/* Soot - a J*va Optimization Framework
 * Copyright (C) 2002 Ondrej Lhotak
 *
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

package soot.jimple.spark.sets;
import soot.*;
import soot.jimple.ClassConstant;
import soot.jimple.spark.pag.Node;

import java.util.*;

/** Implementation of an empty, immutable points-to set.
 * @author Ondrej Lhotak
 */
public class EmptyPointsToSet extends PointsToSetInternal {
    public EmptyPointsToSet( Singletons.Global g ) { super(null); }
    public static EmptyPointsToSet v() { return G.v().soot_jimple_spark_sets_EmptyPointsToSet(); }
    
    public EmptyPointsToSet(Singletons.Global g, Type type) {
    	super(type);
    }

    /** Returns true if this set contains no run-time objects. */
    public boolean isEmpty() { return true; }
    /** Returns true if this set shares some objects with other. */
    public boolean hasNonEmptyIntersection( PointsToSet other ) {
        return false;
    }
    /** Set of all possible run-time types of objects in the set. */
    public Set<Type> possibleTypes() { return Collections.emptySet(); }
    /** Adds contents of other into this set, returns true if this set 
     * changed. */
    public boolean addAll( PointsToSetInternal other,
            PointsToSetInternal exclude ) {
        throw new RuntimeException( "can't add into empty immutable set" );
    }
    /** Calls v's visit method on all nodes in this set. */
    public boolean forall( P2SetVisitor v ) {
        return false;
    }
    /** Adds n to this set, returns true if n was not already in this set. */
    public boolean add( Node n ) {
        throw new RuntimeException( "can't add into empty immutable set" );
    }
    /** Returns true iff the set contains n. */
    public boolean contains( Node n ) {
        return false;
    }

    public Set<String> possibleStringConstants() { return Collections.emptySet(); }
    public Set<ClassConstant> possibleClassConstants() { return Collections.emptySet(); }
    
    /**
     * {@inheritDoc}
     */
    public String toString() {
    	return "{}";
    }

}