This DataObject is a Lock-Free implementation, such that reads and writes can happen concurrently without priority inversions. More...

#include <rtt/base/DataObjectLockFree.hpp>

Inheritance diagram for RTT::base::DataObjectLockFree< T >:

Public Types
typedef DataObjectInterface< T >::value_t	value_t

typedef DataObjectInterface< T >::reference_t	reference_t

typedef DataObjectInterface< T >::param_t	param_t

typedef DataObjectBase::Options	Options

typedef boost::shared_ptr< DataObjectInterface< T > >	shared_ptr
	Used for shared_ptr management. More...

Public Member Functions
	DataObjectLockFree (const Options &options=Options())
	Construct an uninitialized DataObjectLockFree. More...

	DataObjectLockFree (param_t initial_value, const Options &options=Options())
	Construct a DataObjectLockFree. More...

	~DataObjectLockFree ()

virtual value_t	Get () const
	Get a copy of the data. More...

virtual FlowStatus	Get (reference_t pull, bool copy_old_data, bool copy_sample) const
	Get a copy of the Data (non allocating). More...

virtual FlowStatus	Get (reference_t pull, bool copy_old_data=true) const
	Get a copy of the Data (non allocating). More...

virtual bool	Set (param_t push)
	Set the data to a certain value (non blocking). More...

virtual bool	data_sample (param_t sample, bool reset=true)
	Provides a data sample to initialize this data object. More...

virtual value_t	data_sample () const
	Reads back a data sample. More...

virtual void	clear ()
	Clears any data stored by this data object, so that any subsequent Get() without a new Set() will return NoData. More...

Public Attributes
const unsigned int	MAX_THREADS
	The maximum number of threads. More...

Detailed Description

template<class T>
class RTT::base::DataObjectLockFree< T >

This DataObject is a Lock-Free implementation, such that reads and writes can happen concurrently without priority inversions.

When there are more writes than reads, the last write will be returned. The internal buffer can get full if too many concurrent reads are taking to long. In that case, each new read will read the element the previous read returned.

* The following Truth table applies when a Low Priority thread is
* preempted by a High Priority thread :
*
*   L\H | Set | Get |
*   Set | Ok  | Ok  |
*   Get | Ok  | Ok  |
*
* legend : L : Low Priority thread
*          H : High Priority thread
*          Blk: Blocks High Priority thread (bad!)
*          internal::NA : Not allowed !
*

Further, multiple reads may occur before, during and after a write operation simultaneously. The buffer needs readers+2*writers elements to be guaranteed non blocking.

Definition at line 80 of file DataObjectLockFree.hpp.

Member Typedef Documentation

template<class T >

typedef DataObjectBase::Options RTT::base::DataObjectLockFree< T >::Options

Definition at line 88 of file DataObjectLockFree.hpp.

template<class T >

typedef DataObjectInterface<T>::param_t RTT::base::DataObjectLockFree< T >::param_t

Definition at line 86 of file DataObjectLockFree.hpp.

template<class T >

typedef DataObjectInterface<T>::reference_t RTT::base::DataObjectLockFree< T >::reference_t

Definition at line 85 of file DataObjectLockFree.hpp.

template<class T>

typedef boost::shared_ptr<DataObjectInterface<T> > RTT::base::DataObjectInterface< T >::shared_ptr

inherited

Used for shared_ptr management.

Definition at line 68 of file DataObjectInterface.hpp.

template<class T >

typedef DataObjectInterface<T>::value_t RTT::base::DataObjectLockFree< T >::value_t

Definition at line 84 of file DataObjectLockFree.hpp.

Constructor & Destructor Documentation

template<class T >

RTT::base::DataObjectLockFree< T >::DataObjectLockFree ( const Options & options = Options() )

inline

Construct an uninitialized DataObjectLockFree.

Parameters

max_threads The maximum number of threads accessing this DataObject.

Definition at line 141 of file DataObjectLockFree.hpp.

template<class T >

RTT::base::DataObjectLockFree< T >::DataObjectLockFree	(	param_t	initial_value,
		const Options &	options = `Options()`
	)

inline

Construct a DataObjectLockFree.

Parameters

initial_value	The initial value of this DataObject.
max_threads	The maximum number of threads accessing this DataObject.

Note: You have to specify the maximum number of threads explicitly

Definition at line 158 of file DataObjectLockFree.hpp.

References RTT::base::DataObjectLockFree< T >::data_sample().

template<class T >

RTT::base::DataObjectLockFree< T >::~DataObjectLockFree ( )

inline

Definition at line 170 of file DataObjectLockFree.hpp.

Member Function Documentation

template<class T >

virtual void RTT::base::DataObjectLockFree< T >::clear ( )

inlinevirtual

Clears any data stored by this data object, so that any subsequent Get() without a new Set() will return NoData.

Implements RTT::base::DataObjectInterface< T >.

Definition at line 337 of file DataObjectLockFree.hpp.

References RTT::os::CAS(), RTT::NoData, oro_atomic_dec(), and oro_atomic_inc().

template<class T >

virtual bool RTT::base::DataObjectLockFree< T >::data_sample	(	param_t	sample,
		bool	reset = `true`
	)

inlinevirtual

Provides a data sample to initialize this data object.

As such enough storage space can be allocated before the actual writing begins.

Parameters

sample	the data sample
reset	enforce reinitialization even if this operation clears the stored data.

Returns: true if the data object was successfully (re)initialized.

Implements RTT::base::DataObjectInterface< T >.

Definition at line 310 of file DataObjectLockFree.hpp.

References RTT::NoData.

template<class T >

virtual value_t RTT::base::DataObjectLockFree< T >::data_sample ( ) const

inlinevirtual

Reads back a data sample.

Implements RTT::base::DataObjectInterface< T >.

Definition at line 329 of file DataObjectLockFree.hpp.

References RTT::base::DataObjectLockFree< T >::Get().

Referenced by RTT::base::DataObjectLockFree< T >::DataObjectLockFree(), and RTT::base::DataObjectLockFree< T >::Set().

template<class T >

virtual value_t RTT::base::DataObjectLockFree< T >::Get ( ) const

inlinevirtual

Get a copy of the data.

This method will allocate memory twice if data is not a value type. Use Get(reference_t) for the non-allocating version.

Returns: A copy of the data.

Implements RTT::base::DataObjectInterface< T >.

Definition at line 181 of file DataObjectLockFree.hpp.

Referenced by RTT::base::DataObjectLockFree< T >::data_sample(), and RTT::base::DataObjectLockFree< T >::Get().

template<class T >

virtual FlowStatus RTT::base::DataObjectLockFree< T >::Get	(	reference_t	pull,
		bool	copy_old_data,
		bool	copy_sample
	)		const

inlinevirtual

Get a copy of the Data (non allocating).

If pull has reserved enough memory to store the copy, no memory will be allocated.

Parameters

pull	A copy of the data.
copy_old_data	If true, also copy the data if the data object has not been updated since the last call.
copy_sample	If true, copy the data unconditionally.

Definition at line 197 of file DataObjectLockFree.hpp.

References RTT::os::CAS(), RTT::NewData, RTT::NoData, RTT::OldData, oro_atomic_dec(), and oro_atomic_inc().

template<class T >