Fixed calculation of remaining length bug in Unsubscribe encoder

parser/src/main/java/org/dna/mqtt/moquette/proto/UnsubscribeEncoder.java

@@ -32,10 +32,10 @@ public class UnsubscribeEncoder implements MessageEncoder<UnsubscribeMessage> {
         variableHeaderBuff.flip();
         int variableHeaderSize = variableHeaderBuff.remaining();
         byte flags = Utils.encodeFlags(message);
-        IoBuffer buff = IoBuffer.allocate(4 + variableHeaderSize);
+        IoBuffer buff = IoBuffer.allocate(2 + variableHeaderSize);
 
         buff.put((byte) (AbstractMessage.UNSUBSCRIBE << 4 | flags));
-        buff.put(Utils.encodeRemainingLength(4 + variableHeaderSize));
+        buff.put(Utils.encodeRemainingLength(2 + variableHeaderSize));
         buff.put(variableHeaderBuff).flip();
 
         out.write(buff);

parser/src/test/java/org/dna/mqtt/moquette/proto/UnsubscribeEncoderTest.java

@@ -24,6 +24,30 @@ public class UnsubscribeEncoderTest {
         m_msg = new UnsubscribeMessage();
         m_msg.setMessageID(0xAABB);
     }
+    
+    @Test
+    public void testEncodeWithSingleTopic() throws Exception {
+        m_msg.setQos(QOSType.LEAST_ONE);
+        
+        //variable part
+        String topic1 = "/topic";
+        m_msg.addTopic(topic1);
+
+        //Exercise
+        m_encoder.encode(null, m_msg, m_mockProtoEncoder);
+        
+        //Verify
+        assertEquals((byte)0xA2, (byte)m_mockProtoEncoder.getBuffer().get()); //1 byte
+        assertEquals(12, m_mockProtoEncoder.getBuffer().get()); //remaining length
+        
+        //verify M1ssageID
+        assertEquals((byte)0xAA, m_mockProtoEncoder.getBuffer().get());
+        assertEquals((byte)0xBB, m_mockProtoEncoder.getBuffer().get());
+        
+        //Variable part
+        verifyString(topic1, m_mockProtoEncoder.getBuffer());
+    }
+    
 
     @Test
     public void testEncodeWithMultiTopic() throws Exception {
@@ -40,7 +64,7 @@ public class UnsubscribeEncoderTest {
 
         //Verify
         assertEquals((byte)0xA2, (byte)m_mockProtoEncoder.getBuffer().get()); //1 byte
-        assertEquals(18, m_mockProtoEncoder.getBuffer().get()); //remaining length
+        assertEquals(16, m_mockProtoEncoder.getBuffer().get()); //remaining length
         
         //verify M1ssageID
         assertEquals((byte)0xAA, m_mockProtoEncoder.getBuffer().get());