MovingMapCache.java

/*
    GNU General Public License
    CacheWolf is a software for PocketPC, Win and Linux that
    enables paperless caching.
    It supports the sites geocaching.com and opencaching.de

    Copyright (C) 2006  CacheWolf development team
	See http://www.cachewolf.de/ for more information.
    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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
package CacheWolf.navi;

import ewe.fx.Dimension;
import ewe.util.Hashtable;
import ewe.util.Iterator;
import ewe.util.Map;
import ewe.util.Map.MapEntry;
import ewe.util.Vector;

public class MovingMapCache {

	/**
	 * Implements singleton pattern
	 */
	private static MovingMapCache singleton;

	/**
	 * Map<Key,Value> holding map-parts
	 */
	private Map cache;

	/**
	 * Map<String,Dimension> holding dimensions of the images
	 */
	private Map dimensions;

	/**
	 * private Xtor for singleton pattern
	 * 
	 */
	private MovingMapCache() {
		cache = new Hashtable();
		dimensions = new Hashtable();
	}

	public static MovingMapCache movingMapCache() {
		if (singleton == null) {
			singleton = new MovingMapCache();
		}

		return singleton;
	}

	public MapImage get(String filename, int row, int column) {
		Key key = new Key();
		key.filename = filename;
		key.row = row;
		key.column = column;

		Value v = (Value) cache.get(key);
		if (v != null) {
			v.used = true;
			return v.image;
		}
		else {
			return null;
		}
	}

	public void put(String filename, int row, int column, MapImage im) {
		Key key = new Key();
		key.filename = filename;
		key.row = row;
		key.column = column;

		cache.put(key, new Value(im));
	}

	public void clearUsedFlags() {
		for (Iterator i = cache.entries(); i.hasNext();) {
			MapEntry element = (MapEntry) i.next();
			Value v = (Value) element.getValue();
			v.used = false;
		}

	}

	public void cleanCache() {
		//EWE does not suport the remove-operation on Hashtables.
		Vector keysToRemove = new Vector();
		for (Iterator i = cache.entries(); i.hasNext();) {
			MapEntry element = (MapEntry) i.next();
			Value v = (Value) element.getValue();
			if (!v.used) {
				keysToRemove.add(element.getKey());
			}
		}
		for (Iterator i = keysToRemove.iterator(); i.hasNext();) {
			Object element = i.next();
			cache.remove(element);
		}
	}

	private class Key {
		private String filename;
		private int row;
		private int column;

		public int hashCode() {
			final int PRIME = 31;
			int result = 1;
			result = PRIME * result + column;
			result = PRIME * result + ((filename == null) ? 0 : filename.hashCode());
			result = PRIME * result + row;
			return result;
		}

		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (obj == null)
				return false;
			if (!(obj instanceof Key))
				return false;
			final Key other = (Key) obj;
			if (column != other.column)
				return false;
			if (filename == null) {
				if (other.filename != null)
					return false;
			}
			else if (!filename.equals(other.filename))
				return false;
			if (row != other.row)
				return false;
			return true;
		}

	}

	private class Value {
		MapImage image;

		boolean used;

		public Value(MapImage im) {
			image = im;
			used = true;
		}

	}

	public Dimension getDimension(String filename) {
		return (Dimension) dimensions.get(filename);
	}

	public void putDimension(String filename, Dimension rect2) {
		dimensions.put(filename, rect2);
	}

}