closes #4 Refactor DBC parsing into TypeFactory statement handlers

README.md

@@ -151,8 +151,11 @@ Files:
 
 - `dbc_parser.h`
 - `dbc_parser.cpp`
+- `dbc_statement_handler.h`
+- `dbc_statement_handler.cpp`
+- `typefactory.h`
 
-These parse the DBC file itself.
+The parser reads files and reports errors; registered statement handlers parse DBC constructs.
 
 ### Demo
 
@@ -414,6 +417,34 @@ Fields:
 
 ---
 
+### Raw value representation and precision
+
+`DecodedSignalValue::rawValue` is a C++17
+`std::variant<std::int64_t, std::uint64_t>`. For a valid signal, signed definitions
+produce the `int64_t` alternative and unsigned definitions produce the `uint64_t`
+alternative. Raw values remain exact across their full 64-bit ranges. Check
+`valid` before using the value; an invalid result's default value is not decoded data.
+
+Use `std::get` when the numeric type is known, or `std::visit` to handle both:
+
+```cpp
+std::visit([] (auto raw) { std::cout << raw; }, decodedSignal.rawValue);
+```
+
+This replaces the previous `int64_t` field: consumers that read or print
+`rawValue` directly must handle the variant.
+
+Physical conversion uses the active numeric type:
+`physicalValue = static_cast<double>(raw) * factor + offset`.
+`physicalValue` remains a `double` and is approximate for large integers.
+On usual IEEE 754 binary64 implementations, integers are exactly representable
+through 2^53; above that, some integers round to the same floating-point value.
+For example, unsigned `UINT64_MAX` remains exact in `rawValue`, but converts to
+approximately 18446744073709551616 in binary64 before scaling.
+Use `rawValue` whenever exact integer values are required.
+
+---
+
 ## `DecodedFrameValue`
 
 Represents one decoded frame result.
@@ -477,6 +508,36 @@ Parsed fields:
 
 ---
 
+### Frame validation and parse errors
+
+`BO_` definitions require a decimal CAN ID, a nonempty single-token frame name,
+a colon, a decimal payload length, and a transmitter token. Spaces or tabs may
+separate fields, and whitespace before the colon is accepted. Additional trailing
+fields are rejected.
+
+Numeric fields must contain decimal digits only; signs, hexadecimal notation,
+fractional values, suffixes, and overflow are rejected. CAN IDs may contain the
+29-bit identifier plus the optional DBC extended flag (bit 31). Bits 29 and 30
+are rejected rather than silently discarded. For compatibility, unflagged IDs
+above `0x7FF` are still treated as extended.
+
+The payload length must fit `uint8_t` (`0..255`). This is a storage-range check,
+not CAN or CAN FD protocol validation; no new 8-byte or 64-byte limit is imposed.
+
+Parsing stops at the first detected error. Exceptions raised while parsing a
+line are reported as `std::runtime_error` with the supplied file path and the
+one-based physical line number, including blank lines:
+
+```text
+example.dbc:3: Invalid CAN ID: invalid
+```
+
+This change validates frame definitions. Signal syntax and unsupported DBC
+constructs retain their existing behavior; comprehensive validation is still
+planned. File-open errors contain the path but have no line number.
+
+---
+
 ## Signal definition
 
 Example:
@@ -709,20 +770,47 @@ That is why `DecodeDatabase` is a separate layer.
 
 ---
 
-## Why No Abstract Factory Is Used
+## Statement Handler Factory
 
-At the current stage, abstract factory is intentionally avoided.
+`DbcParser` owns file reading, trimming, line numbers, and error reporting.
+Each `ParseFile()` call creates a fresh `DbcParseContext` and a
+`DbcStatementDispatcher`. The context contains the parsed database and current
+frame; handlers receive it by reference and retain no parsing state.
 
-The current design is already clean:
+The dispatcher uses `TypeFactory<std::string, DbcStatementHandler>` to create
+registered handlers once per parsing session, then reuses them for all matching
+lines:
 
-```text
+- `BO_` → `DbcFrameHandler`
-parser → parsed database → decode database
+- `SG_` → `DbcSignalHandler`
-                      ↘ tree builder → UI tree
+- `CM_` → `DbcCommentHandler`
+
+Grammar implementations live in `dbc_statement_handler.cpp`; their interface,
+context, and dispatcher live in `dbc_statement_handler.h`. `typefactory.h`
+provides the generic registry and object creation.
+
+To add a construct, implement a default-constructible handler deriving from
+`DbcStatementHandler` with:
+
+```cpp
+void Handle(const std::string &line, DbcParseContext &context) const override;
 ```
 
-Introducing factory layers now would increase complexity without solving an immediate problem.
+Register it in the dispatcher constructor:
 
-If later the project requires multiple output representations or multiple build strategies, that can be added then.
+```cpp
+RegisterType<DbcValueHandler>("VAL_"); // after implementing DbcValueHandler
+```
+
+Registration creates one handler; replacing a registration replaces that instance.
+Register during initialization before dispatching. A line is routed using its
+full first whitespace-delimited keyword, so `BO_TX_BU_` cannot match `BO_`.
+Unregistered keywords remain ignored. Existing `SG_` and `CM_` syntax policies
+are preserved, including requiring a literal space after those keywords.
+
+This factory handles statements inside DBC files. A separate format-level
+factory can be introduced when another file format is implemented. The decoder
+and database builders remain independent of statement dispatch.
 
 ---
 
@@ -839,3 +927,10 @@ DBC parser → DbcDatabase → DecodeDatabase → DbcDecoder
 ```
 
 This gives FrameTap a much better foundation for real use, because both browsing and decoding are supported without forcing one representation to do the other's job.
+
+## Regression tests
+
+See [tests/README.md](tests/README.md) for compiler and qmake commands.
+Tests cover frame validation and error locations, Intel and Motorola extraction,
+signed and unsigned 64-bit boundaries,
+physical conversion, numeric output, and invalid signal payloads.

dbc.pro

@@ -7,6 +7,7 @@ SOURCES += \
         dbc_decode_builder.cpp \
         dbc_decoder.cpp \
         dbc_parser.cpp \
+        dbc_statement_handler.cpp \
         dbc_tree_builder.cpp \
         main.cpp \
         tree_node.cpp
@@ -16,6 +17,8 @@ HEADERS += \
   dbc_decode_builder.h \
   dbc_decoder.h \
   dbc_parser.h \
+  dbc_statement_handler.h \
+  typefactory.h \
   dbc_tree_builder.h \
   decode_database.h \
   frame_info.h \

dbc_decoder.cpp

@@ -55,10 +55,12 @@ DecodedFrameValue DbcDecoder::Decode (const DecodeDatabase &database,
     if (signal.valueType == ValueType::Signed)
       decoded.rawValue = SignExtend (unsignedValue, signal.length);
     else
-      decoded.rawValue = static_cast<std::int64_t> (unsignedValue);
+      decoded.rawValue = unsignedValue;
 
     decoded.physicalValue =
-      (static_cast<double> (decoded.rawValue) * signal.factor) + signal.offset;
+      std::visit ([&signal] (auto rawValue) {
+        return (static_cast<double> (rawValue) * signal.factor) + signal.offset;
+      }, decoded.rawValue);
     decoded.valid = true;
 
     result.signals.push_back (decoded);
@@ -111,47 +113,43 @@ bool DbcDecoder::ExtractMotorola (const std::vector<std::uint8_t> &data,
    * - startBit points to the most significant bit of the signal
    * - inside a byte, bit numbering goes 7..0
    * - crossing byte boundary moves to the next byte, bit 7
+   * Example: a signal starting at 7 follows 7..0, 15..8, 23..16.
    */
 
   value = 0U;
 
-  std::int32_t currentBit = static_cast<std::int32_t> (startBit);
+  std::size_t byteIndex = startBit / 8U;
+  std::uint32_t bitInByte = startBit % 8U;
 
   for (std::uint32_t bitIndex = 0U; bitIndex < length; ++bitIndex) {
-    if (currentBit < 0)
-      return false;
-
-    const std::uint32_t absoluteBit = static_cast<std::uint32_t> (currentBit);
-    const std::uint32_t byteIndex = absoluteBit / 8U;
-    const std::uint32_t bitFromMsb = absoluteBit % 8U;
-    const std::uint32_t bitInByte = 7U - bitFromMsb;
-
     if (byteIndex >= data.size())
       return false;
 
     value <<= 1U;
     value |= static_cast<std::uint64_t> ((data[byteIndex] >> bitInByte) & 0x01U);
 
-    if ((absoluteBit % 8U) == 7U)
+    if (bitInByte == 0U) {
-      currentBit = static_cast<std::int32_t> ((byteIndex + 1U) * 8U);
+      ++byteIndex;
-    else
+      bitInByte = 7U;
-      --currentBit;
+    } else
+      --bitInByte;
   }
 
   return true;
 }
 
 std::int64_t DbcDecoder::SignExtend (std::uint64_t value, std::uint32_t bitLength) {
-  if ((bitLength == 0U) || (bitLength >= 64U))
+  if ((bitLength == 0U) || (bitLength > 64U))
-    return static_cast<std::int64_t> (value);
+    return 0;
-
-  const std::uint64_t signMask = (static_cast<std::uint64_t> (1U) << (bitLength - 1U));
-  const std::uint64_t valueMask = (static_cast<std::uint64_t> (1U) << bitLength) - 1U;
 
+  const std::uint64_t signMask = std::uint64_t (1U) << (bitLength - 1U);
+  const std::uint64_t valueMask = (bitLength == 64U)
+    ? ~std::uint64_t (0U) : (std::uint64_t (1U) << bitLength) - 1U;
   value &= valueMask;
 
   if ((value & signMask) == 0U)
     return static_cast<std::int64_t> (value);
 
-  return static_cast<std::int64_t> (value | (~valueMask));
+  // The complemented magnitude fits int64_t, including for INT64_MIN.
+  return -1 - static_cast<std::int64_t> ((~value) & valueMask);
 }

dbc_decoder.h

@@ -14,6 +14,7 @@
 
 #include <vector>
 #include <cstdint>
+#include <variant>
 
 #include "decode_database.h"
 
@@ -37,13 +38,13 @@ struct RawCanFrame {
  */
 struct DecodedSignalValue {
   const DecodeSignal *definition; /**< Signal definition. */
-  std::int64_t rawValue;          /**< Extracted raw integer value. */
+  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 (0)
+    , rawValue (std::uint64_t (0U))
     , physicalValue (0.0)
     , valid (false) {
   }

dbc_parser.cpp

@@ -10,9 +10,9 @@
  */
 
 #include "dbc_parser.h"
+#include "dbc_statement_handler.h"
 
 #include <fstream>
-#include <sstream>
 #include <stdexcept>
 #include <cctype>
 
@@ -43,314 +43,28 @@ DbcDatabase DbcParser::ParseFile (const std::string &filePath) const {
     throw std::runtime_error ("Failed to open DBC file: " + filePath);
 
   DbcDatabase database;
-  FrameInfo *currentFrame = nullptr;
+  DbcParseContext context {database, nullptr};
+  const DbcStatementDispatcher dispatcher;
 
+  std::size_t lineNumber = 0U;
   std::string line;
   while (std::getline (input, line)) {
+    ++lineNumber;
     line = Trim (line);
     if (line.empty())
       continue;
 
-    if (IsFrameLine (line)) {
+    try {
-      FrameInfo frame = ParseFrameLine (line);
+      dispatcher.Dispatch (line, context);
-      database.frames.push_back (frame);
+    } catch (const std::exception &error) {
-      currentFrame = &database.frames.back();
+      throw std::runtime_error (filePath + ":" + std::to_string (lineNumber) +
-    } else if (IsSignalLine (line)) {
+                                ": " + error.what());
-      if (currentFrame == nullptr)
+    }
-        throw std::runtime_error ("Signal found before any frame definition.");
-
-      SignalInfo signal = ParseSignalLine (line);
-      currentFrame->signals.push_back (signal);
-    } else if (IsCommentLine (line))
-      ParseCommentLine (line, database);
   }
 
   return database;
 }
 
-bool DbcParser::IsFrameLine (const std::string &line) {
-  return (line.size() >= 4U) && (line.compare (0U, 4U, "BO_ ") == 0);
-}
-
-bool DbcParser::IsSignalLine (const std::string &line) {
-  return (line.size() >= 4U) && (line.compare (0U, 4U, "SG_ ") == 0);
-}
-
-bool DbcParser::IsCommentLine (const std::string &line) {
-  return (line.size() >= 4U) && (line.compare (0U, 4U, "CM_ ") == 0);
-}
-
 std::string DbcParser::Trim (const std::string &text) {
   return TrimText (text);
 }
-
-std::vector<std::string> DbcParser::SplitReceivers (const std::string &text) {
-  std::vector<std::string> receivers;
-  std::string token;
-  std::istringstream stream (text);
-
-  while (std::getline (stream, token, ',')) {
-    token = TrimText (token);
-    if (!token.empty())
-      receivers.push_back (token);
-  }
-
-  return receivers;
-}
-
-void DbcParser::NormalizeCanId (std::uint32_t rawCanId,
-                                std::uint32_t &normalizedCanId,
-                                bool &isExtended) {
-  /*
-   * DBC commonly stores extended identifiers with bit 31 set.
-   * Example:
-   * raw id = 0x80000000 | actual_29_bit_id
-   */
-  if ((rawCanId & 0x80000000U) != 0U) {
-    isExtended = true;
-    normalizedCanId = (rawCanId & 0x1FFFFFFFU);
-  } else {
-    isExtended = (rawCanId > 0x7FFU);
-    normalizedCanId = rawCanId;
-  }
-}
-
-std::uint32_t DbcParser::TryExtractPgn (std::uint32_t canId, bool isExtended, bool &hasPgn) {
-  hasPgn = false;
-
-  if (!isExtended)
-    return 0U;
-
-  if ((canId & 0x1FFFFFFFU) != canId)
-    return 0U;
-
-  const std::uint32_t pf = (canId >> 16U) & 0xFFU;
-  const std::uint32_t ps = (canId >> 8U) & 0xFFU;
-  const std::uint32_t dp = (canId >> 24U) & 0x01U;
-
-  std::uint32_t pgn = 0U;
-
-  if (pf < 240U)
-    pgn = (dp << 16U) | (pf << 8U);
-  else
-    pgn = (dp << 16U) | (pf << 8U) | ps;
-
-  hasPgn = true;
-  return pgn;
-}
-
-FrameInfo DbcParser::ParseFrameLine (const std::string &line) {
-  /*
-   * Example:
-   * BO_ 256 EngineData: 8 EEC1
-   */
-
-  std::istringstream stream (line);
-  std::string token;
-  FrameInfo frame;
-  std::uint32_t rawCanId = 0U;
-
-  stream >> token;
-  if (token != "BO_")
-    throw std::runtime_error ("Invalid frame line: " + line);
-
-  stream >> rawCanId;
-  NormalizeCanId (rawCanId, frame.canId, frame.isExtended);
-
-  stream >> token;
-  if (token.empty())
-    throw std::runtime_error ("Missing frame name: " + line);
-
-  if (token[token.size() - 1U] == ':')
-    token.erase (token.size() - 1U, 1U);
-
-  frame.name = token;
-
-  {
-    unsigned int dlcValue = 0U;
-    stream >> dlcValue;
-    frame.dlc = static_cast<std::uint8_t> (dlcValue);
-  }
-
-  stream >> frame.transmitter;
-  frame.pgn = TryExtractPgn (frame.canId, frame.isExtended, frame.hasPgn);
-
-  return frame;
-}
-
-SignalInfo DbcParser::ParseSignalLine (const std::string &line) {
-  /*
-   * Example:
-   * SG_ EngineSpeed : 0|16@1+ (0.125,0) [0|8000] "rpm" ECU1,ECU2
-   */
-
-  SignalInfo signal;
-
-  std::string work = TrimText (line);
-  if (work.compare (0U, 4U, "SG_ ") != 0)
-    throw std::runtime_error ("Invalid signal line: " + line);
-
-  work.erase (0U, 4U);
-
-  const std::string::size_type colonPos = work.find (':');
-  if (colonPos == std::string::npos)
-    throw std::runtime_error ("Signal line missing ':' : " + line);
-
-  signal.name = TrimText (work.substr (0U, colonPos));
-  std::string rest = TrimText (work.substr (colonPos + 1U));
-
-  const std::string::size_type pipePos = rest.find ('|');
-  const std::string::size_type atPos = rest.find ('@');
-  const std::string::size_type signPos = rest.find_first_of ("+-", atPos);
-  const std::string::size_type factorBegin = rest.find ('(');
-  const std::string::size_type factorComma = rest.find (',', factorBegin);
-  const std::string::size_type factorEnd = rest.find (')', factorComma);
-  const std::string::size_type rangeBegin = rest.find ('[');
-  const std::string::size_type rangeSep = rest.find ('|', rangeBegin);
-  const std::string::size_type rangeEnd = rest.find (']', rangeSep);
-  const std::string::size_type unitBegin = rest.find ('"', rangeEnd);
-  const std::string::size_type unitEnd = rest.find ('"', unitBegin + 1U);
-
-  if ((pipePos == std::string::npos) ||
-      (atPos == std::string::npos) ||
-      (signPos == std::string::npos) ||
-      (factorBegin == std::string::npos) ||
-      (factorComma == std::string::npos) ||
-      (factorEnd == std::string::npos) ||
-      (rangeBegin == std::string::npos) ||
-      (rangeSep == std::string::npos) ||
-      (rangeEnd == std::string::npos) ||
-      (unitBegin == std::string::npos) ||
-      (unitEnd == std::string::npos))
-    throw std::runtime_error ("Unsupported signal syntax: " + line);
-
-  signal.startBit = static_cast<std::uint32_t> (
-                      std::stoul (TrimText (rest.substr (0U, pipePos)))
-                    );
-
-  signal.length = static_cast<std::uint32_t> (
-                    std::stoul (TrimText (rest.substr (pipePos + 1U, atPos - pipePos - 1U)))
-                  );
-
-  {
-    if ((atPos + 1U) >= rest.size())
-      throw std::runtime_error ("Invalid endianness in signal: " + line);
-
-    const char endianChar = rest[atPos + 1U];
-    signal.isLittleEndian = (endianChar == '1');
-  }
-
-  {
-    const char signChar = rest[signPos];
-    signal.isSigned = (signChar == '-');
-  }
-
-  signal.factor = std::stod (
-                    TrimText (rest.substr (factorBegin + 1U, factorComma - factorBegin - 1U))
-                  );
-
-  signal.offset = std::stod (
-                    TrimText (rest.substr (factorComma + 1U, factorEnd - factorComma - 1U))
-                  );
-
-  signal.minimum = std::stod (
-                     TrimText (rest.substr (rangeBegin + 1U, rangeSep - rangeBegin - 1U))
-                   );
-
-  signal.maximum = std::stod (
-                     TrimText (rest.substr (rangeSep + 1U, rangeEnd - rangeSep - 1U))
-                   );
-
-  signal.unit = rest.substr (unitBegin + 1U, unitEnd - unitBegin - 1U);
-
-  {
-    const std::string receiversText = TrimText (rest.substr (unitEnd + 1U));
-    signal.receivers = SplitReceivers (receiversText);
-  }
-
-  return signal;
-}
-
-void DbcParser::ParseCommentLine (const std::string &line, DbcDatabase &database) {
-  /*
-   * Examples:
-   * CM_ BO_ 256 "Frame comment";
-   * CM_ SG_ 256 EngineSpeed "Signal comment";
-   */
-
-  std::istringstream stream (line);
-  std::string token;
-  stream >> token;
-
-  if (token != "CM_")
-    return;
-
-  stream >> token;
-
-  if (token == "BO_") {
-    std::uint32_t rawCanId = 0U;
-    std::uint32_t canId = 0U;
-    bool isExtended = false;
-
-    stream >> rawCanId;
-    NormalizeCanId (rawCanId, canId, isExtended);
-
-    const std::string::size_type quoteBegin = line.find ('"');
-    const std::string::size_type quoteEnd = line.rfind ('"');
-
-    if ((quoteBegin == std::string::npos) ||
-        (quoteEnd == std::string::npos) ||
-        (quoteEnd <= quoteBegin))
-      return;
-
-    FrameInfo *frame = FindFrameById (database, canId, isExtended);
-    if (frame != nullptr)
-      frame->comment = line.substr (quoteBegin + 1U, quoteEnd - quoteBegin - 1U);
-  } else if (token == "SG_") {
-    std::uint32_t rawCanId = 0U;
-    std::uint32_t canId = 0U;
-    bool isExtended = false;
-    std::string signalName;
-
-    stream >> rawCanId;
-    stream >> signalName;
-
-    NormalizeCanId (rawCanId, canId, isExtended);
-
-    const std::string::size_type quoteBegin = line.find ('"');
-    const std::string::size_type quoteEnd = line.rfind ('"');
-
-    if ((quoteBegin == std::string::npos) ||
-        (quoteEnd == std::string::npos) ||
-        (quoteEnd <= quoteBegin))
-      return;
-
-    FrameInfo *frame = FindFrameById (database, canId, isExtended);
-    if (frame != nullptr) {
-      SignalInfo *signal = FindSignalByName (*frame, signalName);
-      if (signal != nullptr)
-        signal->comment = line.substr (quoteBegin + 1U, quoteEnd - quoteBegin - 1U);
-    }
-  }
-}
-
-FrameInfo *DbcParser::FindFrameById (DbcDatabase &database,
-                                     std::uint32_t canId,
-                                     bool isExtended) {
-  for (std::size_t index = 0U; index < database.frames.size(); ++index) {
-    if ((database.frames[index].canId == canId) &&
-        (database.frames[index].isExtended == isExtended))
-      return &database.frames[index];
-  }
-
-  return nullptr;
-}
-
-SignalInfo *DbcParser::FindSignalByName (FrameInfo &frame, const std::string &signalName) {
-  for (std::size_t index = 0U; index < frame.signals.size(); ++index) {
-    if (frame.signals[index].name == signalName)
-      return &frame.signals[index];
-  }
-
-  return nullptr;
-}

dbc_parser.h

@@ -13,8 +13,6 @@
 #define DBC_PARSER_H
 
 #include <string>
-#include <vector>
-#include <cstdint>
 
 #include "dbc_database.h"
 
@@ -39,31 +37,12 @@ class DbcParser {
      * @param filePath Path to input file.
      * @return Parsed database.
      * @throws std::runtime_error on file or parse errors.
+     * Line parse errors include the file path and one-based line number.
      */
     DbcDatabase ParseFile (const std::string &filePath) const;
 
   private:
-    static bool IsFrameLine (const std::string &line);
-    static bool IsSignalLine (const std::string &line);
-    static bool IsCommentLine (const std::string &line);
     static std::string Trim (const std::string &text);
-    static std::vector<std::string> SplitReceivers (const std::string &text);
-    static std::uint32_t TryExtractPgn (std::uint32_t canId, bool isExtended, bool &hasPgn);
-
-    static void NormalizeCanId (std::uint32_t rawCanId,
-                                std::uint32_t &normalizedCanId,
-                                bool &isExtended);
-
-    static FrameInfo ParseFrameLine (const std::string &line);
-    static SignalInfo ParseSignalLine (const std::string &line);
-
-    static void ParseCommentLine (const std::string &line, DbcDatabase &database);
-
-    static FrameInfo *FindFrameById (DbcDatabase &database,
-                                     std::uint32_t canId,
-                                     bool isExtended);
-
-    static SignalInfo *FindSignalByName (FrameInfo &frame, const std::string &signalName);
 };
 
 #endif /* DBC_PARSER_H */

dbc_statement_handler.cpp

@@ -0,0 +1,358 @@
+// SPDX-License-Identifier: MIT
+#include "dbc_statement_handler.h"
+#include <sstream>
+#include <stdexcept>
+#include <cctype>
+#include <charconv>
+#include <limits>
+
+namespace {
+  std::uint32_t ParseDecimal (const std::string &text,
+                              std::uint32_t maximum,
+                              const char *field) {
+    std::uint32_t value = 0U;
+    const auto parsed = std::from_chars (text.data(), text.data() + text.size(), value);
+    if (text.empty() || parsed.ec != std::errc() ||
+        parsed.ptr != text.data() + text.size() || value > maximum)
+      throw std::runtime_error (std::string ("Invalid ") + field + ": " + text);
+    return value;
+  }
+
+  /**
+   * @brief Remove leading and trailing spaces.
+   * @param text Input text.
+   * @return Trimmed text.
+   */
+  std::string TrimText (const std::string &text) {
+    std::string::size_type begin = 0U;
+    while ((begin < text.size()) &&
+           std::isspace (static_cast<unsigned char> (text[begin])))
+      ++begin;
+
+    std::string::size_type end = text.size();
+    while ((end > begin) &&
+           std::isspace (static_cast<unsigned char> (text[end - 1U])))
+      --end;
+
+    return text.substr (begin, end - begin);
+  }
+  FrameInfo *FindFrameById (DbcDatabase &, std::uint32_t, bool);
+  SignalInfo *FindSignalByName (FrameInfo &, const std::string &);
+}
+
+namespace {
+std::vector<std::string> SplitReceivers (const std::string &text) {
+  std::vector<std::string> receivers;
+  std::string token;
+  std::istringstream stream (text);
+
+  while (std::getline (stream, token, ',')) {
+    token = TrimText (token);
+    if (!token.empty())
+      receivers.push_back (token);
+  }
+
+  return receivers;
+}
+
+void NormalizeCanId (std::uint32_t rawCanId,
+                                std::uint32_t &normalizedCanId,
+                                bool &isExtended) {
+  /*
+   * DBC commonly stores extended identifiers with bit 31 set.
+   * Example:
+   * raw id = 0x80000000 | actual_29_bit_id
+   */
+  if ((rawCanId & 0x80000000U) != 0U) {
+    isExtended = true;
+    normalizedCanId = (rawCanId & 0x1FFFFFFFU);
+  } else {
+    isExtended = (rawCanId > 0x7FFU);
+    normalizedCanId = rawCanId;
+  }
+}
+
+std::uint32_t TryExtractPgn (std::uint32_t canId, bool isExtended, bool &hasPgn) {
+  hasPgn = false;
+
+  if (!isExtended)
+    return 0U;
+
+  if ((canId & 0x1FFFFFFFU) != canId)
+    return 0U;
+
+  const std::uint32_t pf = (canId >> 16U) & 0xFFU;
+  const std::uint32_t ps = (canId >> 8U) & 0xFFU;
+  const std::uint32_t dp = (canId >> 24U) & 0x01U;
+
+  std::uint32_t pgn = 0U;
+
+  if (pf < 240U)
+    pgn = (dp << 16U) | (pf << 8U);
+  else
+    pgn = (dp << 16U) | (pf << 8U) | ps;
+
+  hasPgn = true;
+  return pgn;
+}
+
+}
+
+FrameInfo DbcFrameHandler::ParseFrameLine (const std::string &line) {
+  /*
+   * Example:
+   * BO_ 256 EngineData: 8 EEC1
+   */
+
+  std::istringstream stream (line);
+  std::string keyword;
+  std::string idText;
+  if (!(stream >> keyword >> idText) || keyword != "BO_")
+    throw std::runtime_error ("Missing CAN ID in frame definition.");
+
+  const std::uint32_t rawCanId = ParseDecimal (
+    idText, std::numeric_limits<std::uint32_t>::max(), "CAN ID");
+  // Only bit 31 may accompany the actual 29-bit identifier.
+  if ((rawCanId & 0x60000000U) != 0U)
+    throw std::runtime_error ("CAN ID exceeds the 29-bit identifier range.");
+
+  std::string nameText;
+  if (!std::getline (stream, nameText, ':') || stream.eof())
+    throw std::runtime_error ("Missing ':' in frame definition.");
+  std::istringstream nameStream (nameText);
+  FrameInfo frame;
+  std::string extra;
+  if (!(nameStream >> frame.name) || (nameStream >> extra))
+    throw std::runtime_error ("Missing or invalid frame name.");
+
+  std::string lengthText;
+  if (!(stream >> lengthText))
+    throw std::runtime_error ("Missing payload length in frame definition.");
+  frame.dlc = static_cast<std::uint8_t> (ParseDecimal (
+    lengthText, std::numeric_limits<std::uint8_t>::max(), "payload length"));
+  if (!(stream >> frame.transmitter))
+    throw std::runtime_error ("Missing transmitter in frame definition.");
+  if (stream >> extra)
+    throw std::runtime_error ("Unexpected trailing field in frame definition: " + extra);
+
+  NormalizeCanId (rawCanId, frame.canId, frame.isExtended);
+  frame.pgn = TryExtractPgn (frame.canId, frame.isExtended, frame.hasPgn);
+
+  return frame;
+}
+
+SignalInfo DbcSignalHandler::ParseSignalLine (const std::string &line) {
+  /*
+   * Example:
+   * SG_ EngineSpeed : 0|16@1+ (0.125,0) [0|8000] "rpm" ECU1,ECU2
+   */
+
+  SignalInfo signal;
+
+  std::string work = TrimText (line);
+  if (work.compare (0U, 4U, "SG_ ") != 0)
+    throw std::runtime_error ("Invalid signal line: " + line);
+
+  work.erase (0U, 4U);
+
+  const std::string::size_type colonPos = work.find (':');
+  if (colonPos == std::string::npos)
+    throw std::runtime_error ("Signal line missing ':' : " + line);
+
+  signal.name = TrimText (work.substr (0U, colonPos));
+  std::string rest = TrimText (work.substr (colonPos + 1U));
+
+  const std::string::size_type pipePos = rest.find ('|');
+  const std::string::size_type atPos = rest.find ('@');
+  const std::string::size_type signPos = rest.find_first_of ("+-", atPos);
+  const std::string::size_type factorBegin = rest.find ('(');
+  const std::string::size_type factorComma = rest.find (',', factorBegin);
+  const std::string::size_type factorEnd = rest.find (')', factorComma);
+  const std::string::size_type rangeBegin = rest.find ('[');
+  const std::string::size_type rangeSep = rest.find ('|', rangeBegin);
+  const std::string::size_type rangeEnd = rest.find (']', rangeSep);
+  const std::string::size_type unitBegin = rest.find ('"', rangeEnd);
+  const std::string::size_type unitEnd = rest.find ('"', unitBegin + 1U);
+
+  if ((pipePos == std::string::npos) ||
+      (atPos == std::string::npos) ||
+      (signPos == std::string::npos) ||
+      (factorBegin == std::string::npos) ||
+      (factorComma == std::string::npos) ||
+      (factorEnd == std::string::npos) ||
+      (rangeBegin == std::string::npos) ||
+      (rangeSep == std::string::npos) ||
+      (rangeEnd == std::string::npos) ||
+      (unitBegin == std::string::npos) ||
+      (unitEnd == std::string::npos))
+    throw std::runtime_error ("Unsupported signal syntax: " + line);
+
+  signal.startBit = static_cast<std::uint32_t> (
+                      std::stoul (TrimText (rest.substr (0U, pipePos)))
+                    );
+
+  signal.length = static_cast<std::uint32_t> (
+                    std::stoul (TrimText (rest.substr (pipePos + 1U, atPos - pipePos - 1U)))
+                  );
+
+  {
+    if ((atPos + 1U) >= rest.size())
+      throw std::runtime_error ("Invalid endianness in signal: " + line);
+
+    const char endianChar = rest[atPos + 1U];
+    signal.isLittleEndian = (endianChar == '1');
+  }
+
+  {
+    const char signChar = rest[signPos];
+    signal.isSigned = (signChar == '-');
+  }
+
+  signal.factor = std::stod (
+                    TrimText (rest.substr (factorBegin + 1U, factorComma - factorBegin - 1U))
+                  );
+
+  signal.offset = std::stod (
+                    TrimText (rest.substr (factorComma + 1U, factorEnd - factorComma - 1U))
+                  );
+
+  signal.minimum = std::stod (
+                     TrimText (rest.substr (rangeBegin + 1U, rangeSep - rangeBegin - 1U))
+                   );
+
+  signal.maximum = std::stod (
+                     TrimText (rest.substr (rangeSep + 1U, rangeEnd - rangeSep - 1U))
+                   );
+
+  signal.unit = rest.substr (unitBegin + 1U, unitEnd - unitBegin - 1U);
+
+  {
+    const std::string receiversText = TrimText (rest.substr (unitEnd + 1U));
+    signal.receivers = SplitReceivers (receiversText);
+  }
+
+  return signal;
+}
+
+void DbcCommentHandler::ParseCommentLine (const std::string &line, DbcDatabase &database) {
+  /*
+   * Examples:
+   * CM_ BO_ 256 "Frame comment";
+   * CM_ SG_ 256 EngineSpeed "Signal comment";
+   */
+
+  std::istringstream stream (line);
+  std::string token;
+  stream >> token;
+
+  if (token != "CM_")
+    return;
+
+  stream >> token;
+
+  if (token == "BO_") {
+    std::uint32_t rawCanId = 0U;
+    std::uint32_t canId = 0U;
+    bool isExtended = false;
+
+    stream >> rawCanId;
+    NormalizeCanId (rawCanId, canId, isExtended);
+
+    const std::string::size_type quoteBegin = line.find ('"');
+    const std::string::size_type quoteEnd = line.rfind ('"');
+
+    if ((quoteBegin == std::string::npos) ||
+        (quoteEnd == std::string::npos) ||
+        (quoteEnd <= quoteBegin))
+      return;
+
+    FrameInfo *frame = FindFrameById (database, canId, isExtended);
+    if (frame != nullptr)
+      frame->comment = line.substr (quoteBegin + 1U, quoteEnd - quoteBegin - 1U);
+  } else if (token == "SG_") {
+    std::uint32_t rawCanId = 0U;
+    std::uint32_t canId = 0U;
+    bool isExtended = false;
+    std::string signalName;
+
+    stream >> rawCanId;
+    stream >> signalName;
+
+    NormalizeCanId (rawCanId, canId, isExtended);
+
+    const std::string::size_type quoteBegin = line.find ('"');
+    const std::string::size_type quoteEnd = line.rfind ('"');
+
+    if ((quoteBegin == std::string::npos) ||
+        (quoteEnd == std::string::npos) ||
+        (quoteEnd <= quoteBegin))
+      return;
+
+    FrameInfo *frame = FindFrameById (database, canId, isExtended);
+    if (frame != nullptr) {
+      SignalInfo *signal = FindSignalByName (*frame, signalName);
+      if (signal != nullptr)
+        signal->comment = line.substr (quoteBegin + 1U, quoteEnd - quoteBegin - 1U);
+    }
+  }
+}
+
+namespace {
+FrameInfo *FindFrameById (DbcDatabase &database,
+                                     std::uint32_t canId,
+                                     bool isExtended) {
+  for (std::size_t index = 0U; index < database.frames.size(); ++index) {
+    if ((database.frames[index].canId == canId) &&
+        (database.frames[index].isExtended == isExtended))
+      return &database.frames[index];
+  }
+
+  return nullptr;
+}
+
+SignalInfo *FindSignalByName (FrameInfo &frame, const std::string &signalName) {
+  for (std::size_t index = 0U; index < frame.signals.size(); ++index) {
+    if (frame.signals[index].name == signalName)
+      return &frame.signals[index];
+  }
+
+  return nullptr;
+}
+}
+
+void DbcFrameHandler::Handle (const std::string &line, DbcParseContext &context) const {
+  context.database.frames.push_back (ParseFrameLine (line));
+  context.currentFrame = &context.database.frames.back();
+}
+
+void DbcSignalHandler::Handle (const std::string &line, DbcParseContext &context) const {
+  // Preserve the existing signal syntax policy during this refactor.
+  if (line.compare (0U, 4U, "SG_ ") != 0)
+    return;
+  if (context.currentFrame == nullptr)
+    throw std::runtime_error ("Signal found before any frame definition.");
+  context.currentFrame->signals.push_back (ParseSignalLine (line));
+}
+
+void DbcCommentHandler::Handle (const std::string &line, DbcParseContext &context) const {
+  if (line.compare (0U, 4U, "CM_ ") == 0)
+    ParseCommentLine (line, context.database);
+}
+
+DbcStatementDispatcher::DbcStatementDispatcher() {
+  RegisterType<DbcFrameHandler> ("BO_");
+  RegisterType<DbcSignalHandler> ("SG_");
+  RegisterType<DbcCommentHandler> ("CM_");
+}
+
+bool DbcStatementDispatcher::Dispatch (const std::string &line,
+                                       DbcParseContext &context) const {
+  std::istringstream stream (line);
+  std::string keyword;
+  stream >> keyword;
+  const auto handler = m_handlers.find (keyword);
+  if (handler == m_handlers.end())
+    return false;
+  handler->second->Handle (line, context);
+  return true;
+}

dbc_statement_handler.h

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: MIT
+#ifndef DBC_STATEMENT_HANDLER_H
+#define DBC_STATEMENT_HANDLER_H
+
+#include "dbc_database.h"
+#include "typefactory.h"
+#include <string>
+#include <unordered_map>
+
+/** Mutable state belonging to one file parse. Handlers do not retain it. */
+struct DbcParseContext {
+  DbcDatabase &database;
+  FrameInfo *currentFrame = nullptr;
+};
+
+class DbcStatementHandler {
+  public:
+    virtual ~DbcStatementHandler() = default;
+    virtual void Handle (const std::string &line, DbcParseContext &context) const = 0;
+};
+
+class DbcFrameHandler : public DbcStatementHandler {
+  public:
+    void Handle (const std::string &line, DbcParseContext &context) const override;
+  private:
+    static FrameInfo ParseFrameLine (const std::string &line);
+};
+
+class DbcSignalHandler : public DbcStatementHandler {
+  public:
+    void Handle (const std::string &line, DbcParseContext &context) const override;
+  private:
+    static SignalInfo ParseSignalLine (const std::string &line);
+};
+
+class DbcCommentHandler : public DbcStatementHandler {
+  public:
+    void Handle (const std::string &line, DbcParseContext &context) const override;
+  private:
+    static void ParseCommentLine (const std::string &line, DbcDatabase &database);
+};
+
+/** Exact-key dispatch to handlers created once per registration via TypeFactory. */
+class DbcStatementDispatcher {
+  public:
+    DbcStatementDispatcher();
+
+    template <class Handler>
+    void RegisterType (const std::string &keyword) {
+      m_factory.registerType<Handler> (keyword);
+      m_handlers.insert_or_assign (keyword, m_factory.create (keyword));
+    }
+
+    /** Returns false for an unregistered keyword; input must be trimmed. */
+    bool Dispatch (const std::string &line, DbcParseContext &context) const;
+
+  private:
+    TypeFactory<std::string, DbcStatementHandler> m_factory;
+    std::unordered_map<std::string, std::shared_ptr<DbcStatementHandler> > m_handlers;
+};
+
+#endif /* DBC_STATEMENT_HANDLER_H */

main.cpp

@@ -87,8 +87,9 @@ static void PrintDecodedFrame (const DecodedFrameValue &decoded) {
       continue;
 
     std::cout << "  " << signal.definition->name
-              << " raw=" << signal.rawValue
+              << " raw=";
-              << " physical=" << signal.physicalValue
+    std::visit ([] (auto rawValue) { std::cout << rawValue; }, signal.rawValue);
+    std::cout << " physical=" << signal.physicalValue
               << " " << signal.definition->unit
               << "\n";
   }

tests/README.md

@@ -0,0 +1,50 @@
+# Decoder regression tests
+
+Run from the repository root with a C++17 compiler:
+
+```sh
+g++ -std=c++17 -Wall -Wextra -Wpedantic -I. \
+  tests/dbc_decoder_test.cpp dbc_decoder.cpp -o /tmp/dbc_decoder_test
+/tmp/dbc_decoder_test
+```
+
+Alternatively, build the standalone qmake project out of source:
+
+```sh
+mkdir -p /tmp/dbc_decoder_test_build
+cd /tmp/dbc_decoder_test_build
+qmake /absolute/path/to/dbc/tests/dbc_decoder_test.pro
+make
+./dbc_decoder_test
+```
+
+The executable returns a nonzero exit code if any case fails. Checks remain
+active in release builds and do not depend on `assert` or an external test framework.
+
+Coverage includes Motorola bit numbering within and across bytes, unaligned
+signals, signed values, scaling, 64-bit extraction, signed/unsigned boundary values
+(including `INT64_MIN`, `INT64_MAX`, and `UINT64_MAX`), numeric output, invalid lengths, insufficient
+payloads, and Intel regression cases. Frame validity means the definition was
+found; insufficient payloads are checked through signal validity.
+
+## Parser regression tests
+
+Run from the repository root:
+
+```sh
+g++ -std=c++17 -Wall -Wextra -Wpedantic -Werror -I. \
+  tests/dbc_parser_test.cpp dbc_parser.cpp dbc_statement_handler.cpp -o /tmp/dbc_parser_test
+/tmp/dbc_parser_test
+```
+
+For qmake, use `tests/dbc_parser_test.pro` in a separate build directory,
+following the decoder instructions above, then run `./dbc_parser_test`.
+
+Parser tests cover standard and extended CAN IDs, whitespace, payload storage
+boundaries, missing fields, malformed and overflowing numbers, reserved ID bits,
+error paths and line numbers, and integration with signals and comments.
+Temporary DBC fixtures are created in the system temporary directory and removed
+automatically.
+
+Dispatch tests also verify exact keyword matching, handler construction and reuse,
+unknown statements, and independent parsing sessions, including recovery after errors.

tests/dbc_decoder_test.cpp

@@ -0,0 +1,154 @@
+#include "dbc_decoder.h"
+
+#include <iostream>
+#include <limits>
+#include <sstream>
+
+struct DecodeCase {
+  const char *name;
+  ByteOrder byteOrder;
+  std::uint32_t startBit;
+  std::uint32_t length;
+  ValueType valueType;
+  std::vector<std::uint8_t> data;
+  bool valid;
+  std::int64_t rawValue;
+  double factor;
+  double offset;
+  double physicalValue;
+};
+
+int main() {
+  const DecodeCase cases[] = {
+    {"Motorola reproduction", ByteOrder::Motorola, 7U, 16U, ValueType::Unsigned,
+     {0x12, 0x34}, true, 0x1234, 1.0, 0.0, 4660.0},
+    {"Motorola within byte", ByteOrder::Motorola, 5U, 4U, ValueType::Unsigned,
+     {0xAC}, true, 11, 1.0, 0.0, 11.0},
+    {"Motorola unaligned crossing", ByteOrder::Motorola, 3U, 12U, ValueType::Unsigned,
+     {0xAB, 0xCD}, true, 0xBCD, 1.0, 0.0, 3021.0},
+    {"Motorola starts at bit zero", ByteOrder::Motorola, 0U, 2U, ValueType::Unsigned,
+     {0x01, 0x80}, true, 3, 1.0, 0.0, 3.0},
+    {"Motorola second byte", ByteOrder::Motorola, 15U, 16U, ValueType::Unsigned,
+     {0xFF, 0x12, 0x34}, true, 0x1234, 1.0, 0.0, 4660.0},
+    {"Motorola signed scaled", ByteOrder::Motorola, 7U, 16U, ValueType::Signed,
+     {0xFF, 0xFE}, true, -2, 0.5, 10.0, 9.0},
+    {"Motorola 64 bits", ByteOrder::Motorola, 7U, 64U, ValueType::Unsigned,
+     {0, 0, 0, 0, 0, 0, 0x12, 0x34}, true, 0x1234, 1.0, 0.0, 4660.0},
+    {"Motorola 64 bits high bit", ByteOrder::Motorola, 7U, 64U, ValueType::Unsigned,
+     {0x40, 0, 0, 0, 0, 0, 0, 0}, true, 0x4000000000000000LL,
+     1.0, 0.0, 4611686018427387904.0},
+    {"Motorola short payload", ByteOrder::Motorola, 7U, 16U, ValueType::Unsigned,
+     {0x12}, false, 0, 1.0, 0.0, 0.0},
+    {"Motorola empty payload", ByteOrder::Motorola, 7U, 8U, ValueType::Unsigned,
+     {}, false, 0, 1.0, 0.0, 0.0},
+    {"Motorola large start", ByteOrder::Motorola,
+     std::numeric_limits<std::uint32_t>::max(), 8U, ValueType::Unsigned,
+     {0xFF}, false, 0, 1.0, 0.0, 0.0},
+    {"Motorola zero length", ByteOrder::Motorola, 7U, 0U, ValueType::Unsigned,
+     {0xFF}, false, 0, 1.0, 0.0, 0.0},
+    {"Motorola excessive length", ByteOrder::Motorola, 7U, 65U, ValueType::Unsigned,
+     std::vector<std::uint8_t> (9U, 0xFF), false, 0, 1.0, 0.0, 0.0},
+    {"Intel regression", ByteOrder::Intel, 0U, 16U, ValueType::Unsigned,
+     {0x12, 0x34}, true, 0x3412, 1.0, 0.0, 13330.0},
+    {"Intel signed regression", ByteOrder::Intel, 0U, 16U, ValueType::Signed,
+     {0xFE, 0xFF}, true, -2, 0.5, 10.0, 9.0},
+    {"Intel short payload", ByteOrder::Intel, 0U, 16U, ValueType::Unsigned,
+     {0x12}, false, 0, 1.0, 0.0, 0.0}
+  };
+
+  int failures = 0;
+  for (const DecodeCase &test : cases) {
+    DecodeSignal signal;
+    signal.name = test.name;
+    signal.byteOrder = test.byteOrder;
+    signal.startBit = test.startBit;
+    signal.length = test.length;
+    signal.valueType = test.valueType;
+    signal.factor = test.factor;
+    signal.offset = test.offset;
+
+    DecodeFrame definition;
+    definition.canId = 0x123U;
+    definition.dlc = static_cast<std::uint8_t> (test.data.size());
+    definition.signals.push_back (signal);
+    DecodeDatabase database;
+    database.frames.push_back (definition);
+    database.frameIndexByKey.emplace (FrameKey (definition.canId, false), 0U);
+
+    RawCanFrame frame;
+    frame.canId = definition.canId;
+    frame.data = test.data;
+    const DecodedFrameValue result = DbcDecoder().Decode (database, frame);
+    const bool passed = result.valid &&
+      (result.definition == &database.frames[0]) &&
+      (result.signals.size() == 1U) &&
+      (result.signals[0].definition == &database.frames[0].signals[0]) &&
+      (result.signals[0].valid == test.valid) &&
+      (!test.valid || (((test.valueType == ValueType::Signed)
+        ? (std::get_if<std::int64_t> (&result.signals[0].rawValue) &&
+           std::get<std::int64_t> (result.signals[0].rawValue) == test.rawValue)
+        : (std::get_if<std::uint64_t> (&result.signals[0].rawValue) &&
+           std::get<std::uint64_t> (result.signals[0].rawValue) ==
+             static_cast<std::uint64_t> (test.rawValue))) &&
+                      (result.signals[0].physicalValue == test.physicalValue)));
+    if (!passed) {
+      std::cerr << "FAIL: " << test.name << '\n';
+      ++failures;
+    }
+  }
+  std::size_t boundaryCases = 0U;
+  for (ByteOrder order : {ByteOrder::Intel, ByteOrder::Motorola}) {
+    for (ValueType type : {ValueType::Unsigned, ValueType::Signed}) {
+      for (std::uint64_t bits : {std::uint64_t (0U), std::uint64_t (0x7FFFFFFFFFFFFFFFULL),
+                                std::uint64_t (0x8000000000000000ULL),
+                                std::uint64_t (0x8000000000000001ULL),
+                                std::uint64_t (0xFFFFFFFFFFFFFFFFULL)}) {
+        DecodeDatabase database;
+        DecodeFrame definition;
+        DecodeSignal signal;
+        signal.startBit = order == ByteOrder::Intel ? 0U : 7U;
+        signal.length = 64U;
+        signal.byteOrder = order;
+        signal.valueType = type;
+        signal.factor = 0.5;
+        signal.offset = 10.0;
+        definition.signals.push_back (signal);
+        database.frames.push_back (definition);
+        database.frameIndexByKey.emplace (FrameKey (0U, false), 0U);
+        RawCanFrame frame;
+        for (unsigned byte = 0U; byte < 8U; ++byte) {
+          const unsigned shift = (order == ByteOrder::Intel ? byte : 7U - byte) * 8U;
+          frame.data.push_back (static_cast<std::uint8_t> (bits >> shift));
+        }
+        const auto result = DbcDecoder().Decode (database, frame);
+        const std::int64_t signedExpected = bits <= 0x7FFFFFFFFFFFFFFFULL
+          ? static_cast<std::int64_t> (bits)
+          : std::numeric_limits<std::int64_t>::min() +
+            static_cast<std::int64_t> (bits - 0x8000000000000000ULL);
+        const auto &decoded = result.signals.at (0U);
+        const auto expected = type == ValueType::Unsigned
+          ? std::variant<std::int64_t, std::uint64_t> (bits)
+          : std::variant<std::int64_t, std::uint64_t> (signedExpected);
+        const double physical = (type == ValueType::Unsigned
+          ? static_cast<double> (bits) : static_cast<double> (signedExpected)) * 0.5 + 10.0;
+        std::ostringstream actualText;
+        std::ostringstream expectedText;
+        std::visit ([&actualText] (auto raw) { actualText << raw; }, decoded.rawValue);
+        if (type == ValueType::Unsigned)
+          expectedText << bits;
+        else
+          expectedText << signedExpected;
+        if (!decoded.valid || decoded.rawValue != expected ||
+            decoded.physicalValue != physical || actualText.str() != expectedText.str()) {
+          std::cerr << "FAIL: 64-bit boundary " << bits << '\n';
+          ++failures;
+        }
+        ++boundaryCases;
+      }
+    }
+  }
+  if (failures != 0)
+    return 1;
+  std::cout << "All " << sizeof (cases) / sizeof (cases[0]) + boundaryCases << " decoder cases passed.\n";
+  return 0;
+}

tests/dbc_decoder_test.pro

@@ -0,0 +1,7 @@
+TEMPLATE = app
+TARGET = dbc_decoder_test
+CONFIG += console c++17
+CONFIG -= app_bundle qt
+INCLUDEPATH += ..
+SOURCES += dbc_decoder_test.cpp ../dbc_decoder.cpp
+HEADERS += ../dbc_decoder.h ../decode_database.h

tests/dbc_parser_test.cpp

@@ -0,0 +1,133 @@
+#include "dbc_parser.h"
+#include "dbc_statement_handler.h"
+
+#include <chrono>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <stdexcept>
+
+struct Fixture {
+  std::filesystem::path path = std::filesystem::temp_directory_path() /
+    ("dbc_parser_test_" + std::to_string (
+      std::chrono::steady_clock::now().time_since_epoch().count()) + ".dbc");
+  ~Fixture() { std::error_code error; std::filesystem::remove (path, error); }
+  void Write (const std::string &text) const {
+    std::ofstream output (path);
+    output << text;
+    if (!output)
+      throw std::runtime_error ("Cannot write test fixture.");
+  }
+};
+
+class CountingHandler : public DbcStatementHandler {
+  public:
+    inline static int instances = 0;
+    inline static int calls = 0;
+    CountingHandler() { ++instances; }
+    void Handle (const std::string &, DbcParseContext &context) const override {
+      ++calls;
+      context.database.frames.emplace_back();
+    }
+};
+
+int main() {
+  Fixture fixture;
+  int failures = 0;
+  std::size_t count = 0U;
+  const auto check = [&] (bool passed, const std::string &name) {
+    ++count;
+    if (!passed) { ++failures; std::cerr << "FAIL: " << name << '\n'; }
+  };
+  struct ValidCase { const char *line; std::uint32_t id; bool extended; unsigned length; };
+  const ValidCase valid[] = {
+    {"BO_ 0 Frame: 0 ECU", 0U, false, 0U},
+    {"BO_ 2047 Frame: 8 ECU", 2047U, false, 8U},
+    {"BO_ 2048 Frame: 64 ECU", 2048U, true, 64U},
+    {"BO_ 536870911 Frame: 255 ECU", 0x1FFFFFFFU, true, 255U},
+    {"BO_ 2147483649 Frame: 8 ECU", 1U, true, 8U},
+    {"BO_ 2684354559 Frame: 8 ECU", 0x1FFFFFFFU, true, 8U},
+    {"  BO_\t256\tFrame :\t8\tECU  \r", 256U, false, 8U}
+  };
+  for (const auto &test : valid) {
+    fixture.Write (std::string (test.line) + '\n');
+    try {
+      const auto database = DbcParser().ParseFile (fixture.path.string());
+      check (database.frames.size() == 1U && database.frames[0].name == "Frame" &&
+             database.frames[0].canId == test.id &&
+             database.frames[0].isExtended == test.extended &&
+             database.frames[0].dlc == test.length &&
+             database.frames[0].transmitter == "ECU", test.line);
+    } catch (const std::exception &error) { check (false, error.what()); }
+  }
+  const char *invalid[] = {
+    "BO_ invalid", "BO_", "BO_ 1", "BO_ 1 : 8 ECU", "BO_ 1 Frame 8 ECU",
+    "BO_ 1 Frame:", "BO_ 1 Frame: 8", "BO_ 1 Frame: 8 ECU extra",
+    "BO_ 1 Two Names: 8 ECU", "BO_ -1 Frame: 8 ECU", "BO_ +1 Frame: 8 ECU",
+    "BO_ 1x Frame: 8 ECU", "BO_ 0x123 Frame: 8 ECU", "BO_ 1.5 Frame: 8 ECU",
+    "BO_ 4294967296 Frame: 8 ECU", "BO_ 999999999999999999999 Frame: 8 ECU",
+    "BO_ 536870912 Frame: 8 ECU", "BO_ 1073741824 Frame: 8 ECU",
+    "BO_ 2684354560 Frame: 8 ECU", "BO_ 4294967295 Frame: 8 ECU",
+    "BO_ 1 Frame: -1 ECU", "BO_ 1 Frame: +8 ECU", "BO_ 1 Frame: 8x ECU",
+    "BO_ 1 Frame: 8.5 ECU", "BO_ 1 Frame: 256 ECU",
+    "BO_ 1 Frame: 4294967296 ECU", "BO_\tinvalid"
+  };
+  for (const auto *line : invalid) {
+    fixture.Write (std::string ("VERSION \"test\"\n\n") + line + '\n');
+    try {
+      DbcParser().ParseFile (fixture.path.string());
+      check (false, line);
+    } catch (const std::runtime_error &error) {
+      const std::string prefix = fixture.path.string() + ":3: ";
+      check (std::string (error.what()).find (prefix) == 0U &&
+             std::string (error.what()).size() > prefix.size(), line);
+    }
+  }
+  fixture.Write (
+    "BO_TX_BU_ 256 : ECU;\nBO_ 256 Frame: 8 ECU\n"
+    " SG_ Speed : 0|16@1+ (0.5,1) [0|100] \"rpm\" ECU\n"
+    "CM_ BO_ 256 \"Frame comment\";\nCM_ SG_ 256 Speed \"Signal comment\";\n"
+    "BO_ 257 Second: 8 ECU\n");
+  const auto database = DbcParser().ParseFile (fixture.path.string());
+  check (database.frames.size() == 2U && database.frames[0].signals.size() == 1U &&
+         database.frames[0].comment == "Frame comment" &&
+         database.frames[0].signals[0].comment == "Signal comment", "Integration");
+  fixture.Write ("\nSG_ Speed : invalid\n");
+  try {
+    DbcParser().ParseFile (fixture.path.string());
+    check (false, "Signal error location");
+  } catch (const std::runtime_error &error) {
+    check (std::string (error.what()).find (fixture.path.string() + ":2: ") == 0U,
+           "Signal error location");
+  }
+  DbcDatabase dispatchDatabase;
+  DbcParseContext context {dispatchDatabase, nullptr};
+  DbcStatementDispatcher dispatcher;
+  dispatcher.RegisterType<CountingHandler> ("TEST_");
+  check (dispatcher.Dispatch ("TEST_ first", context) &&
+         dispatcher.Dispatch ("TEST_ second", context) &&
+         CountingHandler::instances == 1 && CountingHandler::calls == 2 &&
+         dispatchDatabase.frames.size() == 2U, "Factory dispatch and handler reuse");
+  check (!dispatcher.Dispatch ("TEST_OTHER data", context) &&
+         !dispatcher.Dispatch ("BO_TX_BU_ 1 : ECU;", context) &&
+         !dispatcher.Dispatch ("VAL_ 1 Speed 0 \"Stopped\";", context) &&
+         CountingHandler::calls == 2, "Exact and unknown keyword dispatch");
+  const DbcParser parser;
+  fixture.Write ("BO_ 1 First: 8 ECU\n");
+  check (parser.ParseFile (fixture.path.string()).frames.size() == 1U, "First parse");
+  fixture.Write ("SG_ Speed : invalid\n");
+  try {
+    parser.ParseFile (fixture.path.string());
+    check (false, "Independent parse context");
+  } catch (const std::runtime_error &error) {
+    check (std::string (error.what()).find ("Signal found before any frame") !=
+           std::string::npos, "Independent parse context");
+  }
+  fixture.Write ("BO_ 2 Second: 8 ECU\n");
+  const auto recovered = parser.ParseFile (fixture.path.string());
+  check (recovered.frames.size() == 1U && recovered.frames[0].canId == 2U,
+         "Fresh parse after error");
+  if (failures != 0) return 1;
+  std::cout << "All " << count << " parser cases passed.\n";
+  return 0;
+}

tests/dbc_parser_test.pro

@@ -0,0 +1,7 @@
+TEMPLATE = app
+TARGET = dbc_parser_test
+CONFIG += console c++17
+CONFIG -= app_bundle qt
+INCLUDEPATH += ..
+SOURCES += dbc_parser_test.cpp ../dbc_parser.cpp ../dbc_statement_handler.cpp
+HEADERS += ../dbc_statement_handler.h ../typefactory.h ../dbc_parser.h ../dbc_database.h ../frame_info.h ../signal_info.h

typefactory.h

@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2026 Dim Himro
+
+#ifndef TYPEFACTORY_H
+#define TYPEFACTORY_H
+
+#include <memory>
+#include <type_traits>
+#include <unordered_map>
+#include <utility>   // std::move
+
+/**
+ * @brief Registry-based factory for creating objects by runtime identifier.
+ *
+ * Allows registering derived types and instantiating them using a ClassId key.
+ *
+ * Notes:
+ * - Not thread-safe. Register types during initialization phase only.
+ * - Re-registering the same id overwrites the previous entry ("last wins").
+ * - ClassId must be hashable (std::hash<ClassId> specialization must exist).
+ *
+ * @tparam ClassId -Unique class identifier type (e.g. std::string, int, enum).
+ * @tparam BaseClass -Base type for all created objects.
+ * @tparam Arg - Constructor arguments forwarded to registered derived types (by value).
+ *
+ * Usage example:
+ * @code
+ * #include <string>
+ *
+ * struct Base {
+ *   virtual ~Base() = default;
+ *   virtual int get() = 0;
+ * };
+ *
+ * struct Derived1 : Base {
+ *   explicit Derived1(int start) : m_start(start) {}
+ *   int get() override { return m_start + 1; }
+ *   int m_start = 0;
+ * };
+ *
+ * struct Derived2 : Base {
+ *   explicit Derived2(int start) : m_start(start) {}
+ *   int get() override { return m_start + 2; }
+ *   int m_start = 0;
+ * };
+ *
+ * TypeFactory<std::string, Base, int> factory;
+ * factory.registerType<Derived1>("one");
+ * factory.registerType<Derived2>("two");
+ *
+ * auto a = factory.create("one", 10);
+ * auto b = factory.creator("two")(10); // advanced API: get creator function
+ *
+ * (void)a->get();
+ * (void)b->get();
+ * @endcode
+ */
+template <class ClassId, class BaseClass, class... Args>
+class TypeFactory {
+public:
+  using BasePtr   = std::shared_ptr<BaseClass>;
+  using CreatorFn = BasePtr (*)(Args...);
+
+  TypeFactory() = default;
+
+  /**
+   * @brief Registers a Derived type under the given id.
+   *
+   * Requirements (checked at compile-time):
+   * - Derived must inherit from BaseClass
+   * - Derived must be constructible from Args...
+   *
+   * Re-registering the same id overwrites the previous entry ("last wins").
+   */
+  template <class Derived>
+  void registerType(const ClassId& id) {
+    static_assert(std::is_base_of_v<BaseClass, Derived>,
+                  "Derived must inherit from BaseClass");
+    static_assert(std::is_constructible_v<Derived, Args...>,
+                  "Derived must be constructible from Args...");
+
+    classes.insert_or_assign(id, &instantiate<Derived>);
+  }
+
+  /**
+   * @brief Returns creator function for the given id.
+   * @throws std::out_of_range when id is not registered.
+   */
+  [[nodiscard]] CreatorFn creator(const ClassId& id) const {
+    return classes.at(id);
+  }
+
+  /**
+   * @brief Creates an instance for the given id using provided arguments.
+   * @throws std::out_of_range when id is not registered.
+   */
+  [[nodiscard]] BasePtr create(const ClassId& id, Args... args) const {
+    return creator(id)(std::move(args)...);
+  }
+
+  /**
+   * @brief Checks whether an id is registered.
+   */
+  [[nodiscard]] bool contains(const ClassId& id) const {
+    return classes.find(id) != classes.end();
+  }
+
+protected:
+  // Protected by design: derived factories may extend/inspect the registry.
+  std::unordered_map<ClassId, CreatorFn> classes;
+
+private:
+  template <class Derived>
+  static BasePtr instantiate(Args... args) {
+    return std::make_shared<Derived>(std::move(args)...);
+  }
+};
+#endif // TYPEFACTORY_H