//
// ChangeMonitor.cs
//
// Authors:
// Marek Habersack <mhabersack@novell.com>
//
// Copyright (C) 2010 Novell, Inc. (http://novell.com/)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
namespace System.Runtime.Caching{
public abstract class ChangeMonitor : IDisposable
{
bool initializationComplete;
bool notifyOnChangedCalled;
OnChangedCallback onChangedCallback;
object onChangedState;
public bool HasChanged { get; private set; }
public bool IsDisposed { get; private set; }
public abstract string UniqueId { get; }
protected ChangeMonitor ()
{
}
public void Dispose ()
{
if (IsDisposed)
return;
if (!initializationComplete)
// TODO: check if Dispose (bool) is called in this case
throw new InvalidOperationException ("Initialization is not complete in the derived change-monitor class that called the base Dispose method.");
try {
try {
InvokeOnChangedCallback (onChangedState);
} catch {
// ignore
// TODO: check what happens if the callback throws an exception - is
// Dispose (true) called then?
}
Dispose (true);
} finally {
IsDisposed = true;
}
}
protected abstract void Dispose (bool disposing);
protected void InitializationComplete ()
{
initializationComplete = true;
if (HasChanged)
Dispose ();
}
void InvokeOnChangedCallback (object state)
{
if (onChangedCallback == null)
return;
try {
onChangedCallback (state);
} finally {
onChangedCallback = null;
onChangedState = null;
}
}
public void NotifyOnChanged (OnChangedCallback onChangedCallback)
{
if (onChangedCallback == null)
throw new ArgumentNullException ("onChangedCallback");
if (notifyOnChangedCalled)
throw new InvalidOperationException ("The callback method has already been invoked.");
notifyOnChangedCalled = true;
this.onChangedCallback = onChangedCallback;
if (HasChanged) {
InvokeOnChangedCallback (onChangedState);
return;
}
}
protected void OnChanged (object state)
{
HasChanged = true;
try {
if (onChangedCallback == null)
onChangedState = state;
else
InvokeOnChangedCallback (state);
} catch {
// ignore
// TODO: check what happens if callback throws an exception - is
// Dispose below called?
} finally {
if (initializationComplete)
Dispose ();
}
}
}
}
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