1 /**
2 * This file Copyright (c) 2011 Magnolia International
3 * Ltd. (http://www.magnolia-cms.com). All rights reserved.
4 *
5 *
6 * This file is dual-licensed under both the Magnolia
7 * Network Agreement and the GNU General Public License.
8 * You may elect to use one or the other of these licenses.
9 *
10 * This file is distributed in the hope that it will be
11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
12 * implied warranty of MERCHANTABILITY or FITNESS FOR A
13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
14 * Redistribution, except as permitted by whichever of the GPL
15 * or MNA you select, is prohibited.
16 *
17 * 1. For the GPL license (GPL), you can redistribute and/or
18 * modify this file under the terms of the GNU General
19 * Public License, Version 3, as published by the Free Software
20 * Foundation. You should have received a copy of the GNU
21 * General Public License, Version 3 along with this program;
22 * if not, write to the Free Software Foundation, Inc., 51
23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
24 *
25 * 2. For the Magnolia Network Agreement (MNA), this file
26 * and the accompanying materials are made available under the
27 * terms of the MNA which accompanies this distribution, and
28 * is available at http://www.magnolia-cms.com/mna.html
29 *
30 * Any modifications to this file must keep this entire header
31 * intact.
32 *
33 */
34 package info.magnolia.jcr.iterator;
35
36 import java.util.ArrayDeque;
37 import java.util.Iterator;
38 import java.util.NoSuchElementException;
39 import java.util.Queue;
40 import javax.jcr.RangeIterator;
41
42
43 /**
44 * Base class for implementing filtering JCR iterators. Does not support the remove method because doing so would make
45 * it impossible to implement the getSize method. Should not be a problem since Jackrabbit anyway does not support the
46 * remove method on its iterators.
47 *
48 * @param <T>
49 * @version $Id$
50 */
51 public abstract class FilteringRangeIterator<T> implements RangeIterator {
52
53 private final Iterator<T> iterator;
54 private long position;
55 private long size = 0;
56 private final Queue<T> queue = new ArrayDeque<T>();
57
58 public FilteringRangeIterator(Iterator<T> iterator) {
59 this.iterator = iterator;
60 }
61
62 @Override
63 public boolean hasNext() {
64 while (queue.isEmpty() && iterator.hasNext()) {
65 queueNext();
66 }
67 return !queue.isEmpty();
68 }
69
70 @Override
71 public T next() {
72 if (!hasNext()) {
73 throw new NoSuchElementException();
74 }
75 T t = queue.poll();
76 position++;
77 return t;
78 }
79
80 @Override
81 public void remove() {
82 throw new UnsupportedOperationException("remove");
83 }
84
85 @Override
86 public long getPosition() {
87 return position;
88 }
89
90 @Override
91 public void skip(long skipNum) {
92 while (skipNum-- > 0)
93 next();
94 }
95
96 @Override
97 public long getSize() {
98 while (iterator.hasNext()) {
99 queueNext();
100 }
101 return size;
102 }
103
104 private void queueNext() {
105 T n = iterator.next();
106 if (evaluate(n)) {
107 queue.add(n);
108 size++;
109 }
110 }
111
112 protected abstract boolean evaluate(T t);
113 }