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25 
26 package java.util.zip;
27 
28 import java.io.FilterOutputStream;
29 import java.io.OutputStream;
30 import java.io.IOException;
31 
32 /**
33  * An output stream that also maintains a checksum of the data being
34  * written. The checksum can then be used to verify the integrity of
35  * the output data.
36  *
37  * @see         Checksum
38  * @author      David Connelly
39  * @since 1.1
40  */
41 public class CheckedOutputStream extends FilterOutputStream {
42     private Checksum cksum;
43 
44     /**
45      * Creates an output stream with the specified Checksum.
46      * @param out the output stream
47      * @param cksum the checksum
48      */
CheckedOutputStream(OutputStream out, Checksum cksum)49     public CheckedOutputStream(OutputStream out, Checksum cksum) {
50         super(out);
51         this.cksum = cksum;
52     }
53 
54     /**
55      * Writes a byte. Will block until the byte is actually written.
56      * @param b the byte to be written
57      * @throws    IOException if an I/O error has occurred
58      */
write(int b)59     public void write(int b) throws IOException {
60         out.write(b);
61         cksum.update(b);
62     }
63 
64     /**
65      * Writes an array of bytes. Will block until the bytes are
66      * actually written.
67      * @param b the data to be written
68      * @param off the start offset of the data
69      * @param len the number of bytes to be written
70      * @throws    IOException if an I/O error has occurred
71      */
write(byte[] b, int off, int len)72     public void write(byte[] b, int off, int len) throws IOException {
73         out.write(b, off, len);
74         cksum.update(b, off, len);
75     }
76 
77     /**
78      * Returns the Checksum for this output stream.
79      * @return the Checksum
80      */
getChecksum()81     public Checksum getChecksum() {
82         return cksum;
83     }
84 }
85