001/*
002 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
003 *
004 *  This file is licensed to You under the Eclipse Public License (EPL);
005 *  You may not use this file except in compliance with the License. You
006 *  may obtain a copy of the License at
007 *
008 *      http://www.opensource.org/licenses/eclipse-1.0.php
009 *
010 *  See the COPYRIGHT.txt file distributed with this work for information
011 *  regarding copyright ownership.
012 */
013package org.jikesrvm.compilers.opt.util;
014
015
016/**
017 * Interface to allow building top-sort, by calling TopSort.buildTopSort()
018 */
019public interface TopSortInterface {
020
021  /**
022   * Return the start node if forward = true for forward topsort,
023   * and return the end node if forward = false for backward topsort.
024   * @param forward whether we are viewing the graph in the forward direction
025   * @return the start node if forward = true for forward topsort,
026   *         the end node if forward = false for backward topsort.
027   */
028  SortedGraphNode startNode(boolean forward);
029
030  /**
031   * Return the number of nodes in the graph
032   * @return the number of nodes in the graph
033   */
034  int numberOfNodes();
035
036  /**
037   * Return true if no resetTopSorted(forward) has been executed
038   * since the last setTopSorted(forward) has been executed
039   * @param forward whether we are viewing the graph in the forward direction
040   * @return true if no resetTopSorted(forward) has been executed
041   * since the last setTopSorted(forward) has been executed
042   */
043  boolean isTopSorted(boolean forward);
044
045  /**
046   * Should have a side effect such that isTopSorted(forward)
047   * returns the correct value.
048   * @param forward whether we are viewing the graph in the forward direction
049   */
050  void setTopSorted(boolean forward);
051
052  /**
053   * Should have a side effect such that isTopSorted(forward)
054   * returns the correct value.
055   */
056  void resetTopSorted();
057}
058
059
060