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

   1 // OutgoingQueueBase.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         /// <summary>
  28         /// Handles outgoing messages that get queued when there is no
  29         /// block on the other end to proces it. It also allows receive operations.
  30         /// </summary>
  31         abstract class OutgoingQueueBase<T> {
  32                 protected ConcurrentQueue<T> Store { get; private set; }
  33                 protected BlockingCollection<T> Outgoing { get; private set; }
  34                 int outgoingCount;
  35                 readonly CompletionHelper compHelper;
  36                 readonly Func<bool> externalCompleteTester;
  37                 readonly DataflowBlockOptions options;
  38                 protected AtomicBoolean IsProcessing { get; private set; }
  39                 protected abstract TargetCollectionBase<T> Targets { get; }
  40                 int totalModifiedCount;
  41                 readonly Action<int> decreaseItemsCount;
  42                 volatile bool forceProcessing;
  43
  44                 protected OutgoingQueueBase (
  45                         CompletionHelper compHelper, Func<bool> externalCompleteTester,
  46                         Action<int> decreaseItemsCount, DataflowBlockOptions options)
  47                 {
  48                         IsProcessing = new AtomicBoolean ();
  49                         Store = new ConcurrentQueue<T> ();
  50                         Outgoing = new BlockingCollection<T> (Store);
  51                         this.compHelper = compHelper;
  52                         this.externalCompleteTester = externalCompleteTester;
  53                         this.options = options;
  54                         this.decreaseItemsCount = decreaseItemsCount;
  55                 }
  56
  57                 /// <summary>
  58                 /// Is the queue completed?
  59                 /// Queue is completed after <see cref="Complete"/> is called
  60                 /// and all items are retrieved from it.
  61                 /// </summary>
  62                 public bool IsCompleted {
  63                         get { return Outgoing.IsCompleted; }
  64                 }
  65
  66                 /// <summary>
  67                 /// Current number of items in the queue.
  68                 /// Item are counted the way <see cref="DataflowBlockOptions.BoundedCapacity"/>
  69                 /// counts them, e.g. each item in a batch counts, even if batch is a single object.
  70                 /// </summary>
  71                 public int Count {
  72                         get { return totalModifiedCount; }
  73                 }
  74
  75                 /// <summary>
  76                 /// Calculates the count of items in the given object.
  77                 /// </summary>
  78                 protected virtual int GetModifiedCount (T data)
  79                 {
  80                         return 1;
  81                 }
  82
  83                 /// <summary>
  84                 /// Adds an object to the queue.
  85                 /// </summary>
  86                 public void AddData (T data)
  87                 {
  88                         try {
  89                                 Outgoing.Add (data);
  90                                 Interlocked.Add (ref totalModifiedCount, GetModifiedCount (data));
  91                                 if (Interlocked.Increment (ref outgoingCount) == 1)
  92                                         EnsureProcessing ();
  93                         } catch (InvalidOperationException) {
  94                                 VerifyCompleteness ();
  95                         }
  96                 }
  97
  98                 /// <summary>
  99                 /// Makes sure sending messages to targets is running.
 100                 /// </summary>
 101                 protected void EnsureProcessing ()
 102                 {
 103                         ForceProcessing = true;
 104                         if (IsProcessing.TrySet())
 105                                 Task.Factory.StartNew (Process, CancellationToken.None,
 106                                         TaskCreationOptions.PreferFairness, options.TaskScheduler);
 107                 }
 108
 109                 /// <summary>
 110                 /// Indicates whether sending messages should be forced to start.
 111                 /// </summary>
 112                 protected bool ForceProcessing {
 113                         get { return forceProcessing; }
 114                         set { forceProcessing = value; }
 115                 }
 116
 117                 /// <summary>
 118                 /// Sends messages to targets.
 119                 /// </summary>
 120                 protected abstract void Process ();
 121
 122                 /// <summary>
 123                 /// Adds a target block to send messages to.
 124                 /// </summary>
 125                 /// <returns>
 126                 /// An object that can be used to destroy the link to the added target.
 127                 /// </returns>
 128                 public IDisposable AddTarget (ITargetBlock<T> targetBlock, DataflowLinkOptions linkOptions)
 129                 {
 130                         if (targetBlock == null)
 131                                 throw new ArgumentNullException ("targetBlock");
 132                         if (linkOptions == null)
 133                                 throw new ArgumentNullException ("linkOptions");
 134
 135                         var result = Targets.AddTarget (targetBlock, linkOptions);
 136                         EnsureProcessing ();
 137                         return result;
 138                 }
 139
 140                 /// <summary>
 141                 /// Makes sure the block is completed if it should be.
 142                 /// </summary>
 143                 protected void VerifyCompleteness ()
 144                 {
 145                         if (Outgoing.IsCompleted && externalCompleteTester ())
 146                                 compHelper.Complete ();
 147                 }
 148
 149                 /// <summary>
 150                 /// Is the block faulted or cancelled?
 151                 /// </summary>
 152                 protected bool IsFaultedOrCancelled {
 153                         get { return compHelper.Completion.IsFaulted || compHelper.Completion.IsCanceled; }
 154                 }
 155
 156                 /// <summary>
 157                 /// Used to notify that object was removed from the queue
 158                 /// and to update counts.
 159                 /// </summary>
 160                 protected void DecreaseCounts (T data)
 161                 {
 162                         var modifiedCount = GetModifiedCount (data);
 163                         Interlocked.Add (ref totalModifiedCount, -modifiedCount);
 164                         Interlocked.Decrement (ref outgoingCount);
 165                         decreaseItemsCount (modifiedCount);
 166                 }
 167
 168                 /// <summary>
 169                 /// Marks the queue for completion.
 170                 /// </summary>
 171                 public void Complete ()
 172                 {
 173                         Outgoing.CompleteAdding ();
 174                         VerifyCompleteness ();
 175                 }
 176         }
 177 }