aho_corasick/
error.rs

1use std::error;
2use std::fmt;
3use std::result;
4
5pub type Result<T> = result::Result<T, Error>;
6
7/// An error that occurred during the construction of an Aho-Corasick
8/// automaton.
9#[derive(Clone, Debug)]
10pub struct Error {
11    kind: ErrorKind,
12}
13
14/// The kind of error that occurred.
15#[derive(Clone, Debug)]
16pub enum ErrorKind {
17    /// An error that occurs when constructing an automaton would require the
18    /// use of a state ID that overflows the chosen state ID representation.
19    /// For example, if one is using `u8` for state IDs and builds a DFA with
20    /// 257 states, then the last state's ID will be `256` which cannot be
21    /// represented with `u8`.
22    StateIDOverflow {
23        /// The maximum possible state ID.
24        max: usize,
25    },
26    /// An error that occurs when premultiplication of state IDs is requested
27    /// when constructing an Aho-Corasick DFA, but doing so would overflow the
28    /// chosen state ID representation.
29    ///
30    /// When `max == requested_max`, then the state ID would overflow `usize`.
31    PremultiplyOverflow {
32        /// The maximum possible state id.
33        max: usize,
34        /// The maximum ID required by premultiplication.
35        requested_max: usize,
36    },
37}
38
39impl Error {
40    /// Return the kind of this error.
41    pub fn kind(&self) -> &ErrorKind {
42        &self.kind
43    }
44
45    pub(crate) fn state_id_overflow(max: usize) -> Error {
46        Error { kind: ErrorKind::StateIDOverflow { max } }
47    }
48
49    pub(crate) fn premultiply_overflow(
50        max: usize,
51        requested_max: usize,
52    ) -> Error {
53        Error { kind: ErrorKind::PremultiplyOverflow { max, requested_max } }
54    }
55}
56
57impl error::Error for Error {
58    fn description(&self) -> &str {
59        match self.kind {
60            ErrorKind::StateIDOverflow { .. } => {
61                "state id representation too small"
62            }
63            ErrorKind::PremultiplyOverflow { .. } => {
64                "state id representation too small for premultiplication"
65            }
66        }
67    }
68}
69
70impl fmt::Display for Error {
71    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
72        match self.kind {
73            ErrorKind::StateIDOverflow { max } => write!(
74                f,
75                "building the automaton failed because it required \
76                 building more states that can be identified, where the \
77                 maximum ID for the chosen representation is {}",
78                max,
79            ),
80            ErrorKind::PremultiplyOverflow { max, requested_max } => {
81                if max == requested_max {
82                    write!(
83                        f,
84                        "premultiplication of states requires the ability to \
85                         represent a state ID greater than what can fit on \
86                         this platform's usize, which is {}",
87                        ::std::usize::MAX,
88                    )
89                } else {
90                    write!(
91                        f,
92                        "premultiplication of states requires the ability to \
93                         represent at least a state ID of {}, but the chosen \
94                         representation only permits a maximum state ID of {}",
95                        requested_max, max,
96                    )
97                }
98            }
99        }
100    }
101}
aho_corasick/error.rs

aho_corasick/
error.rs
