/*
 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 2006, University of Maryland
 *
 * 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 edu.umd.cs.findbugs.ba;

import java.util.HashMap;
import java.util.Iterator;

/**
 * Compute a compact numbering of Locations in a CFG. This is useful for
 * analyses that want to use a BitSet to keep track of Locations.
 * 
 * @author David Hovemeyer
 */
public class CompactLocationNumbering {
    private HashMap<Location, Integer> locationToNumberMap;

    private HashMap<Integer, Location> numberToLocationMap;

    /**
     * Constructor.
     * 
     * @param cfg
     *            the CFG containing the Locations to number
     */
    public CompactLocationNumbering(CFG cfg) {
        this.locationToNumberMap = new HashMap<Location, Integer>();
        this.numberToLocationMap = new HashMap<Integer, Location>();
        build(cfg);
    }

    /**
     * Get the size of the numbering, which is the maximum number assigned plus
     * one.
     * 
     * @return the maximum number assigned plus one
     */
    public int getSize() {
        return locationToNumberMap.size();
    }

    /**
     * Get the number of given Location, which will be a non-negative integer in
     * the range 0..getSize() - 1.
     * 
     * @param location
     * @return the number of the location
     */
    public int getNumber(Location location) {
        return locationToNumberMap.get(location).intValue();
    }

    /**
     * Get the Location given its number.
     * 
     * @param number
     *            the number
     * @return Location corresponding to that number
     */
    public Location getLocation(int number) {
        return numberToLocationMap.get(number);
    }

    private void build(CFG cfg) {
        int count = 0;
        for (Iterator<Location> i = cfg.locationIterator(); i.hasNext();) {
            Integer number = count++;
            Location location = i.next();
            locationToNumberMap.put(location, number);
            numberToLocationMap.put(number, location);
        }
    }
}