Changed streamType_t from bitfield struct to union of anonymous bitfield struct and uint16_t to facilitate endianness conversion. Change also fixed a bug in endianness conversion inside M17LinkSetupFrame class due to unaligned memory access.

openrtx/include/protocols/M17/M17Datatypes.h

@@ -39,16 +39,21 @@ using lich_t    = std::array< uint8_t, 12 >;   // Data type for Golay(24,12) enc
  * This structure provides bit field definitions for the "TYPE" field
  * contained in an M17 Link Setup Frame.
  */
-typedef struct
+typedef union
 {
-    uint16_t stream     : 1;    //< Packet/stream indicator: 0 = packet, 1 = stream
-    uint16_t dataType   : 2;    //< Data type indicator
-    uint16_t encType    : 2;    //< Encryption type
-    uint16_t encSubType : 2;    //< Encryption subtype
-    uint16_t CAN        : 4;    //< Channel Access Number
-    uint16_t            : 4;    //< Reserved, padding to 16 bit
+    struct __attribute__((packed))
+    {
+        uint16_t stream     : 1;    //< Packet/stream indicator: 0 = packet, 1 = stream
+        uint16_t dataType   : 2;    //< Data type indicator
+        uint16_t encType    : 2;    //< Encryption type
+        uint16_t encSubType : 2;    //< Encryption subtype
+        uint16_t CAN        : 4;    //< Channel Access Number
+        uint16_t            : 4;    //< Reserved, padding to 16 bit
+    };
+
+    uint16_t value;
 }
-__attribute__((packed)) streamType_t;
+streamType_t;
 
 
 /**

openrtx/src/protocols/M17/M17LinkSetupFrame.cpp

@@ -23,6 +23,7 @@
 #include <M17/M17Callsign.h>
 #include <M17/M17LinkSetupFrame.h>
 
+
 M17LinkSetupFrame::M17LinkSetupFrame()
 {
     clear();
@@ -52,17 +53,16 @@ void M17LinkSetupFrame::setDestination(const std::string& callsign)
 streamType_t M17LinkSetupFrame::getType()
 {
     // NOTE: M17 fields are big-endian, we need to swap bytes
-    uint16_t *a = reinterpret_cast< uint16_t* >(&data.type);
-    uint16_t  b = __builtin_bswap16(*a);
-    return *reinterpret_cast< streamType_t* >(&b);
+    streamType_t type = data.type;
+    type.value = __builtin_bswap16(type.value);
+    return type;
 }
 
 void M17LinkSetupFrame::setType(streamType_t type)
 {
     // NOTE: M17 fields are big-endian, we need to swap bytes
-    uint16_t *a = reinterpret_cast< uint16_t* >(&type);
-    uint16_t  b = __builtin_bswap16(*a);
-    data.type   = *reinterpret_cast< streamType_t* >(&b);
+    type.value = __builtin_bswap16(type.value);
+    data.type  = type;
 }
 
 meta_t& M17LinkSetupFrame::metadata()