McapBag Class Reference

MCAP bag interface, providing most of rosbag.Bag interface. More...

Inheritance diagram for McapBag:

Public Member Functions
	__init__ (self, f, mode="r", **__)
	Opens file and populates metadata.
	__contains__ (self, key)
	Returns whether bag contains given topic.
	__next__ (self)
	Retrieves next message from bag as (topic, message, timestamp).
	autodetect (cls, f)
	Returns whether file is recognizable as MCAP format.
	close (self)
	Closes the bag file.
	get_end_time (self)
	Returns the end time of the bag, as UNIX timestamp.
	get_message_class (self, typename, typehash=None)
	Returns ROS message class for typename, or None if unknown type.
	get_message_count (self, topic_filters=None)
	Returns the number of messages in the bag.
	get_message_definition (self, msg_or_type)
	Returns ROS message type definition full text from bag, including subtype definitions.
	get_message_type_hash (self, msg_or_type)
	Returns ROS message type MD5 hash.
	get_qoses (self, topic, typename)
	Returns topic Quality-of-Service profiles as a list of dicts, or None if not available.
	get_start_time (self)
	Returns the start time of the bag, as UNIX timestamp.
	get_topic_info (self, *_, **__)
	Returns topic and message type metainfo as {(topic, typename, typehash): count}.
	get_type_and_topic_info (self, topic_filters=None)
	Returns thorough metainfo on topic and message types.
	open (self)
	Opens the bag file if not already open.
	read_messages (self, topics=None, start_time=None, end_time=None, raw=False)
	Yields messages from the bag, optionally filtered by topic and timestamp.
	write (self, topic, msg, t=None, raw=False, **__)
	Writes out message to MCAP file.
Public Member Functions inherited from BaseBag
	__bool__ (self)
	__contains__ (self, key)
	Returns whether bag contains given topic.
	__copy__ (self)
	__deepcopy__ (self, memo=None)
	__enter__ (self)
	Context manager entry, opens bag if not open.
	__exit__ (self, exc_type, exc_value, traceback)
	Context manager exit, closes bag.
	__getitem__ (self, key)
	Returns an iterator yielding messages from the bag in given topic, supporting len().
	__iter__ (self)
	Iterates over all messages in the bag.
	__len__ (self)
	Returns the number of messages in the bag.
	__next__ (self)
	Retrieves next message from bag as (topic, message, timestamp).
	__nonzero__ (self)
	__str__ (self)
	Returns informative text for bag, with a full overview of topics and types.
	close (self)
	Closes the bag file.
	flush (self)
	Ensures all changes are written to bag file.
	get_end_time (self)
	Returns the end time of the bag, as UNIX timestamp, or None if bag empty.
	get_message_class (self, typename, typehash=None)
	Returns ROS message type class, or None if unknown message type for bag.
	get_message_count (self, topic_filters=None)
	Returns the number of messages in the bag.
	get_message_definition (self, msg_or_type)
	Returns ROS message type definition full text, including subtype definitions.
	get_message_type_hash (self, msg_or_type)
	Returns ROS message type MD5 hash, or None if unknown message type for bag.
	get_qoses (self, topic, typename)
	Returns topic Quality-of-Service profiles as a list of dicts, or None if not available.
	get_start_time (self)
	Returns the start time of the bag, as UNIX timestamp, or None if bag empty.
	get_topic_info (self, counts=True)
	Returns topic and message type metainfo as {(topic, typename, typehash): count}.
	get_type_and_topic_info (self, topic_filters=None)
	Returns thorough metainfo on topic and message types.
	open (self)
	Opens the bag file if not already open.
	read_messages (self, topics=None, start_time=None, end_time=None, raw=False, **__)
	Yields messages from the bag, optionally filtered by topic and timestamp.
	write (self, topic, msg, t=None, raw=False, **kwargs)
	Writes a message to the bag.

Public Attributes
	get_fields_and_field_types
	SLOT_TYPES

Static Public Attributes
str	MCAP_MAGIC = b"\x89MCAP\x30\r\n"
	MCAP file header magic start bytes.
tuple	MODES = ("r", "w")
	Supported opening modes.
Static Public Attributes inherited from BaseBag
	BagMessage = collections.namedtuple("BagMessage", "topic message timestamp")
	Returned from read_messages() as (topic name, ROS message, ROS timestamp object).
tuple	MODES = ("r", "w", "a")
	Supported opening modes, overridden in subclasses.
	next
bool	STREAMABLE = True
	Whether bag supports reading or writing stream objects, overridden in subclasses.
	TopicTuple
	Returned from get_type_and_topic_info() as (typename, message count, connection count, median frequency).
	TypesAndTopicsTuple = collections.namedtuple("TypesAndTopicsTuple", ["msg_types", "topics"])
	Returned from get_type_and_topic_info() as ({typename: typehash}, {topic name: TopicTuple}).

Properties
	closed = property
	Returns whether file is closed.
	filename = property
	Returns bag file path.
	mode = property
	Returns file open mode.
	size = property
	Returns current file size.
	topics = property
	Returns the list of topics in bag, in alphabetic order.
Properties inherited from BaseBag
	closed = property
	Returns whether file is closed.
	filename = property
	Returns bag file path.
	mode = property
	Returns file open mode.
	size = property
	Returns current file size in bytes.
	stop_on_error = property
	Whether raising read error on unknown message type (ROS2 SQLite .db3 specific).
	topics = property
	Returns the list of topics in bag, in alphabetic order.

Detailed Description

MCAP bag interface, providing most of rosbag.Bag interface.

Bag cannot be appended to, and cannot be read and written at the same time (MCAP API limitation).

Definition at line 47 of file mcap.py.

Constructor & Destructor Documentation

__init__()

__init__	(		self,
			f,
			mode = "r",
		**	__
	)

Opens file and populates metadata.

Parameters

f	bag file path, or a stream object
mode	return reader if "r" or writer if "w"

Definition at line 61 of file mcap.py.

Member Function Documentation

__contains__()

__contains__	(		self,
			key
	)

Returns whether bag contains given topic.

Reimplemented from BaseBag.

Definition at line 363 of file mcap.py.

__next__()

__next__

(

self

)

Retrieves next message from bag as (topic, message, timestamp).

Reimplemented from BaseBag.

Definition at line 368 of file mcap.py.

autodetect()

autodetect	(		cls,
			f
	)

Returns whether file is recognizable as MCAP format.

Definition at line 548 of file mcap.py.

close()

close

(

self

)

Closes the bag file.

Reimplemented from BaseBag.

Definition at line 311 of file mcap.py.

get_end_time()

get_end_time

(

self

)

Returns the end time of the bag, as UNIX timestamp.

Reimplemented from BaseBag.

Definition at line 121 of file mcap.py.

get_message_class()

get_message_class	(		self,
			typename,
			typehash = None
	)

Returns ROS message class for typename, or None if unknown type.

Parameters

typehash

message type definition hash, if any

Reimplemented from BaseBag.

Definition at line 131 of file mcap.py.

get_message_count()

get_message_count	(		self,
			topic_filters = None
	)

Returns the number of messages in the bag.

Parameters

topic_filters

list of topics or a single topic to filter by, if any

Reimplemented from BaseBag.

Definition at line 108 of file mcap.py.

get_message_definition()

get_message_definition	(		self,
			msg_or_type
	)

Returns ROS message type definition full text from bag, including subtype definitions.

Reimplemented from BaseBag.

Definition at line 150 of file mcap.py.

get_message_type_hash()

get_message_type_hash	(		self,
			msg_or_type
	)

Returns ROS message type MD5 hash.

Reimplemented from BaseBag.

Definition at line 159 of file mcap.py.

get_qoses()

get_qoses	(		self,
			topic,
			typename
	)

Returns topic Quality-of-Service profiles as a list of dicts, or None if not available.

Reimplemented from BaseBag.

Definition at line 166 of file mcap.py.

get_start_time()

get_start_time

(

self

)

Returns the start time of the bag, as UNIX timestamp.

Reimplemented from BaseBag.

Definition at line 116 of file mcap.py.

get_topic_info()

get_topic_info	(		self,
		*	_,
		**	__
	)

Returns topic and message type metainfo as {(topic, typename, typehash): count}.

Reimplemented from BaseBag.

Definition at line 171 of file mcap.py.

get_type_and_topic_info()

get_type_and_topic_info	(		self,
			topic_filters = None
	)

Returns thorough metainfo on topic and message types.

Parameters

topic_filters

list of topics or a single topic to filter returned topics-dict by, if any

Returns

TypesAndTopicsTuple(msg_types, topics) namedtuple, msg_types as dict of {typename: typehash}, topics as a dict of {topic: TopicTuple() namedtuple}.

Reimplemented from BaseBag.

Definition at line 184 of file mcap.py.

open()

open

(

self

)

Opens the bag file if not already open.

Reimplemented from BaseBag.

Definition at line 295 of file mcap.py.

read_messages()

read_messages	(		self,
			topics = None,
			start_time = None,
			end_time = None,
			raw = False
	)

Yields messages from the bag, optionally filtered by topic and timestamp.

Parameters

topics	list of topics or a single topic to filter by, if at all
start_time	earliest timestamp of message to return, as ROS time or convertible (int/float/duration/datetime/decimal)
end_time	latest timestamp of message to return, as ROS time or convertible (int/float/duration/datetime/decimal)
raw	if true, then returned messages are tuples of (typename, bytes, typehash, typeclass)

Returns

BagMessage namedtuples of (topic, message, timestamp as rospy/rclpy.Time)

Reimplemented from BaseBag.

Definition at line 233 of file mcap.py.

write()

write	(		self,
			topic,
			msg,
			t = None,
			raw = False,
		**	__
	)

Writes out message to MCAP file.

Parameters

topic	name of topic
msg	ROS1 message
t	message timestamp if not using current ROS time, as ROS time type or convertible (int/float/duration/datetime/decimal)
raw	if true, msg is in raw format, (typename, bytes, typehash, typeclass)

Reimplemented from BaseBag.

Definition at line 260 of file mcap.py.

Member Data Documentation

get_fields_and_field_types

get_fields_and_field_types

Definition at line 450 of file mcap.py.

MCAP_MAGIC

str MCAP_MAGIC = b"\x89MCAP\x30\r\n"

static

MCAP file header magic start bytes.

Definition at line 53 of file mcap.py.

MODES

tuple MODES = ("r", "w")

static

Supported opening modes.

Definition at line 50 of file mcap.py.

SLOT_TYPES

SLOT_TYPES

Definition at line 448 of file mcap.py.

Property Documentation

closed

closed = property

static

Returns whether file is closed.

Definition at line 321 of file mcap.py.

filename

filename = property

static

Returns bag file path.

Definition at line 337 of file mcap.py.

mode

mode = property

static

Returns file open mode.

Definition at line 357 of file mcap.py.

size

size = property

static

Returns current file size.

Definition at line 345 of file mcap.py.

topics

topics = property

static

Returns the list of topics in bag, in alphabetic order.

Definition at line 329 of file mcap.py.

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The documentation for this class was generated from the following file:

• grepros/plugins/mcap.py