al_ustr_find_set - Allegro 5 API

       This  function  finds  the first code point in us, beginning from byte offset start_pos, that matches any
       code point in accept.  Returns the position if a code point was found.  Otherwise returns -1.

       al_ustr_find_set - Allegro 5 API

al_ustr_find_set_cstr(3alleg5), al_ustr_find_cset(3alleg5)

Allegro reference manual                                                               al_ustr_find_set(3alleg5)

              #include <allegro5/allegro.h>

              int al_ustr_find_set(const ALLEGRO_USTR *us, int start_pos,
                 const ALLEGRO_USTR *accept)