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

   1 // JoinBlock.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         /// Block used in all versions of <see cref="DataflowBlock.Choose"/>.
  27         /// </summary>
  28         class ChooserBlock<T1, T2, T3> {
  29                 /// <summary>
  30                 /// Target for one of the sources to choose from.
  31                 /// </summary>
  32                 class ChooseTarget<TMessage> : ITargetBlock<TMessage> {
  33                         readonly ChooserBlock<T1, T2, T3> chooserBlock;
  34                         readonly int index;
  35                         readonly Action<TMessage> action;
  36
  37                         public ChooseTarget (ChooserBlock<T1, T2, T3> chooserBlock,
  38                                              int index, Action<TMessage> action)
  39                         {
  40                                 this.chooserBlock = chooserBlock;
  41                                 this.index = index;
  42                                 this.action = action;
  43                         }
  44
  45                         public DataflowMessageStatus OfferMessage (
  46                                 DataflowMessageHeader messageHeader, TMessage messageValue,
  47                                 ISourceBlock<TMessage> source, bool consumeToAccept)
  48                         {
  49                                 if (!chooserBlock.canAccept)
  50                                         return DataflowMessageStatus.DecliningPermanently;
  51
  52                                 bool lockTaken = false;
  53                                 try {
  54                                         chooserBlock.messageLock.Enter (ref lockTaken);
  55                                         if (!chooserBlock.canAccept)
  56                                                 return DataflowMessageStatus.DecliningPermanently;
  57
  58                                         if (consumeToAccept) {
  59                                                 bool consummed;
  60                                                 messageValue = source.ConsumeMessage (messageHeader, this, out consummed);
  61                                                 if (!consummed)
  62                                                         return DataflowMessageStatus.NotAvailable;
  63                                         }
  64
  65                                         chooserBlock.canAccept = false;
  66                                 } finally {
  67                                         if (lockTaken)
  68                                                 chooserBlock.messageLock.Exit ();
  69                                 }
  70
  71                                 chooserBlock.MessageArrived (index, action, messageValue);
  72                                 return DataflowMessageStatus.Accepted;
  73                         }
  74
  75                         public Task Completion {
  76                                 get { return null; }
  77                         }
  78
  79                         public void Complete ()
  80                         {
  81                         }
  82
  83                         public void Fault (Exception exception)
  84                         {
  85                         }
  86                 }
  87
  88                 readonly TaskCompletionSource<int> completion = new TaskCompletionSource<int> ();
  89
  90                 SpinLock messageLock;
  91                 bool canAccept = true;
  92
  93                 public ChooserBlock (
  94                         Action<T1> action1, Action<T2> action2, Action<T3> action3,
  95                         DataflowBlockOptions dataflowBlockOptions)
  96                 {
  97                         Target1 = new ChooseTarget<T1> (this, 0, action1);
  98                         Target2 = new ChooseTarget<T2> (this, 1, action2);
  99                         if (action3 != null)
 100                                 Target3 = new ChooseTarget<T3> (this, 2, action3);
 101
 102                         if (dataflowBlockOptions.CancellationToken != CancellationToken.None)
 103                                 dataflowBlockOptions.CancellationToken.Register (Cancelled);
 104                 }
 105
 106                 /// <summary>
 107                 /// Causes cancellation of <see cref="Completion"/>.
 108                 /// If a message is already being consumed (and the consumsing succeeds)
 109                 /// or if its action is being invoked, the Task is not cancelled.
 110                 /// </summary>
 111                 void Cancelled ()
 112                 {
 113                         if (!canAccept)
 114                                 return;
 115
 116                         bool lockTaken = false;
 117                         try {
 118                                 messageLock.Enter (ref lockTaken);
 119                                 if (!canAccept)
 120                                         return;
 121
 122                                 completion.SetCanceled ();
 123
 124                                 canAccept = false;
 125                         } finally {
 126                                 if (lockTaken)
 127                                         messageLock.Exit ();
 128                         }
 129                 }
 130
 131                 /// <summary>
 132                 /// Called when all sources have completed,
 133                 /// causes cancellation of <see cref="Completion"/>.
 134                 /// </summary>
 135                 public void AllSourcesCompleted ()
 136                 {
 137                         Cancelled ();
 138                 }
 139
 140                 /// <summary>
 141                 /// Called when message has arrived (and was consumed, if necessary).
 142                 /// This method can be called only once in the lifetime of this object.
 143                 /// </summary>
 144                 void MessageArrived<TMessage> (
 145                         int index, Action<TMessage> action, TMessage value)
 146                 {
 147                         try {
 148                                 action (value);
 149                                 completion.SetResult (index);
 150                         } catch (Exception e) {
 151                                 completion.SetException (e);
 152                         }
 153                 }
 154
 155                 /// <summary>
 156                 /// Target block for the first source block.
 157                 /// </summary>
 158                 public ITargetBlock<T1> Target1 { get; private set; }
 159
 160                 /// <summary>
 161                 /// Target block for the second source block.
 162                 /// </summary>
 163                 public ITargetBlock<T2> Target2 { get; private set; }
 164
 165                 /// <summary>
 166                 /// Target block for the third source block.
 167                 /// Is <c>null</c> if there are only two actions.
 168                 /// </summary>
 169                 public ITargetBlock<T3> Target3 { get; private set; }
 170
 171                 /// <summary>
 172                 /// Task that signifies that an item was accepted and
 173                 /// its action has been called.
 174                 /// </summary>
 175                 public Task<int> Completion {
 176                         get { return completion.Task; }
 177                 }
 178         }
 179 }