rustc_transmute/layout/
dfa.rs

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1use std::fmt;
2use std::sync::atomic::{AtomicU32, Ordering};
3
4use tracing::instrument;
5
6use super::{Byte, Nfa, Ref, nfa};
7use crate::Map;
8
9#[derive(PartialEq, Clone, Debug)]
10pub(crate) struct Dfa<R>
11where
12    R: Ref,
13{
14    pub(crate) transitions: Map<State, Transitions<R>>,
15    pub(crate) start: State,
16    pub(crate) accepting: State,
17}
18
19#[derive(PartialEq, Clone, Debug)]
20pub(crate) struct Transitions<R>
21where
22    R: Ref,
23{
24    byte_transitions: Map<Byte, State>,
25    ref_transitions: Map<R, State>,
26}
27
28impl<R> Default for Transitions<R>
29where
30    R: Ref,
31{
32    fn default() -> Self {
33        Self { byte_transitions: Map::default(), ref_transitions: Map::default() }
34    }
35}
36
37impl<R> Transitions<R>
38where
39    R: Ref,
40{
41    #[cfg(test)]
42    fn insert(&mut self, transition: Transition<R>, state: State) {
43        match transition {
44            Transition::Byte(b) => {
45                self.byte_transitions.insert(b, state);
46            }
47            Transition::Ref(r) => {
48                self.ref_transitions.insert(r, state);
49            }
50        }
51    }
52}
53
54/// The states in a `Nfa` represent byte offsets.
55#[derive(Hash, Eq, PartialEq, PartialOrd, Ord, Copy, Clone)]
56pub(crate) struct State(u32);
57
58#[cfg(test)]
59#[derive(Hash, Eq, PartialEq, Clone, Copy)]
60pub(crate) enum Transition<R>
61where
62    R: Ref,
63{
64    Byte(Byte),
65    Ref(R),
66}
67
68impl fmt::Debug for State {
69    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
70        write!(f, "S_{}", self.0)
71    }
72}
73
74#[cfg(test)]
75impl<R> fmt::Debug for Transition<R>
76where
77    R: Ref,
78{
79    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
80        match &self {
81            Self::Byte(b) => b.fmt(f),
82            Self::Ref(r) => r.fmt(f),
83        }
84    }
85}
86
87impl<R> Dfa<R>
88where
89    R: Ref,
90{
91    #[cfg(test)]
92    pub(crate) fn bool() -> Self {
93        let mut transitions: Map<State, Transitions<R>> = Map::default();
94        let start = State::new();
95        let accepting = State::new();
96
97        transitions.entry(start).or_default().insert(Transition::Byte(Byte::Init(0x00)), accepting);
98
99        transitions.entry(start).or_default().insert(Transition::Byte(Byte::Init(0x01)), accepting);
100
101        Self { transitions, start, accepting }
102    }
103
104    #[instrument(level = "debug")]
105    pub(crate) fn from_nfa(nfa: Nfa<R>) -> Self {
106        let Nfa { transitions: nfa_transitions, start: nfa_start, accepting: nfa_accepting } = nfa;
107
108        let mut dfa_transitions: Map<State, Transitions<R>> = Map::default();
109        let mut nfa_to_dfa: Map<nfa::State, State> = Map::default();
110        let dfa_start = State::new();
111        nfa_to_dfa.insert(nfa_start, dfa_start);
112
113        let mut queue = vec![(nfa_start, dfa_start)];
114
115        while let Some((nfa_state, dfa_state)) = queue.pop() {
116            if nfa_state == nfa_accepting {
117                continue;
118            }
119
120            for (nfa_transition, next_nfa_states) in nfa_transitions[&nfa_state].iter() {
121                let dfa_transitions =
122                    dfa_transitions.entry(dfa_state).or_insert_with(Default::default);
123
124                let mapped_state = next_nfa_states.iter().find_map(|x| nfa_to_dfa.get(x).copied());
125
126                let next_dfa_state = match nfa_transition {
127                    &nfa::Transition::Byte(b) => *dfa_transitions
128                        .byte_transitions
129                        .entry(b)
130                        .or_insert_with(|| mapped_state.unwrap_or_else(State::new)),
131                    &nfa::Transition::Ref(r) => *dfa_transitions
132                        .ref_transitions
133                        .entry(r)
134                        .or_insert_with(|| mapped_state.unwrap_or_else(State::new)),
135                };
136
137                for &next_nfa_state in next_nfa_states {
138                    nfa_to_dfa.entry(next_nfa_state).or_insert_with(|| {
139                        queue.push((next_nfa_state, next_dfa_state));
140                        next_dfa_state
141                    });
142                }
143            }
144        }
145
146        let dfa_accepting = nfa_to_dfa[&nfa_accepting];
147
148        Self { transitions: dfa_transitions, start: dfa_start, accepting: dfa_accepting }
149    }
150
151    pub(crate) fn bytes_from(&self, start: State) -> Option<&Map<Byte, State>> {
152        Some(&self.transitions.get(&start)?.byte_transitions)
153    }
154
155    pub(crate) fn byte_from(&self, start: State, byte: Byte) -> Option<State> {
156        self.transitions.get(&start)?.byte_transitions.get(&byte).copied()
157    }
158
159    pub(crate) fn refs_from(&self, start: State) -> Option<&Map<R, State>> {
160        Some(&self.transitions.get(&start)?.ref_transitions)
161    }
162}
163
164impl State {
165    pub(crate) fn new() -> Self {
166        static COUNTER: AtomicU32 = AtomicU32::new(0);
167        Self(COUNTER.fetch_add(1, Ordering::SeqCst))
168    }
169}
170
171#[cfg(test)]
172impl<R> From<nfa::Transition<R>> for Transition<R>
173where
174    R: Ref,
175{
176    fn from(nfa_transition: nfa::Transition<R>) -> Self {
177        match nfa_transition {
178            nfa::Transition::Byte(byte) => Transition::Byte(byte),
179            nfa::Transition::Ref(r) => Transition::Ref(r),
180        }
181    }
182}
rustc_transmute/layout/dfa.rs

rustc_transmute/layout/
dfa.rs
