recordClass

Record one class row. Returns the named owner the member rows following it belong to — null for a nameless class, which MUST clear the owner or those members would attach to the PREVIOUS class.

A named class with no runtime name still becomes the owner: its members can map even when the class name itself doesn't. Both formats write "" for an unmapped element, and storing that would make mapClass / reverseClass return "" instead of passing the input through.