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 }