1/******************************************************************************* 2 * Copyright (c) 2009, 2015 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 *******************************************************************************/ 12package org.jacoco.core.internal.data; 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 */ 23public final class CRC64 { 24 25 private static final long POLY64REV = 0xd800000000000000L; 26 27 private static final long[] LOOKUPTABLE; 28 29 static { 30 LOOKUPTABLE = new long[0x100]; 31 for (int i = 0; i < 0x100; i++) { 32 long v = i; 33 for (int j = 0; j < 8; j++) { 34 if ((v & 1) == 1) { 35 v = (v >>> 1) ^ POLY64REV; 36 } else { 37 v = (v >>> 1); 38 } 39 } 40 LOOKUPTABLE[i] = v; 41 } 42 } 43 44 /** 45 * Calculates the CRC64 checksum for the given data array. 46 * 47 * @param data 48 * data to calculate checksum for 49 * @return checksum value 50 */ 51 public static long checksum(final byte[] data) { 52 long sum = 0; 53 for (final byte b : data) { 54 final int lookupidx = ((int) sum ^ b) & 0xff; 55 sum = (sum >>> 8) ^ LOOKUPTABLE[lookupidx]; 56 } 57 return sum; 58 } 59 60 private CRC64() { 61 } 62 63} 64