Class Reader

Defined in File reader.hpp

Class Documentation

class Reader

The Reader allows opening and reading messages of a bag.

Public Functions

explicit Reader(std::unique_ptr<reader_interfaces::BaseReaderInterface> reader_impl = std::make_unique<readers::SequentialReader>())

~Reader()

void open(const std::string &uri)

Opens an existing bagfile and prepare it for reading messages. The bagfile must exist. This must be called before any other function is used.

See also

open, which let’s you specify more storage and converter options.

Note

This will open URI with the default storage options

using default storage backend
using no converter options, storing messages with the incoming serialization format

Parameters:: storage_uri – URI of the storage to open.

void open(const rosbag2_storage::StorageOptions &storage_options, const ConverterOptions &converter_options = ConverterOptions())

Throws if file could not be opened. This must be called before any other function is used. The rosbag is automatically closed on destruction.

If the output_serialization_format within the converter_options is not the same as the format of the underlying stored data, a converter will be used to automatically convert the data to the specified output format. Throws if the converter plugin does not exist.

Parameters:

storage_options – Options to configure the storage
converter_options – Options for specifying the output data format

void close(): Closing the reader instance.

bool has_next()

Ask whether the underlying bagfile contains at least one more message.

Throws:: runtime_error – if the Reader is not open.
Returns:: true if storage contains at least one more message

std::shared_ptr<rosbag2_storage::SerializedBagMessage> read_next()

Read next message from storage. Will throw if no more messages are available. The message will be serialized in the format given to open.

Expected usage: if (writer.has_next()) message = writer.read_next();

Throws:: runtime_error – if the Reader is not open.
Returns:: next message in serialized form

template<class MessageT> inline MessageT read_next()

Read next message from storage. Will throw if no more messages are available. The message will be serialized in the format given to open.

Expected usage: if (writer.has_next()) message = writer.read_next();

Throws:: runtime_error – if the Reader is not open.
Returns:: next message in non-serialized form

const rosbag2_storage::BagMetadata &get_metadata() const

Ask bagfile for its full metadata.

Throws:: runtime_error – if the Reader is not open.
Returns:: a const reference to a BagMetadata owned by the Reader

std::vector<rosbag2_storage::TopicMetadata> get_all_topics_and_types() const

Ask bagfile for all topics (including their type identifier) that were recorded.

Throws:: runtime_error – if the Reader is not open.
Returns:: vector of topics with topic name and type as std::string

void set_filter(const rosbag2_storage::StorageFilter &storage_filter)

Set filters to adhere to during reading.

Parameters:: storage_filter – Filter to apply to reading
Throws:: runtime_error – if the Reader is not open.

void reset_filter(): Reset all filters for reading.

void seek(const rcutils_time_point_value_t &timestamp): Skip to a specific timestamp for reading.

inline reader_interfaces::BaseReaderInterface &get_implementation_handle() const

void add_event_callbacks(bag_events::ReaderEventCallbacks &callbacks)

Add callbacks for events that may occur during bag reading.

Parameters:: callbacks – the structure containing the callback to add for each event.