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/*
* 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 java.nio.charset.StandardCharsets;
import org.traccar.BaseFrameDecoder;
public class NavisFrameDecoder extends BaseFrameDecoder {
private static final int NTCB_HEADER_LENGTH = 16;
private static final int NTCB_LENGTH_OFFSET = 12;
private static final int FLEX_HEADER_LENGTH = 2;
private static final int MAX_FRAME_LENGTH = 65551;
private final NavisProtocolDecoder protocolDecoder;
public NavisFrameDecoder(NavisProtocolDecoder protocolDecoder) {
this.protocolDecoder = protocolDecoder;
}
@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);
}
if (protocolDecoder.getFlexDataSize() > 0) {
// FLEX frame
if (buf.readableBytes() > MAX_FRAME_LENGTH) {
throw new TooLongFrameException();
}
if (buf.readableBytes() > FLEX_HEADER_LENGTH) {
int length = 0;
String type = buf.toString(buf.readerIndex(), 2, StandardCharsets.US_ASCII);
switch (type) {
// FLEX 1.0
case "~A":
length = protocolDecoder.getFlexDataSize()
* buf.getByte(buf.readerIndex() + FLEX_HEADER_LENGTH) + 1 + 1;
break;
case "~T":
length = protocolDecoder.getFlexDataSize() + 4 + 1;
break;
case "~C":
length = protocolDecoder.getFlexDataSize() + 1;
break;
// FLEX 2.0 (Extra packages)
case "~E":
length++;
for (int i = 0; i < buf.getByte(buf.readerIndex() + FLEX_HEADER_LENGTH); i++) {
if (buf.readableBytes() > FLEX_HEADER_LENGTH + length + 1) {
length += buf.getUnsignedShort(length + FLEX_HEADER_LENGTH) + 2;
} else {
return null;
}
}
length++;
break;
case "~X":
length = buf.getUnsignedShortLE(buf.readerIndex() + FLEX_HEADER_LENGTH) + 4 + 1;
break;
default:
return null;
}
if (buf.readableBytes() >= FLEX_HEADER_LENGTH + length) {
return buf.readRetainedSlice(buf.readableBytes());
}
}
} else {
// NTCB frame
if (buf.readableBytes() < NTCB_HEADER_LENGTH) {
return null;
}
int length = buf.getUnsignedShortLE(buf.readerIndex() + NTCB_LENGTH_OFFSET);
if (buf.readableBytes() >= NTCB_HEADER_LENGTH + length) {
if (buf.readableBytes() > MAX_FRAME_LENGTH) {
throw new TooLongFrameException();
}
return buf.readRetainedSlice(NTCB_HEADER_LENGTH + length);
}
}
return null;
}
}
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