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

   1 // WriteOnceBlock.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 using System.Collections.Generic;
  25 using System.Collections.Concurrent;
  26
  27 namespace System.Threading.Tasks.Dataflow {
  28         public sealed class WriteOnceBlock<T> : IPropagatorBlock<T, T>, IReceivableSourceBlock<T> {
  29                 readonly CompletionHelper compHelper;
  30                 readonly BlockingCollection<T> messageQueue = new BlockingCollection<T> ();
  31                 readonly MessageBox<T> messageBox;
  32                 readonly DataflowBlockOptions dataflowBlockOptions;
  33                 readonly Func<T, T> cloningFunction;
  34                 readonly BroadcastOutgoingQueue<T> outgoing;
  35                 AtomicBooleanValue written;
  36
  37                 public WriteOnceBlock (Func<T, T> cloningFunction)
  38                         : this (cloningFunction, DataflowBlockOptions.Default)
  39                 {
  40                 }
  41
  42                 public WriteOnceBlock (Func<T, T> cloningFunction,
  43                                        DataflowBlockOptions dataflowBlockOptions)
  44                 {
  45                         if (dataflowBlockOptions == null)
  46                                 throw new ArgumentNullException ("dataflowBlockOptions");
  47
  48                         this.cloningFunction = cloningFunction;
  49                         this.dataflowBlockOptions = dataflowBlockOptions;
  50                         this.compHelper = CompletionHelper.GetNew (dataflowBlockOptions);
  51                         this.messageBox = new PassingMessageBox<T> (this, messageQueue, compHelper,
  52                                 () => true, _ => BroadcastProcess (), dataflowBlockOptions,
  53                                 canAccept: () => written.TrySet ());
  54                         this.outgoing = new BroadcastOutgoingQueue<T> (this, compHelper,
  55                                 () => messageQueue.IsCompleted, messageBox.DecreaseCount,
  56                                 dataflowBlockOptions, cloningFunction != null);
  57                 }
  58
  59                 DataflowMessageStatus ITargetBlock<T>.OfferMessage (
  60                         DataflowMessageHeader messageHeader, T messageValue,
  61                         ISourceBlock<T> source, bool consumeToAccept)
  62                 {
  63                         var result = messageBox.OfferMessage (messageHeader, messageValue, source,
  64                                 consumeToAccept);
  65                         if (result == DataflowMessageStatus.Accepted)
  66                                 messageQueue.CompleteAdding ();
  67                         return result;
  68                 }
  69
  70                 public IDisposable LinkTo (ITargetBlock<T> target,
  71                                            DataflowLinkOptions linkOptions)
  72                 {
  73                         return outgoing.AddTarget (target, linkOptions);
  74                 }
  75
  76                 T ISourceBlock<T>.ConsumeMessage (DataflowMessageHeader messageHeader,
  77                                                   ITargetBlock<T> target,
  78                                                   out bool messageConsumed)
  79                 {
  80                         T message = outgoing.ConsumeMessage (
  81                                 messageHeader, target, out messageConsumed);
  82                         if (messageConsumed && cloningFunction != null)
  83                                 message = cloningFunction (message);
  84                         return message;
  85                 }
  86
  87                 void ISourceBlock<T>.ReleaseReservation (DataflowMessageHeader messageHeader,
  88                                                          ITargetBlock<T> target)
  89                 {
  90                         outgoing.ReleaseReservation (messageHeader, target);
  91                 }
  92
  93                 bool ISourceBlock<T>.ReserveMessage (DataflowMessageHeader messageHeader,
  94                                                      ITargetBlock<T> target)
  95                 {
  96                         return outgoing.ReserveMessage (messageHeader, target);
  97                 }
  98
  99                 public bool TryReceive (Predicate<T> filter, out T item)
 100                 {
 101                         var received = outgoing.TryReceive (filter, out item);
 102                         if (received && cloningFunction != null)
 103                                 item = cloningFunction (item);
 104                         return received;
 105                 }
 106
 107                 bool IReceivableSourceBlock<T>.TryReceiveAll (out IList<T> items)
 108                 {
 109                         T item;
 110                         if (!TryReceive (null, out item)) {
 111                                 items = null;
 112                                 return false;
 113                         }
 114
 115                         items = new[] { item };
 116                         return true;
 117                 }
 118
 119                 /// <summary>
 120                 /// Moves an item from the input queue to the output queue.
 121                 /// </summary>
 122                 void BroadcastProcess ()
 123                 {
 124                         T item;
 125                         if (messageQueue.TryTake (out item))
 126                                 outgoing.AddData (item);
 127                         outgoing.DequeueItem ();
 128                 }
 129
 130                 public void Complete ()
 131                 {
 132                         messageBox.Complete ();
 133                         outgoing.Complete ();
 134                 }
 135
 136                 void IDataflowBlock.Fault (Exception exception)
 137                 {
 138                         compHelper.RequestFault (exception);
 139                 }
 140
 141                 public Task Completion {
 142                         get { return compHelper.Completion; }
 143                 }
 144
 145                 public override string ToString ()
 146                 {
 147                         return NameHelper.GetName (this, dataflowBlockOptions);
 148                 }
 149         }
 150 }