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     */
013    package org.mmtk.utility.deque;
014    
015    import org.mmtk.utility.Constants;
016    
017    import org.mmtk.vm.VM;
018    
019    import org.vmmagic.unboxed.*;
020    import org.vmmagic.pragma.*;
021    
022    /**
023     * This supports <i>unsynchronized</i> enqueuing and dequeuing of
024     * object references
025     */
026    @Uninterruptible public class ObjectReferenceDeque extends LocalDeque
027      implements Constants {
028    
029      /****************************************************************************
030       *
031       * Public instance methods
032       */
033    
034      /**
035       *
036       */
037      public final String name;
038    
039      /**
040       * Constructor
041       *
042       * @param queue The shared queue to which this queue will append
043       * its buffers (when full or flushed) and from which it will aquire new
044       * buffers when it has exhausted its own.
045       */
046      public ObjectReferenceDeque(String n, SharedDeque queue) {
047        super(queue);
048        name = n;
049      }
050    
051      /**
052       * Insert an object into the object queue.
053       *
054       * @param object the object to be inserted into the object queue
055       */
056      @Inline
057      public final void insert(ObjectReference object) {
058        if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!object.isNull());
059        checkTailInsert(1);
060        uncheckedTailInsert(object.toAddress());
061      }
062    
063      /**
064       * Push an object onto the object queue.
065       *
066       * @param object the object to be pushed onto the object queue
067       */
068      @Inline
069      public final void push(ObjectReference object) {
070        if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!object.isNull());
071        checkHeadInsert(1);
072        uncheckedHeadInsert(object.toAddress());
073      }
074    
075      /**
076       * Push an object onto the object queue, force this out of line
077       * ("OOL"), in some circumstances it is too expensive to have the
078       * push inlined, so this call is made.
079       *
080       * @param object the object to be pushed onto the object queue
081       */
082      @NoInline
083      public final void pushOOL(ObjectReference object) {
084        push(object);
085      }
086    
087      /**
088       * Pop an object from the object queue, return zero if the queue
089       * is empty.
090       *
091       * @return The next object in the object queue, or zero if the
092       * queue is empty
093       */
094      @Inline
095      public final ObjectReference pop() {
096        if (checkDequeue(1)) {
097          return uncheckedDequeue().toObjectReference();
098        } else {
099          return ObjectReference.nullReference();
100        }
101      }
102    
103      @Inline
104      public final boolean isEmpty() {
105        return !checkDequeue(1);
106      }
107    
108      @Inline
109      public final boolean isNonEmpty() {
110        return checkDequeue(1);
111      }
112    
113    }