1use crate::util::primitives::StateID;
2
3/// A collection of sentinel state IDs for Aho-Corasick automata.
4///
5/// This specifically enables the technique by which we determine which states
6/// are dead, matches or start states. Namely, by arranging states in a
7/// particular order, we can determine the type of a state simply by looking at
8/// its ID.
9#[derive(Clone, Debug)]
10pub(crate) struct Special {
11 /// The maximum ID of all the "special" states. This corresponds either to
12 /// start_anchored_id when a prefilter is active and max_match_id when a
13 /// prefilter is not active. The idea here is that if there is no prefilter,
14 /// then there is no point in treating start states as special.
15 pub(crate) max_special_id: StateID,
16 /// The maximum ID of all the match states. Any state ID bigger than this
17 /// is guaranteed to be a non-match ID.
18 ///
19 /// It is possible and legal for max_match_id to be equal to
20 /// start_anchored_id, which occurs precisely in the case where the empty
21 /// string is a pattern that was added to the underlying automaton.
22 pub(crate) max_match_id: StateID,
23 /// The state ID of the start state used for unanchored searches.
24 pub(crate) start_unanchored_id: StateID,
25 /// The state ID of the start state used for anchored searches. This is
26 /// always start_unanchored_id+1.
27 pub(crate) start_anchored_id: StateID,
28}
29
30impl Special {
31 /// Create a new set of "special" state IDs with all IDs initialized to
32 /// zero. The general idea here is that they will be updated and set to
33 /// correct values later.
34 pub(crate) fn zero() -> Special {
35 Special {
36 max_special_id: StateID::ZERO,
37 max_match_id: StateID::ZERO,
38 start_unanchored_id: StateID::ZERO,
39 start_anchored_id: StateID::ZERO,
40 }
41 }
42}
43