Unify signed magnitude int decoding

2 files changed, 8 insertions, 2 deletions

diff --git a/src/main/java/org/traccar/helper/BitUtil.java b/src/main/java/org/traccar/helper/BitUtil.java
index b6108edff..829ddebc9 100644
--- a/src/main/java/org/traccar/helper/BitUtil.java
+++ b/src/main/java/org/traccar/helper/BitUtil.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 Anton Tananaev (anton@traccar.org)
+ * Copyright 2015 - 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.
@@ -21,7 +21,7 @@ public final class BitUtil {
     }
 
     public static boolean check(long number, int index) {
-        return (number & (1 << index)) != 0;
+        return (number & (1L << index)) != 0;
     }
 
     public static int between(int number, int from, int to) {
diff --git a/src/main/java/org/traccar/helper/BufferUtil.java b/src/main/java/org/traccar/helper/BufferUtil.java
index 1e1a687fa..0dbe0a4ad 100644
--- a/src/main/java/org/traccar/helper/BufferUtil.java
+++ b/src/main/java/org/traccar/helper/BufferUtil.java
@@ -27,6 +27,12 @@ public final class BufferUtil {
     private BufferUtil() {
     }
 
+    public static int readSignedMagnitudeInt(ByteBuf buffer) {
+        long value = buffer.readUnsignedInt();
+        int result = (int) BitUtil.to(value, 31);
+        return BitUtil.check(value, 31) ? -result : result;
+    }
+
     public static int indexOf(ByteBuf buffer, int fromIndex, int toIndex, byte value, int count) {
         int startIndex = fromIndex;
         for (int i = 0; i < count; i++) {