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

   1 // ActionBlock.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.Concurrent;
  25
  26 namespace System.Threading.Tasks.Dataflow {
  27         public sealed class ActionBlock<TInput> : ITargetBlock<TInput> {
  28                 readonly CompletionHelper compHelper;
  29                 readonly BlockingCollection<TInput> messageQueue = new BlockingCollection<TInput> ();
  30                 readonly ExecutingMessageBoxBase<TInput> messageBox;
  31                 readonly Action<TInput> action;
  32                 readonly Func<TInput, Task> asyncAction;
  33                 readonly ExecutionDataflowBlockOptions dataflowBlockOptions;
  34
  35                 ActionBlock (ExecutionDataflowBlockOptions dataflowBlockOptions)
  36                 {
  37                         if (dataflowBlockOptions == null)
  38                                 throw new ArgumentNullException ("dataflowBlockOptions");
  39
  40                         this.dataflowBlockOptions = dataflowBlockOptions;
  41                         this.compHelper = new CompletionHelper (dataflowBlockOptions);
  42                 }
  43
  44                 public ActionBlock (Action<TInput> action)
  45                         : this (action, ExecutionDataflowBlockOptions.Default)
  46                 {
  47                 }
  48
  49                 public ActionBlock (Action<TInput> action,
  50                                     ExecutionDataflowBlockOptions dataflowBlockOptions)
  51                         : this (dataflowBlockOptions)
  52                 {
  53                         if (action == null)
  54                                 throw new ArgumentNullException ("action");
  55
  56                         this.action = action;
  57                         this.messageBox = new ExecutingMessageBox<TInput> (this, messageQueue, compHelper,
  58                                 () => true, ProcessItem, () => { }, dataflowBlockOptions);
  59                 }
  60
  61                 public ActionBlock (Func<TInput, Task> action)
  62                         : this (action, ExecutionDataflowBlockOptions.Default)
  63                 {
  64                 }
  65
  66                 public ActionBlock (Func<TInput, Task> action,
  67                                     ExecutionDataflowBlockOptions dataflowBlockOptions)
  68                         : this (dataflowBlockOptions)
  69                 {
  70                         if (action == null)
  71                                 throw new ArgumentNullException ("action");
  72
  73                         this.asyncAction = action;
  74                         this.messageBox = new AsyncExecutingMessageBox<TInput, Task> (
  75                                 this, messageQueue, compHelper, () => true, AsyncProcessItem, null,
  76                                 () => { }, dataflowBlockOptions);
  77                 }
  78
  79                 DataflowMessageStatus ITargetBlock<TInput>.OfferMessage (
  80                         DataflowMessageHeader messageHeader, TInput messageValue,
  81                         ISourceBlock<TInput> source, bool consumeToAccept)
  82                 {
  83                         return messageBox.OfferMessage (
  84                                 messageHeader, messageValue, source, consumeToAccept);
  85                 }
  86
  87                 public bool Post (TInput item)
  88                 {
  89                         return messageBox.OfferMessage (
  90                                 new DataflowMessageHeader (1), item, null, false)
  91                                == DataflowMessageStatus.Accepted;
  92                 }
  93
  94                 /// <summary>
  95                 /// Processes one item from the queue if the action is synchronous.
  96                 /// </summary>
  97                 /// <returns>Returns whether an item was processed. Returns <c>false</c> if the queue is empty.</returns>
  98                 bool ProcessItem ()
  99                 {
 100                         TInput data;
 101                         bool dequeued = messageQueue.TryTake (out data);
 102                         if (dequeued)
 103                                 action (data);
 104                         return dequeued;
 105                 }
 106
 107                 /// <summary>
 108                 /// Processes one item from the queue if the action is asynchronous.
 109                 /// </summary>
 110                 /// <param name="task">The Task that was returned by the synchronous part of the action.</param>
 111                 /// <returns>Returns whether an item was processed. Returns <c>false</c> if the queue was empty.</returns>
 112                 bool AsyncProcessItem(out Task task)
 113                 {
 114                         TInput data;
 115                         bool dequeued = messageQueue.TryTake (out data);
 116                         if (dequeued)
 117                                 task = asyncAction (data);
 118                         else
 119                                 task = null;
 120                         return dequeued;
 121                 }
 122
 123                 public void Complete ()
 124                 {
 125                         messageBox.Complete ();
 126                 }
 127
 128                 void IDataflowBlock.Fault (Exception exception)
 129                 {
 130                         compHelper.RequestFault (exception);
 131                 }
 132
 133                 public Task Completion {
 134                         get {
 135                                 return compHelper.Completion;
 136                         }
 137                 }
 138
 139                 public int InputCount {
 140                         get {
 141                                 return messageQueue.Count;
 142                         }
 143                 }
 144
 145                 public override string ToString ()
 146                 {
 147                         return NameHelper.GetName (this, dataflowBlockOptions);
 148                 }
 149         }
 150 }