vendor/regex-automata/src/dfa/start.rs

   1 use core::mem::size_of;
   2
   3 use 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)]
  14 pub 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
  30 impl 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 }