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.util.*;
import java.lang.ref.*;

public class ArrayIdentity {
    private static HashMap<Entry<?>, Entry<?>> set = new HashMap<Entry<?>, Entry<?>>();
    private static ReferenceQueue<Object> cleanq = new ReferenceQueue<Object>();

    private static class Entry<T> extends WeakReference<T[]> {
	private Entry(T[] arr) {
	    super(arr, cleanq);
	}
	
	public boolean equals(Object x) {
	    if(!(x instanceof Entry))
	       return(false);
	    T[] a = get();
	    if(a == null)
		return(false);
	    Entry<?> e = (Entry<?>)x;
	    Object[] ea = e.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 = get();
	    if(a == null)
		return(0);
	    int ret = 1;
	    for(T o : a)
		ret = (ret * 31) + System.identityHashCode(o);
	    return(ret);
	}
    }
    
    private static void clean() {
	Reference<?> ref;
	while((ref = cleanq.poll()) != null)
	    set.remove(ref);
    }
    
    @SuppressWarnings("unchecked")
    private static <T> Entry<T> getcanon(Entry<T> e) {
	return((Entry<T>)set.get(e));
    }

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