mcs/class/System/System.Collections.Concurrent/ConcurrentBag.cs

   1 //
   2 // ConcurrentBag.cs
   3 //
   4 // Author:
   5 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   6 //
   7 // Copyright (c) 2009 Jérémie "Garuma" Laval
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining a copy
  10 // of this software and associated documentation files (the "Software"), to deal
  11 // in the Software without restriction, including without limitation the rights
  12 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13 // copies of the Software, and to permit persons to whom the Software is
  14 // furnished to do so, subject to the following conditions:
  15 //
  16 // The above copyright notice and this permission notice shall be included in
  17 // all copies or substantial portions of the Software.
  18 //
  19 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25 // THE SOFTWARE.
  26
  27 #if NET_4_0
  28 using System;
  29 using System.Collections;
  30 using System.Collections.Generic;
  31 using System.Diagnostics;
  32 using System.Runtime.InteropServices;
  33
  34 using System.Threading;
  35 using System.Threading.Tasks;
  36
  37 namespace System.Collections.Concurrent
  38 {
  39         [ComVisible (false)]
  40         [DebuggerDisplay ("Count={Count}")]
  41         [DebuggerTypeProxy (typeof (CollectionDebuggerView<>))]
  42         public class ConcurrentBag<T> : IProducerConsumerCollection<T>, IEnumerable<T>, IEnumerable
  43         {
  44                 const int hintThreshold = 20;
  45
  46                 int count;
  47
  48                 // We only use the add hints when number of slot is above hintThreshold
  49                 // so to not waste memory space and the CAS overhead
  50                 ConcurrentQueue<int> addHints = new ConcurrentQueue<int> ();
  51
  52                 ConcurrentDictionary<int, CyclicDeque<T>> container = new ConcurrentDictionary<int, CyclicDeque<T>> ();
  53
  54                 public ConcurrentBag ()
  55                 {
  56                 }
  57
  58                 public ConcurrentBag (IEnumerable<T> enumerable) : this ()
  59                 {
  60                         foreach (T item in enumerable)
  61                                 Add (item);
  62                 }
  63
  64                 public void Add (T item)
  65                 {
  66                         int index;
  67                         CyclicDeque<T> bag = GetBag (out index);
  68                         bag.PushBottom (item);
  69
  70                         // Cache operation ?
  71                         if (container.Count > hintThreshold)
  72                                 addHints.Enqueue (index);
  73
  74                         Interlocked.Increment (ref count);
  75                 }
  76
  77                 bool IProducerConsumerCollection<T>.TryAdd (T element)
  78                 {
  79                         Add (element);
  80                         return true;
  81                 }
  82
  83                 public bool TryTake (out T item)
  84                 {
  85                         item = default (T);
  86
  87                         if (count == 0)
  88                                 return false;
  89
  90                         int hintIndex;
  91                         CyclicDeque<T> bag = GetBag (out hintIndex);
  92                         bool hintEnabled = container.Count > hintThreshold;
  93
  94                         if (bag == null || bag.PopBottom (out item) != PopResult.Succeed) {
  95                                 foreach (var other in container) {
  96                                         // Try to retrieve something based on a hint
  97                                         bool result = hintEnabled && addHints.TryDequeue (out hintIndex) && container[hintIndex].PopTop (out item) == PopResult.Succeed;
  98
  99                                         // We fall back to testing our slot
 100                                         if (!result && other.Value != bag)
 101                                                 result = other.Value.PopTop (out item) == PopResult.Succeed;
 102
 103                                         // If we found something, stop
 104                                         if (result) {
 105                                                 Interlocked.Decrement (ref count);
 106                                                 return true;
 107                                         }
 108                                 }
 109                         } else {
 110                                 Interlocked.Decrement (ref count);
 111                                 return true;
 112                         }
 113
 114                         return false;
 115                 }
 116
 117                 public int Count {
 118                         get {
 119                                 return count;
 120                         }
 121                 }
 122
 123                 public bool IsEmpty {
 124                         get {
 125                                 return count == 0;
 126                         }
 127                 }
 128
 129                 object System.Collections.ICollection.SyncRoot  {
 130                         get {
 131                                 return this;
 132                         }
 133                 }
 134
 135                 bool System.Collections.ICollection.IsSynchronized  {
 136                         get {
 137                                 return true;
 138                         }
 139                 }
 140
 141                 IEnumerator IEnumerable.GetEnumerator ()
 142                 {
 143                         return GetEnumeratorInternal ();
 144                 }
 145
 146                 public IEnumerator<T> GetEnumerator ()
 147                 {
 148                         return GetEnumeratorInternal ();
 149                 }
 150
 151                 IEnumerator<T> GetEnumeratorInternal ()
 152                 {
 153                         foreach (var bag in container)
 154                                 foreach (T item in bag.Value.GetEnumerable ())
 155                                         yield return item;
 156                 }
 157
 158                 void System.Collections.ICollection.CopyTo (Array array, int index)
 159                 {
 160                         T[] a = array as T[];
 161                         if (a == null)
 162                                 return;
 163
 164                         CopyTo (a, index);
 165                 }
 166
 167                 public void CopyTo (T[] array, int index)
 168                 {
 169                         int c = count;
 170                         if (array.Length < c + index)
 171                                 throw new InvalidOperationException ("Array is not big enough");
 172
 173                         CopyTo (array, index, c);
 174                 }
 175
 176                 void CopyTo (T[] array, int index, int num)
 177                 {
 178                         int i = index;
 179
 180                         foreach (T item in this) {
 181                                 if (i >= num)
 182                                         break;
 183
 184                                 array[i++] = item;
 185                         }
 186                 }
 187
 188                 public T[] ToArray ()
 189                 {
 190                         int c = count;
 191                         T[] temp = new T[c];
 192
 193                         CopyTo (temp, 0, c);
 194
 195                         return temp;
 196                 }
 197
 198                 int GetIndex ()
 199                 {
 200                         return Thread.CurrentThread.ManagedThreadId;
 201                 }
 202
 203                 CyclicDeque<T> GetBag (out int index)
 204                 {
 205                         index = GetIndex ();
 206                         CyclicDeque<T> value;
 207                         if (container.TryGetValue (index, out value))
 208                                 return value;
 209
 210                         return container.GetOrAdd (index, new CyclicDeque<T> ());
 211                 }
 212         }
 213 }
 214 #endif