Closes #24

core/dbc_decoder.cpp

@@ -10,6 +10,7 @@
  */
 
 #include "dbc_decoder.h"
+#include "j1939.h"
 #include "signal_layout.h"
 #include <cmath>
 #include <stdexcept>
@@ -19,7 +20,17 @@
 std::shared_ptr<const DecodeFrame> DbcDecoder::FindFrame(const DecodeDatabase &database,
                                                          std::uint32_t canId,
                                                          bool isExtended) const {
-    return database.FindFrame(FrameKey(canId, isExtended));
+    return ResolveFrame(database, canId, isExtended).definition;
+}
+
+PgnLookupResult DbcDecoder::ResolveFrame(const DecodeDatabase &database,
+                                         std::uint32_t canId, bool isExtended) {
+    const std::shared_ptr<const DecodeFrame> exact = database.FindFrame(FrameKey(canId, isExtended));
+    if (exact)
+        return {exact, false};
+    if (!isExtended || canId > 0x1FFFFFFFU)
+        return {};
+    return database.FindFrameByPgn(ExtractJ1939Pgn(canId));
 }
 
 DecodedFrameValue DbcDecoder::Decode(const DecodeDatabase &database,
@@ -38,10 +49,15 @@ DecodedFrameValue DbcDecoder::DecodeImpl(const DecodeDatabase &database,
                                          const std::vector<SignalKey> *selection) const {
     DecodedFrameValue result;
     result.key = FrameKey(frame.canId, frame.isExtended);
-    const std::shared_ptr<const DecodeFrame> definition = FindFrame(database, frame.canId, frame.isExtended);
-
+    const PgnLookupResult match = ResolveFrame(database, frame.canId, frame.isExtended);
+    if (match.ambiguous) {
+        result.status = FrameDecodeStatus::AmbiguousFrame;
+        return result;
+    }
+    const std::shared_ptr<const DecodeFrame> definition = match.definition;
     if (definition == nullptr)
         return result;
+    result.key = definition->GetKey();
 
     std::vector<const DecodeSignal *> selected;
     if (selection != nullptr) {