class/corlib/System.Threading.Tasks/SimpleConcurrentBag.cs

   1 #if NET_4_0
   2 //
   3 // SimpleConcurrentBag.cs
   4 //
   5 // Author:
   6 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   7 //
   8 // Copyright (c) 2009 Jérémie "Garuma" Laval
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining a copy
  11 // of this software and associated documentation files (the "Software"), to deal
  12 // in the Software without restriction, including without limitation the rights
  13 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  14 // copies of the Software, and to permit persons to whom the Software is
  15 // furnished to do so, subject to the following conditions:
  16 //
  17 // The above copyright notice and this permission notice shall be included in
  18 // all copies or substantial portions of the Software.
  19 //
  20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  21 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  22 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  23 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  24 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  25 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  26 // THE SOFTWARE.
  27
  28 using System;
  29 using System.Threading;
  30
  31 namespace System.Threading.Tasks
  32 {
  33
  34         internal class SimpleConcurrentBag<T>
  35         {
  36                 readonly IDequeOperations<T>[] deques;
  37                 readonly bool unique;
  38                 int index = -1;
  39
  40                 [ThreadStatic]
  41                 int stealIndex;
  42
  43                 public SimpleConcurrentBag (int num)
  44                 {
  45                         deques = new CyclicDeque<T>[num];
  46                         for (int i = 0; i < deques.Length; i++) {
  47                                 deques[i] = new CyclicDeque<T> ();
  48                         }
  49                         unique = num <= 1;
  50                 }
  51
  52                 public int GetNextIndex ()
  53                 {
  54                         return Interlocked.Increment (ref index);
  55                 }
  56
  57                 public bool TryTake (int index, out T value)
  58                 {
  59                         value = default (T);
  60
  61                         return deques[index].PopBottom (out value) == PopResult.Succeed;
  62                 }
  63
  64                 public bool TrySteal (int index, out T value)
  65                 {
  66                         value = default (T);
  67
  68                         if (unique)
  69                                 return false;
  70
  71                         const int roundThreshold = 3;
  72
  73                         for (int round = 0; round < roundThreshold; ++round) {
  74                                 if (stealIndex == index)
  75                                         stealIndex = (stealIndex + 1) % deques.Length;
  76
  77                                 if (deques[(stealIndex = (stealIndex + 1) % deques.Length)].PopTop (out value) == PopResult.Succeed)
  78                                         return true;
  79                         }
  80
  81                         return false;
  82                 }
  83
  84                 public void Add (int index, T value)
  85                 {
  86                         deques[index].PushBottom (value);
  87                 }
  88         }
  89 }
  90 #endif