Coverage Report - com.sun.grizzly.connectioncache.impl.concurrent.ConcurrentQueueImpl
 
Classes in this File Line Coverage Branch Coverage Complexity
ConcurrentQueueImpl
96 %
25/26
75 %
3/4
0
ConcurrentQueueImpl$Entry
100 %
7/7
N/A
0
ConcurrentQueueImpl$HandleImpl
89 %
17/19
50 %
1/2
0
 
 1  
 /*
 2  
  * 
 3  
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 4  
  * 
 5  
  * Copyright 2007-2008 Sun Microsystems, Inc. All rights reserved.
 6  
  * 
 7  
  * The contents of this file are subject to the terms of either the GNU
 8  
  * General Public License Version 2 only ("GPL") or the Common Development
 9  
  * and Distribution License("CDDL") (collectively, the "License").  You
 10  
  * may not use this file except in compliance with the License. You can obtain
 11  
  * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 12  
  * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 13  
  * language governing permissions and limitations under the License.
 14  
  * 
 15  
  * When distributing the software, include this License Header Notice in each
 16  
  * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 17  
  * Sun designates this particular file as subject to the "Classpath" exception
 18  
  * as provided by Sun in the GPL Version 2 section of the License file that
 19  
  * accompanied this code.  If applicable, add the following below the License
 20  
  * Header, with the fields enclosed by brackets [] replaced by your own
 21  
  * identifying information: "Portions Copyrighted [year]
 22  
  * [name of copyright owner]"
 23  
  * 
 24  
  * Contributor(s):
 25  
  * 
 26  
  * If you wish your version of this file to be governed by only the CDDL or
 27  
  * only the GPL Version 2, indicate your decision by adding "[Contributor]
 28  
  * elects to include this software in this distribution under the [CDDL or GPL
 29  
  * Version 2] license."  If you don't indicate a single choice of license, a
 30  
  * recipient has the option to distribute your version of this file under
 31  
  * either the CDDL, the GPL Version 2 or to extend the choice of license to
 32  
  * its licensees as provided above.  However, if you add GPL Version 2 code
 33  
  * and therefore, elected the GPL Version 2 license, then the option applies
 34  
  * only if the new code is made subject to such option by the copyright
 35  
  * holder.
 36  
  *
 37  
  */
 38  
 
 39  
 package com.sun.grizzly.connectioncache.impl.concurrent;
 40  
 
 41  
 import com.sun.grizzly.connectioncache.spi.concurrent.ConcurrentQueue;
 42  
 
 43  
 public class ConcurrentQueueImpl<V> implements ConcurrentQueue<V> {
 44  
     // This implementation of ConcurrentQueue is unsynchronized, for use in
 45  
     // other implementations that manage concurrency with locks.
 46  
     //
 47  
     // Structure: Head points to a node containing a null value, which is a special marker.
 48  
     // head.next is the first element, head.prev is the last.  The queue is empty if
 49  
     // head.next == head.prev == head.
 50  6
     final Entry<V> head = new Entry<V>( null ) ;
 51  6
     int count = 0 ;
 52  
 
 53  6
     public ConcurrentQueueImpl() {
 54  6
         head.next = head ;
 55  6
         head.prev = head ;
 56  6
     }
 57  
 
 58  1043
     private final class Entry<V> {
 59  1050
         Entry<V> next = null ;
 60  1050
         Entry<V> prev = null ;
 61  
         private HandleImpl<V> handle ;
 62  
 
 63  1050
         Entry( V value ) {
 64  1050
             handle = new HandleImpl<V>( this, value ) ;
 65  1050
         }
 66  
 
 67  
         HandleImpl<V> handle() {
 68  1074
             return handle ;
 69  
         }
 70  
     }
 71  
 
 72  
     private final class HandleImpl<V> implements Handle<V> {
 73  
         private Entry<V> entry ;
 74  
         private final V value ;
 75  
         private boolean valid ;
 76  
 
 77  1050
         HandleImpl( Entry<V> entry, V value ) {
 78  1050
             this.entry = entry ;
 79  1050
             this.value = value ;
 80  1050
             this.valid = true ;
 81  1050
         }
 82  
 
 83  
         Entry<V> entry() {
 84  0
             return entry ;
 85  
         }
 86  
 
 87  
         public V value() {
 88  15
             return value ;
 89  
         }
 90  
 
 91  
         /** Delete the element corresponding to this handle 
 92  
          * from the queue.  Takes constant time.
 93  
          * @return  element deleted from queue, (yes or no)
 94  
   */
 95  
         public boolean remove() {
 96  1043
             if (!valid) {
 97  0
                 return false ;
 98  
             }
 99  
 
 100  1043
             valid = false ;
 101  
 
 102  1043
             entry.next.prev = entry.prev ;
 103  1043
             entry.prev.next = entry.next ;
 104  1043
             count-- ;
 105  
 
 106  1043
             entry.prev = null ;
 107  1043
             entry.next = null ;
 108  1043
             entry.handle = null ;
 109  1043
             entry = null ;
 110  1043
             valid = false ;
 111  1043
             return true ;
 112  
         }
 113  
     }
 114  
 
 115  
     public int size() {
 116  64
         return count ;
 117  
     }
 118  
 
 119  
     /** Add a new element to the tail of the queue.
 120  
      * Returns a handle for the element in the queue.
 121  
      * @param arg  element to append to the queue
 122  
      * @return  {@link Handle} for the element in the queue
 123  
      */
 124  
     public Handle<V> offer( V arg ) {
 125  1044
         if (arg == null)
 126  0
             throw new IllegalArgumentException( "Argument cannot be null" ) ;
 127  
 
 128  1044
         Entry<V> entry = new Entry<V>( arg ) ;
 129  
         
 130  1044
         entry.next = head ;
 131  1044
         entry.prev = head.prev ;
 132  1044
         head.prev.next = entry ;
 133  1044
         head.prev = entry ;
 134  1044
         count++ ;
 135  
 
 136  1044
         return entry.handle() ;
 137  
     }
 138  
 
 139  
     /** Return an element from the head of the queue.
 140  
      * The element is removed from the queue.
 141  
      * @return  an element at the head of the queue
 142  
      */
 143  
     public V poll() {
 144  23
         Entry<V> first = null ;
 145  23
         V value = null ;
 146  
 
 147  23
         first = head.next ;
 148  23
         if (first == head)
 149  8
             return null ;
 150  
         else {
 151  15
             value = first.handle().value() ;
 152  
 
 153  
             // assert that the following expression returns true!
 154  15
             first.handle().remove() ;
 155  
         }
 156  
 
 157  
         // Once first is removed from the queue, it is invisible to other threads,
 158  
         // so we don't need to synchronize here.
 159  15
         first.next = null ;
 160  15
         first.prev = null ;
 161  15
         return value ;
 162  
     }
 163  
 }