refactored code slightly

src/message.h

@@ -0,0 +1,28 @@
+#ifndef _MESSAGE_H_
+#define _MESSAGE_H_
+
+#include <stdint.h>
+
+typedef enum MessageType
+{
+    NOTE_OFF, NOTE_ON,
+    SYSTEM_EXCLUSIVE
+} MessageType;
+
+typedef struct Message
+{
+    uint8_t channel;
+    MessageType type;
+
+    int length;
+    uint8_t* data;
+} Message;
+
+void create_message(Message** message);
+void free_message(Message* message);
+
+int data_length(MessageType type);
+int decode_status_byte(Message* message, uint8_t status);
+int encode_status_byte(const Message* message, uint8_t* status);
+
+#endif