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/* $Id: PathWatcher.cs,v 1.5 2009/06/03 01:10:59 ellson Exp $ $Revision: 1.5 $ */
/* vim:set shiftwidth=4 ts=8: */
/**********************************************************
* This software is part of the graphviz package *
* http://www.graphviz.org/ *
* *
* Copyright (c) 1994-2008 AT&T Corp. *
* and is licensed under the *
* Common Public License, Version 1.0 *
* by AT&T Corp. *
* *
* Information and Software Systems Research *
* AT&T Research, Florham Park NJ *
**********************************************************/
using System;
using System.ComponentModel;
using System.IO;
using System.Threading;
namespace Graphviz
{
public class PathWatcher: IDisposable
{
public event CancelEventHandler Changed;
public ISynchronizeInvoke SynchronizingObject
{
get { return _synchronizingObject; }
set { _synchronizingObject = value; }
}
public string Watched
{
get { return _watched; }
}
public PathWatcher(string watched)
{
_watched = watched;
_synchronizingObject = null;
_lastChange = DateTime.MinValue;
_checker = new Timer(delegate(object state)
{
CheckPath();
});
_watcher = new FileSystemWatcher(Path.GetDirectoryName(watched), Path.GetFileName(watched));
_watcher.NotifyFilter = NotifyFilters.FileName | NotifyFilters.LastWrite;
_watcher.Changed += delegate(object sender, FileSystemEventArgs eventArgs)
{
/* check now */
CheckPath();
};
_watcher.Created += delegate(object sender, FileSystemEventArgs eventArgs)
{
/* check now */
CheckPath();
};
_watcher.Renamed += delegate(object sender, RenamedEventArgs eventArgs)
{
/* if file got changed to our name, check now */
if (eventArgs.Name == _watcher.Filter)
CheckPath();
};
}
public void Start()
{
_watcher.EnableRaisingEvents = true;
}
void IDisposable.Dispose()
{
_checker.Dispose();
}
private void CheckPath()
{
/* schedule a check for the path on the synchronizing object, usually a window */
_synchronizingObject.BeginInvoke((ThreadStart)delegate()
{
if (Changed != null)
{
/* debounce file watch changes: if last write time hadn't actually changed, don't bother notifying */
/* NOTE: we only mutate _lastChange via this synchronized code, so there should be no race condition */
DateTime thisChange = File.GetLastWriteTimeUtc(_watched);
if (_lastChange != thisChange)
{
/* if any registered delegate didn't cancel the event, ask checker to check it again after a while */
CancelEventArgs eventArgs = new CancelEventArgs(true);
Changed(this, eventArgs);
if (eventArgs.Cancel)
_lastChange = thisChange;
else
_checker.Change(RECHECK_DELAY, Timeout.Infinite);
}
}
}, new object[0]);
}
private const int RECHECK_DELAY = 100;
private readonly string _watched;
private ISynchronizeInvoke _synchronizingObject;
private DateTime _lastChange;
private readonly Timer _checker;
private readonly FileSystemWatcher _watcher;
}
}
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