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 Adler-32 checksum of a data
30 * stream. An Adler-32 checksum is almost as reliable as a CRC-32 but
31 * can be computed much faster.
32 *
33 * @see Checksum
34 * @version 1.35, 05/05/07
35 * @author David Connelly
36 */
37 public class Adler32 implements Checksum {
38 private int adler = 1;
39
40 /**
41 * Creates a new Adler32 object.
42 */
43 public Adler32() {
44 }
45
46 /**
47 * Updates checksum with specified byte.
48 *
49 * @param b an array of bytes
50 */
51 public void update(int b) {
52 adler = update(adler, b);
53 }
54
55 /**
56 * Updates checksum with specified array of bytes.
57 */
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 adler = updateBytes(adler, b, off, len);
66 }
67
68 /**
69 * Updates checksum with specified array of bytes.
70 */
71 public void update(byte[] b) {
72 adler = updateBytes(adler, b, 0, b.length);
73 }
74
75 /**
76 * Resets checksum to initial value.
77 */
78 public void reset() {
79 adler = 1;
80 }
81
82 /**
83 * Returns checksum value.
84 */
85 public long getValue() {
86 return (long) adler & 0xffffffffL;
87 }
88
89 private native static int update(int adler, int b);
90
91 private native static int updateBytes(int adler, byte[] b, int off,
92 int len);
93 }
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