Method start_flags_reverse

regex/src/dfa.rs:1463–1487

Computes the set of starting flags for the given position in text. This should only be used when executing the DFA in reverse over the input.

(
        &self,
        text: &[u8],
        at: usize,
    )

    /// This should only be used when executing the DFA in reverse over the
    /// input.
    fn start_flags_reverse(
        &self,
        text: &[u8],
        at: usize,
    ) -> (EmptyFlags, StateFlags) {
        let mut empty_flags = EmptyFlags::default();
        let mut state_flags = StateFlags::default();
        empty_flags.start = at == text.len();
        empty_flags.end = text.is_empty();
        empty_flags.start_line = at == text.len() || text[at] == b'\n';
        empty_flags.end_line = text.is_empty();

        let is_word_last =
            at < text.len() && Byte::byte(text[at]).is_ascii_word();
        let is_word = at > 0 && Byte::byte(text[at - 1]).is_ascii_word();
        if is_word_last {
            state_flags.set_word();
        }
        if is_word == is_word_last {
            empty_flags.not_word_boundary = true;
        } else {
            empty_flags.word_boundary = true;
        }
        (empty_flags, state_flags)
    }

    /// Returns a reference to a State given a pointer to it.
    fn state(&self, si: StatePtr) -> &State {