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

   1 // TargetBuffer.cs
   2 //
   3 // Copyright (c) 2011 Jérémie "garuma" Laval
   4 //
   5 // Permission is hereby granted, free of charge, to any person obtaining a copy
   6 // of this software and associated documentation files (the "Software"), to deal
   7 // in the Software without restriction, including without limitation the rights
   8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   9 // copies of the Software, and to permit persons to whom the Software is
  10 // furnished to do so, subject to the following conditions:
  11 //
  12 // The above copyright notice and this permission notice shall be included in
  13 // all copies or substantial portions of the Software.
  14 //
  15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  21 // THE SOFTWARE.
  22 //
  23 //
  24
  25
  26 using System;
  27 using System.Linq;
  28 using System.Threading.Tasks;
  29 using System.Collections;
  30 using System.Collections.Generic;
  31 using System.Collections.Concurrent;
  32
  33 namespace System.Threading.Tasks.Dataflow
  34 {
  35         internal class TargetBuffer<T> : IEnumerable<ITargetBlock<T>>
  36         {
  37                 ConcurrentQueue<TargetWaiter> targetWaiters = new ConcurrentQueue<TargetWaiter> ();
  38
  39                 class TargetWaiter : IDisposable
  40                 {
  41                         public volatile bool Disabled;
  42                         public readonly ITargetBlock<T> Target;
  43                         public readonly bool UnlinkAfterOne;
  44
  45                         ConcurrentQueue<TargetWaiter> queue;
  46                         AtomicBooleanValue removed;
  47
  48                         public TargetWaiter (ITargetBlock<T> target, bool unlinkAfterOne, ConcurrentQueue<TargetWaiter> queue)
  49                         {
  50                                 Target = target;
  51                                 UnlinkAfterOne = unlinkAfterOne;
  52                                 this.queue = queue;
  53                         }
  54
  55                         public void Dispose ()
  56                         {
  57                                 TargetWaiter t;
  58                                 Disabled = true;
  59
  60                                 Thread.MemoryBarrier ();
  61
  62                                 if (queue.TryPeek (out t) && t == this && removed.TryRelaxedSet ()) {
  63                                         queue.TryDequeue (out t);
  64                                 } else {
  65                                         SpinWait wait = new SpinWait ();
  66                                         while (queue.TryPeek (out t) && t == this)
  67                                                 wait.SpinOnce ();
  68                                 }
  69                         }
  70                 }
  71
  72                 public IDisposable AddTarget (ITargetBlock<T> block, bool unlinkAfterOne)
  73                 {
  74                         TargetWaiter w = new TargetWaiter (block, unlinkAfterOne, targetWaiters);
  75                         targetWaiters.Enqueue (w);
  76
  77                         return w;
  78                 }
  79
  80                 public ITargetBlock<T> Current {
  81                         get {
  82                                 TargetWaiter w;
  83
  84                                 while (true) {
  85                                         if (!targetWaiters.TryPeek (out w))
  86                                                 return null;
  87
  88                                         if (w.Disabled == true) {
  89                                                 w.Dispose ();
  90                                                 continue;
  91                                         } else if (w.UnlinkAfterOne) {
  92                                                 w.Dispose ();
  93                                         }
  94
  95                                         return w.Target;
  96                                 }
  97                         }
  98                 }
  99
 100                 public IEnumerator<ITargetBlock<T>> GetEnumerator ()
 101                 {
 102                         return targetWaiters.Select (w => w.Target).GetEnumerator ();
 103                 }
 104
 105                 IEnumerator IEnumerable.GetEnumerator ()
 106                 {
 107                         return targetWaiters.Select (w => w.Target).GetEnumerator ();
 108                 }
 109         }
 110 }
 111