92 lines
2.2 KiB
Rust
92 lines
2.2 KiB
Rust
use fst::Automaton;
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use lazy_static::lazy_static;
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use levenshtein_automata::{
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LevenshteinAutomatonBuilder as LevBuilder,
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DFA, Distance,
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};
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lazy_static! {
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static ref LEVDIST0: LevBuilder = LevBuilder::new(0, false);
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static ref LEVDIST1: LevBuilder = LevBuilder::new(1, false);
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static ref LEVDIST2: LevBuilder = LevBuilder::new(2, false);
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}
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pub struct DfaExt {
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query_len: usize,
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automaton: DFA,
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}
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impl Automaton for DfaExt {
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type State = <DFA as Automaton>::State;
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fn start(&self) -> Self::State {
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self.automaton.start()
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}
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fn is_match(&self, state: &Self::State) -> bool {
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self.automaton.is_match(state)
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}
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fn can_match(&self, state: &Self::State) -> bool {
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self.automaton.can_match(state)
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}
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fn will_always_match(&self, state: &Self::State) -> bool {
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self.automaton.will_always_match(state)
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}
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fn accept(&self, state: &Self::State, byte: u8) -> Self::State {
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self.automaton.accept(state, byte)
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}
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}
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impl AutomatonExt for DfaExt {
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fn eval<B: AsRef<[u8]>>(&self, s: B) -> Distance {
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self.automaton.eval(s)
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}
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fn query_len(&self) -> usize {
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self.query_len
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}
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}
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#[derive(Copy, Clone)]
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enum PrefixSetting {
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Prefix,
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NoPrefix,
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}
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fn build_dfa_with_setting(query: &str, setting: PrefixSetting) -> DfaExt {
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use self::PrefixSetting::{Prefix, NoPrefix};
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let dfa = match query.len() {
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0 ..= 4 => match setting {
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Prefix => LEVDIST0.build_prefix_dfa(query),
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NoPrefix => LEVDIST0.build_dfa(query),
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},
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5 ..= 8 => match setting {
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Prefix => LEVDIST1.build_prefix_dfa(query),
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NoPrefix => LEVDIST1.build_dfa(query),
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},
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_ => match setting {
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Prefix => LEVDIST2.build_prefix_dfa(query),
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NoPrefix => LEVDIST2.build_dfa(query),
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},
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};
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DfaExt { query_len: query.len(), automaton: dfa }
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}
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pub fn build_prefix_dfa(query: &str) -> DfaExt {
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build_dfa_with_setting(query, PrefixSetting::Prefix)
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}
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pub fn build_dfa(query: &str) -> DfaExt {
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build_dfa_with_setting(query, PrefixSetting::NoPrefix)
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}
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pub trait AutomatonExt: Automaton {
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fn eval<B: AsRef<[u8]>>(&self, s: B) -> Distance;
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fn query_len(&self) -> usize;
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}
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