mcs/class/corlib/System.Runtime.CompilerServices/TaskAwaiter.cs

   1 //
   2 // TaskAwaiter.cs
   3 //
   4 // Authors:
   5 //      Marek Safar  <marek.safar@gmail.com>
   6 //
   7 // Copyright (C) 2011 Novell, Inc (http://www.novell.com)
   8 // Copyright (C) 2011 Xamarin, Inc (http://www.xamarin.com)
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29
  30 #if NET_4_5
  31
  32 using System.Threading;
  33 using System.Threading.Tasks;
  34 using System.Runtime.ExceptionServices;
  35
  36 namespace System.Runtime.CompilerServices
  37 {
  38         public struct TaskAwaiter : ICriticalNotifyCompletion
  39         {
  40                 readonly Task task;
  41
  42                 internal TaskAwaiter (Task task)
  43                 {
  44                         this.task = task;
  45                 }
  46
  47                 public bool IsCompleted {
  48                         get {
  49                                 return task.IsCompleted;
  50                         }
  51                 }
  52
  53                 public void GetResult ()
  54                 {
  55                         if (!task.IsCompleted)
  56                                 task.WaitCore (Timeout.Infinite, CancellationToken.None, true);
  57
  58                         if (task.Status != TaskStatus.RanToCompletion)
  59                                 // Merge current and dispatched stack traces if there is any
  60                                 ExceptionDispatchInfo.Capture (HandleUnexpectedTaskResult (task)).Throw ();
  61                 }
  62
  63                 internal static Exception HandleUnexpectedTaskResult (Task task)
  64                 {
  65                         switch (task.Status) {
  66                         case TaskStatus.Canceled:
  67                                 // Use original exception when we have one
  68                                 if (task.ExceptionSlot.Exception != null)
  69                                         goto case TaskStatus.Faulted;
  70
  71                                 return new TaskCanceledException (task);
  72                         case TaskStatus.Faulted:
  73                                 return task.ExceptionSlot.Exception.InnerException;
  74                         default:
  75                                 throw new ArgumentException (string.Format ("Unexpected task `{0}' status `{1}'", task.Id, task.Status));
  76                         }
  77                 }
  78
  79                 internal static void HandleOnCompleted (Task task, Action continuation, bool continueOnSourceContext, bool manageContext)
  80                 {
  81                         if (continueOnSourceContext && SynchronizationContext.Current != null && SynchronizationContext.Current.GetType () != typeof (SynchronizationContext)) {
  82                                 task.ContinueWith (new SynchronizationContextContinuation (continuation, SynchronizationContext.Current));
  83                         } else {
  84                                 IContinuation cont;
  85                                 Task cont_task;
  86                                 if (continueOnSourceContext && TaskScheduler.Current != TaskScheduler.Default) {
  87                                         cont_task = new Task (TaskActionInvoker.Create (continuation), null, CancellationToken.None, TaskCreationOptions.None, null);
  88                                         cont_task.SetupScheduler (TaskScheduler.Current);
  89                                         cont = new SchedulerAwaitContinuation (cont_task);
  90                                 } else {
  91                                         cont_task = null;
  92                                         cont = new ActionContinuation (continuation);
  93                                 }
  94
  95                                 //
  96                                 // This is awaiter continuation. For finished tasks we get false result and need to
  97                                 // queue the continuation otherwise the task would block
  98                                 //
  99                                 if (task.ContinueWith (cont, false))
 100                                         return;
 101
 102                                 if (cont_task == null) {
 103                                         cont_task = new Task (TaskActionInvoker.Create (continuation), null, CancellationToken.None, TaskCreationOptions.None, null);
 104                                         cont_task.SetupScheduler (TaskScheduler.Current);
 105                                 }
 106
 107                                 cont_task.Schedule ();
 108                         }
 109                 }
 110
 111                 public void OnCompleted (Action continuation)
 112                 {
 113                         if (continuation == null)
 114                                 throw new ArgumentNullException ("continuation");
 115
 116                         HandleOnCompleted (task, continuation, true, true);
 117                 }
 118
 119                 public void UnsafeOnCompleted (Action continuation)
 120                 {
 121                         if (continuation == null)
 122                                 throw new ArgumentNullException ("continuation");
 123
 124                         HandleOnCompleted (task, continuation, true, false);
 125                 }
 126         }
 127 }
 128
 129 #endif