greedypool.java

与postgresql数据库结合的数据库水印软件包

/*
 * 
 * Copyright 2003,2004 The Watermill Team
 *
 * This file is part of Watermill.
 *
 *    Watermill is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    Watermill 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.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with Watermill; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */
package Watermill.kernel;

import java.io.*;
import java.util.*;

public class GreedyPool extends Pool implements Serializable {
    Identifiers identifiers;
    
    public GreedyPool(String ipn,Document id,WSchema iws){
	super(ipn,id,iws);
	
	identifiers=id.getModifiableValuesIdentifiers(wschema.getLocalConstraints());
	Msg.debug("Identifiers:"+identifiers.toString());
	
    } 

    public Watermark watermark(Document doc,int seed){
	Random r=new Random(seed);
	Watermark res=new Watermark();
	Msg.debug("Watermark");
	
	for(Enumeration e=identifiers.elements();e.hasMoreElements();){
	    Identifier id=(Identifier)e.nextElement();
	    Msg.debug("identifier="+id);
	    boolean b=r.nextBoolean();
	    int d=id.maxDistortion;
	    if (b) d=-d;
	    
	    doc.addValue(id,new Value(d));
	    Msg.debug("Trying distortion "+d+" on identifier "+id.toString());
	    
	    if (doc.checkGlobalConstraints(document,wschema.globalConstraints)){
		Msg.debug("Global distortion ok, keeping.");
		res.put(id,new Value(d));
	    }
	    else {
		Msg.debug("Bad global distortion, reverting.");
		doc.addValue(id,new Value(-d));
	    }
	}
	return res;
    }
}