1 /*
2 * Copyright (c) 1996, 2013, 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 import java.nio.ByteBuffer;
29 import sun.nio.ch.DirectBuffer;
30
31 /**
32 * A class that can be used to compute the Adler-32 checksum of a data
33 * stream. An Adler-32 checksum is almost as reliable as a CRC-32 but
34 * can be computed much faster.
35 *
36 * <p> Passing a {@code null} argument to a method in this class will cause
37 * a {@link NullPointerException} to be thrown.
38 *
39 * @see Checksum
40 * @author David Connelly
41 */
42 public
43 class Adler32 implements Checksum {
44
45 private int adler = 1;
46
47 /**
48 * Creates a new Adler32 object.
49 */
50 public Adler32() {
51 }
52
53 /**
54 * Updates the checksum with the specified byte (the low eight
55 * bits of the argument b).
56 *
57 * @param b the byte to update the checksum with
58 */
59 public void update(int b) {
60 adler = update(adler, b);
61 }
62
63 /**
64 * Updates the checksum with the specified array of bytes.
65 *
66 * @throws ArrayIndexOutOfBoundsException
67 * if {@code off} is negative, or {@code len} is negative,
68 * or {@code off+len} is greater than the length of the
69 * array {@code b}
70 */
71 public void update(byte[] b, int off, int len) {
72 if (b == null) {
73 throw new NullPointerException();
74 }
75 if (off < 0 || len < 0 || off > b.length - len) {
76 throw new ArrayIndexOutOfBoundsException();
77 }
78 adler = updateBytes(adler, b, off, len);
79 }
80
81 /**
82 * Updates the checksum with the specified array of bytes.
83 *
84 * @param b the byte array to update the checksum with
85 */
86 public void update(byte[] b) {
87 adler = updateBytes(adler, b, 0, b.length);
88 }
89
90
91 /**
92 * Updates the checksum with the bytes from the specified buffer.
93 *
94 * The checksum is updated using
95 * buffer.{@link java.nio.Buffer#remaining() remaining()}
96 * bytes starting at
97 * buffer.{@link java.nio.Buffer#position() position()}
98 * Upon return, the buffer's position will be updated to its
99 * limit; its limit will not have been changed.
100 *
101 * @param buffer the ByteBuffer to update the checksum with
102 * @since 1.8
103 */
104 public void update(ByteBuffer buffer) {
105 int pos = buffer.position();
106 int limit = buffer.limit();
107 assert (pos <= limit);
108 int rem = limit - pos;
109 if (rem <= 0)
110 return;
111 if (buffer instanceof DirectBuffer) {
112 adler = updateByteBuffer(adler, ((DirectBuffer)buffer).address(), pos, rem);
113 } else if (buffer.hasArray()) {
114 adler = updateBytes(adler, buffer.array(), pos + buffer.arrayOffset(), rem);
115 } else {
116 byte[] b = new byte[rem];
117 buffer.get(b);
118 adler = updateBytes(adler, b, 0, b.length);
119 }
120 buffer.position(limit);
121 }
122
123 /**
124 * Resets the checksum to initial value.
125 */
126 public void reset() {
127 adler = 1;
128 }
129
130 /**
131 * Returns the checksum value.
132 */
133 public long getValue() {
134 return (long)adler & 0xffffffffL;
135 }
136
137 private native static int update(int adler, int b);
138 private native static int updateBytes(int adler, byte[] b, int off,
139 int len);
140 private native static int updateByteBuffer(int adler, long addr,
141 int off, int len);
142 }