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/*
* Copyright 2017 Ivan Muratov (binakot@gmail.com)
*
* 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 org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;
public class Arnavi4FrameDecoder extends FrameDecoder {
private static final int MIN_LENGTH = 4;
private static final int HEADER_LENGTH = 10;
private static final int PACKET_WRAPPER_LENGTH = 8;
private static final int COMMAND_ANSWER_PACKET_LENGTH = 4;
private static final int COMMAND_ANSWER_PARCEL_NUMBER = 0xfd;
private static final byte PACKAGE_END_SIGN = 0x5d;
private boolean firstPacket = true;
@Override
protected Object decode(
ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception {
if (buf.readableBytes() < MIN_LENGTH) {
return null;
}
int length;
if (firstPacket) {
firstPacket = false;
length = HEADER_LENGTH;
} else {
int index = buf.getUnsignedByte(1); // parcel number
if (index == COMMAND_ANSWER_PARCEL_NUMBER) {
length = COMMAND_ANSWER_PACKET_LENGTH;
} else {
int pos = 2; // start sign + parcel number
while (pos + PACKET_WRAPPER_LENGTH < buf.readableBytes()
&& buf.getByte(pos) != PACKAGE_END_SIGN) {
int dataLength = buf.getUnsignedShort(pos + 1);
pos += PACKET_WRAPPER_LENGTH + dataLength; // packet type + data length + unixtime + data + crc
}
if (buf.getByte(pos) != PACKAGE_END_SIGN) { // end sign
return null;
}
length = pos + 1;
}
}
if (buf.readableBytes() >= length) {
return buf.readBytes(length);
}
return null;
}
}
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