Improve eSky frame decoder

2 files changed, 15 insertions, 8 deletions

diff --git a/src/main/java/org/traccar/protocol/EskyFrameDecoder.java b/src/main/java/org/traccar/protocol/EskyFrameDecoder.java
index da24c1273..a374f29b1 100644
--- a/src/main/java/org/traccar/protocol/EskyFrameDecoder.java
+++ b/src/main/java/org/traccar/protocol/EskyFrameDecoder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 - 2018 Anton Tananaev (anton@traccar.org)
+ * Copyright 2017 - 2020 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.
@@ -26,14 +26,18 @@ public class EskyFrameDecoder extends BaseFrameDecoder {
     protected Object decode(
             ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
 
-        buf.readerIndex(buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) 'E'));
-
-        int endIndex = buf.indexOf(buf.readerIndex() + 1, buf.writerIndex(), (byte) 'E');
-        if (endIndex > 0) {
-            return buf.readRetainedSlice(endIndex - buf.readerIndex());
-        } else {
-            return buf.readRetainedSlice(buf.readableBytes()); // assume full frame
+        int startIndex = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) 'E');
+        if (startIndex >= 0) {
+            buf.readerIndex(startIndex);
+            int endIndex = buf.indexOf(buf.readerIndex() + 1, buf.writerIndex(), (byte) 'E');
+            if (endIndex > 0) {
+                return buf.readRetainedSlice(endIndex - buf.readerIndex());
+            } else {
+                return buf.readRetainedSlice(buf.readableBytes()); // assume full frame
+            }
         }
+
+        return null;
     }
 
 }
diff --git a/src/test/java/org/traccar/protocol/EskyFrameDecoderTest.java b/src/test/java/org/traccar/protocol/EskyFrameDecoderTest.java
index ed587e4f3..20b5dfcd5 100644
--- a/src/test/java/org/traccar/protocol/EskyFrameDecoderTest.java
+++ b/src/test/java/org/traccar/protocol/EskyFrameDecoderTest.java
@@ -10,6 +10,9 @@ public class EskyFrameDecoderTest extends ProtocolTest {
 
         EskyFrameDecoder decoder = new EskyFrameDecoder();
 
+        verifyNull(
+                decoder.decode(null, null, binary("00")));
+
         verifyFrame(
                 binary("454f3b303b3836313331313030363436313930383b523b363b3138303432303130343735313b322e39373839363b3130312e36353039313b302e37353b3332303b333339383b313b7c"),
                 decoder.decode(null, null, binary("454f3b303b3836313331313030363436313930383b523b363b3138303432303130343735313b322e39373839363b3130312e36353039313b302e37353b3332303b333339383b313b7c")));