1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
|
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.commons.compress.archivers.dump;
import java.io.IOException;
import java.util.Arrays;
import org.apache.commons.compress.archivers.zip.ZipEncoding;
import org.apache.commons.compress.utils.ByteUtils;
/**
* Various utilities for dump archives.
*/
class DumpArchiveUtil {
/**
* Private constructor to prevent instantiation.
*/
private DumpArchiveUtil() {
}
/**
* Calculate checksum for buffer.
*
* @param buffer buffer containing tape segment header
* @returns checksum
*/
public static int calculateChecksum(final byte[] buffer) {
int calc = 0;
for (int i = 0; i < 256; i++) {
calc += DumpArchiveUtil.convert32(buffer, 4 * i);
}
return DumpArchiveConstants.CHECKSUM -
(calc - DumpArchiveUtil.convert32(buffer, 28));
}
/**
* Verify that the buffer contains a tape segment header.
*
* @param buffer
*/
public static final boolean verify(final byte[] buffer) {
// verify magic. for now only accept NFS_MAGIC.
final int magic = convert32(buffer, 24);
if (magic != DumpArchiveConstants.NFS_MAGIC) {
return false;
}
//verify checksum...
final int checksum = convert32(buffer, 28);
return checksum == calculateChecksum(buffer);
}
/**
* Get the ino associated with this buffer.
*
* @param buffer
*/
public static final int getIno(final byte[] buffer) {
return convert32(buffer, 20);
}
/**
* Read 8-byte integer from buffer.
*
* @param buffer
* @param offset
* @return the 8-byte entry as a long
*/
public static final long convert64(final byte[] buffer, final int offset) {
return ByteUtils.fromLittleEndian(buffer, offset, 8);
}
/**
* Read 4-byte integer from buffer.
*
* @param buffer
* @param offset
* @return the 4-byte entry as an int
*/
public static final int convert32(final byte[] buffer, final int offset) {
return (int) ByteUtils.fromLittleEndian(buffer, offset, 4);
}
/**
* Read 2-byte integer from buffer.
*
* @param buffer
* @param offset
* @return the 2-byte entry as an int
*/
public static final int convert16(final byte[] buffer, final int offset) {
return (int) ByteUtils.fromLittleEndian(buffer, offset, 2);
}
/**
* Decodes a byte array to a string.
*/
static String decode(final ZipEncoding encoding, final byte[] b, final int offset, final int len)
throws IOException {
return encoding.decode(Arrays.copyOfRange(b, offset, offset + len));
}
}
|
