mcs/class/corlib/System.Threading.Tasks/CyclicDeque.cs

   1 //
   2 // CyclicDeque.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.Collections.Generic;
  31 using System.Threading;
  32
  33 #if INSIDE_MONO_PARALLEL
  34 namespace Mono.Threading.Tasks
  35 #else
  36 namespace System.Threading.Tasks
  37 #endif
  38 {
  39 #if INSIDE_MONO_PARALLEL
  40         public
  41 #endif
  42         class CyclicDeque<T> : IConcurrentDeque<T>
  43         {
  44                 const int BaseSize = 11;
  45
  46                 int bottom;
  47                 int top;
  48                 int upperBound;
  49                 CircularArray<T> array = new CircularArray<T> (BaseSize);
  50
  51                 public void PushBottom (T obj)
  52                 {
  53                         int b = bottom;
  54                         var a = array;
  55
  56                         // Take care of growing
  57                         var size = b - top - upperBound;
  58                         if (size >= a.Size) {
  59                                 upperBound = top;
  60                                 a = a.Grow (b, upperBound);
  61                                 array = a;
  62                         }
  63
  64                         // Register the new value
  65                         a.segment[b % a.size] = obj;
  66                         Interlocked.Increment (ref bottom);
  67                 }
  68
  69                 public PopResult PopBottom (out T obj)
  70                 {
  71                         obj = default (T);
  72
  73                         int b = Interlocked.Decrement (ref bottom);
  74                         var a = array;
  75                         int t = top;
  76                         int size = b - t;
  77
  78                         if (size < 0) {
  79                                 // Set bottom to t
  80                                 Interlocked.Add (ref bottom, t - b);
  81                                 return PopResult.Empty;
  82                         }
  83
  84                         obj = a.segment[b % a.size];
  85                         if (size > 0)
  86                                 return PopResult.Succeed;
  87                         Interlocked.Add (ref bottom, t + 1 - b);
  88
  89                         if (Interlocked.CompareExchange (ref top, t + 1, t) != t)
  90                                 return PopResult.Empty;
  91
  92                         return PopResult.Succeed;
  93                 }
  94
  95                 public bool PeekBottom (out T obj)
  96                 {
  97                         obj = default (T);
  98
  99                         int b = Interlocked.Decrement (ref bottom);
 100                         var a = array;
 101                         int t = top;
 102                         int size = b - t;
 103
 104                         if (size < 0)
 105                                 return false;
 106
 107                         obj = a.segment[b % a.size];
 108                         return true;
 109                 }
 110
 111                 public PopResult PopTop (out T obj)
 112                 {
 113                         obj = default (T);
 114
 115                         int t = top;
 116                         int b = bottom;
 117
 118                         if (b - t <= 0)
 119                                 return PopResult.Empty;
 120
 121                         if (Interlocked.CompareExchange (ref top, t + 1, t) != t)
 122                                 return PopResult.Abort;
 123
 124                         var a = array;
 125                         obj = a.segment[t % a.size];
 126
 127                         return PopResult.Succeed;
 128                 }
 129
 130                 internal bool PeekTop (out T obj)
 131                 {
 132                         obj = default (T);
 133
 134                         int t = top;
 135                         int b = bottom;
 136
 137                         if (b - t <= 0)
 138                                 return false;
 139
 140                         var a = array;
 141                         obj = a.segment[t % a.size];
 142
 143                         return true;
 144                 }
 145
 146                 public IEnumerable<T> GetEnumerable ()
 147                 {
 148                         var a = array;
 149                         return a.GetEnumerable (bottom, ref top);
 150                 }
 151
 152                 public bool IsEmpty {
 153                         get {
 154                                 int t = top;
 155                                 int b = bottom;
 156                                 return b - t <= 0;
 157                         }
 158                 }
 159         }
 160
 161         internal class CircularArray<T>
 162         {
 163                 readonly int baseSize;
 164                 public readonly int size;
 165                 public readonly T[] segment;
 166
 167                 public CircularArray (int baseSize)
 168                 {
 169                         this.baseSize = baseSize;
 170                         this.size = 1 << baseSize;
 171                         this.segment = new T[size];
 172                 }
 173
 174                 public int Size {
 175                         get {
 176                                 return size;
 177                         }
 178                 }
 179
 180                 public T this[int index] {
 181                         get {
 182                                 return segment[index % size];
 183                         }
 184                         set {
 185                                 segment[index % size] = value;
 186                         }
 187                 }
 188
 189                 public CircularArray<T> Grow (int bottom, int top)
 190                 {
 191                         var grow = new CircularArray<T> (baseSize + 1);
 192
 193                         for (int i = top; i < bottom; i++) {
 194                                 grow.segment[i] = segment[i % size];
 195                         }
 196
 197                         return grow;
 198                 }
 199
 200                 public IEnumerable<T> GetEnumerable (int bottom, ref int top)
 201                 {
 202                         int instantTop = top;
 203                         T[] slice = new T[bottom - instantTop];
 204                         int destIndex = -1;
 205                         for (int i = instantTop; i < bottom; i++)
 206                                 slice[++destIndex] = segment[i % size];
 207
 208                         return RealGetEnumerable (slice, bottom, top, instantTop);
 209                 }
 210
 211                 IEnumerable<T> RealGetEnumerable (T[] slice, int bottom, int realTop, int initialTop)
 212                 {
 213                         int destIndex = (int)(realTop - initialTop - 1);
 214                         for (int i = realTop; i < bottom; ++i)
 215                                 yield return slice[++destIndex];
 216                 }
 217         }
 218 }
 219 #endif