1 /* 2 * Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.util.zip; 27 28 /** 29 * A class that can be used to compute the CRC-32 of a data stream. 30 * 31 * @see Checksum 32 * @author David Connelly 33 */ 34 public 35 class CRC32 implements Checksum { 36 private int crc; 37 38 /** 39 * Creates a new CRC32 object. 40 */ CRC32()41 public CRC32() { 42 } 43 44 45 /** 46 * Updates the CRC-32 checksum with the specified byte (the low 47 * eight bits of the argument b). 48 * 49 * @param b the byte to update the checksum with 50 */ update(int b)51 public void update(int b) { 52 crc = update(crc, b); 53 } 54 55 /** 56 * Updates the CRC-32 checksum with the specified array of bytes. 57 */ update(byte[] b, int off, int len)58 public void update(byte[] b, int off, int len) { 59 if (b == null) { 60 throw new NullPointerException(); 61 } 62 if (off < 0 || len < 0 || off > b.length - len) { 63 throw new ArrayIndexOutOfBoundsException(); 64 } 65 crc = updateBytes(crc, b, off, len); 66 } 67 68 /** 69 * Updates the CRC-32 checksum with the specified array of bytes. 70 * 71 * @param b the array of bytes to update the checksum with 72 */ update(byte[] b)73 public void update(byte[] b) { 74 crc = updateBytes(crc, b, 0, b.length); 75 } 76 77 /** 78 * Resets CRC-32 to initial value. 79 */ reset()80 public void reset() { 81 crc = 0; 82 } 83 84 /** 85 * Returns CRC-32 value. 86 */ getValue()87 public long getValue() { 88 return (long)crc & 0xffffffffL; 89 } 90 update(int crc, int b)91 private native static int update(int crc, int b); updateBytes(int crc, byte[] b, int off, int len)92 private native static int updateBytes(int crc, byte[] b, int off, int len); 93 } 94