mcs/class/System.Runtime.Caching/System.Runtime.Caching/ChangeMonitor.cs

   1 //
   2 // ChangeMonitor.cs
   3 //
   4 // Authors:
   5 //      Marek Habersack <mhabersack@novell.com>
   6 //
   7 // Copyright (C) 2010 Novell, Inc. (http://novell.com/)
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining
  10 // a copy of this software and associated documentation files (the
  11 // "Software"), to deal in the Software without restriction, including
  12 // without limitation the rights to use, copy, modify, merge, publish,
  13 // distribute, sublicense, and/or sell copies of the Software, and to
  14 // permit persons to whom the Software is furnished to do so, subject to
  15 // the following conditions:
  16 //
  17 // The above copyright notice and this permission notice shall be
  18 // included in all copies or substantial portions of the Software.
  19 //
  20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  21 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  22 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  23 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  24 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  25 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  26 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  27 //
  28 using System;
  29
  30 namespace System.Runtime.Caching
  31 {
  32         public abstract class ChangeMonitor : IDisposable
  33         {
  34                 bool initializationComplete;
  35                 bool notifyOnChangedCalled;
  36                 OnChangedCallback onChangedCallback;
  37                 object onChangedState;
  38
  39                 public bool HasChanged { get; private set; }
  40                 public bool IsDisposed { get; private set; }
  41                 public abstract string UniqueId { get; }
  42
  43                 protected ChangeMonitor ()
  44                 {
  45                 }
  46
  47                 public void Dispose ()
  48                 {
  49                         if (IsDisposed)
  50                                 return;
  51
  52                         if (!initializationComplete)
  53                                 // TODO: check if Dispose (bool) is called in this case
  54                                 throw new InvalidOperationException ("Initialization is not complete in the derived change-monitor class that called the base Dispose method.");
  55
  56                         try {
  57                                 try {
  58                                         InvokeOnChangedCallback (onChangedState);
  59                                 } catch {
  60                                         // ignore
  61                                         // TODO: check what happens if the callback throws an exception - is
  62                                         // Dispose (true) called then?
  63                                 }
  64
  65                                 Dispose (true);
  66                         } finally {
  67                                 IsDisposed = true;
  68                         }
  69                 }
  70
  71                 protected abstract void Dispose (bool disposing);
  72
  73                 protected void InitializationComplete ()
  74                 {
  75                         initializationComplete = true;
  76                         if (HasChanged)
  77                                 Dispose ();
  78                 }
  79
  80                 void InvokeOnChangedCallback (object state)
  81                 {
  82                         if (onChangedCallback == null)
  83                                 return;
  84
  85                         try {
  86                                 onChangedCallback (state);
  87                         } finally {
  88                                 onChangedCallback = null;
  89                                 onChangedState = null;
  90                         }
  91                 }
  92
  93                 public void NotifyOnChanged (OnChangedCallback onChangedCallback)
  94                 {
  95                         if (onChangedCallback == null)
  96                                 throw new ArgumentNullException ("onChangedCallback");
  97
  98                         if (notifyOnChangedCalled)
  99                                 throw new InvalidOperationException ("The callback method has already been invoked.");
 100
 101                         notifyOnChangedCalled = true;
 102                         this.onChangedCallback = onChangedCallback;
 103                         if (HasChanged) {
 104                                 InvokeOnChangedCallback (onChangedState);
 105                                 return;
 106                         }
 107
 108                 }
 109
 110                 protected void OnChanged (object state)
 111                 {
 112                         HasChanged = true;
 113                         try {
 114                                 if (onChangedCallback == null)
 115                                         onChangedState = state;
 116                                 else
 117                                         InvokeOnChangedCallback (state);
 118                         } catch {
 119                                 // ignore
 120                                 // TODO: check what happens if callback throws an exception - is
 121                                 // Dispose below called?
 122                         } finally {
 123                                 if (initializationComplete)
 124                                         Dispose ();
 125                         }
 126                 }
 127         }
 128 }