Closes #15

core/dbc_decoder.h

@@ -34,6 +34,15 @@ enum class SignalDecodeStatus {
     InsufficientPayload,
     SelectorUnavailable,
     Inactive,
+    Valid,
+    PhysicalConversionFailed
+};
+
+/** Frame summary: short payload takes precedence over individual signal errors. */
+enum class FrameDecodeStatus {
+    UnknownFrame,
+    InsufficientPayload,
+    SignalErrors,
     Valid
 };
 
@@ -43,8 +52,8 @@ enum class SignalDecodeStatus {
 struct DecodedSignalValue {
     std::shared_ptr<const DecodeSignal> definition; /**< Owning immutable definition. */
     SignalKey key;                                  /**< Stable application identifier. */
-    RawSignalValue rawValue = std::uint64_t(0U);    /**< Exact signed or unsigned raw value. */
-    double physicalValue = 0.0;                     /**< Converted physical value. */
+    RawSignalValue rawValue = std::uint64_t(0U);    /**< Exact raw value for Valid or PhysicalConversionFailed. */
+    double physicalValue = 0.0;                     /**< Conversion result, possibly NaN/Inf on failure. */
     bool valid = false;                             /**< true if decoding succeeded. */
     SignalDecodeStatus status = SignalDecodeStatus::InvalidDefinition;
 
@@ -64,6 +73,7 @@ struct DecodedFrameValue {
     FrameKey key;                                  /**< Stable application identifier. */
     std::vector<DecodedSignalValue> signals;       /**< Decoded signal values. */
     bool valid = false;                            /**< true if frame was matched. */
+    FrameDecodeStatus status = FrameDecodeStatus::UnknownFrame; /**< Inspect signals for individual failures. */
 
     DecodedFrameValue() = default;
 };
@@ -88,12 +98,15 @@ public:
      * @brief Decode one raw CAN frame.
      * @param database Runtime decode database.
      * @param frame Raw CAN frame.
+     * Short payloads decode available signals; bytes beyond declared DLC are ignored.
      * @return Decoded frame value.
      */
     DecodedFrameValue Decode(const DecodeDatabase &database,
                              const RawCanFrame &frame) const;
 
 private:
+    static bool IsValidDefinition(const DecodeSignal &signal, std::uint8_t dlc);
+
     struct SelectorState {
         const DecodeSignal *definition = nullptr;
         bool valid = false;
@@ -103,6 +116,7 @@ private:
 
     static SelectorState ReadSelector(const DecodeFrame &definition, const RawCanFrame &frame);
     static DecodedSignalValue DecodeOneSignal(const DecodeSignal &signal,
+                                              std::uint8_t dlc,
                                               const RawCanFrame &frame,
                                               const SelectorState &selector);