Decode destination callsign.

include/m17cxx/LinkSetupFrame.h

@@ -17,6 +17,9 @@ struct LinkSetupFrame
     using encoded_call_t = std::array<uint8_t, 6>;
     using frame_t = std::array<uint8_t, 30>;
     using nonce_t = std::string_view;               // std::span would be better here.
+    
+    static constexpr encoded_call_t BROADCAST_ADDRESS = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
+    static constexpr call_t BROADCAST_CALL = {'B', 'R', 'O', 'A', 'D', 'C', 'A', 'S', 'T', 0};
 
     enum TxType { PACKET, STREAM };
     enum DataType { DT_RESERVED, DATA, VOICE, MIXED };
@@ -93,12 +96,19 @@ struct LinkSetupFrame
     {
         static const char callsign_map[] = "xABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-/.";
 
+        call_t result;
+
+        if (callsign == BROADCAST_ADDRESS)
+        {
+            result = BROADCAST_CALL;
+            return result;
+        }
+
         uint64_t encoded = 0;       // This only works on little endian architectures.
         auto p = reinterpret_cast<uint8_t*>(&encoded);
         std::copy(callsign.rbegin(), callsign.rend(), p);
 
         // decode each base-40 digit and map them to the appriate character.
-        call_t result;
         result.fill(0);
         size_t index = 0;
         while (encoded)
@@ -110,7 +120,6 @@ struct LinkSetupFrame
         return result;
     }
 
-
     LinkSetupFrame()
     {}
 

include/m17cxx/M17FrameDecoder.h

@@ -168,8 +168,9 @@ struct M17FrameDecoder
         std::cerr << "\nSRC: ";
         for (auto x : src) if (x) std::cerr << x;
         std::copy(lsf.begin(), lsf.begin() + 6, encoded_call.begin());
+        auto dest = LinkSetupFrame::decode_callsign(encoded_call);
         std::cerr << ", DEST: ";
-        for (auto x : encoded_call) if (x) std::cerr << std::hex << std::setw(2) << std::setfill('0') << int(x);
+        for (auto x : dest) if (x) std::cerr << x;
         uint16_t type = (lsf[12] << 8) | lsf[13];
         std::cerr << ", TYPE: " << std::setw(4) << std::setfill('0') << type;
         std::cerr << ", NONCE: ";