1 /**
2 * Copyright 2009, Frederic Bregier, and individual contributors by the @author tags. See the
3 * COPYRIGHT.txt in the distribution for a full listing of individual contributors.
4 *
5 * This is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser
6 * General Public License as published by the Free Software Foundation; either version 3.0 of the
7 * License, or (at your option) any later version.
8 *
9 * This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
10 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU Lesser General Public License for more details.
12 *
13 * You should have received a copy of the GNU Lesser General Public License along with this
14 * software; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
15 * Boston, MA 02110-1301 USA, or see the FSF site: http://www.fsf.org.
16 */
17 package org.waarp.gateway.ftp.config;
18
19 import java.util.concurrent.atomic.AtomicInteger;
20
21 /**
22 * Circular Value used by passive connections to find the next valid port to propose to the client.
23 *
24 * @author Frederic Bregier
25 *
26 */
27 class CircularIntValue {
28 /**
29 * Min value
30 */
31 private final int min;
32
33 /**
34 * Max value
35 */
36 private final int max;
37
38 /**
39 * Current Value
40 */
41 private AtomicInteger current;
42
43 /**
44 * Create a circular range of values
45 *
46 * @param min
47 * @param max
48 */
49 public CircularIntValue(int min, int max) {
50 this.min = min;
51 this.max = max;
52 current = new AtomicInteger(this.min - 1);
53 }
54
55 /**
56 * Get the next value
57 *
58 * @return the next value
59 */
60 public int getNext() {
61 synchronized (current) {
62 if (!current.compareAndSet(max, min)) {
63 current.incrementAndGet();
64 }
65 return current.get();
66 }
67 }
68 }