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path: root/src/org/traccar/protocol/Gt02ProtocolDecoder.java
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/*
 * Copyright 2012 - 2015 Anton Tananaev (anton.tananaev@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 java.net.SocketAddress;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.traccar.BaseProtocolDecoder;
import org.traccar.helper.BitUtil;
import org.traccar.helper.DateBuilder;
import org.traccar.helper.UnitsConverter;
import org.traccar.model.Event;
import org.traccar.model.Position;

public class Gt02ProtocolDecoder extends BaseProtocolDecoder {

    public Gt02ProtocolDecoder(Gt02Protocol protocol) {
        super(protocol);
    }

    private String readImei(ChannelBuffer buf) {
        int b = buf.readUnsignedByte();
        StringBuilder imei = new StringBuilder();
        imei.append(b & 0x0F);
        for (int i = 0; i < 7; i++) {
            b = buf.readUnsignedByte();
            imei.append((b & 0xF0) >> 4);
            imei.append(b & 0x0F);
        }
        return imei.toString();
    }

    public static final int MSG_HEARTBEAT = 0x1A;
    public static final int MSG_DATA = 0x10;

    @Override
    protected Object decode(
            Channel channel, SocketAddress remoteAddress, Object msg) throws Exception {

        ChannelBuffer buf = (ChannelBuffer) msg;

        buf.skipBytes(2); // header
        buf.readByte(); // size

        // Zero for location messages
        buf.readByte(); // voltage
        buf.readByte(); // gsm signal

        String imei = readImei(buf);
        long index = buf.readUnsignedShort();
        int type = buf.readUnsignedByte();

        if (type == MSG_HEARTBEAT) {

            if (channel != null) {
                byte[] response = {0x54, 0x68, 0x1A, 0x0D, 0x0A};
                channel.write(ChannelBuffers.wrappedBuffer(response));
            }

        } else if (type == MSG_DATA) {

            Position position = new Position();
            position.setProtocol(getProtocolName());
            position.set(Event.KEY_INDEX, index);

            if (!identify(imei, channel)) {
                return null;
            }
            position.setDeviceId(getDeviceId());

            DateBuilder dateBuilder = new DateBuilder()
                    .setDate(buf.readUnsignedByte(), buf.readUnsignedByte(), buf.readUnsignedByte())
                    .setTime(buf.readUnsignedByte(), buf.readUnsignedByte(), buf.readUnsignedByte());
            position.setTime(dateBuilder.getDate());

            double latitude = buf.readUnsignedInt() / (60.0 * 30000.0);
            double longitude = buf.readUnsignedInt() / (60.0 * 30000.0);

            position.setSpeed(UnitsConverter.knotsFromKph(buf.readUnsignedByte()));
            position.setCourse(buf.readUnsignedShort());

            buf.skipBytes(3); // reserved

            long flags = buf.readUnsignedInt();
            position.setValid(BitUtil.check(flags, 0));
            if (!BitUtil.check(flags, 1)) {
                latitude = -latitude;
            }
            if (!BitUtil.check(flags, 2)) {
                longitude = -longitude;
            }

            position.setLatitude(latitude);
            position.setLongitude(longitude);

            return position;
        }

        return null;
    }

}