1 /*
2 * Copyright 1996-2005 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * 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 * @author David Connelly
33 */
34 public
35 class CRC32 implements Checksum {
36 private int crc;
37
38 /**
39 * Creates a new CRC32 object.
40 */
41 public CRC32() {
42 }
43
44
45 /**
46 * Updates CRC-32 with specified byte.
47 */
48 public void update(int b) {
49 crc = update(crc, b);
50 }
51
52 /**
53 * Updates CRC-32 with specified array of bytes.
54 */
55 public void update(byte[] b, int off, int len) {
56 if (b == null) {
57 throw new NullPointerException();
58 }
59 if (off < 0 || len < 0 || off > b.length - len) {
60 throw new ArrayIndexOutOfBoundsException();
61 }
62 crc = updateBytes(crc, b, off, len);
63 }
64
65 /**
66 * Updates checksum with specified array of bytes.
67 *
68 * @param b the array of bytes to update the checksum with
69 */
70 public void update(byte[] b) {
71 crc = updateBytes(crc, b, 0, b.length);
72 }
73
74 /**
75 * Resets CRC-32 to initial value.
76 */
77 public void reset() {
78 crc = 0;
79 }
80
81 /**
82 * Returns CRC-32 value.
83 */
84 public long getValue() {
85 return (long)crc & 0xffffffffL;
86 }
87
88 private native static int update(int crc, int b);
89 private native static int updateBytes(int crc, byte[] b, int off, int len);
90 }
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