Refactor method encodeId and encodeContent

- Replace method getCalibrationByteFromHexString with xor checksum
- Rewrite method encodeContent with ByteBuf instead of String
- Refactor encodeId by replacing short variable names and use ByteBuf

2 files changed, 44 insertions, 48 deletions

diff --git a/src/main/java/org/traccar/protocol/GatorProtocolEncoder.java b/src/main/java/org/traccar/protocol/GatorProtocolEncoder.java
index efe8715e3..296ff4f13 100644
--- a/src/main/java/org/traccar/protocol/GatorProtocolEncoder.java
+++ b/src/main/java/org/traccar/protocol/GatorProtocolEncoder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 - Hossain Mohammad Seym
+ * Copyright 2023 Hossain Mohammad Seym (seym45@gmail.com)
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,14 +19,11 @@ import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import org.traccar.BaseProtocolEncoder;
 import org.traccar.Protocol;
-import org.traccar.config.Keys;
 import org.traccar.helper.Checksum;
-import org.traccar.helper.DataConverter;
-import org.traccar.helper.model.AttributeUtil;
 import org.traccar.model.Command;
-import org.traccar.model.Device;
 
-import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.List;
 
 public class GatorProtocolEncoder extends BaseProtocolEncoder {
 
@@ -34,65 +31,57 @@ public class GatorProtocolEncoder extends BaseProtocolEncoder {
         super(protocol);
     }
 
+    public static ByteBuf encodeId(long deviceId) {
+        ByteBuf buf = Unpooled.buffer();
 
-    public static String encodeId(long deviceId) {
-        StringBuilder encodedId = new StringBuilder();
-
-        String imei = String.valueOf(deviceId);
-        String a = imei.substring(1, 3);
-        String b = imei.substring(3, 5);
-        String c = imei.substring(5, 7);
-        String d = imei.substring(7, 9);
-        String e = imei.substring(9);
-        String[] arr = {b, c, d, e};
+        String deviceIdStrVal = String.valueOf(deviceId);
+        List<String> partialDigits = new ArrayList<>();
+        for (int i = 1; i < deviceIdStrVal.length(); i += 2) {
+            partialDigits.add(deviceIdStrVal.substring(i, i + 2));
+        }
 
-        String binaryFirstDigit = Integer.toBinaryString(Integer.valueOf(a) - 30);
-        binaryFirstDigit = String.format("%4s", binaryFirstDigit).replace(' ', '0');
+        int firstDigit = Integer.parseInt(partialDigits.get(0)) - 30;
 
-        for (int i = 0; i < 4; i++) {
-            int sum = Integer.parseInt(arr[i]) + Integer.parseInt(String.valueOf(binaryFirstDigit.charAt(i)) + "0000000", 2);
-            arr[i] = Integer.toHexString(sum).toUpperCase();
-            arr[i] = String.format("%2s", arr[i]).replace(' ', '0');
-        }
+        for (int i = 1; i < partialDigits.size(); i++) {
+            int shiftCount = 4 - i;
+            int addend = ((firstDigit & (1 << shiftCount)) >> shiftCount) << 7;
+            int sum = Integer.parseInt(partialDigits.get(i)) | addend;
 
-        for (String s : arr) {
-            encodedId.append(s);
+            buf.writeByte(sum);
         }
 
-        return encodedId.toString();
+        return buf;
     }
 
-    private static String getCalibrationByteFromHexString(String data) {
-        String response = "";
-        int calib = 0;
-        int length = data.length() / 2;
-        for (int i = 0; i < length; i++) {
-            calib = calib ^ Integer.parseInt(data.substring(i * 2, i * 2 + 2), 16);
-        }
-        response = Integer.toHexString(calib).toUpperCase();
-        response = String.format("%2s", response).replace(' ', '0');
-        return response;
-    }
 
-    private ByteBuf encodeContent(long deviceId, String mainOrder, String content) {
-        String pseudoIPAddress = encodeId(deviceId);
+    private ByteBuf encodeContent(long deviceId, int mainOrder) {
+        ByteBuf buf = Unpooled.buffer();
+
+        buf.writeByte(0x24);
+        buf.writeByte(0x24);
+        buf.writeByte(mainOrder);
+        buf.writeByte(0x00);
+
         int length = 4 + 1 + 1; // ip 4 bytes, calibration byte and end byte
-        String hexStringLength = String.format("%02X", length);
+        buf.writeByte(length);
 
-        String packet = "2424" + mainOrder + "00" + hexStringLength + pseudoIPAddress;
-        String calibration = getCalibrationByteFromHexString(packet);
-        packet = packet + calibration + "0D";
-        return Unpooled.wrappedBuffer(DataConverter.parseHex(packet));
-    }
+        ByteBuf pseudoIPAddress = encodeId(deviceId);
+        buf.writeBytes(pseudoIPAddress);
+
+        int checksum = Checksum.xor(buf.nioBuffer());
+        buf.writeByte(checksum);
 
+        buf.writeByte(0x0D);
+
+        return buf;
+    }
 
     @Override
     protected Object encodeCommand(Command command) {
 
         switch (command.getType()) {
-            // According to Protocol Documentation, 0x30 is for rollcall command
             case Command.TYPE_POSITION_SINGLE:
-                return encodeContent(command.getDeviceId(), "30", null);
+                return encodeContent(command.getDeviceId(), 0x30);
             default:
                 return null;
         }
diff --git a/src/test/java/org/traccar/protocol/GatorProtocolEncoderTest.java b/src/test/java/org/traccar/protocol/GatorProtocolEncoderTest.java
index a3bc3af2b..babd7285d 100644
--- a/src/test/java/org/traccar/protocol/GatorProtocolEncoderTest.java
+++ b/src/test/java/org/traccar/protocol/GatorProtocolEncoderTest.java
@@ -1,5 +1,7 @@
 package org.traccar.protocol;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 import org.junit.jupiter.api.Test;
 import org.traccar.ProtocolTest;
 import org.traccar.model.Command;
@@ -11,7 +13,12 @@ public class GatorProtocolEncoderTest extends ProtocolTest {
     @Test
     void testEncodeId() throws Exception {
         var encoder = inject(new GatorProtocolEncoder(null));
-        assertEquals("2008958C", encoder.encodeId(13332082112L));
+        ByteBuf pseudoId = Unpooled.buffer();
+        pseudoId.writeByte(0x20);
+        pseudoId.writeByte(0x08);
+        pseudoId.writeByte(0x95);
+        pseudoId.writeByte(0x8C);
+        assertEquals(pseudoId, encoder.encodeId(13332082112L));
     }
 
     @Test