Register a set of callbacks for being notified of changes in availability of objects within the system.
The set of objects reported is scoped based on the given query filter.
For the duration of the DOFOperation, the Query callbacks will be used to notify the application as objects matching the query are added or removed from the system. As with any DOFOperation, this Operation can be extended or cancelled.
There is no request to the network to identify additional objects that may be available. The Object IDs returned may be limited by the Interest operations that exist (see DOFSystem_BeginInterest).
- Resource Management:
- This function allocates resources that must later be freed by calling DOFOperation_Destroy.
- Parameters
-
| sys | The System on which to establish the query. This must not be NULL. |
| query | The set of Objects and/or Interfaces to watch (or NULL to watch everything). |
| timeout | The duration for the Query operation, in milliseconds. |
| callback | The callback to use while the Query is in effect. This may be NULL to ignore all notification of matching providers, but the operation would thus have no effect. |
| context | Application context data associated with the operation. |
- Returns
- A representation of the operation, or NULL if
- an invalid parameter is detected; or
- insufficient resources exist to create the operation.
- See Also
- DOFSystem_BeginInterest
