Closes #11

core/dbc_decoder.h

@@ -0,0 +1,104 @@
+/**
+ * @file dbc_decoder.h
+ * @brief
+ *
+ * Created: 2026-03-13
+ * Author: Deeaitch (Dim. Himro)
+ *
+ * Licensed under the MIT License.
+ * See LICENSE file in the project root for full license text.
+ */
+
+#ifndef DBC_DECODER_H
+#define DBC_DECODER_H
+
+#include <cstdint>
+#include <variant>
+#include <vector>
+
+#include "decode_database.h"
+
+/**
+ * @brief Raw CAN frame used for runtime or trace decoding.
+ */
+struct RawCanFrame {
+    std::uint32_t canId;            /**< Normalized CAN ID. */
+    bool isExtended;                /**< true for extended frame. */
+    std::vector<std::uint8_t> data; /**< Payload bytes. */
+
+    RawCanFrame()
+        : canId(0U), isExtended(false), data() {
+    }
+};
+
+/**
+ * @brief One decoded signal value.
+ */
+struct DecodedSignalValue {
+    const DecodeSignal *definition;                     /**< Signal definition. */
+    std::variant<std::int64_t, std::uint64_t> rawValue; /**< Exact signed or unsigned raw value. */
+    double physicalValue;                               /**< Converted physical value. */
+    bool valid;                                         /**< true if decoding succeeded. */
+
+    DecodedSignalValue()
+        : definition(nullptr), rawValue(std::uint64_t(0U)), physicalValue(0.0), valid(false) {
+    }
+};
+
+/**
+ * @brief Fully decoded frame.
+ */
+struct DecodedFrameValue {
+    const DecodeFrame *definition;           /**< Frame definition. */
+    std::vector<DecodedSignalValue> signals; /**< Decoded signal values. */
+    bool valid;                              /**< true if frame was matched. */
+
+    DecodedFrameValue()
+        : definition(nullptr), signals(), valid(false) {
+    }
+};
+
+/**
+ * @brief Runtime CAN decoder using prebuilt decode database.
+ */
+class DbcDecoder {
+public:
+    /**
+     * @brief Find frame definition by CAN ID.
+     * @param database Runtime decode database.
+     * @param canId Normalized CAN ID.
+     * @param isExtended true for extended frame.
+     * @return Pointer to frame definition or nullptr.
+     */
+    const DecodeFrame *FindFrame(const DecodeDatabase &database,
+                                 std::uint32_t canId,
+                                 bool isExtended) const;
+
+    /**
+     * @brief Decode one raw CAN frame.
+     * @param database Runtime decode database.
+     * @param frame Raw CAN frame.
+     * @return Decoded frame value.
+     */
+    DecodedFrameValue Decode(const DecodeDatabase &database,
+                             const RawCanFrame &frame) const;
+
+private:
+    static bool ExtractUnsigned(const std::vector<std::uint8_t> &data,
+                                const DecodeSignal &signal,
+                                std::uint64_t &value);
+
+    static bool ExtractIntel(const std::vector<std::uint8_t> &data,
+                             std::uint32_t startBit,
+                             std::uint32_t length,
+                             std::uint64_t &value);
+
+    static bool ExtractMotorola(const std::vector<std::uint8_t> &data,
+                                std::uint32_t startBit,
+                                std::uint32_t length,
+                                std::uint64_t &value);
+
+    static std::int64_t SignExtend(std::uint64_t value, std::uint32_t bitLength);
+};
+
+#endif /* DBC_DECODER_H */