A connection policy object describes how a given connection should behave. More...

#include <rtt/ConnPolicy.hpp>

Public Member Functions
	ConnPolicy (int type=DATA, int lock_policy=LOCK_FREE)
	The default policy is data driven, lock-free and local.
Static Public Member Functions
static ConnPolicy	buffer (int size, int lock_policy=LOCK_FREE, bool init_connection=false, bool pull=false)
	Create a policy for a (lock-free) buffer connection of a given size.
static ConnPolicy	data (int lock_policy=LOCK_FREE, bool init_connection=true, bool pull=false)
	Create a policy for a (lock-free) shared data connection of a given size.
Public Attributes
int	type
	This is the type for the data holding element in the connection.
bool	init
	If true, one should initialize the connection's value with the last value written on the writer port.
int	lock_policy
	This is the locking policy on the connection.
bool	pull
	If true, then the sink will have to pull data.
int	size
	If the connection is a buffered connection, the size of the buffer.
int	transport
	The prefered transport used.
int	data_size
	Suggest the payload size of the data sent over this channel.
std::string	name_id
	The name of this connection.
Static Public Attributes
static const int	DATA = 0
static const int	BUFFER = 1
static const int	UNSYNC = 0
static const int	LOCKED = 1
static const int	LOCK_FREE = 2

Detailed Description

A connection policy object describes how a given connection should behave.

Various parameters are available:

the connection type: DATA or BUFFER. On a data connection, the reader will have only access to the last written value. On a buffered connection, a size number of elements can be stored until the reader reads them.
the locking policy: LOCKED, LOCK_FREE or UNSYNC. This defines how locking is done in the connection. For now, only three policies are available. LOCKED uses mutexes, LOCK_FREE uses a lock free method and UNSYNC means there's no synchronisation at all (not thread safe). The latter should be used only when there is no contention (simultaneous write-read).
if, upon connection, the last value that has been written on the writer end should be written on the connection as well to initialize it. This flag has an effect only if the writer has keepsLastWrittenValue() set to true (see OutputPortInterface::keepLastWrittenValue()).
if the data is pushed or pulled on the connection. This has an effect only on multi-process communication. In the pushed case (the default), new data is actively pushed to the reader's process. In the pulled case, data must be requested by the reader.
the transport type. Can be used to force a certain kind of transports. The number is a RTT transport id. When the transport type is zero, local in-process communication is used, unless one of the ports is remote. If the transport type deviates from the default remote transport of one of the ports, an out-of-band transport is setup using that type.
the data size. Some protocols require a hint on big the data will be, especially if the data is dynamically sized (like std::vector<double>). If you leave this empty (recommended), the protocol will try to guess it. The unit of data size is protocol dependent.
the name of the connection. Can be used to coordinate out of band transport such that they can find each other by name. In practice, the name contains a port number or file descriptor to be opened. You only need to provide a name_id if you're using out-of-band transports without supervisor, for example, when using MQueues without Corba.

Definition at line 90 of file ConnPolicy.hpp.

Constructor & Destructor Documentation

RTT::ConnPolicy::ConnPolicy	(	int	type = `DATA`,
		int	lock_policy = `LOCK_FREE`
	)		`[explicit]`

The default policy is data driven, lock-free and local.

It is unsafe to rely on these defaults. It is prefered to use the above buffer() and data() functions.

Parameters:

type
lock_policy

Returns:

Definition at line 71 of file ConnPolicy.cpp.

Member Function Documentation

ConnPolicy RTT::ConnPolicy::buffer	(	int	size,
		int	lock_policy = `LOCK_FREE`,
		bool	init_connection = `false`,
		bool	pull = `false`
	)		`[static]`

Create a policy for a (lock-free) buffer connection of a given size.

Parameters:

size	The size of the buffer in this connection
lock_policy	The locking policy
init_connection	If an initial sample should be pushed into the buffer upon creation.
pull	In inter-process cases, should the consumer pull itself ?

Returns:: the specified policy.

Definition at line 54 of file ConnPolicy.cpp.

References init, pull, and size.

Referenced by RTT::base::OutputPortInterface::createBufferConnection().

ConnPolicy RTT::ConnPolicy::data	(	int	lock_policy = `LOCK_FREE`,
		bool	init_connection = `true`,
		bool	pull = `false`
	)		`[static]`

Create a policy for a (lock-free) shared data connection of a given size.

Parameters:

lock_policy	The locking policy
init_connection	If the data object should be initialised with the last value of the OutputPort upon creation.
pull	In inter-process cases, should the consumer pull data itself ?

Returns:: the specified policy.

Definition at line 63 of file ConnPolicy.cpp.

References init, and pull.

Referenced by RTT::base::OutputPortInterface::createDataConnection().

Member Data Documentation

int RTT::ConnPolicy::data_size [mutable]

Suggest the payload size of the data sent over this channel.

Connections can use this value to optimize transmission or prepare the communication channel for real-time communication. This value might be overruled by the transport protocol if it can make a better guess. The interpretation of data_size is transport specific. It may be bytes, it may be something else. Leave this value set to zero, unless the transport documents otherwise.

Definition at line 160 of file ConnPolicy.hpp.

Referenced by RTT::internal::ConnFactory::createAndCheckStream().

bool RTT::ConnPolicy::init

If true, one should initialize the connection's value with the last value written on the writer port.

This is only possible if the writer port has the keepsLastWrittenValue() flag set (i.e. if it remembers what was the last written value).

Definition at line 136 of file ConnPolicy.hpp.

Referenced by buffer(), and data().

std::string RTT::ConnPolicy::name_id [mutable]

The name of this connection.

May be used by transports to define a 'topic' or lookup name to connect two data streams. If you leave this empty (recommended), the protocol will choose an appropriate name itself. Only specify a name to work around name clashes or if the transport protocol documents to do so.

Definition at line 168 of file ConnPolicy.hpp.

Referenced by RTT::corba::RemoteInputPort::buildRemoteChannelOutput(), RTT::internal::ConnFactory::createAndCheckStream(), RTT::corba::RemoteOutputPort::createConnection(), RTT::internal::ConnFactory::createOutOfBandConnection(), and RTT::internal::ConnFactory::createStream().

bool RTT::ConnPolicy::pull

If true, then the sink will have to pull data.

Otherwise, it is pushed from the source. In both cases, the reader side is notified that new data is available by base::ChannelElementBase::signal()

Definition at line 143 of file ConnPolicy.hpp.

Referenced by buffer(), RTT::corba::RemoteInputPort::buildRemoteChannelOutput(), and data().

int RTT::ConnPolicy::transport

The prefered transport used.

0 is local (in process), a higher number is used for inter-process or networked communication transports.

Definition at line 150 of file ConnPolicy.hpp.

Referenced by RTT::corba::RemoteInputPort::buildRemoteChannelOutput(), RTT::internal::ConnFactory::createAndCheckStream(), and RTT::internal::ConnFactory::createConnection().