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                         var slot = task.ExceptionSlot;
  66                         switch (task.Status) {
  67                         case TaskStatus.Canceled:
  68                                 // Use original exception when we have one
  69                                 if (slot.Exception != null)
  70                                         goto case TaskStatus.Faulted;
  71
  72                                 return new TaskCanceledException (task);
  73                         case TaskStatus.Faulted:
  74                                 // Mark the exception as observed when GetResult throws
  75                                 slot.Observed = true;
  76                                 return slot.Exception.InnerException;
  77                         default:
  78                                 throw new ArgumentException (string.Format ("Unexpected task `{0}' status `{1}'", task.Id, task.Status));
  79                         }
  80                 }
  81
  82                 internal static void HandleOnCompleted (Task task, Action continuation, bool continueOnSourceContext, bool manageContext)
  83                 {
  84                         if (continueOnSourceContext && SynchronizationContext.Current != null && SynchronizationContext.Current.GetType () != typeof (SynchronizationContext)) {
  85                                 task.ContinueWith (new SynchronizationContextContinuation (continuation, SynchronizationContext.Current));
  86                         } else {
  87                                 IContinuation cont;
  88                                 Task cont_task;
  89                                 if (continueOnSourceContext && !TaskScheduler.IsDefault) {
  90                                         cont_task = new Task (TaskActionInvoker.Create (continuation), null, CancellationToken.None, TaskCreationOptions.None, null);
  91                                         cont_task.SetupScheduler (TaskScheduler.Current);
  92                                         cont = new SchedulerAwaitContinuation (cont_task);
  93                                 } else {
  94                                         cont_task = null;
  95                                         cont = new AwaiterActionContinuation (continuation);
  96                                 }
  97
  98                                 //
  99                                 // This is awaiter continuation. For finished tasks we get false result and need to
 100                                 // queue the continuation otherwise the task would block
 101                                 //
 102                                 if (task.ContinueWith (cont, false))
 103                                         return;
 104
 105                                 if (cont_task == null) {
 106                                         cont_task = new Task (TaskActionInvoker.Create (continuation), null, CancellationToken.None, TaskCreationOptions.None, null);
 107                                         cont_task.SetupScheduler (TaskScheduler.Current);
 108                                 }
 109
 110                                 cont_task.Schedule (true);
 111                         }
 112                 }
 113
 114                 public void OnCompleted (Action continuation)
 115                 {
 116                         if (continuation == null)
 117                                 throw new ArgumentNullException ("continuation");
 118
 119                         HandleOnCompleted (task, continuation, true, true);
 120                 }
 121
 122                 public void UnsafeOnCompleted (Action continuation)
 123                 {
 124                         if (continuation == null)
 125                                 throw new ArgumentNullException ("continuation");
 126
 127                         HandleOnCompleted (task, continuation, true, false);
 128                 }
 129         }
 130 }
 131
 132 #endif