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Java > Open Source Codes > java > util > zip > CRC32


1 /*
2  * @(#)CRC32.java 1.32 05/08/09
3  *
4  * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
5  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6  */
7
8 package java.util.zip;
9
10 /**
11  * A class that can be used to compute the CRC-32 of a data stream.
12  *
13  * @see Checksum
14  * @version 1.32, 08/09/05
15  * @author David Connelly
16  */
17 public
18 class CRC32 implements Checksum JavaDoc {
19     private int crc;
20
21     /**
22      * Creates a new CRC32 object.
23      */
24     public CRC32() {
25     }
26    
27
28     /**
29      * Updates CRC-32 with specified byte.
30      */
31     public void update(int b) {
32     crc = update(crc, b);
33     }
34
35     /**
36      * Updates CRC-32 with specified array of bytes.
37      */
38     public void update(byte[] b, int off, int len) {
39     if (b == null) {
40         throw new NullPointerException JavaDoc();
41     }
42         if (off < 0 || len < 0 || off > b.length - len) {
43         throw new ArrayIndexOutOfBoundsException JavaDoc();
44     }
45     crc = updateBytes(crc, b, off, len);
46     }
47
48     /**
49      * Updates checksum with specified array of bytes.
50      *
51      * @param b the array of bytes to update the checksum with
52      */
53     public void update(byte[] b) {
54     crc = updateBytes(crc, b, 0, b.length);
55     }
56
57     /**
58      * Resets CRC-32 to initial value.
59      */
60     public void reset() {
61     crc = 0;
62     }
63
64     /**
65      * Returns CRC-32 value.
66      */
67     public long getValue() {
68     return (long)crc & 0xffffffffL;
69     }
70
71     private native static int update(int crc, int b);
72     private native static int updateBytes(int crc, byte[] b, int off, int len);
73 }
74
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