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
26package java.util.zip;
27
28import java.nio.ByteBuffer;
29import sun.nio.ch.DirectBuffer;
30
31/**
32 * A class that can be used to compute the CRC-32 of a data stream.
33 *
34 * <p> Passing a {@code null} argument to a method in this class will cause
35 * a {@link NullPointerException} to be thrown.
36 *
37 * @see         Checksum
38 * @author      David Connelly
39 */
40public
41class CRC32 implements Checksum {
42    private int crc;
43
44    /**
45     * Creates a new CRC32 object.
46     */
47    public CRC32() {
48    }
49
50
51    /**
52     * Updates the CRC-32 checksum with the specified byte (the low
53     * eight bits of the argument b).
54     *
55     * @param b the byte to update the checksum with
56     */
57    public void update(int b) {
58        crc = update(crc, b);
59    }
60
61    /**
62     * Updates the CRC-32 checksum with the specified array of bytes.
63     *
64     * @throws  ArrayIndexOutOfBoundsException
65     *          if {@code off} is negative, or {@code len} is negative,
66     *          or {@code off+len} is greater than the length of the
67     *          array {@code b}
68     */
69    public void update(byte[] b, int off, int len) {
70        if (b == null) {
71            throw new NullPointerException();
72        }
73        if (off < 0 || len < 0 || off > b.length - len) {
74            throw new ArrayIndexOutOfBoundsException();
75        }
76        crc = updateBytes(crc, b, off, len);
77    }
78
79    /**
80     * Updates the CRC-32 checksum with the specified array of bytes.
81     *
82     * @param b the array of bytes to update the checksum with
83     */
84    public void update(byte[] b) {
85        crc = updateBytes(crc, b, 0, b.length);
86    }
87
88    /**
89     * Updates the checksum with the bytes from the specified buffer.
90     *
91     * The checksum is updated using
92     * buffer.{@link java.nio.Buffer#remaining() remaining()}
93     * bytes starting at
94     * buffer.{@link java.nio.Buffer#position() position()}
95     * Upon return, the buffer's position will
96     * be updated to its limit; its limit will not have been changed.
97     *
98     * @param buffer the ByteBuffer to update the checksum with
99     * @since 1.8
100     */
101    public void update(ByteBuffer buffer) {
102        int pos = buffer.position();
103        int limit = buffer.limit();
104        assert (pos <= limit);
105        int rem = limit - pos;
106        if (rem <= 0)
107            return;
108        if (buffer instanceof DirectBuffer) {
109            crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem);
110        } else if (buffer.hasArray()) {
111            crc = updateBytes(crc, buffer.array(), pos + buffer.arrayOffset(), rem);
112        } else {
113            byte[] b = new byte[rem];
114            buffer.get(b);
115            crc = updateBytes(crc, b, 0, b.length);
116        }
117        buffer.position(limit);
118    }
119
120    /**
121     * Resets CRC-32 to initial value.
122     */
123    public void reset() {
124        crc = 0;
125    }
126
127    /**
128     * Returns CRC-32 value.
129     */
130    public long getValue() {
131        return (long)crc & 0xffffffffL;
132    }
133
134    private native static int update(int crc, int b);
135    private native static int updateBytes(int crc, byte[] b, int off, int len);
136
137    private native static int updateByteBuffer(int adler, long addr,
138                                               int off, int len);
139}
140