al_get_file_userdata - Allegro 5 API

       Returns  a  pointer  to  the custom userdata that is attached to the file handle.  This is intended to be
       used by functions that extend ALLEGRO_FILE_INTERFACE(3alleg5).

Allegro reference manual                                                           al_get_file_userdata(3alleg5)

       al_get_file_userdata - Allegro 5 API

              #include <allegro5/allegro.h>

              void *al_get_file_userdata(ALLEGRO_FILE *f)