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use std::collections::HashMap;
use std::mem;
use std::rc::Rc;
use dense;
use error::Result;
use nfa::{self, NFA};
use sparse_set::SparseSet;
use state_id::{dead_id, StateID};
type DFARepr<S> = dense::Repr<Vec<S>, S>;
#[derive(Debug)]
pub(crate) struct Determinizer<'a, S: StateID> {
nfa: &'a NFA,
dfa: DFARepr<S>,
builder_states: Vec<Rc<State>>,
cache: HashMap<Rc<State>, S>,
stack: Vec<nfa::StateID>,
scratch_nfa_states: Vec<nfa::StateID>,
longest_match: bool,
}
#[derive(Debug, Eq, Hash, PartialEq)]
struct State {
is_match: bool,
nfa_states: Vec<nfa::StateID>,
}
impl<'a, S: StateID> Determinizer<'a, S> {
pub fn new(nfa: &'a NFA) -> Determinizer<'a, S> {
let dead = Rc::new(State::dead());
let mut cache = HashMap::default();
cache.insert(dead.clone(), dead_id());
Determinizer {
nfa,
dfa: DFARepr::empty().anchored(nfa.is_anchored()),
builder_states: vec![dead],
cache,
stack: vec![],
scratch_nfa_states: vec![],
longest_match: false,
}
}
pub fn with_byte_classes(mut self) -> Determinizer<'a, S> {
let byte_classes = self.nfa.byte_classes().clone();
self.dfa = DFARepr::empty_with_byte_classes(byte_classes)
.anchored(self.nfa.is_anchored());
self
}
pub fn longest_match(mut self, yes: bool) -> Determinizer<'a, S> {
self.longest_match = yes;
self
}
pub fn build(mut self) -> Result<DFARepr<S>> {
let representative_bytes: Vec<u8> =
self.dfa.byte_classes().representatives().collect();
let mut sparse = self.new_sparse_set();
let mut uncompiled = vec![self.add_start(&mut sparse)?];
while let Some(dfa_id) = uncompiled.pop() {
for &b in &representative_bytes {
let (next_dfa_id, is_new) =
self.cached_state(dfa_id, b, &mut sparse)?;
self.dfa.add_transition(dfa_id, b, next_dfa_id);
if is_new {
uncompiled.push(next_dfa_id);
}
}
}
let is_match: Vec<bool> =
self.builder_states.iter().map(|s| s.is_match).collect();
self.dfa.shuffle_match_states(&is_match);
Ok(self.dfa)
}
fn cached_state(
&mut self,
dfa_id: S,
b: u8,
sparse: &mut SparseSet,
) -> Result<(S, bool)> {
sparse.clear();
self.next(dfa_id, b, sparse);
let state = self.new_state(sparse);
if let Some(&cached_id) = self.cache.get(&state) {
mem::replace(&mut self.scratch_nfa_states, state.nfa_states);
return Ok((cached_id, false));
}
self.add_state(state).map(|s| (s, true))
}
fn next(&mut self, dfa_id: S, b: u8, next_nfa_states: &mut SparseSet) {
next_nfa_states.clear();
for i in 0..self.builder_states[dfa_id.to_usize()].nfa_states.len() {
let nfa_id = self.builder_states[dfa_id.to_usize()].nfa_states[i];
match *self.nfa.state(nfa_id) {
nfa::State::Union { .. }
| nfa::State::Fail
| nfa::State::Match => {}
nfa::State::Range { range: ref r } => {
if r.start <= b && b <= r.end {
self.epsilon_closure(r.next, next_nfa_states);
}
}
nfa::State::Sparse { ref ranges } => {
for r in ranges.iter() {
if r.start > b {
break;
} else if r.start <= b && b <= r.end {
self.epsilon_closure(r.next, next_nfa_states);
break;
}
}
}
}
}
}
fn epsilon_closure(&mut self, start: nfa::StateID, set: &mut SparseSet) {
if !self.nfa.state(start).is_epsilon() {
set.insert(start);
return;
}
self.stack.push(start);
while let Some(mut id) = self.stack.pop() {
loop {
if set.contains(id) {
break;
}
set.insert(id);
match *self.nfa.state(id) {
nfa::State::Range { .. }
| nfa::State::Sparse { .. }
| nfa::State::Fail
| nfa::State::Match => break,
nfa::State::Union { ref alternates } => {
id = match alternates.get(0) {
None => break,
Some(&id) => id,
};
self.stack.extend(alternates[1..].iter().rev());
}
}
}
}
}
fn add_start(&mut self, sparse: &mut SparseSet) -> Result<S> {
sparse.clear();
self.epsilon_closure(self.nfa.start(), sparse);
let state = self.new_state(&sparse);
let id = self.add_state(state)?;
self.dfa.set_start_state(id);
Ok(id)
}
fn add_state(&mut self, state: State) -> Result<S> {
let id = self.dfa.add_empty_state()?;
let rstate = Rc::new(state);
self.builder_states.push(rstate.clone());
self.cache.insert(rstate, id);
Ok(id)
}
fn new_state(&mut self, set: &SparseSet) -> State {
let mut state = State {
is_match: false,
nfa_states: mem::replace(&mut self.scratch_nfa_states, vec![]),
};
state.nfa_states.clear();
for &id in set {
match *self.nfa.state(id) {
nfa::State::Range { .. } => {
state.nfa_states.push(id);
}
nfa::State::Sparse { .. } => {
state.nfa_states.push(id);
}
nfa::State::Fail => {
break;
}
nfa::State::Match => {
state.is_match = true;
if !self.longest_match {
break;
}
}
nfa::State::Union { .. } => {}
}
}
state
}
fn new_sparse_set(&self) -> SparseSet {
SparseSet::new(self.nfa.len())
}
}
impl State {
fn dead() -> State {
State { nfa_states: vec![], is_match: false }
}
}