Class McapWriter

Class Documentation

class McapWriter

Provides a write interface to an MCAP file.

Public Functions

~McapWriter()
Status open(std::string_view filename, const McapWriterOptions &options)

Open a new MCAP file for writing and write the header.

Parameters:

  • filename – Filename of the MCAP file to write.

  • options – Options for MCAP writing. profile is required.

Returns:

A non-success status if the file could not be opened for writing.

void open(IWritable &writer, const McapWriterOptions &options)

Open a new MCAP file for writing and write the header.

Parameters:

  • writer – An implementation of the IWritable interface. Output bytes will be written to this object.

  • options – Options for MCAP writing. profile is required.

void open(std::ostream &stream, const McapWriterOptions &options)

Open a new MCAP file for writing and write the header.

Parameters:

  • stream – Output stream to write to.

  • options – Options for MCAP writing. profile is required.

void close()

Write the MCAP footer, flush pending writes to the output stream, and reset internal state.

void terminate()

Reset internal state without writing the MCAP footer or flushing pending writes. This should only be used in error cases as the output MCAP file will be truncated.

void addSchema(Schema &schema)

Add a new schema to the MCAP file and set schema.id to a generated schema id. The schema id is used when adding channels to the file.

Parameters:

schema – Description of the schema to register. The id field is ignored and will be set to a generated schema id.

void addChannel(Channel &channel)

Add a new channel to the MCAP file and set channel.id to a generated channel id. The channel id is used when adding messages to the file.

Parameters:

channel – Description of the channel to register. The id value is ignored and will be set to a generated channel id.

Status write(const Message &message)

Write a message to the output stream.

Parameters:

msg – Message to add.

Returns:

A non-zero error code on failure.

Status write(Attachment &attachment)

Write an attachment to the output stream.

Parameters:

attachment – Attachment to add. The attachment.crc will be calculated and set if configuration options allow CRC calculation.

Returns:

A non-zero error code on failure.

Status write(const Metadata &metadata)

Write a metadata record to the output stream.

Parameters:

metadata – Named group of key/value string pairs to add.

Returns:

A non-zero error code on failure.

const Statistics &statistics() const

Current MCAP file-level statistics. This is written as a Statistics record in the Summary section of the MCAP file.

IWritable *dataSink()

Returns a pointer to the IWritable data destination backing this writer. Will return nullptr if the writer is not open.

void closeLastChunk()

finishes the current chunk in progress and writes it to the file, if a chunk is in progress.

Public Static Functions

static void writeMagic(IWritable &output)
static uint64_t write(IWritable &output, const Header &header)
static uint64_t write(IWritable &output, const Footer &footer, bool crcEnabled)
static uint64_t write(IWritable &output, const Schema &schema)
static uint64_t write(IWritable &output, const Channel &channel)
static uint64_t write(IWritable &output, const Message &message)
static uint64_t write(IWritable &output, const Attachment &attachment)
static uint64_t write(IWritable &output, const Metadata &metadata)
static uint64_t write(IWritable &output, const Chunk &chunk)
static uint64_t write(IWritable &output, const MessageIndex &index)
static uint64_t write(IWritable &output, const ChunkIndex &index)
static uint64_t write(IWritable &output, const AttachmentIndex &index)
static uint64_t write(IWritable &output, const MetadataIndex &index)
static uint64_t write(IWritable &output, const Statistics &stats)
static uint64_t write(IWritable &output, const SummaryOffset &summaryOffset)
static uint64_t write(IWritable &output, const DataEnd &dataEnd)
static uint64_t write(IWritable &output, const Record &record)
static void write(IWritable &output, const std::string_view str)
static void write(IWritable &output, const ByteArray bytes)
static void write(IWritable &output, OpCode value)
static void write(IWritable &output, uint16_t value)
static void write(IWritable &output, uint32_t value)
static void write(IWritable &output, uint64_t value)
static void write(IWritable &output, const std::byte *data, uint64_t size)
static void write(IWritable &output, const KeyValueMap &map, uint32_t size = 0)