1 /*******************************************************************************
2 * Copyright (c) 2009, 2012 Mountainminds GmbH & Co. KG and Contributors
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * Marc R. Hoffmann - initial API and implementation
10 *
11 *******************************************************************************/
12 package com.jsql.util.bruter;
13
14 /**
15 * CRC64 checksum calculator based on the polynom specified in ISO 3309. The
16 * implementation is based on the following publications:
17 *
18 * <ul>
19 * <li>http://en.wikipedia.org/wiki/Cyclic_redundancy_check</li>
20 * <li>http://www.geocities.com/SiliconValley/Pines/8659/crc.htm</li>
21 * </ul>
22 */
23 public class Crc64Helper {
24
25 private static final long POLY64REV = 0xd800000000000000L;
26
27 private static final long[] LOOKUPTABLE;
28
29 private Crc64Helper() {
30 // Util class
31 }
32
33 static {
34 LOOKUPTABLE = new long[0x100];
35 for (int i = 0; i < 0x100; i++) {
36 long v = i;
37 for (int j = 0; j < 8; j++) {
38 if ((v & 1) == 1) {
39 v = (v >>> 1) ^ Crc64Helper.POLY64REV;
40 } else {
41 v = v >>> 1;
42 }
43 }
44 Crc64Helper.LOOKUPTABLE[i] = v;
45 }
46 }
47
48 /**
49 * Calculates the CRC64 checksum for the given data array.
50 *
51 * @param data
52 * data to calculate checksum for
53 * @return checksum value
54 */
55 public static String generateCRC64(final byte[] data) {
56 long sum = 0;
57 for (byte element : data) {
58 final int lookupidx = ((int) sum ^ element) & 0xff;
59 sum = (sum >>> 8) ^ Crc64Helper.LOOKUPTABLE[lookupidx];
60 }
61 return String.valueOf(sum);
62 }
63 }