Detailed Description

A LCM interface for logging LCM messages to a file or playing back from a existing log.

Note the user is responsible for offsetting the clock used to generate the log and the clock used for playback. For example, if the log is generated by some external logger (the lcm-logger binary), which uses the unix epoch time clock to record message arrival time, the user needs to offset those timestamps properly to match and the clock used for playback.

#include <drake/lcm/drake_lcm_log.h>

Public Member Functions
	DrakeLcmLog (const std::string &file_name, bool is_write, bool overwrite_publish_time_with_system_clock=false)
	Constructs a DrakeLcmLog. More...

	~DrakeLcmLog () override

void	Publish (const std::string &channel, const void *data, int data_size, std::optional< double > time_sec) override
	Writes an entry occurred at `timestamp` with content `data` to the log file. More...

std::shared_ptr< DrakeSubscriptionInterface >	Subscribe (const std::string &channel, HandlerFunction handler) override
	Subscribes `handler` to `channel`. More...

std::shared_ptr< DrakeSubscriptionInterface >	SubscribeMultichannel (std::string_view regex, MultichannelHandlerFunction) override
	This function is not yet supported for LCM logs, and will always throw. More...

std::shared_ptr< DrakeSubscriptionInterface >	SubscribeAllChannels (MultichannelHandlerFunction) override
	Subscribe to all channels; this is useful for logging and redirecting LCM traffic without regard to its content. More...

int	HandleSubscriptions (int) override
	This is a no-op for Read mode, and an exception in Write mode. More...

double	GetNextMessageTime () const
	Returns the time in seconds for the next logged message's occurrence time or infinity if there are no more messages in the current log. More...

void	DispatchMessageAndAdvanceLog (double current_time)
	Let `MSG` be the next message event in the log, if `current_time` matches `MSG`'s timestamp, for every DrakeLcmMessageHandlerInterface `sub` that's subscribed to `MSG`'s channel, invoke `sub`'s HandleMessage method. More...

bool	is_write () const
	Returns true if this instance is constructed in write-only mode. More...

double	timestamp_to_second (uint64_t timestamp) const
	Converts `timestamp` (in microseconds) to time (in seconds) relative to the starting time passed to the constructor. More...

uint64_t	second_to_timestamp (double sec) const
	Converts time (in seconds) relative to the starting time passed to the constructor to a timestamp in microseconds. More...

std::string	get_lcm_url () const override
	Returns a URL describing the transport of this LCM interface. More...

Does not allow copy, move, or assignment
	DrakeLcmLog (const DrakeLcmLog &)=delete

DrakeLcmLog &	operator= (const DrakeLcmLog &)=delete

	DrakeLcmLog (DrakeLcmLog &&)=delete

DrakeLcmLog &	operator= (DrakeLcmLog &&)=delete

Public Member Functions inherited from DrakeLcmInterface
virtual	~DrakeLcmInterface ()

	DrakeLcmInterface (const DrakeLcmInterface &)=delete

DrakeLcmInterface &	operator= (const DrakeLcmInterface &)=delete

	DrakeLcmInterface (DrakeLcmInterface &&)=delete

DrakeLcmInterface &	operator= (DrakeLcmInterface &&)=delete

Static Public Member Functions
static bool	available ()
	Returns true if the LCM runtime library is enabled in this build of Drake. More...

Additional Inherited Members
Public Types inherited from DrakeLcmInterface
using	HandlerFunction = std::function< void(const void *, int)>
	A callback used by DrakeLcmInterface::Subscribe(), with arguments: More...

using	MultichannelHandlerFunction = std::function< void(std::string_view, const void *, int)>
	A callback used by DrakeLcmInterface::SubscribeMultipleChannels (which therefore needs the receiving channel passed in). More...

Protected Member Functions inherited from DrakeLcmInterface
	DrakeLcmInterface ()

Constructor & Destructor Documentation

◆ DrakeLcmLog() [1/3]

DrakeLcmLog ( const DrakeLcmLog & )

delete

◆ DrakeLcmLog() [2/3]

DrakeLcmLog ( DrakeLcmLog && )

delete

◆ DrakeLcmLog() [3/3]

DrakeLcmLog	(	const std::string &	file_name,
		bool	is_write,
		bool	overwrite_publish_time_with_system_clock = `false`
	)

Constructs a DrakeLcmLog.

Parameters

file_name	Log's file name for reading or writing.
is_write	If false, this instance reads from the Lcm log identified by `file_name`. If true, this instance writes to the Lcm log whose name is given by `file_name`.
overwrite_publish_time_with_system_clock	This parameter only affects the Publish method in write-only mode. If true, override the `second` parameter passed to Publish method, and use host system's clock to generate the timestamp for the logged message. This is used to mimic lcm-logger's behavior. It also implicitly records how fast the messages are generated in real time.

Exceptions

std::exception if unable to open file.

◆ ~DrakeLcmLog()

~DrakeLcmLog ( )

override

Member Function Documentation

◆ available()

static bool available ( )

static

Returns true if the LCM runtime library is enabled in this build of Drake.

When false, functions that require the runtime (which at the moment is all functions, including the constructor) will throw an error. See //tools/flags:with_lcm_runtime.

◆ DispatchMessageAndAdvanceLog()

void DispatchMessageAndAdvanceLog ( double current_time )

Let MSG be the next message event in the log, if current_time matches MSG's timestamp, for every DrakeLcmMessageHandlerInterface sub that's subscribed to MSG's channel, invoke sub's HandleMessage method.

Then, this function advances the log by exactly one message. This function does nothing if MSG is null (end of log) or current_time does not match MSG's timestamp.

Exceptions

std::exception if this instance is not constructed in read-only mode.

◆ get_lcm_url()

std::string get_lcm_url ( ) const

overridevirtual

Returns a URL describing the transport of this LCM interface.

When the URL refers to a transport offered by LCM itself (e.g., memq or udpm), then this function must return the conventional URL spelling. If the implementation of DrakeLcmInterface is using a non-standard back end, the result implementation-defined.

In either case, it is always formatted using URI syntax rules per the RFC(s).

Implements DrakeLcmInterface.

◆ GetNextMessageTime()

double GetNextMessageTime ( ) const

Returns the time in seconds for the next logged message's occurrence time or infinity if there are no more messages in the current log.

Exceptions

std::exception if this instance is not constructed in read-only mode.

◆ HandleSubscriptions()

int HandleSubscriptions ( int )

overridevirtual

This is a no-op for Read mode, and an exception in Write mode.

Implements DrakeLcmInterface.

◆ is_write()

bool is_write ( ) const

Returns true if this instance is constructed in write-only mode.

◆ operator=() [1/2]

DrakeLcmLog& operator= ( DrakeLcmLog && )

delete

◆ operator=() [2/2]

DrakeLcmLog& operator= ( const DrakeLcmLog & )

delete

◆ Publish()

void Publish	(	const std::string &	channel,
		const void *	data,
		int	data_size,
		std::optional< double >	time_sec
	)

overridevirtual

Writes an entry occurred at timestamp with content data to the log file.

The current implementation blocks until writing is done.

Parameters

channel	Channel name.
data	Pointer to raw bytes.
data_size	Number of bytes in `data`.
time_sec	Time in seconds when the message is published. Since messages are save to the log file in the order of Publish calls, this function should only be called with non-decreasing `second`. Note that this parameter can be overwritten by the host system's clock if `overwrite_publish_time_with_system_clock` is true at construction time.

Exceptions

std::exception if this instance is not constructed in write-only mode.

Implements DrakeLcmInterface.

◆ second_to_timestamp()

uint64_t second_to_timestamp ( double sec ) const

Converts time (in seconds) relative to the starting time passed to the constructor to a timestamp in microseconds.

◆ Subscribe()

std::shared_ptr<DrakeSubscriptionInterface> Subscribe	(	const std::string &	channel,
		HandlerFunction	handler
	)

overridevirtual

Subscribes handler to channel.

Multiple handlers can subscribe to the same channel.

Exceptions

std::exception if this instance is not constructed in read-only mode.

Returns: nullptr because this implementation does not support unsubscribe.

Implements DrakeLcmInterface.

◆ SubscribeAllChannels()

std::shared_ptr<DrakeSubscriptionInterface> SubscribeAllChannels ( MultichannelHandlerFunction )

overridevirtual

Subscribe to all channels; this is useful for logging and redirecting LCM traffic without regard to its content.

Exceptions

std::exception if this instance is not constructed in read-only mode.

Returns: nullptr because this implementation does not support unsubscribe.

Implements DrakeLcmInterface.

◆ SubscribeMultichannel()

std::shared_ptr<DrakeSubscriptionInterface> SubscribeMultichannel	(	std::string_view	regex,
		MultichannelHandlerFunction
	)

overridevirtual

This function is not yet supported for LCM logs, and will always throw.

Implements DrakeLcmInterface.

◆ timestamp_to_second()

double timestamp_to_second ( uint64_t timestamp ) const

Converts timestamp (in microseconds) to time (in seconds) relative to the starting time passed to the constructor.

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

drake/lcm/drake_lcm_log.h

Detailed Description

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ DrakeLcmLog() [1/3]

◆ DrakeLcmLog() [2/3]

◆ DrakeLcmLog() [3/3]

◆ ~DrakeLcmLog()

Member Function Documentation

◆ available()

◆ DispatchMessageAndAdvanceLog()

◆ get_lcm_url()

◆ GetNextMessageTime()

◆ HandleSubscriptions()

◆ is_write()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ Publish()

◆ second_to_timestamp()

◆ Subscribe()

◆ SubscribeAllChannels()

◆ SubscribeMultichannel()

◆ timestamp_to_second()