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

   1 // SemaphoreSlim.cs
   2 //
   3 // Copyright (c) 2008 Jérémie "Garuma" Laval
   4 //
   5 // Permission is hereby granted, free of charge, to any person obtaining a copy
   6 // of this software and associated documentation files (the "Software"), to deal
   7 // in the Software without restriction, including without limitation the rights
   8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   9 // copies of the Software, and to permit persons to whom the Software is
  10 // furnished to do so, subject to the following conditions:
  11 //
  12 // The above copyright notice and this permission notice shall be included in
  13 // all copies or substantial portions of the Software.
  14 //
  15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  21 // THE SOFTWARE.
  22 //
  23 //
  24
  25 using System;
  26 using System.Diagnostics;
  27
  28 #if NET_4_0 || MOBILE
  29 namespace System.Threading
  30 {
  31         [System.Diagnostics.DebuggerDisplayAttribute ("Current Count = {currCount}")]
  32         public class SemaphoreSlim : IDisposable
  33         {
  34                 const int spinCount = 10;
  35                 const int deepSleepTime = 20;
  36
  37                 readonly int maxCount;
  38                 int currCount;
  39                 bool isDisposed;
  40
  41                 EventWaitHandle handle;
  42
  43                 public SemaphoreSlim (int initialCount) : this (initialCount, int.MaxValue)
  44                 {
  45                 }
  46
  47                 public SemaphoreSlim (int initialCount, int maxCount)
  48                 {
  49                         if (initialCount < 0 || initialCount > maxCount || maxCount < 0)
  50                                 throw new ArgumentOutOfRangeException ("The initialCount  argument is negative, initialCount is greater than maxCount, or maxCount is not positive.");
  51
  52                         this.maxCount = maxCount;
  53                         this.currCount = initialCount;
  54                         this.handle = new ManualResetEvent (initialCount == 0);
  55                 }
  56
  57                 ~SemaphoreSlim ()
  58                 {
  59                         Dispose(false);
  60                 }
  61
  62                 public void Dispose ()
  63                 {
  64                         Dispose(true);
  65                 }
  66
  67                 protected virtual void Dispose (bool disposing)
  68                 {
  69                         isDisposed = true;
  70                 }
  71
  72                 void CheckState ()
  73                 {
  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 int Release ()
  85                 {
  86                         return Release(1);
  87                 }
  88
  89                 public int Release (int releaseCount)
  90                 {
  91                         CheckState ();
  92                         if (releaseCount < 1)
  93                                 throw new ArgumentOutOfRangeException ("releaseCount", "releaseCount is less than 1");
  94
  95                         // As we have to take care of the max limit we resort to CAS
  96                         int oldValue, newValue;
  97                         do {
  98                                 oldValue = currCount;
  99                                 newValue = (currCount + releaseCount);
 100                                 newValue = newValue > maxCount ? maxCount : newValue;
 101                         } while (Interlocked.CompareExchange (ref currCount, newValue, oldValue) != oldValue);
 102
 103                         handle.Set ();
 104
 105                         return oldValue;
 106                 }
 107
 108                 public void Wait ()
 109                 {
 110                         Wait (CancellationToken.None);
 111                 }
 112
 113                 public bool Wait (TimeSpan timeout)
 114                 {
 115                         return Wait ((int)timeout.TotalMilliseconds, CancellationToken.None);
 116                 }
 117
 118                 public bool Wait (int millisecondsTimeout)
 119                 {
 120                         return Wait (millisecondsTimeout, CancellationToken.None);
 121                 }
 122
 123                 public void Wait (CancellationToken cancellationToken)
 124                 {
 125                         Wait (-1, cancellationToken);
 126                 }
 127
 128                 public bool Wait (TimeSpan timeout, CancellationToken cancellationToken)
 129                 {
 130                         CheckState();
 131                         return Wait ((int)timeout.TotalMilliseconds, cancellationToken);
 132                 }
 133
 134                 public bool Wait (int millisecondsTimeout, CancellationToken cancellationToken)
 135                 {
 136                         CheckState ();
 137                         if (millisecondsTimeout < -1)
 138                                 throw new ArgumentOutOfRangeException ("millisecondsTimeout",
 139                                                                        "millisecondsTimeout is a negative number other than -1");
 140
 141                         Watch sw = Watch.StartNew ();
 142
 143                         Func<bool> stopCondition = () => millisecondsTimeout >= 0 && sw.ElapsedMilliseconds > millisecondsTimeout;
 144
 145                         do {
 146                                 bool shouldWait;
 147                                 int result;
 148
 149                                 do {
 150                                         cancellationToken.ThrowIfCancellationRequested ();
 151                                         if (stopCondition ())
 152                                                 return false;
 153
 154                                         shouldWait = true;
 155                                         result = currCount;
 156
 157                                         if (result > 0)
 158                                                 shouldWait = false;
 159                                         else
 160                                                 break;
 161                                 } while (Interlocked.CompareExchange (ref currCount, result - 1, result) != result);
 162
 163                                 if (!shouldWait) {
 164                                         if (result == 1)
 165                                                 handle.Reset ();
 166                                         break;
 167                                 }
 168
 169                                 SpinWait wait = new SpinWait ();
 170
 171                                 while (Thread.VolatileRead (ref currCount) <= 0) {
 172                                         cancellationToken.ThrowIfCancellationRequested ();
 173                                         if (stopCondition ())
 174                                                 return false;
 175
 176                                         if (wait.Count > spinCount)
 177                                                 handle.WaitOne (Math.Min (Math.Max (millisecondsTimeout - (int)sw.ElapsedMilliseconds, 1), deepSleepTime));
 178                                         else
 179                                                 wait.SpinOnce ();
 180                                 }
 181                         } while (true);
 182
 183                         return true;
 184                 }
 185
 186                 public WaitHandle AvailableWaitHandle {
 187                         get {
 188                                 return handle;
 189                         }
 190                 }
 191         }
 192 }
 193 #endif