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#[cfg(feature = "levenshtein")] pub use self::levenshtein::{Levenshtein, LevenshteinError}; #[cfg(feature = "levenshtein")] mod levenshtein; /// Automaton describes types that behave as a finite automaton. /// /// All implementors of this trait are represented by *byte based* automata. /// Stated differently, all transitions in the automata correspond to a single /// byte in the input. /// /// This implementation choice is important for a couple reasons: /// /// 1. The set of possible transitions in each node is small, which may make /// efficient memory usage easier. /// 2. The finite state transducers in this crate are all byte based, so any /// automata used on them must also be byte based. /// /// In practice, this does present somewhat of a problem, for example, if /// you're storing UTF-8 encoded strings in a finite state transducer. Consider /// using a `Levenshtein` automaton, which accepts a query string and an edit /// distance. The edit distance should apply to some notion of *character*, /// which could be represented by at least 1-4 bytes in a UTF-8 encoding (for /// some definition of "character"). Therefore, the automaton must have UTF-8 /// decoding built into it. This can be tricky to implement, so you may find /// the [`utf8-ranges`](https://crates.io/crates/utf8-ranges) crate useful. pub trait Automaton { /// The type of the state used in the automaton. type State; /// Returns a single start state for this automaton. /// /// This method should always return the same value for each /// implementation. fn start(&self) -> Self::State; /// Returns true if and only if `state` is a match state. fn is_match(&self, state: &Self::State) -> bool; /// Returns true if and only if `state` can lead to a match in zero or more /// steps. /// /// If this returns `false`, then no sequence of inputs from this state /// should ever produce a match. If this does not follow, then those match /// states may never be reached. In other words, behavior may be incorrect. /// /// If this returns `true` even when no match is possible, then behavior /// will be correct, but callers may be forced to do additional work. fn can_match(&self, _state: &Self::State) -> bool { true } /// Returns true if and only if `state` matches and must match no matter /// what steps are taken. /// /// If this returns `true`, then every sequence of inputs from this state /// produces a match. If this does not follow, then those match states may /// never be reached. In other words, behavior may be incorrect. /// /// If this returns `false` even when every sequence of inputs will lead to /// a match, then behavior will be correct, but callers may be forced to do /// additional work. fn will_always_match(&self, _state: &Self::State) -> bool { false } /// Return the next state given `state` and an input. fn accept(&self, state: &Self::State, byte: u8) -> Self::State; /// Returns an automaton that matches the strings that start with something /// this automaton matches. fn starts_with(self) -> StartsWith<Self> where Self: Sized, { StartsWith(self) } /// Returns an automaton that matches the strings matched by either this or /// the other automaton. fn union<Rhs: Automaton>(self, rhs: Rhs) -> Union<Self, Rhs> where Self: Sized, { Union(self, rhs) } /// Returns an automaton that matches the strings matched by both this and /// the other automaton. fn intersection<Rhs: Automaton>(self, rhs: Rhs) -> Intersection<Self, Rhs> where Self: Sized, { Intersection(self, rhs) } /// Returns an automaton that matches the strings not matched by this /// automaton. fn complement(self) -> Complement<Self> where Self: Sized, { Complement(self) } } impl<'a, T: Automaton> Automaton for &'a T { type State = T::State; fn start(&self) -> T::State { (*self).start() } fn is_match(&self, state: &T::State) -> bool { (*self).is_match(state) } fn can_match(&self, state: &T::State) -> bool { (*self).can_match(state) } fn will_always_match(&self, state: &T::State) -> bool { (*self).will_always_match(state) } fn accept(&self, state: &T::State, byte: u8) -> T::State { (*self).accept(state, byte) } } /// An automaton that matches if the input equals to a specific string. /// /// It can be used in combination with [`StartsWith`] to search strings /// starting with a given prefix. /// /// ```rust /// extern crate fst; /// /// use fst::{Automaton, IntoStreamer, Streamer, Set}; /// use fst::automaton::Str; /// /// # fn main() { example().unwrap(); } /// fn example() -> Result<(), Box<dyn std::error::Error>> { /// let paths = vec!["/home/projects/bar", "/home/projects/foo", "/tmp/foo"]; /// let set = Set::from_iter(paths)?; /// /// // Build our prefix query. /// let prefix = Str::new("/home").starts_with(); /// /// // Apply our query to the set we built. /// let mut stream = set.search(prefix).into_stream(); /// /// let matches = stream.into_strs()?; /// assert_eq!(matches, vec!["/home/projects/bar", "/home/projects/foo"]); /// Ok(()) /// } /// ``` #[derive(Clone, Debug)] pub struct Str<'a> { string: &'a [u8], } impl<'a> Str<'a> { /// Constructs automaton that matches an exact string. #[inline] pub fn new(string: &'a str) -> Str<'a> { Str { string: string.as_bytes() } } } impl<'a> Automaton for Str<'a> { type State = Option<usize>; #[inline] fn start(&self) -> Option<usize> { Some(0) } #[inline] fn is_match(&self, pos: &Option<usize>) -> bool { *pos == Some(self.string.len()) } #[inline] fn can_match(&self, pos: &Option<usize>) -> bool { pos.is_some() } #[inline] fn accept(&self, pos: &Option<usize>, byte: u8) -> Option<usize> { // if we aren't already past the end... if let Some(pos) = *pos { // and there is still a matching byte at the current position... if self.string.get(pos).cloned() == Some(byte) { // then move forward return Some(pos + 1); } } // otherwise we're either past the end or didn't match the byte None } } /// An automaton that matches if the input contains a specific subsequence. /// /// It can be used to build a simple fuzzy-finder. /// /// ```rust /// extern crate fst; /// /// use fst::{IntoStreamer, Streamer, Set}; /// use fst::automaton::Subsequence; /// /// # fn main() { example().unwrap(); } /// fn example() -> Result<(), Box<dyn std::error::Error>> { /// let paths = vec!["/home/projects/bar", "/home/projects/foo", "/tmp/foo"]; /// let set = Set::from_iter(paths)?; /// /// // Build our fuzzy query. /// let subseq = Subsequence::new("hpf"); /// /// // Apply our fuzzy query to the set we built. /// let mut stream = set.search(subseq).into_stream(); /// /// let matches = stream.into_strs()?; /// assert_eq!(matches, vec!["/home/projects/foo"]); /// Ok(()) /// } /// ``` #[derive(Clone, Debug)] pub struct Subsequence<'a> { subseq: &'a [u8], } impl<'a> Subsequence<'a> { /// Constructs automaton that matches input containing the /// specified subsequence. #[inline] pub fn new(subsequence: &'a str) -> Subsequence<'a> { Subsequence { subseq: subsequence.as_bytes() } } } impl<'a> Automaton for Subsequence<'a> { type State = usize; #[inline] fn start(&self) -> usize { 0 } #[inline] fn is_match(&self, &state: &usize) -> bool { state == self.subseq.len() } #[inline] fn can_match(&self, _: &usize) -> bool { true } #[inline] fn will_always_match(&self, &state: &usize) -> bool { state == self.subseq.len() } #[inline] fn accept(&self, &state: &usize, byte: u8) -> usize { if state == self.subseq.len() { return state; } state + (byte == self.subseq[state]) as usize } } /// An automaton that always matches. /// /// This is useful in a generic context as a way to express that no automaton /// should be used. #[derive(Clone, Debug)] pub struct AlwaysMatch; impl Automaton for AlwaysMatch { type State = (); #[inline] fn start(&self) -> () { () } #[inline] fn is_match(&self, _: &()) -> bool { true } #[inline] fn can_match(&self, _: &()) -> bool { true } #[inline] fn will_always_match(&self, _: &()) -> bool { true } #[inline] fn accept(&self, _: &(), _: u8) -> () { () } } /// An automaton that matches a string that begins with something that the /// wrapped automaton matches. #[derive(Clone, Debug)] pub struct StartsWith<A>(A); /// The `Automaton` state for `StartsWith<A>`. pub struct StartsWithState<A: Automaton>(StartsWithStateKind<A>); enum StartsWithStateKind<A: Automaton> { Done, Running(A::State), } impl<A: Automaton> Automaton for StartsWith<A> { type State = StartsWithState<A>; fn start(&self) -> StartsWithState<A> { StartsWithState({ let inner = self.0.start(); if self.0.is_match(&inner) { StartsWithStateKind::Done } else { StartsWithStateKind::Running(inner) } }) } fn is_match(&self, state: &StartsWithState<A>) -> bool { match state.0 { StartsWithStateKind::Done => true, StartsWithStateKind::Running(_) => false, } } fn can_match(&self, state: &StartsWithState<A>) -> bool { match state.0 { StartsWithStateKind::Done => true, StartsWithStateKind::Running(ref inner) => self.0.can_match(inner), } } fn will_always_match(&self, state: &StartsWithState<A>) -> bool { match state.0 { StartsWithStateKind::Done => true, StartsWithStateKind::Running(_) => false, } } fn accept( &self, state: &StartsWithState<A>, byte: u8, ) -> StartsWithState<A> { StartsWithState(match state.0 { StartsWithStateKind::Done => StartsWithStateKind::Done, StartsWithStateKind::Running(ref inner) => { let next_inner = self.0.accept(inner, byte); if self.0.is_match(&next_inner) { StartsWithStateKind::Done } else { StartsWithStateKind::Running(next_inner) } } }) } } /// An automaton that matches when one of its component automata match. #[derive(Clone, Debug)] pub struct Union<A, B>(A, B); /// The `Automaton` state for `Union<A, B>`. pub struct UnionState<A: Automaton, B: Automaton>(A::State, B::State); impl<A: Automaton, B: Automaton> Automaton for Union<A, B> { type State = UnionState<A, B>; fn start(&self) -> UnionState<A, B> { UnionState(self.0.start(), self.1.start()) } fn is_match(&self, state: &UnionState<A, B>) -> bool { self.0.is_match(&state.0) || self.1.is_match(&state.1) } fn can_match(&self, state: &UnionState<A, B>) -> bool { self.0.can_match(&state.0) || self.1.can_match(&state.1) } fn will_always_match(&self, state: &UnionState<A, B>) -> bool { self.0.will_always_match(&state.0) || self.1.will_always_match(&state.1) } fn accept(&self, state: &UnionState<A, B>, byte: u8) -> UnionState<A, B> { UnionState( self.0.accept(&state.0, byte), self.1.accept(&state.1, byte), ) } } /// An automaton that matches when both of its component automata match. #[derive(Clone, Debug)] pub struct Intersection<A, B>(A, B); /// The `Automaton` state for `Intersection<A, B>`. pub struct IntersectionState<A: Automaton, B: Automaton>(A::State, B::State); impl<A: Automaton, B: Automaton> Automaton for Intersection<A, B> { type State = IntersectionState<A, B>; fn start(&self) -> IntersectionState<A, B> { IntersectionState(self.0.start(), self.1.start()) } fn is_match(&self, state: &IntersectionState<A, B>) -> bool { self.0.is_match(&state.0) && self.1.is_match(&state.1) } fn can_match(&self, state: &IntersectionState<A, B>) -> bool { self.0.can_match(&state.0) && self.1.can_match(&state.1) } fn will_always_match(&self, state: &IntersectionState<A, B>) -> bool { self.0.will_always_match(&state.0) && self.1.will_always_match(&state.1) } fn accept( &self, state: &IntersectionState<A, B>, byte: u8, ) -> IntersectionState<A, B> { IntersectionState( self.0.accept(&state.0, byte), self.1.accept(&state.1, byte), ) } } /// An automaton that matches exactly when the automaton it wraps does not. #[derive(Clone, Debug)] pub struct Complement<A>(A); /// The `Automaton` state for `Complement<A>`. pub struct ComplementState<A: Automaton>(A::State); impl<A: Automaton> Automaton for Complement<A> { type State = ComplementState<A>; fn start(&self) -> ComplementState<A> { ComplementState(self.0.start()) } fn is_match(&self, state: &ComplementState<A>) -> bool { !self.0.is_match(&state.0) } fn can_match(&self, state: &ComplementState<A>) -> bool { !self.0.will_always_match(&state.0) } fn will_always_match(&self, state: &ComplementState<A>) -> bool { !self.0.can_match(&state.0) } fn accept( &self, state: &ComplementState<A>, byte: u8, ) -> ComplementState<A> { ComplementState(self.0.accept(&state.0, byte)) } }