ArrayIdentity.java

/*
 *  This file is part of the Haven & Hearth game client.
 *  Copyright (C) 2009 Fredrik Tolf <fredrik@dolda2000.com>, and
 *                     Björn Johannessen <johannessen.bjorn@gmail.com>
 *
 *  Redistribution and/or modification of this file is subject to the
 *  terms of the GNU Lesser General Public License, version 3, as
 *  published by the Free Software Foundation.
 *
 *  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.
 *
 *  Other parts of this source tree adhere to other copying
 *  rights. Please see the file `COPYING' in the root directory of the
 *  source tree for details.
 *
 *  A copy the GNU Lesser General Public License is distributed along
 *  with the source tree of which this file is a part in the file
 *  `doc/LPGL-3'. If it is missing for any reason, please see the Free
 *  Software Foundation's website at <http://www.fsf.org/>, or write
 *  to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 *  Boston, MA 02111-1307 USA
 */

package haven;

import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Iterator;

public class ArrayIdentity {
	private static HashMap<Entry<?>, Entry<?>> set = new HashMap<Entry<?>, Entry<?>>();
	private static int cleanint = 0;

	private static class Entry<T> {
		WeakReference<T[]> arr;

		private Entry(T[] arr) {
			this.arr = new WeakReference<T[]>(arr);
		}

		public boolean equals(Object x) {
			if (!(x instanceof Entry))
				return (false);
			T[] a = arr.get();
			if (a == null)
				return (false);
			Entry<?> e = (Entry<?>) x;
			Object[] ea = e.arr.get();
			if (ea == null)
				return (false);
			if (ea.length != a.length)
				return (false);
			for (int i = 0; i < a.length; i++) {
				if (a[i] != ea[i])
					return (false);
			}
			return (true);
		}

		public int hashCode() {
			T[] a = arr.get();
			if (a == null)
				return (0);
			int ret = 1;
			for (T o : a)
				ret = (ret * 31) + System.identityHashCode(o);
			return (ret);
		}
	}

	private static synchronized void clean() {
		for (Iterator<Entry<?>> i = set.keySet().iterator(); i.hasNext();) {
			Entry<?> e = i.next();
			if (e.arr.get() == null)
				i.remove();
		}
	}

	@SuppressWarnings("unchecked")
	private static <T> Entry<T> getcanon(Entry<T> e) {
		return ((Entry<T>) set.get(e));
	}

	public static <T> T[] intern(T[] arr) {
		synchronized (ArrayIdentity.class) {
			if (cleanint++ > 100) {
				clean();
				cleanint = 0;
			}
		}
		Entry<T> e = new Entry<T>(arr);
		synchronized (ArrayIdentity.class) {
			Entry<T> e2 = getcanon(e);
			T[] ret;
			if (e2 == null) {
				set.put(e, e);
				ret = arr;
			} else {
				ret = e2.arr.get();
				if (ret == null) {
					set.remove(e2);
					set.put(e, e);
					ret = arr;
				}
			}
			return (ret);
		}
	}
}