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Java > Open Source Codes > org > jruby > util > CRC32Ext


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27 package org.jruby.util;
28
29 import java.lang.reflect.Field JavaDoc;
30
31 import java.util.zip.CRC32 JavaDoc;
32 import java.util.zip.Checksum JavaDoc;
33
34 /**
35  * This class is a wrapper around Adler32 which provides the capability to
36  * update the running total. This functionality is provided by quite risky
37  * reflection and should be fixed in a better way later on.
38  */
39 public class CRC32Ext implements Checksum JavaDoc {
40     private int crc;
41     private final CRC32 JavaDoc intern;
42
43     private static final Field JavaDoc intern_crc;
44
45     static {
46         try {
47             intern_crc = CRC32 JavaDoc.class.getDeclaredField("crc");
48             intern_crc.setAccessible(true);
49         } catch(final NoSuchFieldException JavaDoc nsfe) {
50             throw new RuntimeException JavaDoc("This class have stopped working, it should be updated and FIXED now.");
51         }
52     }
53
54     /**
55      * Creates the basic object with default initial adler.
56      */
57     public CRC32Ext() {
58         this(1);
59     }
60
61     /**
62      * Creates the basic object with the adler provided.
63      *
64      * @param adler the number to use as starting point for the CRC-32 algorithm
65      */
66     public CRC32Ext(final int crc) {
67         super();
68         this.crc=crc;
69         this.intern = new CRC32 JavaDoc();
70         setCRCRef(this.crc);
71     }
72
73     /**
74      * Sets the adler running total to the specified value.
75      *
76      * @param adler the number to use as current value for the CRC-32 algorithm
77      */
78     public void setAdler(final int crc) {
79         this.crc = crc;
80         setCRCRef(this.crc);
81     }
82
83     /**
84      * @see java.util.zip.Checksum#update
85      */
86     public void update(final int b) {
87         this.intern.update(b);
88     }
89
90     /**
91      * @see java.util.zip.Checksum#update
92      */
93     public void update(final byte[] b, final int off, final int len) {
94         this.intern.update(b,off,len);
95     }
96
97     /**
98      * @see java.util.zip.Checksum#update
99      */
100     public void update(final byte[] b) {
101         this.intern.update(b);
102     }
103
104     /**
105      * @see java.util.zip.Checksum#reset
106      */
107     public void reset() {
108         this.intern.reset();
109     this.crc = 1;
110     }
111
112     /**
113      * @see java.util.zip.Checksum#getValue
114      */
115     public long getValue() {
116     return this.intern.getValue();
117     }
118
119     /**
120      * Helper method to set the reference through reflection.
121      *
122      * @param val the value to set.
123      */
124     private void setCRCRef(final int val) {
125         try {
126             intern_crc.setInt(intern,val);
127         } catch(final IllegalAccessException JavaDoc e) {
128             throw new IllegalStateException JavaDoc(e.toString());
129         }
130     }
131 }
132
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