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 || BOOTSTRAP_NET_4_0
  28
  29 using System;
  30 using System.Threading.Tasks;
  31 using System.Collections.Generic;
  32
  33 namespace System.Collections.Concurrent
  34 {
  35         // Represent a chunk partitioner
  36         internal class EnumerablePartitioner<T> : OrderablePartitioner<T>
  37         {
  38                 IEnumerable<T> source;
  39
  40                 const int InitialPartitionSize = 1;
  41                 const int PartitionMultiplier = 2;
  42
  43                 int initialPartitionSize;
  44                 int partitionMultiplier;
  45
  46                 int index = 0;
  47                 readonly object syncLock = new object ();
  48
  49                 public EnumerablePartitioner (IEnumerable<T> source)
  50                         : this (source, InitialPartitionSize, PartitionMultiplier)
  51                 {
  52
  53                 }
  54
  55                 // This is used to get striped partitionning (for Take and Skip for instance
  56                 public EnumerablePartitioner (IEnumerable<T> source, int initialPartitionSize, int partitionMultiplier)
  57                          : base (true, false, true)
  58                 {
  59                         this.source = source;
  60                         this.initialPartitionSize = initialPartitionSize;
  61                         this.partitionMultiplier = partitionMultiplier;
  62                 }
  63
  64                 public override IList<IEnumerator<KeyValuePair<long, T>>> GetOrderablePartitions (int partitionCount)
  65                 {
  66                         if (partitionCount <= 0)
  67                                 throw new ArgumentOutOfRangeException ("partitionCount");
  68
  69                         IEnumerator<KeyValuePair<long, T>>[] enumerators
  70                                 = new IEnumerator<KeyValuePair<long, T>>[partitionCount];
  71
  72                         IEnumerator<T> src = source.GetEnumerator ();
  73
  74                         for (int i = 0; i < enumerators.Length; i++) {
  75                                 enumerators[i] = GetPartitionEnumerator (src);
  76                         }
  77
  78                         return enumerators;
  79                 }
  80
  81                 IEnumerator<KeyValuePair<long, T>> GetPartitionEnumerator (IEnumerator<T> src)
  82                 {
  83                         int count = initialPartitionSize;
  84                         List<T> list = new List<T> ();
  85
  86                         while (true) {
  87                                 list.Clear ();
  88                                 int ind = -1;
  89
  90                                 lock (syncLock) {
  91                                         ind = index;
  92
  93                                         for (int i = 0; i < count; i++) {
  94                                                 if (!src.MoveNext ()) {
  95                                                         if (list.Count == 0)
  96                                                                 yield break;
  97                                                         else
  98                                                                 break;
  99                                                 }
 100
 101                                                 list.Add (src.Current);
 102                                                 index++;
 103                                         }
 104                                 }
 105
 106
 107
 108                                 for (int i = 0; i < list.Count; i++)
 109                                         yield return new KeyValuePair<long, T> (ind + i, list[i]);
 110
 111                                 count *= partitionMultiplier;
 112                         }
 113                 }
 114         }
 115 }
 116 #endif