mcs/class/corlib/System.Threading/SemaphoreSlim.cs

   1 #if NET_4_0
   2 // SemaphoreSlim.cs
   3 //
   4 // Copyright (c) 2008 Jérémie "Garuma" Laval
   5 //
   6 // Permission is hereby granted, free of charge, to any person obtaining a copy
   7 // of this software and associated documentation files (the "Software"), to deal
   8 // in the Software without restriction, including without limitation the rights
   9 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10 // copies of the Software, and to permit persons to whom the Software is
  11 // furnished to do so, subject to the following conditions:
  12 //
  13 // The above copyright notice and this permission notice shall be included in
  14 // all copies or substantial portions of the Software.
  15 //
  16 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22 // THE SOFTWARE.
  23 //
  24 //
  25
  26 using System;
  27 using System.Diagnostics;
  28
  29 namespace System.Threading
  30 {
  31         public class SemaphoreSlim: IDisposable, ISupportsCancellation
  32         {
  33                 readonly int max;
  34
  35                 int currCount;
  36
  37                 bool isCanceled;
  38                 bool isDisposed;
  39
  40                 SpinWait wait = new SpinWait();
  41
  42                 public SemaphoreSlim(int initial): this (initial, int.MaxValue)
  43                 {
  44                 }
  45
  46                 public SemaphoreSlim(int initial, int max)
  47                 {
  48                         if (initial < 0 || initial > max || max < 0)
  49                                 throw new ArgumentOutOfRangeException("The initial  argument is negative, initial is greater than max, or max is not positive.");
  50
  51                         this.max = max;
  52                         this.currCount = initial;
  53                 }
  54
  55                 ~SemaphoreSlim()
  56                 {
  57                         Dispose(false);
  58                 }
  59
  60                 public void Dispose()
  61                 {
  62                         Dispose(true);
  63                 }
  64
  65                 protected virtual void Dispose(bool managedRes)
  66                 {
  67                         isDisposed = true;
  68                 }
  69
  70                 void CheckState()
  71                 {
  72                         if (isCanceled)
  73                                 throw new OperationCanceledException("The SemaphoreSlim is canceled.");
  74                         if (isDisposed)
  75                                 throw new ObjectDisposedException("The SemaphoreSlim has been disposed.");
  76                 }
  77
  78                 public int CurrentCount {
  79                         get {
  80                                 return currCount;
  81                         }
  82                 }
  83
  84                 public bool IsCanceled {
  85                         get {
  86                                 return isCanceled;
  87                         }
  88                 }
  89
  90                 public void Cancel()
  91                 {
  92                         isCanceled = true;
  93                 }
  94
  95                 public int Release()
  96                 {
  97                         return Release(1);
  98                 }
  99
 100                 public int Release(int releaseCount)
 101                 {
 102                         CheckState();
 103                         if (releaseCount < 0)
 104                                 throw new ArgumentOutOfRangeException("releaseCount", " The releaseCount must be positive.");
 105
 106                         // As we have to take care of the max limit we resort to CAS
 107                         int oldValue, newValue;
 108                         do {
 109                                 oldValue = currCount;
 110                                 newValue = (currCount + releaseCount);
 111                                 newValue = newValue > max ? max : newValue;
 112                         } while (Interlocked.CompareExchange(ref currCount, newValue, oldValue) != oldValue);
 113
 114                         return oldValue;
 115                 }
 116
 117                 public void Wait()
 118                 {
 119                         CheckState();
 120                         do {
 121                                 int result = Interlocked.Decrement(ref currCount);
 122                                 if (result >= 0)
 123                                         break;
 124
 125                                 // We revert back the operation
 126                                 Interlocked.Increment(ref currCount);
 127                                 while (Thread.VolatileRead(ref currCount) <= 0) {
 128                                         wait.SpinOnce();
 129                                 }
 130                         } while(true);
 131                 }
 132
 133                 public bool Wait(TimeSpan ts)
 134                 {
 135                         CheckState();
 136                         return Wait((int)ts.TotalMilliseconds);
 137                 }
 138
 139                 public bool Wait(int millisecondsTimeout)
 140                 {
 141                         CheckState();
 142                         if (millisecondsTimeout < -1)
 143                                 throw new ArgumentOutOfRangeException("millisecondsTimeout",
 144                                                                       "millisecondsTimeout is a negative number other than -1");
 145                         if (millisecondsTimeout == -1) {
 146                                 Wait();
 147                                 return true;
 148                         }
 149
 150                         do {
 151                                 int result = Interlocked.Decrement(ref currCount);
 152                                 if (result >= 0)
 153                                         break;
 154
 155                                 // We revert back the operation
 156                                 result = Interlocked.Increment(ref currCount);
 157                                 Stopwatch sw = Stopwatch.StartNew();
 158                                 while (Thread.VolatileRead(ref currCount) <= 0) {
 159                                         if (sw.ElapsedMilliseconds > millisecondsTimeout) {
 160                                                 sw.Stop();
 161                                                 return false;
 162                                         }
 163                                         wait.SpinOnce();
 164                                 }
 165                         } while(true);
 166
 167                         return true;
 168                 }
 169
 170                 public WaitHandle AvailableWaitHandle {
 171                         get {
 172                                 return null;
 173                         }
 174                 }
 175         }
 176 }
 177 #endif