Function CSTL_string_rfind

pub unsafe extern "C" fn CSTL_string_rfind(
    instance: CSTL_StringCRef,
    ptr: *const c_char,
    off: usize,
) -> usize

Find the last before offset off substring equal to the null-terminated string ptr and return its position from the start of the string.

If no match is found CSTL_string_npos is returned.