mcs/class/System.Threading.Tasks.Dataflow/System.Threading.Tasks.Dataflow/ReceiveBlock.cs

   1 // ReceiveBlock.cs
   2 //
   3 // Copyright (c) 2011 Jérémie "garuma" Laval
   4 // Copyright (c) 2012 Petr Onderka
   5 //
   6 // Permission is hereby granted, free of charge, to any person obtaining a copy
   7 // of this software and associated documentation files (the "Software"), to deal
   8 // in the Software without restriction, including without limitation the rights
   9 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10 // copies of the Software, and to permit persons to whom the Software is
  11 // furnished to do so, subject to the following conditions:
  12 //
  13 // The above copyright notice and this permission notice shall be included in
  14 // all copies or substantial portions of the Software.
  15 //
  16 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22 // THE SOFTWARE.
  23
  24 namespace System.Threading.Tasks.Dataflow {
  25         /// <summary>
  26         /// This internal block is used by the <see cref="DataflowBlock.Receive"/> methods
  27         /// to retrieve elements in either blocking or asynchronous way.
  28         /// </summary>
  29         class ReceiveBlock<TOutput> : ITargetBlock<TOutput> {
  30                 readonly TaskCompletionSource<TOutput> completion =
  31                         new TaskCompletionSource<TOutput> ();
  32
  33                 readonly CancellationToken token;
  34                 CancellationTokenRegistration cancellationRegistration;
  35                 readonly Timer timeoutTimer;
  36
  37                 IDisposable linkBridge;
  38
  39                 public ReceiveBlock (CancellationToken token, int timeout)
  40                 {
  41                         this.token = token;
  42                         cancellationRegistration = token.Register (() =>
  43                         {
  44                                 lock (completion) {
  45                                         completion.TrySetCanceled ();
  46                                 }
  47                                 CompletionSet ();
  48                         });
  49                         timeoutTimer = new Timer (
  50                                 _ =>
  51                                 {
  52                                         lock (completion) {
  53                                                 completion.TrySetException (new TimeoutException ());
  54                                         }
  55                                         CompletionSet ();
  56                                 }, null, timeout,
  57                                 Timeout.Infinite);
  58                 }
  59
  60                 public DataflowMessageStatus OfferMessage (
  61                         DataflowMessageHeader messageHeader, TOutput messageValue,
  62                         ISourceBlock<TOutput> source, bool consumeToAccept)
  63                 {
  64                         if (!messageHeader.IsValid)
  65                                 return DataflowMessageStatus.Declined;
  66
  67                         if (completion.Task.Status != TaskStatus.WaitingForActivation)
  68                                 return DataflowMessageStatus.DecliningPermanently;
  69
  70                         lock (completion) {
  71                                 if (completion.Task.Status != TaskStatus.WaitingForActivation)
  72                                         return DataflowMessageStatus.DecliningPermanently;
  73
  74                                 if (consumeToAccept) {
  75                                         bool consummed;
  76                                         if (!source.ReserveMessage (messageHeader, this))
  77                                                 return DataflowMessageStatus.NotAvailable;
  78                                         messageValue = source.ConsumeMessage (messageHeader, this, out consummed);
  79                                         if (!consummed)
  80                                                 return DataflowMessageStatus.NotAvailable;
  81                                 }
  82
  83                                 completion.TrySetResult (messageValue);
  84                         }
  85                         CompletionSet ();
  86                         return DataflowMessageStatus.Accepted;
  87                 }
  88
  89                 /// <summary>
  90                 /// Synchronously waits until an item is available.
  91                 /// </summary>
  92                 /// <param name="bridge">The disposable object returned by <see cref="ISourceBlock{TOutput}.LinkTo"/>.</param>
  93                 public TOutput WaitAndGet (IDisposable bridge)
  94                 {
  95                         try {
  96                                 return AsyncGet (bridge).Result;
  97                         } catch (AggregateException e) {
  98                                 if (e.InnerException is TaskCanceledException)
  99                                         throw new OperationCanceledException (token);
 100                                 // resets the stack trace, but that shouldn't matter here
 101                                 throw e.InnerException;
 102                         }
 103                 }
 104
 105                 /// <summary>
 106                 /// Asynchronously waits until an item is available.
 107                 /// </summary>
 108                 /// <param name="bridge">The disposable object returned by <see cref="ISourceBlock{TOutput}.LinkTo"/>.</param>
 109                 public Task<TOutput> AsyncGet (IDisposable bridge)
 110                 {
 111                         linkBridge = bridge;
 112
 113                         return completion.Task;
 114                 }
 115
 116                 /// <summary>
 117                 /// Called after the result has been set,
 118                 /// cleans up after this block.
 119                 /// </summary>
 120                 void CompletionSet ()
 121                 {
 122                         if (linkBridge != null) {
 123                                 linkBridge.Dispose ();
 124                                 linkBridge = null;
 125                         }
 126
 127                         cancellationRegistration.Dispose ();
 128                         timeoutTimer.Dispose ();
 129                 }
 130
 131                 public Task Completion {
 132                         get { throw new NotSupportedException (); }
 133                 }
 134
 135                 public void Complete ()
 136                 {
 137                         lock (completion) {
 138                                 completion.TrySetException (new InvalidOperationException (
 139                                         "No item could be received from the source."));
 140                         }
 141                         CompletionSet ();
 142                 }
 143
 144                 public void Fault (Exception exception)
 145                 {
 146                         Complete ();
 147                 }
 148         }
 149 }