- Qt 6.10
- Qt Serial Bus
- C++ Classes
- QCanDbcFileParser
- Qt 6.10.2 Reference Documentation

# QCanDbcFileParser Class

The QCanDbcFileParser class can be used to parse DBC files. More...

Header: | `#include <QCanDbcFileParser>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS SerialBus)` `target_link_libraries(mytarget PRIVATE Qt6::SerialBus)`
qmake: | `QT += serialbus`
Since: | Qt 6.5
Status: | Preliminary

This class is under development and is subject to change.

- List of all members, including inherited members

## Public Types

enum class | Error { None, FileReading, Parsing }
| MessageValueDescriptions
| SignalValueDescriptions
| ValueDescriptions

## Public Functions

| QCanDbcFileParser()
| ~QCanDbcFileParser()
QCanDbcFileParser::Error | error() const
QString | errorString() const
QList<QCanMessageDescription> | messageDescriptions() const
QCanDbcFileParser::MessageValueDescriptions | messageValueDescriptions() const
bool | parse(const QString &fileName)
bool | parse(const QStringList &fileNames)
`(since 6.7)` bool | parseData(QStringView data)
QStringList | warnings() const

## Static Public Members

QCanUniqueIdDescription | uniqueIdDescription()

## Detailed Description

A CAN database or CAN DBC file is an ASCII text file that contains information on how to decode and interpret raw CAN bus data. Some more details about the format can be found here or here.

The QCanDbcFileParser class takes the input DBC file, parses it, and provides a list of QCanMessageDescriptions as an output. These message descriptions can be forwarded to QCanFrameProcessor, and later used as rules to encode or decode QCanBusFrames.

Use one of parse() overloads to specify a file or a list of files that will be processed. Both overloads return `true` if the parsing completes successfully and `false` otherwise.

Call the error() method to get the error which occurred during the parsing. If the parsing completes successfully, this method will return None. Otherwise, you can use an errorString() method to get the string representation of an error.

During the parsing some non-critical problems may occur as well. Such problems will be logged, but the parsing process will not be aborted. You can use the warnings() method to get the full list of such problems after the parsing is completed.

If the parsing completes successfully, call messageDescriptions() to get a list of the message descriptions that were extracted during the last parse() call. Call messageValueDescriptions() to get the textual descriptions of signal raw values, if they are available.

Use the static uniqueIdDescription() function to get a QCanUniqueIdDescription for the DBC format.

     QCanDbcFileParser fileParser;
     const bool result = fileParser.parse(u"path/to/file.dbc"_s);
     // Check result, call error() and warnings() if needed

     // Prepare a QCanFrameProcessor to decode or encode DBC frames
     QCanFrameProcessor frameProcessor;
     frameProcessor.setUniqueIdDescription(QCanDbcFileParser::uniqueIdDescription());
     frameProcessor.setMessageDescriptions(fileParser.messageDescriptions());

Note: The parser is stateful, which means that all the results (like extracted message descriptions, error code, or warnings) are reset once the next parsing starts.

#### Supported Keywords

The current implementation supports only a subset of keywords that you can find in a DBC file:

- `BO_` - message description.
- `SG_` - signal description.
- `SIG_VALTYPE_` - signal type description.
- `SG_MUL_VAL_` - extended multiplexing description.
- `CM_` - comments (only for message and signal descriptions).
- `VAL_` - textual descriptions for raw signal values.

Lines starting from other keywords are simply ignored.

See also QCanMessageDescription and QCanFrameProcessor.

## Member Type Documentation

### enum class QCanDbcFileParser::Error

This enum represents the possible errors that can happen during the parsing of a DBC file.

Constant | Value | Description
--- | --- | ---
`QCanDbcFileParser::Error::None` | `0` | No error occurred.
`QCanDbcFileParser::Error::FileReading` | `1` | An error occurred while opening or reading the file.
`QCanDbcFileParser::Error::Parsing` | `2` | An error occurred while parsing the content of the file.

### `[alias]` QCanDbcFileParser::MessageValueDescriptions

This is a type alias for `QHash<QtCanBus::UniqueId, SignalValueDescriptions>`.

The keys of the hash represent message unique ids, and the values of the hash contain the corresponding QCanDbcFileParser::SignalValueDescriptions entries.

See also QCanDbcFileParser::SignalValueDescriptions.

### `[alias]` QCanDbcFileParser::SignalValueDescriptions

This is a type alias for `QHash<QString, ValueDescriptions>`.

The keys of the hash represent signal names, and the values of the hash contain the corresponding QCanDbcFileParser::ValueDescriptions entries.

See also QCanDbcFileParser::ValueDescriptions.

### `[alias]` QCanDbcFileParser::ValueDescriptions

This is a type alias for `QHash<quint32, QString>`.

The keys of the hash represent raw signal values, and the values of the hash represent corresponding string descriptions.

## Member Function Documentation

### QCanDbcFileParser::QCanDbcFileParser()

Constructs a DBC file parser.

### `[noexcept]` QCanDbcFileParser::~QCanDbcFileParser()

Destroys this DBC file parser.

### QCanDbcFileParser::Error QCanDbcFileParser::error() const

Returns the last error which occurred during the parsing.

See also errorString() and parse().

### QString QCanDbcFileParser::errorString() const

Returns the text representation of the last error which occurred during the parsing or an empty string if there was no error.

See also error().

### QList<QCanMessageDescription> QCanDbcFileParser::messageDescriptions() const

Returns the list of message descriptions that were extracted during the last parse() call.

See also parse() and error().

### QCanDbcFileParser::MessageValueDescriptions QCanDbcFileParser::messageValueDescriptions() const

Returns the textual descriptions for signal raw values.

DBC supports the possibility to provide textual descriptions to signal raw values. If such data exists in the parsed DBC file(s), it can be accessed using this function.

The textual descriptions are unique for a certain signal within a specific message, so the returned structure contains the information about the message unique id and the signal name, as well as the actual value descriptions.

See also QCanDbcFileParser::MessageValueDescriptions, QCanDbcFileParser::SignalValueDescriptions, and QCanDbcFileParser::ValueDescriptions.

### bool QCanDbcFileParser::parse(const QString &fileName)

Parses the file fileName. Returns `true` if the parsing completed successfully or `false` otherwise.

If the parsing completed successfully, call the messageDescriptions() method to get the list of all extracted message descriptions.

If the parsing failed, call the error() and errorString() methods to get the information about the error.

Call the warnings() method to get the list of warnings that were logged during the parsing.

Note: This method expects the file contents to be encoded in UTF-8. If the file has a different encoding, decode it first, and use parseData() to extract the DBC information.

See also messageDescriptions(), error(), warnings(), and parseData().

### bool QCanDbcFileParser::parse(const QStringList &fileNames)

Parses a list of files fileNames. Returns `true` if the parsing completed successfully or `false` otherwise.

If the parsing completed successfully, call the messageDescriptions() method to get the list of all extracted message descriptions.

The parsing stops at the first error. Call the error() and errorString() methods to get the information about the error.

Call the warnings() method to get the list of warnings that were logged during the parsing.

Note: This method expects the file contents to be encoded in UTF-8. If the file has a different encoding, decode it first, and use parseData() to extract the DBC information.

This is an overloaded function.

See also messageDescriptions(), error(), warnings(), and parseData().

### `[since 6.7]` bool QCanDbcFileParser::parseData(QStringView data)

Parses the input data data and returns `true` if the parsing completed successfully or `false` otherwise.

If the parsing completed successfully, call the messageDescriptions() method to get the list of all extracted message descriptions.

If the parsing failed, call the error() and errorString() methods to get the information about the error.

Call the warnings() method to get the list of warnings that were logged during the parsing.

The method expects that data is the content of a valid DBC file, properly converted to QStringView.

Use this method when the input file has an encoding different from UTF-8.

     // Read the data from a DBC file with custom encoding
     const QByteArray initialData = ...;
     // Convert to UTF-16 using QStringDecoder or some other way
     const QString decodedData = ...;
     QCanDbcFileParser parser;
     const bool result = parser.parseData(decodedData);

This function was introduced in Qt 6.7.

See also messageDescriptions(), error(), warnings(), and parse().

### `[static]` QCanUniqueIdDescription QCanDbcFileParser::uniqueIdDescription()

Returns a unique identifier description. DBC protocol always uses the Frame Id as an identifier, and therefore the unique identifier description is always the same.

Use this method to get an instance of QCanUniqueIdDescription and pass it to QCanFrameProcessor.

See also QCanFrameProcessor::setUniqueIdDescription().

### QStringList QCanDbcFileParser::warnings() const

Returns the list of non-critical problems which occurred during the parsing.

A typical problem can be a malformed message or signal description. In such cases the malformed message or signal is skipped, but the rest of the file can be processed as usual.

See also error() and parse().