1/*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements.  See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License.  You may obtain a copy of the License at
8 *
9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18package java.util.zip;
19
20import java.util.Arrays;
21
22/**
23 * The CRC32 class is used to compute a CRC32 checksum from data provided as
24 * input value. See also {@link Adler32} which is almost as good, but cheaper.
25 */
26public class CRC32 implements Checksum {
27
28    private long crc = 0L;
29
30    long tbytes = 0L;
31
32    /**
33     * Returns the CRC32 checksum for all input received.
34     *
35     * @return The checksum for this instance.
36     */
37    public long getValue() {
38        return crc;
39    }
40
41    /**
42     * Resets the CRC32 checksum to it initial state.
43     */
44    public void reset() {
45        tbytes = crc = 0;
46
47    }
48
49    /**
50     * Updates this checksum with the byte value provided as integer.
51     *
52     * @param val
53     *            represents the byte to update the checksum.
54     */
55    public void update(int val) {
56        crc = updateByteImpl((byte) val, crc);
57    }
58
59    /**
60     * Updates this checksum with the bytes contained in buffer {@code buf}.
61     *
62     * @param buf
63     *            the buffer holding the data to update the checksum with.
64     */
65    public void update(byte[] buf) {
66        update(buf, 0, buf.length);
67    }
68
69    /**
70     * Update this {@code CRC32} checksum with the contents of {@code buf},
71     * starting from {@code offset} and reading {@code byteCount} bytes of data.
72     */
73    public void update(byte[] buf, int offset, int byteCount) {
74        Arrays.checkOffsetAndCount(buf.length, offset, byteCount);
75        tbytes += byteCount;
76        crc = updateImpl(buf, offset, byteCount, crc);
77    }
78
79    private native long updateImpl(byte[] buf, int offset, int byteCount, long crc1);
80
81    private native long updateByteImpl(byte val, long crc1);
82}
83