1 /*
2 * Copyright 1996-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.util.zip;
27
28 import java.io.FilterInputStream;
29 import java.io.InputStream;
30 import java.io.IOException;
31
32 /**
33 * An input stream that also maintains a checksum of the data being read.
34 * The checksum can then be used to verify the integrity of the input data.
35 *
36 * @see Checksum
37 * @author David Connelly
38 */
39 public
40 class CheckedInputStream extends FilterInputStream {
41 private Checksum cksum;
42
43 /**
44 * Creates an input stream using the specified Checksum.
45 * @param in the input stream
46 * @param cksum the Checksum
47 */
48 public CheckedInputStream(InputStream in, Checksum cksum) {
49 super(in);
50 this.cksum = cksum;
51 }
52
53 /**
54 * Reads a byte. Will block if no input is available.
55 * @return the byte read, or -1 if the end of the stream is reached.
56 * @exception IOException if an I/O error has occurred
57 */
58 public int read() throws IOException {
59 int b = in.read();
60 if (b != -1) {
61 cksum.update(b);
62 }
63 return b;
64 }
65
66 /**
67 * Reads into an array of bytes. If <code>len</code> is not zero, the method
68 * blocks until some input is available; otherwise, no
69 * bytes are read and <code>0</code> is returned.
70 * @param buf the buffer into which the data is read
71 * @param off the start offset in the destination array <code>b</code>
72 * @param len the maximum number of bytes read
73 * @return the actual number of bytes read, or -1 if the end
74 * of the stream is reached.
75 * @exception NullPointerException If <code>buf</code> is <code>null</code>.
76 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
77 * <code>len</code> is negative, or <code>len</code> is greater than
78 * <code>buf.length - off</code>
79 * @exception IOException if an I/O error has occurred
80 */
81 public int read(byte[] buf, int off, int len) throws IOException {
82 len = in.read(buf, off, len);
83 if (len != -1) {
84 cksum.update(buf, off, len);
85 }
86 return len;
87 }
88
89 /**
90 * Skips specified number of bytes of input.
91 * @param n the number of bytes to skip
92 * @return the actual number of bytes skipped
93 * @exception IOException if an I/O error has occurred
94 */
95 public long skip(long n) throws IOException {
96 byte[] buf = new byte[512];
97 long total = 0;
98 while (total < n) {
99 long len = n - total;
100 len = read(buf, 0, len < buf.length ? (int)len : buf.length);
101 if (len == -1) {
102 return total;
103 }
104 total += len;
105 }
106 return total;
107 }
108
109 /**
110 * Returns the Checksum for this input stream.
111 * @return the Checksum value
112 */
113 public Checksum getChecksum() {
114 return cksum;
115 }
116 }
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