 132                                                 continue;
 133
 134                                         if (throwOnFirstException) {
 135                                                 cb ();
 136                                         } else {
 137                                                 try {
 138                                                         cb ();
 139                                                 } catch (Exception e) {
 140                                                         if (exceptions == null)
 141                                                                 exceptions = new List<Exception> ();
 142
 143                                                         exceptions.Add (e);
 144                                                 }
 145                                         }
 146                                 }
 147                         } finally {
 148                                 callbacks.Clear ();
 149                         }
 150
 151                         if (exceptions != null)
 152                                 throw new AggregateException (exceptions);
 153                 }
 154
 155 #if NET_4_5
 156                 public void CancelAfter (TimeSpan delay)
 157                 {
 158                         CancelAfter (CheckTimeout (delay));
 159                 }
 160
 161                 public void CancelAfter (int millisecondsDelay)
 162                 {
 163                         if (millisecondsDelay < -1)
 164                                 throw new ArgumentOutOfRangeException ("millisecondsDelay");
 165
 166                         CheckDisposed ();
 167
 168                         if (canceled || millisecondsDelay == Timeout.Infinite)
 169                                 return;
 170
 171                         if (timer == null) {
 172                                 // Have to be carefull not to create secondary background timer
 173                                 var t = new Timer (timer_callback, this, Timeout.Infinite, Timeout.Infinite);
 174                                 if (Interlocked.CompareExchange (ref timer, t, null) != null)
 175                                         t.Dispose ();
 176                         }
 177
 178                         timer.Change (millisecondsDelay, Timeout.Infinite);
 179                 }
 180 #endif
 181
 182                 public static CancellationTokenSource CreateLinkedTokenSource (CancellationToken token1, CancellationToken token2)
 183                 {
 184                         return CreateLinkedTokenSource (new [] { token1, token2 });
 185                 }
 186
 187                 public static CancellationTokenSource CreateLinkedTokenSource (params CancellationToken[] tokens)
 188                 {
 189                         if (tokens == null)
 190                                 throw new ArgumentNullException ("tokens");
 191
 192                         if (tokens.Length == 0)
 193                                 throw new ArgumentException ("Empty tokens array");
 194
 195                         CancellationTokenSource src = new CancellationTokenSource ();
 196                         Action action = src.Cancel;
 197
 198                         foreach (CancellationToken token in tokens) {
 199                                 if (token.CanBeCanceled)
 200                                         token.Register (action);
 201                         }
 202
 203                         return src;
 204                 }
 205
 206                 static int CheckTimeout (TimeSpan delay)
 207                 {
 208                         try {
 209                                 return checked ((int) delay.TotalMilliseconds);
 210                         } catch (OverflowException) {
 211                                 throw new ArgumentOutOfRangeException ("delay");
 212                         }
 213                 }
 214
 215                 void CheckDisposed ()
 216                 {
 217                         if (disposed)
 218                                 throw new ObjectDisposedException (GetType ().Name);
 219                 }
 220
 221                 public void Dispose ()
 222                 {
 223                         Dispose (true);
 224                 }
 225
 226 #if NET_4_5
 227                 protected virtual
 228 #endif
 229                 void Dispose (bool disposing)
 230                 {
 231                         if (disposing && !disposed) {
 232                                 disposed = true;
 233                                 Thread.MemoryBarrier ();
 234
 235                                 callbacks = null;
 236 #if NET_4_5
 237                                 if (timer != null)
 238                                         timer.Dispose ();
 239 #endif
 240                                 handle.Dispose ();
 241                         }
 242                 }
 243
 244                 internal CancellationTokenRegistration Register (Action callback, bool useSynchronizationContext)
 245                 {
 246                         CheckDisposed ();
 247
 248                         var tokenReg = new CancellationTokenRegistration (Interlocked.Increment (ref currId), this);
 249
 250                         /* If the source is already canceled we execute the callback immediately
 251                          * if not, we try to add it to the queue and if it is currently being processed
 252                          * we try to execute it back ourselves to be sure the callback is ran
 253                          */
 254                         if (canceled)
 255                                 callback ();
 256                         else {
 257                                 callbacks.TryAdd (tokenReg, callback);
 258                                 if (canceled && callbacks.TryRemove (tokenReg, out callback))
 259                                         callback ();
 260                         }
 261
 262                         return tokenReg;
 263                 }
 264
 265                 internal void RemoveCallback (CancellationTokenRegistration reg)
 266                 {
 267                         // Ignore call if the source has been disposed
 268                         if (disposed)
 269                                 return;
 270                         Action dummy;
 271                         var cbs = callbacks;
 272                         if (cbs != null)
 273                                 cbs.TryRemove (reg, out dummy);
 274                 }
 275         }
 276 }
 277 #endif