Adler32.java revision 12745:f068a4ffddd2 
1/*
2 * Copyright (c) 1996, 2015, 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
26package java.util.zip;
27
28import java.nio.ByteBuffer;
29import sun.nio.ch.DirectBuffer;
30
31import jdk.internal.HotSpotIntrinsicCandidate;
32
33/**
34 * A class that can be used to compute the Adler-32 checksum of a data
35 * stream. An Adler-32 checksum is almost as reliable as a CRC-32 but
36 * can be computed much faster.
37 *
38 * <p> Passing a {@code null} argument to a method in this class will cause
39 * a {@link NullPointerException} to be thrown.</p>
40 *
41 * @author      David Connelly
42 */
43public
44class Adler32 implements Checksum {
45
46    private int adler = 1;
47
48    /**
49     * Creates a new Adler32 object.
50     */
51    public Adler32() {
52    }
53
54    /**
55     * Updates the checksum with the specified byte (the low eight
56     * bits of the argument b).
57     */
58    @Override
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, or
68     *         {@code off+len} is negative or greater than the length of
69     *         the array {@code b}.
70     */
71    @Override
72    public void update(byte[] b, int off, int len) {
73        if (b == null) {
74            throw new NullPointerException();
75        }
76        if (off < 0 || len < 0 || off > b.length - len) {
77            throw new ArrayIndexOutOfBoundsException();
78        }
79        adler = updateBytes(adler, b, off, len);
80    }
81
82    /**
83     * Updates the checksum with the bytes from the specified buffer.
84     *
85     * The checksum is updated with the remaining bytes in the buffer, starting
86     * at the buffer's position. Upon return, the buffer's position will be
87     * updated to its limit; its limit will not have been changed.
88     *
89     * @since 1.8
90     */
91    @Override
92    public void update(ByteBuffer buffer) {
93        int pos = buffer.position();
94        int limit = buffer.limit();
95        assert (pos <= limit);
96        int rem = limit - pos;
97        if (rem <= 0)
98            return;
99        if (buffer instanceof DirectBuffer) {
100            adler = updateByteBuffer(adler, ((DirectBuffer)buffer).address(), pos, rem);
101        } else if (buffer.hasArray()) {
102            adler = updateBytes(adler, buffer.array(), pos + buffer.arrayOffset(), rem);
103        } else {
104            byte[] b = new byte[Math.min(buffer.remaining(), 4096)];
105            while (buffer.hasRemaining()) {
106                int length = Math.min(buffer.remaining(), b.length);
107                buffer.get(b, 0, length);
108                update(b, 0, length);
109            }
110        }
111        buffer.position(limit);
112    }
113
114    /**
115     * Resets the checksum to initial value.
116     */
117    @Override
118    public void reset() {
119        adler = 1;
120    }
121
122    /**
123     * Returns the checksum value.
124     */
125    @Override
126    public long getValue() {
127        return (long)adler & 0xffffffffL;
128    }
129
130    private static native int update(int adler, int b);
131
132    @HotSpotIntrinsicCandidate
133    private static native int updateBytes(int adler, byte[] b, int off,
134                                          int len);
135    @HotSpotIntrinsicCandidate
136    private static native int updateByteBuffer(int adler, long addr,
137                                               int off, int len);
138}
139