/*
 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
 *
 *  This file is licensed to You under the Eclipse Public License (EPL);
 *  You may not use this file except in compliance with the License. You
 *  may obtain a copy of the License at
 *
 *      http://www.opensource.org/licenses/eclipse-1.0.php
 *
 *  See the COPYRIGHT.txt file distributed with this work for information
 *  regarding copyright ownership.
 */
package org.jikesrvm.compilers.opt.regalloc;

import java.util.Comparator;

/**
 * Implements a set of Basic Intervals, sorted by end number.
 * <p>
 * This version uses container-mapping as a function in the comparator.
 */
class IncreasingEndMappedIntervalSet extends IntervalSet {
  /** Support for Set serialization */
  static final long serialVersionUID = -3121737650157210290L;

  /**
   * Imposes an ascending ordering based on the end points of basic intervals.
   * For mapped basic intervals, the register numbers are also compared.
   * <p>
   * Note that this ordering would be inconsistent with equals if both objects
   * of type {@link BasicInterval} and {@link MappedBasicInterval} were contained
   * in the set. A comparison of a MappedBasicInterval with a BasicInterval may
   * consider both to be the same because their begin and end are the same but
   * the equals methods would not consider the objects as equal.
   */
  private static class EndComparator implements Comparator<BasicInterval> {
    @Override
    public int compare(BasicInterval b1, BasicInterval b2) {
      int result = b1.getEnd() - b2.getEnd();
      if (result == 0) {
        result = b1.getBegin() - b2.getBegin();
      }
      if (result == 0) {
        if (b1 instanceof MappedBasicInterval) {
          if (b2 instanceof MappedBasicInterval) {
            MappedBasicInterval mb1 = (MappedBasicInterval) b1;
            MappedBasicInterval mb2 = (MappedBasicInterval) b2;
            return mb1.container.getRegister().number - mb2.container.getRegister().number;
          }
        }
      }
      return result;
    }
  }

  static final IncreasingEndMappedIntervalSet.EndComparator c = new EndComparator();

  IncreasingEndMappedIntervalSet() {
    super(c);
  }
}