al_ustr_find_cset - Allegro 5 API

       This function finds the first code point in us, beginning from byte offset start_pos, that does not match
       any  code  point  in  reject.   In  other words it finds a code point in the complementary set of reject.
       Returns the byte position of that code point, if any.  Otherwise returns -1.

       al_ustr_find_cset - Allegro 5 API

al_ustr_find_cset_cstr(3alleg5), al_ustr_find_set(3alleg5)

Allegro reference manual                                                              al_ustr_find_cset(3alleg5)

              #include <allegro5/allegro.h>

              int al_ustr_find_cset(const ALLEGRO_USTR *us, int start_pos,
                 const ALLEGRO_USTR *reject)