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.mmtk.utility.deque;
014
015import org.mmtk.vm.VM;
016import org.vmmagic.pragma.Uninterruptible;
017import org.vmmagic.unboxed.Address;
018
019/**
020 * This supports <i>unsynchronized</i> enqueuing and dequeuing of
021 * address pairs
022 */
023@Uninterruptible public class AddressPairDeque extends LocalDeque {
024
025  /****************************************************************************
026   *
027   * Public instance methods
028   */
029
030  /**
031   * Constructor
032   *
033   * @param queue The shared queue to which this queue will append
034   * its buffers (when full or flushed) and from which it will acquire new
035   * buffers when it has exhausted its own.
036   */
037  public AddressPairDeque(SharedDeque queue) {
038    super(queue);
039  }
040
041  /**
042   * Insert an address pair into the address queue.
043   *
044   * @param addr1 the first address to be inserted into the address queue
045   * @param addr2 the second address to be inserted into the address queue
046   */
047  public final void insert(Address addr1, Address addr2) {
048    if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!addr1.isZero());
049    if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!addr2.isZero());
050    checkTailInsert(2);
051    uncheckedTailInsert(addr1);
052    uncheckedTailInsert(addr2);
053  }
054
055  /**
056   * Push an address pair onto the address queue.
057   *
058   * @param addr1 the first value to be pushed onto the address queue
059   * @param addr2 the second value to be pushed onto the address queue
060   */
061  public final void push(Address addr1, Address addr2) {
062    if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!addr1.isZero());
063    if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!addr2.isZero());
064    checkHeadInsert(2);
065    uncheckedHeadInsert(addr2);
066    uncheckedHeadInsert(addr1);
067  }
068
069  /**
070   * Pop the first address in a pair from the address queue, return
071   * zero if the queue is empty.
072   *
073   * @return The next address in the address queue, or zero if the
074   * queue is empty
075   */
076  public final Address pop1() {
077    if (checkDequeue(2))
078      return uncheckedDequeue();
079    else
080      return Address.zero();
081  }
082
083  /**
084   * Pop the second address in a pair from the address queue.
085   *
086   * @return The next address in the address queue
087   */
088  public final Address pop2() {
089    return uncheckedDequeue();
090  }
091
092  public final boolean isEmpty() {
093    return !checkDequeue(2);
094  }
095}