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/*
 * Bytecode Analysis Framework
 * Copyright (C) 2003,2004 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.Comparator;

/**
 * A BlockOrder for visiting the blocks of a CFG in the reverse of the order in
 * which they are finished in a depth first search. This is the most efficient
 * visitation order for forward dataflow analyses.
 *
 * @see BlockOrder
 * @see DepthFirstSearch
 * @see CFG
 * @see BasicBlock
 */
public class ReversePostOrder extends AbstractBlockOrder {
    /**
     * A Comparator to order the blocks in the reverse of the order in which
     * they would be finished by a depth first search.
     */
    private static class ReversePostfixComparator implements Comparator {
        private final DepthFirstSearch dfs;

        public ReversePostfixComparator(DepthFirstSearch dfs) {
            this.dfs = dfs;
        }

        @Override
        public int compare(BasicBlock aa, BasicBlock bb) {
            return dfs.getFinishTime(bb) - dfs.getFinishTime(aa);
        }
    }

    /**
     * Constructor.
     *
     * @param cfg
     *            the CFG for the method
     * @param dfs
     *            the DepthFirstSearch on the method
     */
    public ReversePostOrder(CFG cfg, DepthFirstSearch dfs) {
        super(cfg, new ReversePostfixComparator(dfs));
    }
}