blob: 2480629acad8d3f86807a8412fdd7f97f3f5d3f6 (
plain)
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
|
/*
* Copyright 2019 Anton Tananaev (anton@traccar.org)
*
* Licensed 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.traccar.protocol;
import io.netty.buffer.ByteBuf;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.TooLongFrameException;
import org.traccar.BaseFrameDecoder;
public class NavisFrameDecoder extends BaseFrameDecoder {
private static final int NTCB_HEADER_LENGHT = 16;
private static final int NTCB_LENGHT_OFFSET = 12;
private static final int MAX_FRAME_LENGHT = 65551;
private static byte src8Checksum(ByteBuf buf, int length) {
byte sum = (byte) 0xFF;
for (int i = 0; i < length; i++) {
sum ^= buf.getUnsignedByte(i);
for (int j = 0; j < 8; j++) {
sum = (sum & 0x80) != 0 ? (byte) ((sum << 1) ^ 0x31) : (byte) (sum << 1);
}
}
return sum;
}
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
// Check minimum length
if (buf.readableBytes() < 1) {
return null;
}
if (buf.getByte(buf.readerIndex()) == 0x7F) {
// FLEX keep alive frame
return buf.readRetainedSlice(1);
} else if (buf.getByte(buf.readerIndex()) == 0x7E /* "~" */) {
// FLEX frame
if (buf.readableBytes() > MAX_FRAME_LENGHT) {
throw new TooLongFrameException();
}
if (src8Checksum(buf, buf.readableBytes() - 1) == buf.getByte(buf.readableBytes() - 1)) {
return buf.readRetainedSlice(buf.readableBytes());
}
} else {
// NTCB frame
if (buf.readableBytes() < NTCB_HEADER_LENGHT) {
return null;
}
int length = buf.getUnsignedShortLE(buf.readerIndex() + NTCB_LENGHT_OFFSET);
if (buf.readableBytes() >= NTCB_HEADER_LENGHT + length) {
if (buf.readableBytes() > MAX_FRAME_LENGHT) {
throw new TooLongFrameException();
}
return buf.readRetainedSlice(NTCB_HEADER_LENGHT + length);
}
}
return null;
}
}
|
