01 /*
02 * Copyright 1996-2005 Sun Microsystems, Inc. All Rights Reserved.
03 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
04 *
05 * This code is free software; you can redistribute it and/or modify it
06 * under the terms of the GNU General Public License version 2 only, as
07 * published by the Free Software Foundation. Sun designates this
08 * particular file as subject to the "Classpath" exception as provided
09 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any 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 * @version 1.38, 05/05/07
33 * @author David Connelly
34 */
35 public class CRC32 implements Checksum {
36 private int crc;
37
38 /**
39 * Creates a new CRC32 object.
40 */
41 public CRC32() {
42 }
43
44 /**
45 * Updates CRC-32 with specified byte.
46 */
47 public void update(int b) {
48 crc = update(crc, b);
49 }
50
51 /**
52 * Updates CRC-32 with specified array of bytes.
53 */
54 public void update(byte[] b, int off, int len) {
55 if (b == null) {
56 throw new NullPointerException();
57 }
58 if (off < 0 || len < 0 || off > b.length - len) {
59 throw new ArrayIndexOutOfBoundsException();
60 }
61 crc = updateBytes(crc, b, off, len);
62 }
63
64 /**
65 * Updates checksum with specified array of bytes.
66 *
67 * @param b the array of bytes to update the checksum with
68 */
69 public void update(byte[] b) {
70 crc = updateBytes(crc, b, 0, b.length);
71 }
72
73 /**
74 * Resets CRC-32 to initial value.
75 */
76 public void reset() {
77 crc = 0;
78 }
79
80 /**
81 * Returns CRC-32 value.
82 */
83 public long getValue() {
84 return (long) crc & 0xffffffffL;
85 }
86
87 private native static int update(int crc, int b);
88
89 private native static int updateBytes(int crc, byte[] b, int off,
90 int len);
91 }
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