/*!
Provides implementations of `fst::Automaton` for Aho-Corasick automata.
This works by providing two wrapper types, [`Anchored`] and [`Unanchored`].
The former executes an anchored search on an FST while the latter executes
an unanchored search. Building these wrappers is fallible and will fail if
the underlying Aho-Corasick automaton does not support the type of search it
represents.
*/
use crate::{
automaton::{Automaton, StateID},
Anchored as AcAnchored, Input, MatchError,
};
/// Represents an unanchored Aho-Corasick search of a finite state transducer.
///
/// Wrapping an Aho-Corasick automaton in `Unanchored` will fail if the
/// underlying automaton does not support unanchored searches.
///
/// # Example
///
/// This shows how to build an FST of keys and then run an unanchored search on
/// those keys using an Aho-Corasick automaton.
///
/// ```
/// use aho_corasick::{nfa::contiguous::NFA, transducer::Unanchored};
/// use fst::{Automaton, IntoStreamer, Set, Streamer};
///
/// let set = Set::from_iter(&["abcd", "bc", "bcd", "xyz"]).unwrap();
/// let nfa = NFA::new(&["bcd", "x"]).unwrap();
/// // NFAs always support both unanchored and anchored searches.
/// let searcher = Unanchored::new(&nfa).unwrap();
///
/// let mut stream = set.search(searcher).into_stream();
/// let mut results = vec![];
/// while let Some(key) = stream.next() {
/// results.push(std::str::from_utf8(key).unwrap().to_string());
/// }
/// assert_eq!(vec!["abcd", "bcd", "xyz"], results);
/// ```
#[derive(Clone, Debug)]
pub struct Unanchored<A>(A);
impl<A: Automaton> Unanchored<A> {
/// Create a new `Unanchored` implementation of the `fst::Automaton` trait.
///
/// If the given Aho-Corasick automaton does not support unanchored
/// searches, then this returns an error.
pub fn new(aut: A) -> Result<Unanchored<A>, MatchError> {
let input = Input::new("").anchored(AcAnchored::No);
let _ = aut.start_state(&input)?;
Ok(Unanchored(aut))
}
/// Returns a borrow to the underlying automaton.
pub fn as_ref(&self) -> &A {
&self.0
}
/// Unwrap this value and return the inner automaton.
pub fn into_inner(self) -> A {
self.0
}
}
impl<A: Automaton> fst::Automaton for Unanchored<A> {
type State = StateID;
#[inline]
fn start(&self) -> StateID {
let input = Input::new("").anchored(AcAnchored::No);
self.0.start_state(&input).expect("support for unanchored searches")
}
#[inline]
fn is_match(&self, state: &StateID) -> bool {
self.0.is_match(*state)
}
#[inline]
fn accept(&self, state: &StateID, byte: u8) -> StateID {
if fst::Automaton::is_match(self, state) {
return *state;
}
self.0.next_state(AcAnchored::No, *state, byte)
}
#[inline]
fn can_match(&self, state: &StateID) -> bool {
!self.0.is_dead(*state)
}
}
/// Represents an anchored Aho-Corasick search of a finite state transducer.
///
/// Wrapping an Aho-Corasick automaton in `Unanchored` will fail if the
/// underlying automaton does not support unanchored searches.
///
/// # Example
///
/// This shows how to build an FST of keys and then run an anchored search on
/// those keys using an Aho-Corasick automaton.
///
/// ```
/// use aho_corasick::{nfa::contiguous::NFA, transducer::Anchored};
/// use fst::{Automaton, IntoStreamer, Set, Streamer};
///
/// let set = Set::from_iter(&["abcd", "bc", "bcd", "xyz"]).unwrap();
/// let nfa = NFA::new(&["bcd", "x"]).unwrap();
/// // NFAs always support both unanchored and anchored searches.
/// let searcher = Anchored::new(&nfa).unwrap();
///
/// let mut stream = set.search(searcher).into_stream();
/// let mut results = vec![];
/// while let Some(key) = stream.next() {
/// results.push(std::str::from_utf8(key).unwrap().to_string());
/// }
/// assert_eq!(vec!["bcd", "xyz"], results);
/// ```
///
/// This is like the example above, except we use an Aho-Corasick DFA, which
/// requires explicitly configuring it to support anchored searches. (NFAs
/// unconditionally support both unanchored and anchored searches.)
///
/// ```
/// use aho_corasick::{dfa::DFA, transducer::Anchored, StartKind};
/// use fst::{Automaton, IntoStreamer, Set, Streamer};
///
/// let set = Set::from_iter(&["abcd", "bc", "bcd", "xyz"]).unwrap();
/// let dfa = DFA::builder()
/// .start_kind(StartKind::Anchored)
/// .build(&["bcd", "x"])
/// .unwrap();
/// // We've explicitly configured our DFA to support anchored searches.
/// let searcher = Anchored::new(&dfa).unwrap();
///
/// let mut stream = set.search(searcher).into_stream();
/// let mut results = vec![];
/// while let Some(key) = stream.next() {
/// results.push(std::str::from_utf8(key).unwrap().to_string());
/// }
/// assert_eq!(vec!["bcd", "xyz"], results);
/// ```
#[derive(Clone, Debug)]
pub struct Anchored<A>(A);
impl<A: Automaton> Anchored<A> {
/// Create a new `Anchored` implementation of the `fst::Automaton` trait.
///
/// If the given Aho-Corasick automaton does not support anchored searches,
/// then this returns an error.
pub fn new(aut: A) -> Result<Anchored<A>, MatchError> {
let input = Input::new("").anchored(AcAnchored::Yes);
let _ = aut.start_state(&input)?;
Ok(Anchored(aut))
}
/// Returns a borrow to the underlying automaton.
pub fn as_ref(&self) -> &A {
&self.0
}
/// Unwrap this value and return the inner automaton.
pub fn into_inner(self) -> A {
self.0
}
}
impl<A: Automaton> fst::Automaton for Anchored<A> {
type State = StateID;
#[inline]
fn start(&self) -> StateID {
let input = Input::new("").anchored(AcAnchored::Yes);
self.0.start_state(&input).expect("support for unanchored searches")
}
#[inline]
fn is_match(&self, state: &StateID) -> bool {
self.0.is_match(*state)
}
#[inline]
fn accept(&self, state: &StateID, byte: u8) -> StateID {
if fst::Automaton::is_match(self, state) {
return *state;
}
self.0.next_state(AcAnchored::Yes, *state, byte)
}
#[inline]
fn can_match(&self, state: &StateID) -> bool {
!self.0.is_dead(*state)
}
}
#[cfg(test)]
mod tests {
use alloc::{string::String, vec, vec::Vec};
use fst::{Automaton, IntoStreamer, Set, Streamer};
use crate::{
dfa::DFA,
nfa::{contiguous, noncontiguous},
StartKind,
};
use super::*;
fn search<A: Automaton, D: AsRef<[u8]>>(
set: &Set<D>,
aut: A,
) -> Vec<String> {
let mut stream = set.search(aut).into_stream();
let mut results = vec![];
while let Some(key) = stream.next() {
results.push(String::from(core::str::from_utf8(key).unwrap()));
}
results
}
#[test]
fn unanchored() {
let set =
Set::from_iter(&["a", "bar", "baz", "wat", "xba", "xbax", "z"])
.unwrap();
let patterns = vec!["baz", "bax"];
let expected = vec!["baz", "xbax"];
let aut = Unanchored(noncontiguous::NFA::new(&patterns).unwrap());
let got = search(&set, &aut);
assert_eq!(got, expected);
let aut = Unanchored(contiguous::NFA::new(&patterns).unwrap());
let got = search(&set, &aut);
assert_eq!(got, expected);
let aut = Unanchored(DFA::new(&patterns).unwrap());
let got = search(&set, &aut);
assert_eq!(got, expected);
}
#[test]
fn anchored() {
let set =
Set::from_iter(&["a", "bar", "baz", "wat", "xba", "xbax", "z"])
.unwrap();
let patterns = vec!["baz", "bax"];
let expected = vec!["baz"];
let aut = Anchored(noncontiguous::NFA::new(&patterns).unwrap());
let got = search(&set, &aut);
assert_eq!(got, expected);
let aut = Anchored(contiguous::NFA::new(&patterns).unwrap());
let got = search(&set, &aut);
assert_eq!(got, expected);
let aut = Anchored(
DFA::builder()
.start_kind(StartKind::Anchored)
.build(&patterns)
.unwrap(),
);
let got = search(&set, &aut);
assert_eq!(got, expected);
}
}
