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use core::mem::size_of;
use crate::util::wire::{self, DeserializeError, Endian, SerializeError};
/// The kind of anchored starting configurations to support in a DFA.
///
/// Fully compiled DFAs need to be explicitly configured as to which anchored
/// starting configurations to support. The reason for not just supporting
/// everything unconditionally is that it can use more resources (such as
/// memory and build time). The downside of this is that if you try to execute
/// a search using an [`Anchored`](crate::Anchored) mode that is not supported
/// by the DFA, then the search will return an error.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum StartKind {
/// Support both anchored and unanchored searches.
Both,
/// Support only unanchored searches. Requesting an anchored search will
/// panic.
///
/// Note that even if an unanchored search is requested, the pattern itself
/// may still be anchored. For example, `^abc` will only match `abc` at the
/// start of a haystack. This will remain true, even if the regex engine
/// only supported unanchored searches.
Unanchored,
/// Support only anchored searches. Requesting an unanchored search will
/// panic.
Anchored,
}
impl StartKind {
pub(crate) fn from_bytes(
slice: &[u8],
) -> Result<(StartKind, usize), DeserializeError> {
wire::check_slice_len(slice, size_of::<u32>(), "start kind bytes")?;
let (n, nr) = wire::try_read_u32(slice, "start kind integer")?;
match n {
0 => Ok((StartKind::Both, nr)),
1 => Ok((StartKind::Unanchored, nr)),
2 => Ok((StartKind::Anchored, nr)),
_ => Err(DeserializeError::generic("unrecognized start kind")),
}
}
pub(crate) fn write_to<E: Endian>(
&self,
dst: &mut [u8],
) -> Result<usize, SerializeError> {
let nwrite = self.write_to_len();
if dst.len() < nwrite {
return Err(SerializeError::buffer_too_small("start kind"));
}
let n = match *self {
StartKind::Both => 0,
StartKind::Unanchored => 1,
StartKind::Anchored => 2,
};
E::write_u32(n, dst);
Ok(nwrite)
}
pub(crate) fn write_to_len(&self) -> usize {
size_of::<u32>()
}
#[cfg_attr(feature = "perf-inline", inline(always))]
pub(crate) fn has_unanchored(&self) -> bool {
matches!(*self, StartKind::Both | StartKind::Unanchored)
}
#[cfg_attr(feature = "perf-inline", inline(always))]
pub(crate) fn has_anchored(&self) -> bool {
matches!(*self, StartKind::Both | StartKind::Anchored)
}
}