/*
 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
 *
 *  This file is licensed to You under the Common Public License (CPL);
 *  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/cpl1.0.php
 *
 *  See the COPYRIGHT.txt file distributed with this work for information
 *  regarding copyright ownership.
 */
package org.mmtk.plan.refcount;

import org.mmtk.utility.sanitychecker.SanityChecker;
import org.mmtk.utility.sanitychecker.SanityCheckerLocal;

import org.mmtk.vm.VM;

import org.vmmagic.pragma.*;
import org.vmmagic.unboxed.*;

/**
 * This class performs sanity checks for reference counting collectors.
 */
@Uninterruptible public class RCSanityCheckerLocal extends SanityCheckerLocal {

  /**
   * Return the expected reference count. For non-reference counting
   * collectors this becomes a true/false relationship.
   *
   * @param object The object to check.
   * @param sanityRootRC The number of root references to the object.
   * @return The expected (root excluded) reference count.
   */
  protected int sanityExpectedRC(ObjectReference object,
                                 int sanityRootRC) {
    if (VM.activePlan.global().getSanityChecker().preGCSanity()) {
      return SanityChecker.UNSURE;
    }

    if (RCBase.isRCObject(object)) {
      if (!RCHeader.isLiveRC(object)) {
        return SanityChecker.DEAD;
      }
      return RCHeader.getRC(object) - sanityRootRC;
    } else {
      return SanityChecker.UNSURE;
    }
  }

}