dds::sub::CoherentAccess Class Reference

Class for RAII way of beginning/ending coherent access. More...

#include "CoherentAccess.hpp"

Inherits dds::core::Value< D >.

Public Member Functions
	CoherentAccess (const dds::sub::Subscriber &sub)
	~CoherentAccess ()
void	end ()
bool	operator!= (const Value &other) const
D *	operator-> ()
const D *	operator-> () const
bool	operator== (const Value &other) const

Detailed Description

Class for RAII way of beginning/ending coherent access.

Coherent access indicates that the application is about to access the data samples in any of the DataReader objects attached to the Subscriber.

The application is required to use this operation only if Presentation QosPolicy of the Subscriber to which the DataReader belongs has the access_scope set to "GROUP". In the aforementioned case, the operation must be called prior to calling any of the sample-accessing operations, i.e. read and take on DataReader. Otherwise the sample-accessing operations will throw a PreconditionNotMetError exception.

Once the application has finished accessing the data samples it must end the coherent access. It is not required for the application to begin or end access if the Presentation QosPolicy has the access_scope set to something other than GROUP. Beginning or ending access in this case is not considered an error and has no effect. Beginning and ending access may be nested. In that case, the application end access as many times as it began access.

dds::domain::DomainParticipant participant(org::eclipse::cyclonedds::domain::default_id());
dds::topic::Topic<Foo::Bar> topic(participant, "TopicName");
 
dds::sub::qos::SubscriberQos sQos sQos = participant.default_subscriber_qos()
                                         << dds::core::policy::Presentation::TopicAccessScope(false, true);
dds::sub::Subscriber subscriber(participant, sQos);
 
{
    std::vector< dds::sub::DataReader<Foo::Bar> > readers;
    // Start coherent access.
    dds::sub::CoherentAccess coherentAccess(subscriber);
    // Find (previously created with the subscriber) datareaders that now got data.
    dds::sub::find< dds::sub::DataReader<Foo::Bar> >(subscriber,
                                                     dds::sub::status::DataState::any(),
                                                     back_inserter(readers));
    // Get data from the readers
    for (size_type i = 0; i < rv.size(); i++) {
        dds::sub::LoanedSamples<Foo::Bar> samples = readers[i].read()
        dds::sub::LoanedSamples<Type1>::const_iterator it;
        for (it = samples.begin(); it != samples.end(); iterator++) {
            const dds::sub::Sample<Foo::Bar>& sample = *it;
            const Foo::Bar& data = sample.data();
            const dds::sub::SampleInfo& info = sample.info();
            // Use sample data and meta information.
        }
    }
}
// CoherentAccess went out of scope: it is ended implicitly

See also

Subscription

dds::sub::Subscriber

Definition at line 94 of file CoherentAccess.hpp.

Constructor & Destructor Documentation

CoherentAccess()

dds::sub::CoherentAccess::CoherentAccess ( const dds::sub::Subscriber &  sub )

explicit

Creating a CoherentAccess object, which will begin ‘coherent access’ of received samples using DataReader objects attached to this Subscriber.

Parameters

sub	The Subscriber to begin the coherent access on.

Exceptions

dds::core::Error	An internal error has occurred.
dds::core::AlreadyClosedError	The Subscriber has already been closed.
dds::core::NotEnabledError	The Subscriber has not yet been enabled.
dds::core::OutOfResourcesError	The Data Distribution Service ran out of resources to complete this operation.
dds::core::NullReferenceError	The Subscriber was not properly created and references to dds::core::null.

~CoherentAccess()

dds::sub::CoherentAccess::~CoherentAccess

(

)

The destruction of the CoherentAccess will implicitly end the coherent access if not already ended by a call to end().

When there is a problem with which end() would normally throw an exception, then that exception is swallowed. Errors can be found in the logs.

Member Function Documentation

end()

void dds::sub::CoherentAccess::end

(

)

This operation will explicitly end the coherent access.

If the Subscriber already ended its coherent access (by a call to this very operation), then a call to this operation will have no effect.

Exceptions

dds::core::Error	An internal error has occurred.
dds::core::AlreadyClosedError	The Subscriber has already been closed.
dds::core::NotEnabledError	The Subscriber has not yet been enabled.
dds::core::NullReferenceError	The Subscriber was not properly created and references to dds::core::null.

operator!=()

template<typename D >

bool dds::core::Value< D >::operator!= ( const Value< D > &  other ) const

inherited

Compare this Value with another Value

Parameters

other

Value

Returns

true if not equal

operator->() [1/2]

template<typename D >

D* dds::core::Value< D >::operator-> ( )

inherited

The operator->() is provided to be able to directly invoke functions on the delegate.

The decision to provide direct access to the delegate was motivated by the need for providing a way that was not invasive with respect to the CXXDDS API and yet would allow for vendor-specific extension. Thus vendor-specific extensions can be invoked on the Value and on all its subclasses as follows:

my_dds_value.standard_function();
my_dds_value->vendor_specific_extension();

Returns

a reference to delegate.

operator->() [2/2]

template<typename D >

const D* dds::core::Value< D >::operator-> ( ) const

inherited

The operator->() is provided to be able to directly invoke functions on the delegate.

The decision to provide direct access to the delegate was motivated by the need for providing a way that was not invasive with respect to the CXXDDS API and yet would allow for vendor-specific extension. Thus vendor-specific extensions can be invoked on the Value and on all its subclasses as follows:

my_dds_value.standard_function();
my_dds_value->vendor_specific_extension();

Returns

a reference to delegate.

operator==()

template<typename D >

bool dds::core::Value< D >::operator== ( const Value< D > &  other ) const

inherited

Compare this Value with another Value

Parameters

other

Value

Returns

true if equal

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

• dds/sub/CoherentAccess.hpp