Refactor G1RUS protocol

3 files changed, 165 insertions, 314 deletions

diff --git a/src/main/java/org/traccar/protocol/G1rusFrameDecoder.java b/src/main/java/org/traccar/protocol/G1rusFrameDecoder.java
new file mode 100644
index 000000000..8c67207ad
--- /dev/null
+++ b/src/main/java/org/traccar/protocol/G1rusFrameDecoder.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2022 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.buffer.Unpooled;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelHandlerContext;
+import org.traccar.BaseFrameDecoder;
+
+public class G1rusFrameDecoder extends BaseFrameDecoder {
+
+    @Override
+    protected Object decode(
+            ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
+
+        ByteBuf result = Unpooled.buffer();
+
+        while (buf.isReadable()) {
+            int b = buf.readUnsignedByte();
+            if (b == 0x1B) {
+                int ext = buf.readUnsignedByte();
+                if (ext == 0x00) {
+                    result.writeByte(0x1B);
+                } else {
+                    result.writeByte(0xF8);
+                }
+            } else {
+                result.writeByte(b);
+            }
+        }
+
+        return result;
+    }
+
+}
diff --git a/src/main/java/org/traccar/protocol/G1rusProtocol.java b/src/main/java/org/traccar/protocol/G1rusProtocol.java
index 0d77a8add..f1823762d 100644
--- a/src/main/java/org/traccar/protocol/G1rusProtocol.java
+++ b/src/main/java/org/traccar/protocol/G1rusProtocol.java
@@ -1,6 +1,20 @@
+/*
+ * Copyright 2022 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.handler.codec.string.StringDecoder;
 import io.netty.handler.codec.string.StringEncoder;
 import org.traccar.BaseProtocol;
 import org.traccar.PipelineBuilder;
@@ -16,9 +30,11 @@ public class G1rusProtocol extends BaseProtocol {
         addServer(new TrackerServer(config, getName(), false) {
             @Override
             protected void addProtocolHandlers(PipelineBuilder pipeline, Config config) {
+                pipeline.addLast(new G1rusFrameDecoder());
                 pipeline.addLast(new StringEncoder());
                 pipeline.addLast(new G1rusProtocolDecoder(G1rusProtocol.this));
             }
         });
     }
+
 }
diff --git a/src/main/java/org/traccar/protocol/G1rusProtocolDecoder.java b/src/main/java/org/traccar/protocol/G1rusProtocolDecoder.java
index b1b7230e1..e974e446d 100644
--- a/src/main/java/org/traccar/protocol/G1rusProtocolDecoder.java
+++ b/src/main/java/org/traccar/protocol/G1rusProtocolDecoder.java
@@ -1,20 +1,30 @@
+/*
+ * Copyright 2022 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 com.google.common.primitives.Ints;
-import com.google.common.primitives.Longs;
-import com.google.common.primitives.Shorts;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.Channel;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Protocol;
+import org.traccar.helper.BitUtil;
 import org.traccar.model.Position;
-import org.traccar.session.ConnectionManager;
 import org.traccar.session.DeviceSession;
 
 import java.net.SocketAddress;
-import java.text.SimpleDateFormat;
+import java.nio.charset.StandardCharsets;
 import java.util.Date;
 import java.util.LinkedList;
 import java.util.List;
@@ -24,352 +34,128 @@ public class G1rusProtocolDecoder extends BaseProtocolDecoder {
         super(protocol);
     }
 
-    private static final Logger LOGGER = LoggerFactory.getLogger(ConnectionManager.class);
+    public static final int MSG_HEARTBEAT = 0;
+    public static final int MSG_REGULAR = 1;
+    public static final int MSG_SMS_FORWARD = 2;
+    public static final int MSG_SERIAL = 3;
+    public static final int MSG_MIXED = 4;
 
-    /* Constants */
-    private static final int G1RUS_HEAD_TAIL = 0xF8;
-
-    private static final int G1RUS_TYPE_HEARTBEAT = 0;
-
-    private static final int G1RUS_TYPE_BCD_MASK = 0b00111111;
-    private static final int G1RUS_TYPE_REGULAR = 1;
-    private static final int G1RUS_TYPE_SMS_FORWARD = 2;
-    private static final int G1RUS_TYPE_SERIAL_PASS_THROUGH = 3;
-    private static final int G1RUS_TYPE_MIXED = 4;
-
-    private static final int G1RUS_TYPE_EVENT_MASK = 0b01000000;
-    private static final int G1RUS_TYPE_NON_EVENT = 0;
-    private static final int G1RUS_TYPE_EVENT = 1;
-
-    private static final int G1RUS_TYPE_IMEI_MASK = 0b10000000;
-    private static final int G1RUS_TYPE_IMEI_LONG = 0;
-    private static final int G1RUS_TYPE_IMEI_SHORT = 1;
-
-    private static final int G1RUS_DATA_SYS_MASK = 0b00000001;
-    private static final int G1RUS_DATA_GPS_MASK = 0b00000010;
-    private static final int G1RUS_DATA_GSM_MASK = 0b00000100;
-    private static final int G1RUS_DATA_COT_MASK = 0b00001000;
-    private static final int G1RUS_DATA_ADC_MASK = 0b00010000;
-    private static final int G1RUS_DATA_DTT_MASK = 0b00100000;
-    /* Reserved */
-    private static final int G1RUS_DATA_ETD_MASK = 0b10000000;
-
-    private static final int G1RUS_GPS_SIGN_MASK = 0b00000001;
-    private static final int G1RUS_GPS_POS_MASK  = 0b00000010;
-    private static final int G1RUS_GPS_SPD_MASK  = 0b00000100;
-    private static final int G1RUS_GPS_AZTH_MASK = 0b00001000;
-    private static final int G1RUS_GPS_ALT_MASK  = 0b00010000;
-    private static final int G1RUS_GPS_HDOP_MASK = 0b00100000;
-    private static final int G1RUS_GPS_VDOP_MASK = 0b01000000;
-    private static final int G1RUS_GPS_STAT_MASK = 0b10000000;
-
-    private static final int G1RUS_ADC_DATA_MASK = 0b0000111111111111;
+    private String readString(ByteBuf buf) {
+        int length = buf.readUnsignedByte() & 0xF;
+        return buf.readCharSequence(length, StandardCharsets.US_ASCII).toString();
+    }
 
-    private static final int G1RUS_ESCAPE_CHAR = 0x1B;
+    private Position decodeRegular(DeviceSession deviceSession, ByteBuf buf, int type) {
 
+        Position position = new Position(getProtocolName());
+        position.setDeviceId(deviceSession.getDeviceId());
+        position.setTime(new Date((buf.readUnsignedIntLE() + 946684800) * 1000L));
 
-    private short readUnsignedByteUnescaped(ByteBuf buf) {
-        short first = buf.readUnsignedByte();
-        if (first != G1RUS_ESCAPE_CHAR) {
-            return first;
-        } else { /* first == 0x1B */
-            byte second = (byte) buf.readUnsignedByte();
-            if (second == 0x00) {
-                return first;
-            } else { /* second == 0xE3 */
-                return (short) 0xF8;
-            }
+        if (BitUtil.check(type, 6)) {
+            position.set(Position.KEY_EVENT, buf.readUnsignedByte());
         }
-    }
 
+        int dataMask = buf.readUnsignedShort();
 
-    private void skipBytesUnescaped(ByteBuf buf, int howMany) {
-        for (int i = 0; i < howMany; ++i) {
-            readUnsignedByteUnescaped(buf);
+        if (BitUtil.check(dataMask, 0)) {
+            buf.readUnsignedByte(); // length
+            readString(buf); // device name
+            position.set(Position.KEY_VERSION_FW, readString(buf));
+            position.set(Position.KEY_VERSION_HW, readString(buf));
         }
-    }
-
 
-    private void readBytesUnescaped(ByteBuf buf, byte[] to) {
-        for (int i = 0; i < to.length; ++i) {
-            to[i] = (byte) readUnsignedByteUnescaped(buf);
+        if (BitUtil.check(dataMask, 1)) {
+            buf.readUnsignedByte(); // length
+            int locationMask = buf.readUnsignedShort();
+            if (BitUtil.check(locationMask, 0)) {
+                int validity = buf.readUnsignedByte();
+                position.set(Position.KEY_SATELLITES, BitUtil.to(validity, 5));
+                position.setValid(BitUtil.between(validity, 5, 7) == 2);
+            }
+            if (BitUtil.check(locationMask, 1)) {
+                position.setLatitude(buf.readInt() / 1000000.0);
+                position.setLongitude(buf.readInt() / 1000000.0);
+            }
+            if (BitUtil.check(locationMask, 2)) {
+                position.setSpeed(buf.readUnsignedShort());
+            }
+            if (BitUtil.check(locationMask, 3)) {
+                position.setCourse(buf.readUnsignedShort());
+            }
+            if (BitUtil.check(locationMask, 4)) {
+                position.setAltitude(buf.readShort());
+            }
+            if (BitUtil.check(locationMask, 5)) {
+                position.set(Position.KEY_HDOP, buf.readUnsignedShort());
+            }
+            if (BitUtil.check(locationMask, 6)) {
+                position.set(Position.KEY_VDOP, buf.readUnsignedShort());
+            }
         }
-    }
 
-    private void readBytesUnescaped(ByteBuf buf, byte[] to, int dstIndex, int length) {
-        for (int i = dstIndex; i < length; ++i) {
-            to[i] = (byte) readUnsignedByteUnescaped(buf);
+        if (BitUtil.check(dataMask, 2)) {
+            buf.skipBytes(buf.readUnsignedByte());
         }
-    }
-
-
-    private int readUnsignedShortUnescaped(ByteBuf buf) {
-        byte[] shortBuf = new byte[2];
-        readBytesUnescaped(buf, shortBuf);
-        return Shorts.fromByteArray(shortBuf);
-    }
 
-
-    private int readIntUnescaped(ByteBuf buf) {
-        byte[] intBuf = new byte[4];
-        readBytesUnescaped(buf, intBuf);
-        return Ints.fromByteArray(intBuf);
-    }
-
-
-    private void decodeSYSSub(ByteBuf buf) {
-        LOGGER.debug("<SYS>");
-
-        skipBytesUnescaped(buf, 1); /* Total length */
-
-        /* NOTE: assuming order:
-         * Device name -> Firmware version -> Hardware version.
-         * TODO: actually check it.
-         */
-
-        /* Device name */
-        short devNameLen = readUnsignedByteUnescaped(buf);
-        byte[] devName = new byte[devNameLen & 0xF];
-        readBytesUnescaped(buf, devName);
-        String devNameString = new String(devName);
-        LOGGER.debug("Device name: " + devNameString);
-
-        /* Firmware version */
-        short firmwareLen = readUnsignedByteUnescaped(buf);
-        byte[] firmware = new byte[firmwareLen & 0xF];
-        readBytesUnescaped(buf, firmware);
-        String firmwareString = new String(firmware);
-        LOGGER.debug("Firmware version: " + firmwareString);
-
-        /* Hardware version */
-        short hardwareLen = readUnsignedByteUnescaped(buf);
-        byte[] hardware = new byte[hardwareLen & 0xF];
-        readBytesUnescaped(buf, hardware);
-        String hardwareString = new String(hardware);
-        LOGGER.debug("Hardware version: " + hardwareString);
-
-        LOGGER.debug("</SYS>");
-    }
-
-
-    private void decodeGPSSub(ByteBuf buf, Position position) {
-        LOGGER.debug("<GPS>");
-
-        skipBytesUnescaped(buf, 1); /* Total length */
-
-        int subMask = readUnsignedShortUnescaped(buf);
-        if ((subMask & G1RUS_GPS_SIGN_MASK) == G1RUS_GPS_SIGN_MASK) {
-            short signValid = readUnsignedByteUnescaped(buf);
-            LOGGER.debug("Fix sign: " + ((signValid & 0b1100000) >> 5));
-            LOGGER.debug("Satellite number: " + (signValid & 0b0011111));
-            position.setValid(((signValid & 0b1100000) >> 5) == 2);
-            position.set(Position.KEY_SATELLITES, signValid & 0b0011111);
-        }
-        if ((subMask & G1RUS_GPS_POS_MASK) == G1RUS_GPS_POS_MASK) {
-            byte[] posBuf = new byte[4];
-            readBytesUnescaped(buf, posBuf);
-            position.setLatitude((float) Ints.fromByteArray(posBuf) / 1000000);
-            LOGGER.debug("Latitude: " + position.getLatitude());
-
-            readBytesUnescaped(buf, posBuf);
-            position.setLongitude((float) Ints.fromByteArray(posBuf) / 1000000);
-            LOGGER.debug("Longitude: " + position.getLongitude());
-        }
-        if ((subMask & G1RUS_GPS_SPD_MASK) == G1RUS_GPS_SPD_MASK) {
-            position.setSpeed(readUnsignedShortUnescaped(buf));
-            LOGGER.debug("Speed: " + position.getSpeed());
+        if (BitUtil.check(dataMask, 3)) {
+            buf.skipBytes(buf.readUnsignedByte());
         }
-        if ((subMask & G1RUS_GPS_AZTH_MASK) == G1RUS_GPS_AZTH_MASK) {
-            position.setCourse(readUnsignedShortUnescaped(buf));
-            LOGGER.debug("Course: " + position.getCourse());
-        }
-        if ((subMask & G1RUS_GPS_ALT_MASK) == G1RUS_GPS_ALT_MASK) {
-            position.setAltitude(readUnsignedShortUnescaped(buf));
-            LOGGER.debug("Altitude: " + position.getAltitude());
-        }
-        if ((subMask & G1RUS_GPS_HDOP_MASK) == G1RUS_GPS_HDOP_MASK) {
-            position.set(Position.KEY_HDOP, readUnsignedShortUnescaped(buf));
-            LOGGER.debug("HDOP: " + position.getAttributes().get(Position.KEY_HDOP));
-        }
-        if ((subMask & G1RUS_GPS_VDOP_MASK) == G1RUS_GPS_VDOP_MASK) {
-            position.set(Position.KEY_VDOP, readUnsignedShortUnescaped(buf));
-            LOGGER.debug("VDOP: " + position.getAttributes().get(Position.KEY_VDOP));
-        }
-
-        LOGGER.debug("</GPS>");
-    }
-
-
-    private int getADValue(int rawValue) {
-        final int AD_MIN = -10;
-        final int AD_MAX = 100;
-
-        return rawValue * (AD_MAX - AD_MIN) / 4096 + AD_MIN;
-    }
-
-
-    private void decodeADCSub(ByteBuf buf, Position position) {
-        LOGGER.debug("<ADC>");
-
-        skipBytesUnescaped(buf, 1);
-
-        /* NOTE: assuming order:
-         * External battery voltage -> Backup battery voltage -> Device temperature voltage.
-         * TODO: actually check this.
-         */
-
-        int externalVoltage = readUnsignedShortUnescaped(buf) & G1RUS_ADC_DATA_MASK;
-        LOGGER.debug("External voltage: " + getADValue(externalVoltage) + "V [" + externalVoltage + "]");
-
-        int backupVoltage = readUnsignedShortUnescaped(buf) & G1RUS_ADC_DATA_MASK;
-        LOGGER.debug("Backup voltage: " + getADValue(backupVoltage) + "V [" + backupVoltage + "]");
-        position.set(Position.KEY_BATTERY, getADValue(backupVoltage));
-
-        int temperature = readUnsignedShortUnescaped(buf) & G1RUS_ADC_DATA_MASK;
-        LOGGER.debug("Device temperature: " + getADValue(temperature) + "°C [" + temperature + "]");
-        position.set(Position.KEY_DEVICE_TEMP, getADValue(temperature));
 
-        LOGGER.debug("</ADC>");
-    }
-
-
-    private Position decodeRegular(Channel channel, SocketAddress remoteAddress, ByteBuf buf, long imei, short packetType) {
-        int timestamp_ = readIntUnescaped(buf);
-        long timestamp = (946684800 + timestamp_) * 1000L; /* Convert received time to proper UNIX timestamp */
-        LOGGER.debug("Date and time: " + new SimpleDateFormat("yyyy.MM.dd HH:mm:ss").format(new Date(timestamp)));
-
-        if ((packetType & G1RUS_TYPE_EVENT_MASK) != G1RUS_TYPE_NON_EVENT) {
-            skipBytesUnescaped(buf, 1); /* Event ID */
+        if (BitUtil.check(dataMask, 4)) {
+            buf.readUnsignedByte(); // length
+            position.set(Position.KEY_POWER, buf.readUnsignedShort() * 110 / 4096 - 10);
+            position.set(Position.KEY_BATTERY, buf.readUnsignedShort() * 110 / 4096 - 10);
+            position.set(Position.KEY_DEVICE_TEMP, buf.readUnsignedShort() * 110 / 4096 - 10);
         }
 
-        DeviceSession deviceSession = null;
-        Position position = null;
-
-        int dataUploadingMask = readUnsignedShortUnescaped(buf);
-        if ((dataUploadingMask & G1RUS_DATA_SYS_MASK) == G1RUS_DATA_SYS_MASK) {
-            decodeSYSSub(buf);
+        if (BitUtil.check(dataMask, 5)) {
+            buf.skipBytes(buf.readUnsignedByte());
         }
-        if ((dataUploadingMask & G1RUS_DATA_GPS_MASK) == G1RUS_DATA_GPS_MASK) {
-            deviceSession = getDeviceSession(channel, remoteAddress, String.valueOf(imei));
-            if (deviceSession == null) {
-                return null;
-            }
-            position = new Position(getProtocolName());
-            position.setDeviceId(deviceSession.getDeviceId());
-            position.setTime(new Date(timestamp));
 
-            decodeGPSSub(buf, position);
-        }
-        if ((dataUploadingMask & G1RUS_DATA_GSM_MASK) == G1RUS_DATA_GSM_MASK) {
-            skipBytesUnescaped(buf, readUnsignedByteUnescaped(buf));
-        }
-        if ((dataUploadingMask & G1RUS_DATA_COT_MASK) == G1RUS_DATA_COT_MASK) {
-            skipBytesUnescaped(buf, readUnsignedByteUnescaped(buf));
-        }
-        if ((dataUploadingMask & G1RUS_DATA_ADC_MASK) == G1RUS_DATA_ADC_MASK) {
-            if (deviceSession == null) {
-                skipBytesUnescaped(buf, readUnsignedByteUnescaped(buf));
-            } else {
-                decodeADCSub(buf, position);
-            }
-        }
-        if ((dataUploadingMask & G1RUS_DATA_DTT_MASK) == G1RUS_DATA_DTT_MASK) {
-            skipBytesUnescaped(buf, readUnsignedByteUnescaped(buf));
-        }
-        if ((dataUploadingMask & G1RUS_DATA_ETD_MASK) == G1RUS_DATA_ETD_MASK) {
-            skipBytesUnescaped(buf, readUnsignedByteUnescaped(buf));
+        if (BitUtil.check(dataMask, 7)) {
+            buf.skipBytes(buf.readUnsignedByte());
         }
 
         return position;
     }
 
-
-    private Object decodeSMSForward(ByteBuf buf) {
-        return null;
-    }
-
-
-    private Object decodeSerialPassThrough(ByteBuf buf) {
-        return null;
-    }
-
-
-    private void printPacketType(short packetType) {
-        LOGGER.debug("Packet type: " + (packetType == G1RUS_TYPE_HEARTBEAT ? "HEARTBEAT" :
-                    "[" + ((packetType & G1RUS_TYPE_IMEI_MASK) == G1RUS_TYPE_IMEI_LONG ? "IMEI_LONG" : "IMEI_SHORT") + "]" +
-                    "[" + ((packetType & G1RUS_TYPE_EVENT_MASK) == G1RUS_TYPE_NON_EVENT ? "NON-EVENT" : "EVENT") + "]" +
-                    "[" + ((packetType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_REGULAR ? "REGULAR" : (packetType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_SMS_FORWARD ? "SMS FORWARD" : (packetType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_SERIAL_PASS_THROUGH ? "PASS THROUGH" : (packetType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_MIXED ? "MIXED PACKED" : "RESERVED/INVALID") + "]"));
-    }
-
-
     @Override
     protected Object decode(Channel channel, SocketAddress remoteAddress, Object msg) throws Exception {
+
         ByteBuf buf = (ByteBuf) msg;
 
-        if (buf.readUnsignedByte() != G1RUS_HEAD_TAIL) {
+        int type = buf.readUnsignedByte();
+        String imei = String.valueOf(buf.readLong());
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
 
-        LOGGER.debug("Protocol version: " + readUnsignedByteUnescaped(buf));
-
-        short packetType = readUnsignedByteUnescaped(buf);
-        printPacketType(packetType);
-
-        byte[] imei = new byte[8];
-        readBytesUnescaped(buf, imei, 0, 7);
-        long imeiLong = Longs.fromByteArray(imei);
-        LOGGER.debug("IMEI: " + imeiLong);
+        if (BitUtil.to(type, 6) == MSG_REGULAR) {
 
-        List<Position> positions = null;
+            return decodeRegular(deviceSession, buf, type);
 
-        if (packetType == G1RUS_TYPE_HEARTBEAT) {
-            return null;
-        } else if ((packetType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_REGULAR) {
-            positions = new LinkedList<>();
-            Position position = decodeRegular(channel, remoteAddress, buf, imeiLong, packetType);
-            if (position != null) {
-                positions.add(position);
-            }
-        } else if ((packetType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_SMS_FORWARD) {
-            return decodeSMSForward(buf);
-        } else if ((packetType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_SERIAL_PASS_THROUGH) {
-            return decodeSerialPassThrough(buf);
-        } else if ((packetType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_MIXED) {
-            positions = new LinkedList<>();
+        } else if (BitUtil.to(type, 6) == MSG_MIXED) {
 
+            List<Position> positions = new LinkedList<>();
             while (buf.readableBytes() > 5) {
-                int subPacketLength = readUnsignedShortUnescaped(buf);
-                short subPacketType = readUnsignedByteUnescaped(buf);
-                printPacketType(subPacketType);
-
-                if ((subPacketType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_REGULAR) {
-                    Position position = decodeRegular(channel, remoteAddress, buf, imeiLong, subPacketType);
-                    if (position != null) {
-                        positions.add(position);
-                    }
+                int length = buf.readUnsignedShort();
+                int subtype = buf.readUnsignedByte();
+                if (BitUtil.to(subtype, 6) == MSG_REGULAR) {
+                    positions.add(decodeRegular(deviceSession, buf, subtype));
                 } else {
-                    skipBytesUnescaped(buf, subPacketLength - 1);
+                    buf.skipBytes(length);
                 }
-                /* else if ((subPacketType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_SMS_FORWARD) {
-                    skipBytesUnescaped(buf, subPacketLength - 1);
-                    *//*decodeSMSForward(buf);*//*
-                } else if ((subPacketType & G1RUS_TYPE_BCD_MASK) == G1RUS_TYPE_SERIAL_PASS_THROUGH) {
-                    skipBytesUnescaped(buf, subPacketLength - 1);
-                    *//*decodeSerialPassThrough(buf);*//*
-                }*/
             }
-        } else {
-            LOGGER.error("Unknown packet type!");
-        }
+            return positions.isEmpty() ? null : positions;
 
-        skipBytesUnescaped(buf, 2); /* CRC */ /* TODO: actually check it */
-        short tail = buf.readUnsignedByte();
-        if (tail == G1RUS_HEAD_TAIL) {
-            LOGGER.debug("Tail: OK");
-        } else {
-            LOGGER.error("Tail: FAIL!");
         }
 
-        return positions;
+        buf.skipBytes(2);
+        buf.readUnsignedByte(); // tail
+
+        return null;
+
     }
+
 }