dds::sub::status::InstanceState Class Reference

Indicates if the samples are from a live dds::pub::DataWriter or not. More...

#include <dds/sub/status/DataState.hpp>

Inherits std::bitset< OMG_DDS_STATE_BIT_COUNT >.

Public Types
typedef std::bitset< OMG_DDS_STATE_BIT_COUNT >	MaskType
	An std::bitset of InstanceStates. More...

Public Member Functions
	InstanceState (const MaskType &other)
	Create an InstanceState from MaskType. More...

Static Public Member Functions
static const InstanceState	alive ()
	Creates an alive InstanceState object. More...
static const InstanceState	not_alive_disposed ()
	Creates a not_alive_disposed InstanceState object. More...
static const InstanceState	not_alive_no_writers ()
	Creates a not_alive_no_writers InstanceState object. More...
static const InstanceState	not_alive_mask ()
	Creates an InstanceState object representing any not alive state. More...
static const InstanceState	any ()
	Creates an InstanceState object representing any instance state. More...

Related Functions
(Note that these are not member functions.)
std::ostream &	operator<< (std::ostream &os, const InstanceState &s)
	Prints an instance state as a readable string. More...

Detailed Description

Indicates if the samples are from a live dds::pub::DataWriter or not.

For each instance, the middleware internally maintains an instance state. The instance state can be:

• dds::sub::status::InstanceState::alive() indicates that (a) samples have been received for the instance, (b) there are live dds::pub::DataWriter entities writing the instance, and (c) the instance has not been explicitly disposed (or else more samples have been received after it was disposed).

• dds::sub::status::InstanceState::not_alive_disposed() indicates the instance was explicitly disposed by a dds::pub::DataWriter by means of the dispose operation.

• dds::sub::status::InstanceState::not_alive_no_writers() indicates the instance has been declared as not-alive by the dds::sub::DataReader because it detected that there are no live dds::pub::DataWriter entities writing that instance.

The precise behavior events that cause the instance state to change depends on the setting of the OWNERSHIP QoS:

• If OWNERSHIP is set to dds::core::policy::OwnershipKind_def::EXCLUSIVE, then the instance state becomes dds::sub::status::InstanceState::not_alive_disposed() only if the dds::pub::DataWriter that "owns" the instance explicitly disposes it. The instance state becomes dds::sub::status::InstanceState::alive() again only if the dds::pub::DataWriter that owns the instance writes it.

• If OWNERSHIP is set to dds::core::policy::OwnershipKind_def::SHARED, then the instance state becomes dds::sub::status::InstanceState::not_alive_disposed() if any dds::pub::DataWriter explicitly disposes the instance. The instance state becomes dds::sub::status::InstanceState::alive() as soon as any dds::pub::DataWriter writes the instance again.

The instance state available in the dds::sub::SampleInfo is a snapshot of the instance state of the instance at the time the collection was obtained (i.e. at the time read or take was called). The instance state is therefore the same for all samples in the returned collection that refer to the same instance.

For example, you can check if an instance is disposed as follows:

for (auto sample : reader.take()) {
    if (sample.info().state().instance_state() ==
            dds::sub::status::InstanceState::not_alive_disposed()) {
        // ...
    }
}

Member Typedef Documentation

MaskType

typedef std::bitset<OMG_DDS_STATE_BIT_COUNT > dds::sub::status::InstanceState::MaskType

An std::bitset of InstanceStates.

Constructor & Destructor Documentation

InstanceState()

dds::sub::status::InstanceState::InstanceState ( const MaskType &  other )

inline

Create an InstanceState from MaskType.

Parameters

other

The MaskType to create the InstanceState with

Member Function Documentation

alive()

static const InstanceState dds::sub::status::InstanceState::alive ( )

inlinestatic

Creates an alive InstanceState object.

The instance is currently in existence.

Referenced by dds::sub::status::DataState::any_data(), dds::sub::status::DataState::new_data(), and dds::sub::status::DataState::new_instance().

not_alive_disposed()

static const InstanceState dds::sub::status::InstanceState::not_alive_disposed ( )

inlinestatic

Creates a not_alive_disposed InstanceState object.

Indicates that the instance has been disposed by a DataWriter.

not_alive_no_writers()

static const InstanceState dds::sub::status::InstanceState::not_alive_no_writers ( )

inlinestatic

Creates a not_alive_no_writers InstanceState object.

Indicates that none of the DataWriters that are currently alive (according to the dds::core::policy::Liveliness policy) are writing the instance.

not_alive_mask()

static const InstanceState dds::sub::status::InstanceState::not_alive_mask ( )

inlinestatic

Creates an InstanceState object representing any not alive state.

This is equivalent to not_alive_disposed() | not_alive_no_writers()

any()

static const InstanceState dds::sub::status::InstanceState::any ( )

inlinestatic

Creates an InstanceState object representing any instance state.

This is equivalent to not_alive_mask() | alive().

Referenced by dds::sub::status::DataState::any().

Friends And Related Function Documentation

operator<<()

std::ostream & operator<< ( std::ostream &  os, const InstanceState &  s  )

related

Prints an instance state as a readable string.