unsafe fn searcher_kind_two_way(
    searcher: &Searcher,
    _prestate: &mut PrefilterState,
    haystack: &[u8],
    needle: &[u8],
) -> Option<usize> {
    if rabinkarp::is_fast(haystack, needle) {
        searcher.rabinkarp.find(haystack, needle)
    } else {
        searcher.kind.two_way.find(haystack, needle)
    }
}
Reads from the `two_way` field of `SearcherKind` to handle the case of
searching for an arbitrary needle without prefilter acceleration. Works on
all platforms.

# Safety

Callers must ensure that the `searcher.kind.two_way` union field is set.
src/memmem/searcher.rs