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efc57d658d readme 2026-03-13 13:03:29 -04:00
2a90b2d79d DBC parser initial commit. 2026-03-13 13:00:01 -04:00
13 changed files with 823 additions and 2 deletions

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.gitignore vendored Normal file
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*.user

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# dbc
# dbc parser skeleton
some experiments with parsing dbc files
A minimal DBC parser skeleton for the **FrameTap** project.
The purpose of this module is to read a DBC file and convert it into a simple internal representation that can later be:
- displayed as a tree
- connected to `Qt Model/View`
- used for signal selection
- extended toward runtime CAN frame decoding
---
## Overview
The architecture is intentionally simple:
1. `dbc_parser` reads a DBC file
2. parsed data is stored in `DbcDatabase`
3. `dbc_tree_builder` converts it into a `TreeNode` hierarchy
4. the resulting tree can later be adapted to `QAbstractItemModel`
This keeps the parser independent from Qt and makes it easier to test and evolve.
---
## Currently supported
### Frame definitions
Supported frame lines:
```text
BO_ 256 EngineData: 8 EEC1

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dbc.pro Normal file
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TEMPLATE = app
CONFIG += console c++17
CONFIG -= app_bundle
CONFIG -= qt
SOURCES += \
dbc_parser.cpp \
dbc_tree_builder.cpp \
main.cpp \
tree_node.cpp
HEADERS += \
dbc_database.h \
dbc_parser.h \
dbc_tree_builder.h \
frame_info.h \
signal_info.h \
tree_node.h

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dbc_database.h Normal file
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#ifndef DBC_DATABASE_H
#define DBC_DATABASE_H
#include <vector>
#include "frame_info.h"
/**
* @brief Parsed DBC content stored in a simple internal form.
*/
struct DbcDatabase {
std::vector<FrameInfo> frames; /**< All frames found in DBC file. */
};
#endif /* DBC_DATABASE_H */

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dbc_parser.cpp Normal file
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#include "dbc_parser.h"
#include <fstream>
#include <sstream>
#include <stdexcept>
#include <algorithm>
#include <cctype>
namespace {
/**
* @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);
}
}
DbcDatabase DbcParser::ParseFile (const std::string &filePath) const {
std::ifstream input (filePath.c_str());
if (!input.is_open())
throw std::runtime_error ("Failed to open DBC file: " + filePath);
DbcDatabase database;
FrameInfo *currentFrame = nullptr;
std::string line;
while (std::getline (input, line)) {
line = Trim (line);
if (line.empty())
continue;
if (IsFrameLine (line)) {
FrameInfo frame = ParseFrameLine (line);
database.frames.push_back (frame);
currentFrame = &database.frames.back();
} else if (IsSignalLine (line)) {
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;
}
std::uint32_t DbcParser::TryExtractPgn (std::uint32_t canId, bool &hasPgn) {
hasPgn = false;
/*
* Very simplified J1939 PGN extraction.
* Assumes 29-bit identifier.
*/
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 Vector__XXX
*/
std::istringstream stream (line);
std::string token;
FrameInfo frame;
stream >> token;
if (token != "BO_")
throw std::runtime_error ("Invalid frame line: " + line);
stream >> frame.canId;
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.hasPgn);
return frame;
}
SignalInfo DbcParser::ParseSignalLine (const std::string &line) {
/*
* Example:
* SG_ EngineSpeed : 0|16@1+ (0.125,0) [0|8000] "rpm" Vector__XXX
*/
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 canId = 0U;
stream >> canId;
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);
if (frame != nullptr)
frame->comment = line.substr (quoteBegin + 1U, quoteEnd - quoteBegin - 1U);
} else if (token == "SG_") {
std::uint32_t canId = 0U;
std::string signalName;
stream >> canId;
stream >> signalName;
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);
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) {
for (std::size_t index = 0U; index < database.frames.size(); ++index) {
if (database.frames[index].canId == canId)
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;
}

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dbc_parser.h Normal file
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#ifndef DBC_PARSER_H
#define DBC_PARSER_H
#include <string>
#include <vector>
#include <cstdint>
#include "dbc_database.h"
/**
* @brief Minimal DBC parser.
*
* Supports:
* - BO_
* - SG_
* - CM_ BO_
* - CM_ SG_
*
* Ignores:
* - attributes
* - multiplexing
* - value tables
*/
class DbcParser {
public:
/**
* @brief Parse DBC file.
* @param filePath Path to input file.
* @return Parsed database.
* @throws std::runtime_error on file or parse errors.
*/
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 &hasPgn);
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);
static SignalInfo *FindSignalByName (FrameInfo &frame, const std::string &signalName);
};
#endif /* DBC_PARSER_H */

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dbc_tree_builder.cpp Normal file
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#include "dbc_tree_builder.h"
std::unique_ptr<TreeNode> DbcTreeBuilder::Build (const DbcDatabase &database) const {
std::unique_ptr<TreeNode> root (new TreeNode());
for (std::size_t frameIndex = 0U; frameIndex < database.frames.size(); ++frameIndex) {
const FrameInfo &frame = database.frames[frameIndex];
std::unique_ptr<TreeNode> frameNode (new TreeNode (frame));
for (std::size_t signalIndex = 0U; signalIndex < frame.signals.size(); ++signalIndex) {
const SignalInfo &signal = frame.signals[signalIndex];
std::unique_ptr<TreeNode> signalNode (new TreeNode (signal));
frameNode->AddChild (std::move (signalNode));
}
root->AddChild (std::move (frameNode));
}
return root;
}

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dbc_tree_builder.h Normal file
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#ifndef DBC_TREE_BUILDER_H
#define DBC_TREE_BUILDER_H
#include <memory>
#include "dbc_database.h"
#include "tree_node.h"
/**
* @brief Builds a simple tree from parsed DBC database.
*/
class DbcTreeBuilder {
public:
/**
* @brief Build tree representation of parsed DBC data.
* @param database Parsed database.
* @return Root node of the tree.
*/
std::unique_ptr<TreeNode> Build (const DbcDatabase &database) const;
};
#endif /* DBC_TREE_BUILDER_H */

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frame_info.h Normal file
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#ifndef FRAME_INFO_H
#define FRAME_INFO_H
#include <string>
#include <vector>
#include <cstdint>
#include "signal_info.h"
/**
* @brief Describes one CAN frame from a DBC file.
*/
struct FrameInfo {
std::string name; /**< Frame name. */
std::uint32_t canId; /**< Raw CAN identifier from DBC. */
std::uint32_t pgn; /**< J1939 PGN if applicable. */
bool hasPgn; /**< true if PGN was derived. */
std::uint8_t dlc; /**< Frame payload length. */
std::string transmitter; /**< Transmitter ECU name. */
std::string comment; /**< Optional frame comment. */
std::vector<SignalInfo> signals; /**< Signals contained in the frame. */
FrameInfo()
: name()
, canId (0U)
, pgn (0U)
, hasPgn (false)
, dlc (0U)
, transmitter()
, comment()
, signals() {
}
};
#endif /* FRAME_INFO_H */

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#include <iostream>
#include <memory>
#include <cstddef>
#include "dbc_parser.h"
#include "dbc_tree_builder.h"
#include "tree_node.h"
static void PrintReceivers (const std::vector<std::string> &receivers) {
for (std::size_t index = 0U; index < receivers.size(); ++index) {
if (index != 0U)
std::cout << ",";
std::cout << receivers[index];
}
}
static void PrintTree (const TreeNode *node, int indent) {
if (node == nullptr)
return;
for (int i = 0; i < indent; ++i)
std::cout << " ";
switch (node->GetType()) {
case NodeType::Root:
std::cout << "[root] " << node->GetName() << "\n";
break;
case NodeType::Frame: {
const FrameInfo *frame = node->GetFrame();
std::cout << "[frame] " << node->GetName();
if (frame != nullptr) {
std::cout << " id=" << frame->canId
<< " dlc=" << static_cast<unsigned int> (frame->dlc)
<< " tx=" << frame->transmitter;
if (frame->hasPgn)
std::cout << " pgn=" << frame->pgn;
if (!frame->comment.empty())
std::cout << " comment=\"" << frame->comment << "\"";
}
std::cout << "\n";
break;
}
case NodeType::Signal: {
const SignalInfo *signal = node->GetSignal();
std::cout << "[signal] " << node->GetName();
if (signal != nullptr) {
std::cout << " start=" << signal->startBit
<< " len=" << signal->length
<< " unit=" << signal->unit
<< " rx=";
PrintReceivers (signal->receivers);
if (!signal->comment.empty())
std::cout << " comment=\"" << signal->comment << "\"";
}
std::cout << "\n";
break;
}
default:
std::cout << "[unknown]\n";
break;
}
for (std::size_t i = 0U; i < node->GetChildCount(); ++i)
PrintTree (node->GetChild (i), indent + 1);
}
int main (int argc, char *argv[]) {
if (argc < 2) {
std::cerr << "Usage: dbc_demo <file.dbc>\n";
return 1;
}
try {
DbcParser parser;
DbcDatabase database = parser.ParseFile (argv[1]);
DbcTreeBuilder builder;
std::unique_ptr<TreeNode> root = builder.Build (database);
PrintTree (root.get(), 0);
} catch (const std::exception &ex) {
std::cerr << "Error: " << ex.what() << "\n";
return 2;
}
return 0;
}

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signal_info.h Normal file
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#ifndef SIGNAL_INFO_H
#define SIGNAL_INFO_H
#include <string>
#include <vector>
#include <cstdint>
/**
* @brief Describes one signal inside a DBC frame.
*/
struct SignalInfo {
std::string name; /**< Signal name. */
std::uint32_t startBit; /**< Start bit in DBC notation. */
std::uint32_t length; /**< Signal length in bits. */
bool isLittleEndian; /**< true for Intel, false for Motorola. */
bool isSigned; /**< true if signal is signed. */
double factor; /**< Scaling factor. */
double offset; /**< Physical offset. */
double minimum; /**< Minimum physical value. */
double maximum; /**< Maximum physical value. */
std::string unit; /**< Physical unit. */
std::vector<std::string> receivers; /**< Receivers of this signal. */
std::string comment; /**< Optional signal comment. */
SignalInfo()
: name()
, startBit (0U)
, length (0U)
, isLittleEndian (true)
, isSigned (false)
, factor (1.0)
, offset (0.0)
, minimum (0.0)
, maximum (0.0)
, unit()
, receivers()
, comment() {
}
};
#endif /* SIGNAL_INFO_H */

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#include "tree_node.h"
TreeNode::TreeNode()
: m_type (NodeType::Root)
, m_name ("dbc")
, m_children()
, m_frame()
, m_signal() {
}
TreeNode::TreeNode (const FrameInfo &frame)
: m_type (NodeType::Frame)
, m_name (frame.name)
, m_children()
, m_frame (new FrameInfo (frame))
, m_signal() {
}
TreeNode::TreeNode (const SignalInfo &signal)
: m_type (NodeType::Signal)
, m_name (signal.name)
, m_children()
, m_frame()
, m_signal (new SignalInfo (signal)) {
}
void TreeNode::AddChild (std::unique_ptr<TreeNode> child) {
if (child)
m_children.push_back (std::move (child));
}
std::size_t TreeNode::GetChildCount() const {
return m_children.size();
}
const TreeNode *TreeNode::GetChild (std::size_t index) const {
if (index >= m_children.size())
return nullptr;
return m_children[index].get();
}
TreeNode *TreeNode::GetChild (std::size_t index) {
if (index >= m_children.size())
return nullptr;
return m_children[index].get();
}
NodeType TreeNode::GetType() const {
return m_type;
}
const std::string &TreeNode::GetName() const {
return m_name;
}
const FrameInfo *TreeNode::GetFrame() const {
return m_frame.get();
}
const SignalInfo *TreeNode::GetSignal() const {
return m_signal.get();
}

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tree_node.h Normal file
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#ifndef TREE_NODE_H
#define TREE_NODE_H
#include <string>
#include <vector>
#include <memory>
#include <cstddef>
#include "frame_info.h"
#include "signal_info.h"
/**
* @brief Type of a tree node.
*/
enum class NodeType {
Root,
Frame,
Signal
};
/**
* @brief Tree node for later use in model/view or other hierarchy consumers.
*/
class TreeNode {
public:
/**
* @brief Create root node.
*/
TreeNode();
/**
* @brief Create frame node.
* @param frame Frame payload.
*/
explicit TreeNode (const FrameInfo &frame);
/**
* @brief Create signal node.
* @param signal Signal payload.
*/
explicit TreeNode (const SignalInfo &signal);
~TreeNode() = default;
TreeNode (const TreeNode &) = delete;
TreeNode &operator= (const TreeNode &) = delete;
TreeNode (TreeNode &&) = default;
TreeNode &operator= (TreeNode &&) = default;
/**
* @brief Add child node.
* @param child Child node to add.
*/
void AddChild (std::unique_ptr<TreeNode> child);
/**
* @brief Get child count.
* @return Number of children.
*/
std::size_t GetChildCount() const;
/**
* @brief Get child by index.
* @param index Child index.
* @return Child pointer or nullptr if index is invalid.
*/
const TreeNode *GetChild (std::size_t index) const;
/**
* @brief Get mutable child by index.
* @param index Child index.
* @return Child pointer or nullptr if index is invalid.
*/
TreeNode *GetChild (std::size_t index);
/**
* @brief Get node type.
* @return Node type.
*/
NodeType GetType() const;
/**
* @brief Get display name.
* @return Node name.
*/
const std::string &GetName() const;
/**
* @brief Get frame payload if node is frame.
* @return Pointer to frame info or nullptr.
*/
const FrameInfo *GetFrame() const;
/**
* @brief Get signal payload if node is signal.
* @return Pointer to signal info or nullptr.
*/
const SignalInfo *GetSignal() const;
private:
NodeType m_type;
std::string m_name;
std::vector<std::unique_ptr<TreeNode> > m_children;
std::unique_ptr<FrameInfo> m_frame;
std::unique_ptr<SignalInfo> m_signal;
};
#endif /* TREE_NODE_H */