class QCanDbcFileParser

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

Synopsis

Methods

• def __init__()

• def error()

• def errorString()

• def messageDescriptions()

• def messageValueDescriptions()

• def parse()

• def parseData()

• def warnings()

Static functions

• def uniqueIdDescription()

Note

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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 QCanMessageDescription s as an output. These message descriptions can be forwarded to QCanFrameProcessor , and later used as rules to encode or decode QCanBusFrame s.

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 QCanFrameProcessor

class Error

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

Constant	Description
QCanDbcFileParser.Error.None	No error occurred.
QCanDbcFileParser.Error.FileReading	An error occurred while opening or reading the file.
QCanDbcFileParser.Error.Parsing	An error occurred while parsing the content of the file.

__init__()

Constructs a DBC file parser.

error()

Return type:

Error

Returns the last error which occurred during the parsing.

See also

errorString() parse()

errorString()

Return type:

str

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()

messageDescriptions()

Return type:

.list of QCanMessageDescription

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

See also

parse() error()

messageValueDescriptions()

Return type:

Dictionary with keys of type .QtCanBus.UniqueId and values of type QString.

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 QCanDbcFileParser::ValueDescriptions

parse(fileName)

Parameters:

fileName – str

Return type:

bool

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() parseData()

parse(fileNames)

Parameters:

fileNames – list of strings

Return type:

bool

This is an overloaded function.

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.

See also

messageDescriptions() error() warnings() parseData()

parseData(data)

Parameters:

data – str

Return type:

bool

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);

See also

messageDescriptions() error() warnings() parse()

static uniqueIdDescription()

Return type:

QCanUniqueIdDescription

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

setUniqueIdDescription()

warnings()

Return type:

list of strings

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() parse()