[go: up one dir, main page]

aho-corasick 0.1.0

Fast multiple substring searching with finite state machines.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144

/*!
A fast implementation of the Aho-Corasick string search algorithm.
*/

use std::fmt;

#[derive(Clone, Debug)]
pub struct Builder {
    pats: Vec<String>,
}

impl Builder {
    pub fn new() -> Builder {
        Builder { pats: vec![] }
    }

    pub fn add<S: Into<String>>(mut self, s: S) -> Builder {
        self.pats.push(s.into());
        self
    }

    pub fn build(self) -> Automaton {
        Automaton::new(self.pats)
    }
}

type PatIdx = usize;
type StateIdx = usize;

#[derive(Clone)]
pub struct Automaton {
    pats: Vec<String>,
    states: Vec<State>,
}

#[derive(Clone)]
struct State {
    out: Vec<PatIdx>,
    fail: StateIdx,
    goto: Vec<StateIdx>, // indexed by alphabet
}

impl Automaton {
    fn new(pats: Vec<String>) -> Automaton {
        Automaton {
            pats: vec![], // filled in later, avoid wrath of borrow checker
            states: vec![State::new()],
        }.build(pats)
    }

    fn build(mut self, pats: Vec<String>) -> Automaton {
        let rooti = self.add_state(State::new());
        for (pati, pat) in pats.iter().enumerate() {
            let mut previ = rooti;
            for &b in pat.as_bytes() {
                if let Some(si) = self.states[previ].goto(b) {
                    previ = si;
                } else {
                    let nexti = self.add_state(State::new());
                    self.states[previ].goto[b as usize] = nexti;
                    previ = nexti;
                }
            }
            self.states[previ].out.push(pati);
        }
        for v in &mut self.states[rooti].goto {
            if *v == 0 {
                *v = 1;
            }
        }
        self.pats = pats;
        self
    }

    fn add_state(&mut self, state: State) -> StateIdx {
        let i = self.states.len();
        self.states.push(state);
        i
    }
}

impl State {
    fn new() -> State {
        State {
            out: vec![],
            fail: 1,
            goto: vec![0; 256],
        }
    }

    fn goto(&self, b: u8) -> Option<StateIdx> {
        let i = self.goto[b as usize];
        if i == 0 { None } else { Some(i) }
    }

}

impl fmt::Debug for Automaton {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use std::iter::repeat;

        try!(writeln!(f, "{}", repeat('-').take(79).collect::<String>()));
        try!(writeln!(f, "Patterns: {:?}", self.pats));
        for (i, state) in self.states.iter().enumerate().skip(1) {
            try!(writeln!(f, "{:3}: {}", i, state.debug(i == 1)));
        }
        write!(f, "{}", repeat('-').take(79).collect::<String>())
    }
}

impl State {
    fn debug(&self, root: bool) -> String {
        format!("State {{ out: {:?}, fail: {:?}, goto: {{{}}} }}",
                self.out, self.fail, self.dense_goto_string(root))
    }

    fn dense_goto_string(&self, root: bool) -> String {
        use std::char::from_u32;

        let mut goto = vec![];
        for (i, &state) in self.goto.iter().enumerate() {
            if (!root && state == 0) || (root && state == 1) { continue; }
            goto.push(format!("{} => {}", from_u32(i as u32).unwrap(), state));
        }
        goto.connect(", ")
    }
}

impl fmt::Debug for State {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", self.debug(false))
    }
}

#[cfg(test)]
mod tests {
    use super::Builder;

    #[test]
    fn scratch() {
        let aut = Builder::new().add("he").add("she").build();
        println!("{:?}", aut);
    }
}