Question

In order to select an object for access, the user must first obtain the object handle. This can be done using the VPI routines (that are supported in the tool being used) for traversing the HDL hierarchy and obtaining an object handle based on the type of object relationship to another (top) handle.

Any tool that implements this read API (e.g. waveform tool) shall implement at least a basic subset of the design navigation VPI routines that shall include vpi_handle_by_name() to permit the user to get a vpiHandle from an object name. It is left up to tool implementation to support additional design navigation relationships. Therefore, if the application wishes to access similar elements from one database to another, it shall use the name of the object, and then call vpi_handle_by_name(), to get the object handle from the relevant database. This level of indirection is always safe to do when switching the database query context, and shall be guaranteed to work.

It should be noted that an object’s vpiHandle depends on the access mode specified in vpi_load_extension() and the database accessed (identified by the returned extension pointer, see Section 30.10). A handle obtained through a post process access mode (vpiAccessPostProcess) from a waveform tool for example is not interchangeable in general with a handle obtained through interactive access mode (vpiAccessLimitedInteractive or vpiAccessInteractive) from a simulator. Also handles obtained through post process access mode of different databases are not interchangeable. This is because objects, their data, and relationships in a stored database could be quite different from those in the simulation model, and those in other databases.