1use core::mem::size_of;
2
3use crate::util::wire::{self, DeserializeError, Endian, SerializeError};
4
5/// The kind of anchored starting configurations to support in a DFA.
6///
7/// Fully compiled DFAs need to be explicitly configured as to which anchored
8/// starting configurations to support. The reason for not just supporting
9/// everything unconditionally is that it can use more resources (such as
10/// memory and build time). The downside of this is that if you try to execute
11/// a search using an [`Anchored`](crate::Anchored) mode that is not supported
12/// by the DFA, then the search will return an error.
13#[derive(Clone, Copy, Debug, Eq, PartialEq)]
14pub enum StartKind {
15 /// Support both anchored and unanchored searches.
16 Both,
17 /// Support only unanchored searches. Requesting an anchored search will
18 /// panic.
19 ///
20 /// Note that even if an unanchored search is requested, the pattern itself
21 /// may still be anchored. For example, `^abc` will only match `abc` at the
22 /// start of a haystack. This will remain true, even if the regex engine
23 /// only supported unanchored searches.
24 Unanchored,
25 /// Support only anchored searches. Requesting an unanchored search will
26 /// panic.
27 Anchored,
28}
29
30impl StartKind {
31 pub(crate) fn from_bytes(
32 slice: &[u8],
33 ) -> Result<(StartKind, usize), DeserializeError> {
34 wire::check_slice_len(slice, size_of::<u32>(), "start kind bytes")?;
35 let (n, nr) = wire::try_read_u32(slice, "start kind integer")?;
36 match n {
37 0 => Ok((StartKind::Both, nr)),
38 1 => Ok((StartKind::Unanchored, nr)),
39 2 => Ok((StartKind::Anchored, nr)),
40 _ => Err(DeserializeError::generic("unrecognized start kind")),
41 }
42 }
43
44 pub(crate) fn write_to<E: Endian>(
45 &self,
46 dst: &mut [u8],
47 ) -> Result<usize, SerializeError> {
48 let nwrite = self.write_to_len();
49 if dst.len() < nwrite {
50 return Err(SerializeError::buffer_too_small("start kind"));
51 }
52 let n = match *self {
53 StartKind::Both => 0,
54 StartKind::Unanchored => 1,
55 StartKind::Anchored => 2,
56 };
57 E::write_u32(n, dst);
58 Ok(nwrite)
59 }
60
61 pub(crate) fn write_to_len(&self) -> usize {
62 size_of::<u32>()
63 }
64
65 #[cfg_attr(feature = "perf-inline", inline(always))]
66 pub(crate) fn has_unanchored(&self) -> bool {
67 matches!(*self, StartKind::Both | StartKind::Unanchored)
68 }
69
70 #[cfg_attr(feature = "perf-inline", inline(always))]
71 pub(crate) fn has_anchored(&self) -> bool {
72 matches!(*self, StartKind::Both | StartKind::Anchored)
73 }
74}
75