[message] add Message::Type (#4977)

src/core/common/message.cpp

@@ -61,7 +61,7 @@ MessagePool::MessagePool(Instance &aInstance)
 #endif
 }
 
-Message *MessagePool::New(uint8_t aType, uint16_t aReserveHeader, uint8_t aPriority)
+Message *MessagePool::New(Message::Type aType, uint16_t aReserveHeader, uint8_t aPriority)
 {
     otError  error = OT_ERROR_NONE;
     Message *message;
@@ -87,7 +87,7 @@ exit:
     return message;
 }
 
-Message *MessagePool::New(uint8_t aType, uint16_t aReserveHeader, const otMessageSettings *aSettings)
+Message *MessagePool::New(Message::Type aType, uint16_t aReserveHeader, const otMessageSettings *aSettings)
 {
     Message *message;
     bool     linkSecurityEnabled;

src/core/common/message.hpp

@@ -230,7 +230,11 @@ class Message : public Buffer
     friend class PriorityQueue;
 
 public:
-    enum
+    /**
+     * This enumeration represents the message type.
+     *
+     */
+    enum Type
     {
         kTypeIp6         = 0, ///< A full uncompressed IPv6 packet
         kType6lowpan     = 1, ///< A 6lowpan frame
@@ -331,7 +335,7 @@ public:
      * @returns The type of the message.
      *
      */
-    uint8_t GetType(void) const { return GetMetadata().mType; }
+    Type GetType(void) const { return static_cast<Type>(GetMetadata().mType); }
 
     /**
      * This method sets the message type.
@@ -339,7 +343,7 @@ public:
      * @param[in]  aType  The message type.
      *
      */
-    void SetType(uint8_t aType) { GetMetadata().mType = aType; }
+    void SetType(Type aType) { GetMetadata().mType = aType; }
 
     /**
      * This method returns the sub type of the message.
@@ -1135,7 +1139,7 @@ public:
      * @returns A pointer to the message or NULL if no message buffers are available.
      *
      */
-    Message *New(uint8_t aType, uint16_t aReserveHeader, uint8_t aPriority = kDefaultMessagePriority);
+    Message *New(Message::Type aType, uint16_t aReserveHeader, uint8_t aPriority = kDefaultMessagePriority);
 
     /**
      * This method is used to obtain a new message with specified settings.
@@ -1150,7 +1154,7 @@ public:
      * @returns A pointer to the message or NULL if no message buffers are available.
      *
      */
-    Message *New(uint8_t aType, uint16_t aReserveHeader, const otMessageSettings *aSettings);
+    Message *New(Message::Type aType, uint16_t aReserveHeader, const otMessageSettings *aSettings);
 
     /**
      * This method is used to free a message and return all message buffers to the buffer pool.

src/core/thread/mesh_forwarder.cpp

@@ -476,11 +476,14 @@ otError MeshForwarder::HandleFrameRequest(Mac::TxFrame &aFrame)
         // there is a pending indirect supervision message in the send
         // queue for it. The message would be then converted to a
         // direct tx.
+
+        // Fall through
+#endif
+
+    default:
         mMessageNextOffset = mSendMessage->GetLength();
         error              = OT_ERROR_ABORT;
         ExitNow();
-
-#endif
     }
 
     aFrame.SetIsARetransmission(false);