Feature/zeroing rx buffer remain (#90)

* Added zeroing rx buffer remain

* Added zeroing rx buffer remain

* Added safety margin for the rx-buffer in the different ports.

* Added safety margin for the receive buffer.

* Added DoxyGen comments.

* Fixed checking return value when calculating distance between opening and closing tag on multiple properties.

ports/atmega168/main.c

@@ -135,7 +135,18 @@ static void input_switch_read(void)
     }
 }
 
-static uint8_t PDUBuffer[MAX_MPDU];
+
+/** Static receive buffer, initialized with zeros by the C Library Startup Code. */
+
+static uint8_t PDUBuffer[MAX_MPDU + 16 /* Add a little safety margin to the buffer,
+                                        * so that in the rare case, the message
+                                        * would be filled up to MAX_MPDU and some
+                                        * decoding functions would overrun, these
+                                        * decoding functions will just end up in
+                                        * a safe field of static zeros. */];
+
+/** Main */
+
 int main(void)
 {
     uint16_t pdu_len = 0;
@@ -153,7 +164,7 @@ int main(void)
         task_milliseconds();
         /* other tasks */
         /* BACnet handling */
-        pdu_len = datalink_receive(&src, &PDUBuffer[0], sizeof(PDUBuffer), 0);
+        pdu_len = datalink_receive(&src, &PDUBuffer[0], MAX_MPDU, 0);
         if (pdu_len) {
             LED_NPDU_ON();
             npdu_handler(&src, &PDUBuffer[0], pdu_len);