1/*
2 * Copyright (c) 1996, 2014, 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 java.util.Objects;
30
31import sun.nio.ch.DirectBuffer;
32import jdk.internal.HotSpotIntrinsicCandidate;
33
34/**
35 * A class that can be used to compute the CRC-32 of a data stream.
36 *
37 * <p> Passing a {@code null} argument to a method in this class will cause
38 * a {@link NullPointerException} to be thrown.</p>
39 *
40 * @author      David Connelly
41 * @since 1.1
42 */
43public
44class CRC32 implements Checksum {
45    private int crc;
46
47    /**
48     * Creates a new CRC32 object.
49     */
50    public CRC32() {
51    }
52
53
54    /**
55     * Updates the CRC-32 checksum with the specified byte (the low
56     * eight bits of the argument b).
57     */
58    @Override
59    public void update(int b) {
60        crc = update(crc, b);
61    }
62
63    /**
64     * Updates the CRC-32 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        crc = updateBytes(crc, b, off, len);
80    }
81
82    /**
83     * Updates the CRC-32 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            crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem);
101        } else if (buffer.hasArray()) {
102            crc = updateBytes(crc, 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 CRC-32 to initial value.
116     */
117    @Override
118    public void reset() {
119        crc = 0;
120    }
121
122    /**
123     * Returns CRC-32 value.
124     */
125    @Override
126    public long getValue() {
127        return (long)crc & 0xffffffffL;
128    }
129
130    @HotSpotIntrinsicCandidate
131    private static native int update(int crc, int b);
132
133    private static int updateBytes(int crc, byte[] b, int off, int len) {
134        updateBytesCheck(b, off, len);
135        return updateBytes0(crc, b, off, len);
136    }
137
138    @HotSpotIntrinsicCandidate
139    private static native int updateBytes0(int crc, byte[] b, int off, int len);
140
141    private static void updateBytesCheck(byte[] b, int off, int len) {
142        if (len <= 0) {
143            return;  // not an error because updateBytesImpl won't execute if len <= 0
144        }
145
146        Objects.requireNonNull(b);
147
148        if (off < 0 || off >= b.length) {
149            throw new ArrayIndexOutOfBoundsException(off);
150        }
151
152        int endIndex = off + len - 1;
153        if (endIndex < 0 || endIndex >= b.length) {
154            throw new ArrayIndexOutOfBoundsException(endIndex);
155        }
156    }
157
158    private static int updateByteBuffer(int alder, long addr,
159                                        int off, int len) {
160        updateByteBufferCheck(addr);
161        return updateByteBuffer0(alder, addr, off, len);
162    }
163
164    @HotSpotIntrinsicCandidate
165    private static native int updateByteBuffer0(int alder, long addr,
166                                                int off, int len);
167
168    private static void updateByteBufferCheck(long addr) {
169        // Performs only a null check because bounds checks
170        // are not easy to do on raw addresses.
171        if (addr == 0L) {
172            throw new NullPointerException();
173        }
174    }
175
176    static {
177        ZipUtils.loadLibrary();
178    }
179}
180