/**
 *   Copyright (c) Rich Hickey. All rights reserved.
 *   The use and distribution terms for this software are covered by the
 *   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
 *   which can be found in the file epl-v10.html at the root of this distribution.
 *   By using this software in any fashion, you are agreeing to be bound by
 * 	 the terms of this license.
 *   You must not remove this notice, or any other, from this software.
 **/

/* rich Nov 8, 2009 */

package clojure.lang;

public final class MethodImplCache{

static public class Entry{
	final public Class c;
	final public IFn fn;

	public Entry(Class c, IFn fn){
		this.c = c;
		this.fn = fn;
	}
}

public final IPersistentMap protocol;
public final Keyword methodk;
public final int shift;
public final int mask;
public final Object[] table;    //[class, entry. class, entry ...]

volatile Entry mre = null;

public MethodImplCache(IPersistentMap protocol, Keyword methodk){
	this(protocol, methodk, 0, 0, RT.EMPTY_ARRAY);
}

public MethodImplCache(IPersistentMap protocol, Keyword methodk, int shift, int mask, Object[] table){
	this.protocol = protocol;
	this.methodk = methodk;
	this.shift = shift;
	this.mask = mask;
	this.table = table;
}

public IFn fnFor(Class c){
	Entry last = mre;
	if(last != null && last.c == c)
		return last.fn;
	return findFnFor(c);
}

IFn findFnFor(Class c){
	int idx = ((Util.hash(c) >> shift) & mask) << 1;
	if(idx < table.length && table[idx] == c)
		{
		Entry e = ((Entry) table[idx + 1]);
		mre = e;
		return  e != null ? e.fn : null;
		}
	return null;
}


}