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      public final String name;
034    
035      /**
036       * Constructor
037       *
038       * @param queue The shared queue to which this queue will append
039       * its buffers (when full or flushed) and from which it will aquire new
040       * buffers when it has exhausted its own.
041       */
042      public ObjectReferenceDeque(String n, SharedDeque queue) {
043        super(queue);
044        name = n;
045      }
046    
047      /**
048       * Insert an object into the object queue.
049       *
050       * @param object the object to be inserted into the object queue
051       */
052      @Inline
053      public final void insert(ObjectReference object) {
054        if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!object.isNull());
055        checkTailInsert(1);
056        uncheckedTailInsert(object.toAddress());
057      }
058    
059      /**
060       * Push an object onto the object queue.
061       *
062       * @param object the object to be pushed onto the object queue
063       */
064      @Inline
065      public final void push(ObjectReference object) {
066        if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!object.isNull());
067        checkHeadInsert(1);
068        uncheckedHeadInsert(object.toAddress());
069      }
070    
071      /**
072       * Push an object onto the object queue, force this out of line
073       * ("OOL"), in some circumstnaces it is too expensive to have the
074       * push inlined, so this call is made.
075       *
076       * @param object the object to be pushed onto the object queue
077       */
078      @NoInline
079      public final void pushOOL(ObjectReference object) {
080        push(object);
081      }
082    
083      /**
084       * Pop an object from the object queue, return zero if the queue
085       * is empty.
086       *
087       * @return The next object in the object queue, or zero if the
088       * queue is empty
089       */
090      @Inline
091      public final ObjectReference pop() {
092        if (checkDequeue(1)) {
093          return uncheckedDequeue().toObjectReference();
094        } else {
095          return ObjectReference.nullReference();
096        }
097      }
098    
099      @Inline
100      public final boolean isEmpty() {
101        return !checkDequeue(1);
102      }
103    
104      @Inline
105      public final boolean isNonEmpty() {
106        return checkDequeue(1);
107      }
108    
109    }