1 package com.jsql.util.bruter;
2
3 /*******************************************************************************
4 * Copyright (c) 2009, 2012 Mountainminds GmbH & Co. KG and Contributors
5 * All rights reserved. This program and the accompanying materials
6 * are made available under the terms of the Eclipse Public License v1.0
7 * which accompanies this distribution, and is available at
8 * http://www.eclipse.org/legal/epl-v10.html
9 *
10 * Contributors:
11 * Marc R. Hoffmann - initial API and implementation
12 *
13 *******************************************************************************/
14
15 /**
16 * CRC64 checksum calculator based on the polynom specified in ISO 3309. The
17 * implementation is based on the following publications:
18 *
19 * <ul>
20 * <li>http://en.wikipedia.org/wiki/Cyclic_redundancy_check</li>
21 * <li>http://www.geocities.com/SiliconValley/Pines/8659/crc.htm</li>
22 * </ul>
23 */
24 public class Crc64Helper {
25
26 private static final long POLY64REV = 0xd800000000000000L;
27
28 private static final long[] LOOKUPTABLE;
29
30 private Crc64Helper() {
31 // Util class
32 }
33
34 static {
35
36 LOOKUPTABLE = new long[0x100];
37
38 for (int i = 0; i < 0x100; i++) {
39
40 long v = i;
41
42 for (int j = 0; j < 8; j++) {
43 if ((v & 1) == 1) {
44 v = (v >>> 1) ^ POLY64REV;
45 } else {
46 v = v >>> 1;
47 }
48 }
49
50 LOOKUPTABLE[i] = v;
51 }
52 }
53
54 /**
55 * Calculates the CRC64 checksum for the given data array.
56 *
57 * @param data
58 * data to calculate checksum for
59 * @return checksum value
60 */
61 public static String generateCRC64(final byte[] data) {
62
63 long sum = 0;
64 for (byte element : data) {
65
66 final int lookupidx = ((int) sum ^ element) & 0xff;
67 sum = (sum >>> 8) ^ LOOKUPTABLE[lookupidx];
68 }
69
70 return String.valueOf(sum);
71 }
72 }