User Data For Functions
\ void *sqlite3_user_data(sqlite3_context*);\
The sqlite3_user_data() interface returns a copy of the pointer that was the pUserData parameter (the 5th parameter) of the sqlite3_create_function() and sqlite3_create_function16() routines that originally registered the application defined function.
This routine must be called from the same thread in which the application-defined function is running.