void * opaque
You get a pointer to one of these when you open a file for reading, writing, or appending via PhysicsFS.
As you can see from the lack of meaningful fields, you should treat this as opaque data. Don't try to manipulate the file handle, just pass the pointer you got, unmolested, to various PhysicsFS APIs.
|Fri May 22 2020||Version 3.0.2|