mcs/class/corlib/System.Collections.Concurrent.Partitioners/EnumerablePartitioner.cs

   1 //
   2 // EnumerablePartitioner.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
  29 using System;
  30 using System.Threading;
  31 using System.Threading.Tasks;
  32 using System.Collections.Generic;
  33
  34 namespace System.Collections.Concurrent.Partitioners
  35 {
  36         // Represent a chunk partitioner
  37         internal class EnumerablePartitioner<T> : OrderablePartitioner<T>
  38         {
  39                 IEnumerable<T> source;
  40
  41                 const int InitialPartitionSize = 1;
  42                 const int PartitionMultiplier = 2;
  43
  44                 int initialPartitionSize;
  45                 int partitionMultiplier;
  46
  47                 public EnumerablePartitioner (IEnumerable<T> source)
  48                         : this (source, InitialPartitionSize, PartitionMultiplier)
  49                 {
  50
  51                 }
  52
  53                 // This is used to get striped partitionning (for Take and Skip for instance
  54                 public EnumerablePartitioner (IEnumerable<T> source, int initialPartitionSize, int partitionMultiplier)
  55                          : base (true, false, true)
  56                 {
  57                         this.source = source;
  58                         this.initialPartitionSize = initialPartitionSize;
  59                         this.partitionMultiplier = partitionMultiplier;
  60                 }
  61
  62                 public override IList<IEnumerator<KeyValuePair<long, T>>> GetOrderablePartitions (int partitionCount)
  63                 {
  64                         if (partitionCount <= 0)
  65                                 throw new ArgumentOutOfRangeException ("partitionCount");
  66
  67                         IEnumerator<KeyValuePair<long, T>>[] enumerators
  68                                 = new IEnumerator<KeyValuePair<long, T>>[partitionCount];
  69
  70                         PartitionerState state = new PartitionerState ();
  71                         IEnumerator<T> src = source.GetEnumerator ();
  72                         bool isSimple = initialPartitionSize == 1 && partitionMultiplier == 1;
  73
  74                         for (int i = 0; i < enumerators.Length; i++) {
  75                                 enumerators[i] = isSimple ? GetPartitionEnumeratorSimple (src, state, i == enumerators.Length - 1) : GetPartitionEnumerator (src, state);
  76                         }
  77
  78                         return enumerators;
  79                 }
  80
  81                 // This partitioner that is simpler than the general case (don't use a list) is called in the case
  82                 // of initialPartitionSize == partitionMultiplier == 1
  83                 IEnumerator<KeyValuePair<long, T>> GetPartitionEnumeratorSimple (IEnumerator<T> src,
  84                                                                                  PartitionerState state,
  85                                                                                  bool last)
  86                 {
  87                         long index = -1;
  88                         var value = default (T);
  89
  90                         try {
  91                                 do {
  92                                         lock (state.SyncLock) {
  93                                                 if (!src.MoveNext ())
  94                                                         break;
  95
  96                                                 index = state.Index++;
  97                                                 value = src.Current;
  98                                         }
  99
 100                                         yield return new KeyValuePair<long, T> (index, value);
 101                                 } while (true);
 102                         } finally {
 103                                 if (last)
 104                                         src.Dispose ();
 105                         }
 106                 }
 107
 108                 IEnumerator<KeyValuePair<long, T>> GetPartitionEnumerator (IEnumerator<T> src, PartitionerState state)
 109                 {
 110                         int count = initialPartitionSize;
 111                         List<T> list = new List<T> ();
 112
 113                         while (true) {
 114                                 list.Clear ();
 115                                 long ind = -1;
 116
 117                                 lock (state.SyncLock) {
 118                                         ind = state.Index;
 119
 120                                         for (int i = 0; i < count; i++) {
 121                                                 if (!src.MoveNext ()) {
 122                                                         if (list.Count == 0)
 123                                                                 yield break;
 124                                                         else
 125                                                                 break;
 126                                                 }
 127
 128                                                 list.Add (src.Current);
 129                                                 state.Index++;
 130                                         }
 131                                 }
 132
 133                                 for (int i = 0; i < list.Count; i++)
 134                                         yield return new KeyValuePair<long, T> (ind + i, list[i]);
 135
 136                                 count *= partitionMultiplier;
 137                         }
 138                 }
 139
 140                 class PartitionerState
 141                 {
 142                         public long Index = 0;
 143                         public readonly object SyncLock = new object ();
 144                 }
 145         }
 146 }
 147 #endif