org.exist.xquery.CachedResult Maven / Gradle / Ivy

Go to download
/*
 * eXist-db Open Source Native XML Database
 * Copyright (C) 2001 The eXist-db Authors
 *
 * [email protected]
 * http://www.exist-db.org
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.exist.xquery;

import org.exist.xquery.value.Item;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.Type;

/**
 * This class is used to hold an intermediate result that can be cached.
 * Caching results is effective if a subexpression is executed more than once
 * and the current evaluation context doesn't change between invocations.
 * 
 * @author wolf
 */
public class CachedResult {

	final protected Sequence cachedResult;
	final protected Sequence cachedContext;
	final protected Item cachedItem;	
	final protected int timestamp;
	
	public CachedResult(Sequence context, Item contextItem, Sequence result) {
		this.cachedContext = context;
		this.cachedResult = result;
		this.cachedItem = contextItem;
		this.timestamp = context.getState();
	}
	
	public Sequence getResult() {
		return cachedResult;
	}
	
	public boolean isValid(Sequence context, Item contextItem) {
        if (context == null)
            {return false;}
		if(Type.subTypeOf(context.getItemType(), Type.NODE) &&
			cachedContext == context && cachedItem == contextItem) {
			if(context.hasChanged(timestamp)) {
				return false;
			} else {
				cachedResult.setIsCached(true);
				return true;
			}
		}
		return false;
	}
}