1 /*
2 * Copyright (c) 1996, 2006, Oracle and/or its affiliates. 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * 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 * @since 1.1
39 */
40 public
41 class CheckedInputStream extends FilterInputStream {
42 private Checksum cksum;
43
44 /**
45 * Creates an input stream using the specified Checksum.
46 * @param in the input stream
47 * @param cksum the Checksum
48 */
49 public CheckedInputStream(InputStream in, Checksum cksum) {
50 super(in);
51 this.cksum = cksum;
52 }
53
54 /**
55 * Reads a byte. Will block if no input is available.
56 * @return the byte read, or -1 if the end of the stream is reached.
57 * @exception IOException if an I/O error has occurred
58 */
59 public int read() throws IOException {
60 int b = in.read();
61 if (b != -1) {
62 cksum.update(b);
63 }
64 return b;
65 }
66
67 /**
68 * Reads into an array of bytes. If <code>len</code> is not zero, the method
69 * blocks until some input is available; otherwise, no
70 * bytes are read and <code>0</code> is returned.
71 * @param buf the buffer into which the data is read
72 * @param off the start offset in the destination array <code>b</code>
73 * @param len the maximum number of bytes read
74 * @return the actual number of bytes read, or -1 if the end
75 * of the stream is reached.
76 * @exception NullPointerException If <code>buf</code> is <code>null</code>.
77 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
78 * <code>len</code> is negative, or <code>len</code> is greater than
79 * <code>buf.length - off</code>
80 * @exception IOException if an I/O error has occurred
81 */
82 public int read(byte[] buf, int off, int len) throws IOException {
83 len = in.read(buf, off, len);
84 if (len != -1) {
85 cksum.update(buf, off, len);
86 }
87 return len;
88 }
89
90 /**
91 * Skips specified number of bytes of input.
92 * @param n the number of bytes to skip
93 * @return the actual number of bytes skipped
94 * @exception IOException if an I/O error has occurred
95 */
96 public long skip(long n) throws IOException {
97 byte[] buf = new byte[512];
98 long total = 0;
99 while (total < n) {
100 long len = n - total;
101 len = read(buf, 0, len < buf.length ? (int)len : buf.length);
102 if (len == -1) {
103 return total;
104 }
105 total += len;
106 }
107 return total;
108 }
109
110 /**
111 * Returns the Checksum for this input stream.
112 * @return the Checksum value
113 */
114 public Checksum getChecksum() {
115 return cksum;
116 }
117 }
118