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.Iterator;
37 import java.util.NoSuchElementException;
38 import javax.jcr.RangeIterator;
39
40
41 /**
42 * Base class for implementing filtering JCR iterators. Does not support getSize() since that would require iterating
43 * through the entire target iterator to count the number of nodes that match the predicate.
44 *
45 * @param <T>
46 * @version $Id$
47 */
48 public abstract class FilteringRangeIterator<T> implements RangeIterator {
49
50 private final Iterator<T> iterator;
51 private long position;
52 private T next;
53
54 public FilteringRangeIterator(Iterator<T> iterator) {
55 this.iterator = iterator;
56 }
57
58 @Override
59 public boolean hasNext() {
60 while (next == null && iterator.hasNext()) {
61 T n = iterator.next();
62 if (evaluate(n)) {
63 next = n;
64 }
65 }
66 return next != null;
67 }
68
69 @Override
70 public T next() {
71 if (!hasNext()) {
72 throw new NoSuchElementException();
73 }
74 T t = next;
75 next = null;
76 position++;
77 return t;
78 }
79
80 @Override
81 public void remove() {
82 iterator.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 // getSize() is optional and we don't support it since that would require walking through the entire iterator
99 return -1;
100 }
101
102 protected abstract boolean evaluate(T t);
103 }