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 multiplier = 2;
  45                 const int hintThreshold = 20;
  46
  47                 int size = Environment.ProcessorCount + 1;
  48                 int count;
  49
  50                 // We only use the add hints when number of slot is above hintThreshold
  51                 // so to not waste memory space and the CAS overhead
  52                 ConcurrentQueue<int> addHints = new ConcurrentQueue<int> ();
  53
  54                 CyclicDeque<T>[] container;
  55
  56                 object syncLock = new object ();
  57
  58                 public ConcurrentBag ()
  59                 {
  60                         container = new CyclicDeque<T>[size];
  61                         for (int i = 0; i < container.Length; i++)
  62                                 container[i] = new CyclicDeque<T> ();
  63                 }
  64
  65                 public ConcurrentBag (IEnumerable<T> enumerable) : this ()
  66                 {
  67                         foreach (T item in enumerable)
  68                                 Add (item);
  69                 }
  70
  71                 public bool TryAdd (T item)
  72                 {
  73                         Add (item);
  74
  75                         return true;
  76                 }
  77
  78                 public void Add (T item)
  79                 {
  80                         Interlocked.Increment (ref count);
  81                         GrowIfNecessary ();
  82
  83                         int index;
  84                         CyclicDeque<T> bag = GetBag (out index);
  85                         bag.PushBottom (item);
  86
  87                         // Cache operation ?
  88                         if (size > hintThreshold)
  89                                 addHints.Enqueue (index);
  90                 }
  91
  92                 public bool TryTake (out T item)
  93                 {
  94                         item = default (T);
  95
  96                         if (count == 0)
  97                                 return false;
  98
  99                         int hintIndex;
 100                         CyclicDeque<T> bag = GetBag (out hintIndex);
 101                         bool hintEnabled = size > hintThreshold;
 102
 103                         if (bag == null || bag.PopBottom (out item) != PopResult.Succeed) {
 104                                 for (int i = 0; i < container.Length; i++) {
 105                                         // Try to retrieve something based on a hint
 106                                         bool result = hintEnabled && addHints.TryDequeue (out hintIndex) && container[hintIndex].PopTop (out item) == PopResult.Succeed;
 107
 108                                         // We fall back to testing our slot
 109                                         if (!result && container[i] != null)
 110                                                 result = container[i].PopTop (out item) == PopResult.Succeed;
 111
 112                                         // If we found something, stop
 113                                         if (result) {
 114                                                 Interlocked.Decrement (ref count);
 115                                                 return true;
 116                                         }
 117                                 }
 118                         } else {
 119                                 Interlocked.Decrement (ref count);
 120                                 return true;
 121                         }
 122
 123                         return false;
 124                 }
 125
 126                 public int Count {
 127                         get {
 128                                 return count;
 129                         }
 130                 }
 131
 132                 public bool IsEmpty {
 133                         get {
 134                                 return count == 0;
 135                         }
 136                 }
 137
 138                 object System.Collections.ICollection.SyncRoot  {
 139                         get {
 140                                 return this;
 141                         }
 142                 }
 143
 144                 bool System.Collections.ICollection.IsSynchronized  {
 145                         get {
 146                                 return true;
 147                         }
 148                 }
 149
 150                 IEnumerator IEnumerable.GetEnumerator ()
 151                 {
 152                         return GetEnumeratorInternal ();
 153                 }
 154
 155                 IEnumerator<T> IEnumerable<T>.GetEnumerator ()
 156                 {
 157                         return GetEnumeratorInternal ();
 158                 }
 159
 160                 IEnumerator<T> GetEnumeratorInternal ()
 161                 {
 162                         for (int i = 0; i < size; i++) {
 163                                 CyclicDeque<T> bag = container[i];
 164                                 foreach (T item in bag.GetEnumerable ()) {
 165                                         yield return item;
 166                                 }
 167                         }
 168                 }
 169
 170                 void System.Collections.ICollection.CopyTo (Array array, int index)
 171                 {
 172                         T[] a = array as T[];
 173                         if (a == null)
 174                                 return;
 175
 176                         CopyTo (a, index);
 177                 }
 178
 179                 public void CopyTo (T[] array, int index)
 180                 {
 181                         int c = count;
 182                         if (array.Length < c + index)
 183                                 throw new InvalidOperationException ("Array is not big enough");
 184
 185                         CopyTo (array, index, c);
 186                 }
 187
 188                 void CopyTo (T[] array, int index, int num)
 189                 {
 190                         int i = index;
 191
 192                         foreach (T item in this) {
 193                                 if (i >= num)
 194                                         break;
 195
 196                                 array[i++] = item;
 197                         }
 198                 }
 199
 200                 public T[] ToArray ()
 201                 {
 202                         int c = count;
 203                         T[] temp = new T[c];
 204
 205                         CopyTo (temp, 0, c);
 206
 207                         return temp;
 208                 }
 209
 210                 int GetIndex ()
 211                 {
 212                         return Thread.CurrentThread.ManagedThreadId - 1;
 213                 }
 214
 215                 void GrowIfNecessary ()
 216                 {
 217                         int index = GetIndex ();
 218                         int currentSize = size;
 219
 220                         while (index > currentSize - 1) {
 221                                 currentSize = size;
 222                                 Grow (currentSize);
 223                         }
 224                 }
 225
 226                 CyclicDeque<T> GetBag (out int i)
 227                 {
 228                         i = GetIndex ();
 229
 230                         return i < container.Length ? (container[i] == null) ? (container[i] = new CyclicDeque<T> ()) : container[i] : null;
 231                 }
 232
 233                 void Grow (int referenceSize)
 234                 {
 235                         lock (syncLock) {
 236                                 if (referenceSize != size)
 237                                         return;
 238
 239                                 CyclicDeque<T>[] slice = new CyclicDeque<T>[size * multiplier];
 240                                 int i = 0;
 241                                 Array.Copy (container, slice, container.Length);
 242
 243                                 container = slice;
 244                                 size = slice.Length;
 245                         }
 246                 }
 247         }
 248 }
 249 #endif