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 */
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 private byte[] tmpbuf;
90
91 /**
92 * Skips specified number of bytes of input.
93 * @param n the number of bytes to skip
94 * @return the actual number of bytes skipped
95 * @exception IOException if an I/O error has occurred
96 */
97 public long skip(long n) throws IOException {
98 if (tmpbuf == null) {
99 tmpbuf = new byte[512];
100 }
101 long total = 0;
102 while (total < n) {
103 long len = n - total;
104 len = read(buf, 0, len < tmpbuf.length ? (int)len : tmpbuf.length);
105 if (len == -1) {
106 return total;
107 }
108 total += len;
109 }
110 return total;
111 }
112
113 /**
114 * Returns the Checksum for this input stream.
115 * @return the Checksum value
116 */
117 public Checksum getChecksum() {
118 return cksum;
119 }
120 }