From caa4924336f865139c93136fd56ebb4bae5f4260 Mon Sep 17 00:00:00 2001
From: Joe Finney <joe@comp.lancs.ac.uk>
Date: Fri, 26 Feb 2016 16:27:13 +0000
Subject: [PATCH] microbit: Added validation case in
 MicroBitRadioDatagram::recv()

Introduced missed validation case in MicroBitRadioDatagram::recv().
Added PacketBuffer::EmptyPacket as a NULL reference.
---
 inc/PacketBuffer.h                            | 2 ++
 source/PacketBuffer.cpp                       | 3 +++
 source/ble-services/MicroBitRadioDatagram.cpp | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/inc/PacketBuffer.h b/inc/PacketBuffer.h
index 7ef932f..a0c40ca 100644
--- a/inc/PacketBuffer.h
+++ b/inc/PacketBuffer.h
@@ -233,6 +233,8 @@ class PacketBuffer
      * @endcode
      */
     void setRSSI(uint8_t rssi);
+
+    static PacketBuffer EmptyPacket;
 };
 
 #endif
diff --git a/source/PacketBuffer.cpp b/source/PacketBuffer.cpp
index 32cb783..54f8ca7 100644
--- a/source/PacketBuffer.cpp
+++ b/source/PacketBuffer.cpp
@@ -1,5 +1,8 @@
 #include "MicroBit.h"
 
+// Create the EmptyPacket reference.
+PacketBuffer PacketBuffer::EmptyPacket = PacketBuffer(1);
+
 /**
  * Default Constructor. 
  * Creates an empty Packet Buffer. 
diff --git a/source/ble-services/MicroBitRadioDatagram.cpp b/source/ble-services/MicroBitRadioDatagram.cpp
index c6727fd..8f96a73 100644
--- a/source/ble-services/MicroBitRadioDatagram.cpp
+++ b/source/ble-services/MicroBitRadioDatagram.cpp
@@ -57,6 +57,9 @@ int MicroBitRadioDatagram::recv(uint8_t *buf, int len)
  */
 PacketBuffer MicroBitRadioDatagram::recv()
 {
+    if (rxQueue == NULL)
+        return PacketBuffer::EmptyPacket;
+
     FrameBuffer *p = rxQueue;
     rxQueue = rxQueue->next;