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
|
/*
Copyright (c) 2010 James Ahlborn
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA
*/
package com.healthmarketscience.jackcess;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;
/**
* Default implementation of CodecProvider which does not have any actual
* encoding/decoding support. See {@link CodecProvider} for details on a more
* useful implementation.
*
* @author James Ahlborn
*/
public class DefaultCodecProvider implements CodecProvider
{
/** common instance of DefaultCodecProvider */
public static final CodecProvider INSTANCE =
new DefaultCodecProvider();
/** common instance of {@link DummyHandler} */
public static final CodecHandler DUMMY_HANDLER =
new DummyHandler();
/** common instance of {@link UnsupportedHandler} */
public static final CodecHandler UNSUPPORTED_HANDLER =
new UnsupportedHandler();
/**
* {@inheritDoc}
* <p>
* This implementation returns DUMMY_HANDLER for databases with no encoding
* and UNSUPPORTED_HANDLER for databases with any encoding.
*/
public CodecHandler createHandler(PageChannel channel, Charset charset)
throws IOException
{
JetFormat format = channel.getFormat();
switch(format.CODEC_TYPE) {
case NONE:
// no encoding, all good
return DUMMY_HANDLER;
case JET:
case OFFICE:
// check for an encode key. if 0, not encoded
ByteBuffer bb = channel.createPageBuffer();
channel.readPage(bb, 0);
int codecKey = bb.getInt(format.OFFSET_ENCODING_KEY);
return((codecKey == 0) ? DUMMY_HANDLER : UNSUPPORTED_HANDLER);
case MSISAM:
// always encoded, we don't handle it
return UNSUPPORTED_HANDLER;
default:
throw new RuntimeException("Unknown codec type " + format.CODEC_TYPE);
}
}
/**
* CodecHandler implementation which does nothing, useful for databases with
* no extra encoding.
*/
public static class DummyHandler implements CodecHandler
{
public void decodePage(ByteBuffer page, int pageNumber) throws IOException
{
// does nothing
}
public ByteBuffer encodePage(ByteBuffer page, int pageNumber,
int pageOffset)
throws IOException
{
// does nothing
return page;
}
}
/**
* CodecHandler implementation which always throws
* UnsupportedCodecException, useful for databases with unsupported
* encodings.
*/
public static class UnsupportedHandler implements CodecHandler
{
public void decodePage(ByteBuffer page, int pageNumber) throws IOException
{
throw new UnsupportedCodecException("Decoding not supported. Please choose a CodecProvider which supports reading the current database encoding.");
}
public ByteBuffer encodePage(ByteBuffer page, int pageNumber,
int pageOffset)
throws IOException
{
throw new UnsupportedCodecException("Encoding not supported. Please choose a CodecProvider which supports writing the current database encoding.");
}
}
}
|
