--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/internal/FileChangeMonitor.java	Thu May 09 21:06:48 2013 +0200
@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2013 TMate Software Ltd
+ *  
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * For information on how to redistribute this software under
+ * the terms of a license other than GNU General Public License
+ * contact TMate Software at support@hg4j.com
+ */
+package org.tmatesoft.hg.internal;
+
+import java.io.File;
+
+/**
+ * This shall become interface/abstract class accessible from SessionContext,
+ * with plugable implementations, e.g. Java7 (file monitoring facilities) based,
+ * or any other convenient means. It shall allow both "check at the moment asked" 
+ * and "collect changes and dispatch on demand" implementation approaches, so that
+ * implementors may use best available technology   
+ * 
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+public class FileChangeMonitor {
+	private final File file;
+	private long lastModified;
+	private long length;
+	
+	/**
+	 * First round: support for 1-monitor-1-file only
+	 * Next round: 1-monitor-N files
+	 */
+	public FileChangeMonitor(File f) {
+		file = f;
+	}
+	
+	// shall work for files that do not exist
+	public void touch(Object source) {
+		lastModified = file.lastModified();
+		length = file.length();
+	}
+	
+	public void check(Object source, Action onChange) {
+		if (changed(source)) {
+			onChange.changed();
+		}
+	}
+
+	public boolean changed(Object source) {
+		if (file.lastModified() != lastModified) {
+			return true;
+		}
+		return file.length() != length; 
+	}
+	
+	public interface Action {
+		public void changed();
+	}
+}