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/**
 *   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;

import java.util.Map;

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 ...]
public final Map map;

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;
    this.map = null;
}

public MethodImplCache(IPersistentMap protocol, Keyword methodk, Map map){
    this.protocol = protocol;
    this.methodk = methodk;
    this.shift = 0;
    this.mask = 0;
    this.table = null;
    this.map = map;
}

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

IFn findFnFor(Class c){
    if (map != null)
        {
        Entry e = (Entry) map.get(c);
        mre = e;
        return  e != null ? e.fn : null;
        }
    else
        {
        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;
        }
}


}