Instance States
[Data Samples]

DDS_InstanceStateKind and associated elements More...

Typedefs
typedef DDS_UnsignedLong	DDS_InstanceStateMask
	A bit-mask (list) of instance states, i.e. DDS_InstanceStateKind.
Enumerations
enum	DDS_InstanceStateKind {   DDS_ALIVE_INSTANCE_STATE = 0x0001 << 0,   DDS_NOT_ALIVE_DISPOSED_INSTANCE_STATE = 0x0001 << 1,   DDS_NOT_ALIVE_NO_WRITERS_INSTANCE_STATE = 0x0001 << 2 }
	Indicates is the samples are from a live DDS_DataWriter or not. More...
Variables
const DDS_InstanceStateMask	DDS_ANY_INSTANCE_STATE
	Any instance state ALIVE_INSTANCE_STATE | NOT_ALIVE_DISPOSED_INSTANCE_STATE | NOT_ALIVE_NO_WRITERS_INSTANCE_STATE.
const DDS_InstanceStateMask	DDS_NOT_ALIVE_INSTANCE_STATE
	Not alive instance state NOT_ALIVE_DISPOSED_INSTANCE_STATE | NOT_ALIVE_NO_WRITERS_INSTANCE_STATE.

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Detailed Description

DDS_InstanceStateKind and associated elements

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Typedef Documentation

typedef DDS_UnsignedLong DDS_InstanceStateMask

A bit-mask (list) of instance states, i.e. DDS_InstanceStateKind.

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Enumeration Type Documentation

enum DDS_InstanceStateKind

Indicates is the samples are from a live DDS_DataWriter or not.

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

• DDS_ALIVE_INSTANCE_STATE indicates that (a) samples have been received for the instance, (b) there are live DDS_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_NOT_ALIVE_DISPOSED_INSTANCE_STATE indicates the instance was explicitly disposed by a DDS_DataWriter by means of the dispose operation.

• DDS_NOT_ALIVE_NO_WRITERS_INSTANCE_STATE indicates the instance has been declared as not-alive by the DDS_DataReader because it detected that there are no live DDS_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_EXCLUSIVE_OWNERSHIP_QOS, then the instance state becomes DDS_NOT_ALIVE_DISPOSED_INSTANCE_STATE only if the DDS_DataWriter that "owns" the instance explicitly disposes it. The instance state becomes DDS_ALIVE_INSTANCE_STATE again only if the DDS_DataWriter that owns the instance writes it.

• If OWNERSHIP is set to DDS_SHARED_OWNERSHIP_QOS, then the instance state becomes DDS_NOT_ALIVE_DISPOSED_INSTANCE_STATE if any DDS_DataWriter explicitly disposes the instance. The instance state becomes DDS_ALIVE_INSTANCE_STATE as soon as any DDS_DataWriter writes the instance again.

The instance state available in the DDS_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.

Enumerator:

DDS_ALIVE_INSTANCE_STATE	Instance is currently in existence.
DDS_NOT_ALIVE_DISPOSED_INSTANCE_STATE	Not alive disposed instance. The instance has been disposed by a DataWriter.
DDS_NOT_ALIVE_NO_WRITERS_INSTANCE_STATE	Not alive no writers for instance. None of the DDS_DataWriter objects are currently alive (according to the LIVELINESS) are writing the instance.

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Variable Documentation

const DDS_InstanceStateMask DDS_ANY_INSTANCE_STATE

Any instance state ALIVE_INSTANCE_STATE | NOT_ALIVE_DISPOSED_INSTANCE_STATE | NOT_ALIVE_NO_WRITERS_INSTANCE_STATE.

Examples:

HelloWorld_subscriber.c.

const DDS_InstanceStateMask DDS_NOT_ALIVE_INSTANCE_STATE

Not alive instance state NOT_ALIVE_DISPOSED_INSTANCE_STATE | NOT_ALIVE_NO_WRITERS_INSTANCE_STATE.