Function erlang_nif_sys::erlang_nif_sys_api::enif_make_existing_atom

pub unsafe extern "C" fn enif_make_existing_atom(
    env: *mut ErlNifEnv, 
    name: *const c_uchar, 
    atom: *mut ERL_NIF_TERM, 
    arg1: ErlNifCharEncoding
) -> c_int

See enif_make_existing_atom in the Erlang docs.