1 /*
2 * Copyright (c) 1998, 2005 Gargoyle Software Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are met:
6 *
7 * 1. Redistributions of source code must retain the above copyright notice,
8 * this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright notice,
10 * this list of conditions and the following disclaimer in the documentation
11 * and/or other materials provided with the distribution.
12 * 3. The end-user documentation included with the redistribution, if any, must
13 * include the following acknowledgment:
14 *
15 * "This product includes software developed by Gargoyle Software Inc.
16 * (http://www.GargoyleSoftware.com/)."
17 *
18 * Alternately, this acknowledgment may appear in the software itself, if
19 * and wherever such third-party acknowledgments normally appear.
20 * 4. The name "Gargoyle Software" must not be used to endorse or promote
21 * products derived from this software without prior written permission.
22 * For written permission, please contact info@GargoyleSoftware.com.
23 * 5. Products derived from this software may not be called "GSBase", nor may
24 * "GSBase" appear in their name, without prior written permission of
25 * Gargoyle Software Inc.
26 *
27 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
28 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
29 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GARGOYLE
30 * SOFTWARE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
32 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
33 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
36 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 */
38 package com.gargoylesoftware.base.trace;
39
40 import com.gargoylesoftware.base.util.DetailedNullPointerException;
41
42 /***
43 * <p style="color: orange">Internal use only.</p>.
44 *
45 * @version $Revision: 1.8 $
46 * @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>
47 */
48 public class TraceItemQueue {
49 private TraceItem firstItem_;
50 private TraceItem lastItem_;
51 private int itemCount_;
52
53 /***
54 *
55 */
56 public TraceItemQueue() {
57 firstItem_ = null;
58 lastItem_ = null;
59 itemCount_ = 0;
60 }
61
62 /***
63 * @param item The item to push.
64 */
65 public synchronized void push( final TraceItem item ) {
66 assertNotNull("item", item);
67 if( item.getPrevItem() != null || item.getNextItem() != null ) {
68 throw new IllegalArgumentException("Pointers are not null");
69 }
70
71 if( itemCount_ == 0 ) {
72 lastItem_ = item;
73 }
74
75 if( firstItem_ != null ) {
76 firstItem_.setPrevItem( item );
77 }
78 item.setNextItem( firstItem_ );
79 firstItem_ = item;
80 itemCount_++;
81 }
82
83 /***
84 * Return the next item on the queue or null if the queue is empty
85 * @return The next item or null.
86 */
87 public synchronized TraceItem pop() {
88 // System.out.println("***TraceItemQueue.pop() "+this);
89 checkValidity();
90 final TraceItem popItem = lastItem_;
91
92 if( popItem != null ) {
93 lastItem_ = lastItem_.getPrevItem();
94 if( lastItem_ == null ) {
95 firstItem_ = null;
96 }
97 else {
98 lastItem_.setNextItem( null );
99 }
100 popItem.setPrevItem( null );
101 popItem.setNextItem( null );
102 itemCount_--;
103 }
104
105 return popItem;
106 }
107
108 private void checkValidity() {
109 if( itemCount_ == 0 ) {
110 if( firstItem_ != null ) {
111 throw new IllegalStateException("firstItem should be null: "+this);
112 }
113 if( lastItem_ != null ) {
114 throw new IllegalStateException("lastItem should be null: "+this);
115 }
116 }
117 }
118 /***
119 * @return the number of items in the queue.
120 */
121 public synchronized int size() {
122 return itemCount_;
123 }
124
125 /***
126 * @return The string representation of this object.
127 */
128 public String toString() {
129 return getClass().getName()+" itemCount=["+itemCount_
130 +"] firstItem=["+firstItem_+"] lastItem=["+lastItem_+"]";
131 }
132
133
134 /***
135 * Verify that the specified value is not null. If it is then throw an exception
136 *
137 * @param fieldName The name of the field to check
138 * @param fieldValue The value of the field to check
139 * @exception DetailedNullPointerException If fieldValue is null
140 */
141 protected final void assertNotNull( final String fieldName, final Object fieldValue )
142 throws DetailedNullPointerException {
143
144 if( fieldValue == null ) {
145 throw new DetailedNullPointerException(fieldName);
146 }
147 }
148 }
149