1use std::error;
2use std::fmt;
3use std::result;
4
5use regex_syntax;
6
7pub type Result<T> = result::Result<T, Error>;
8
9/// An error that occurred during the construction of a DFA.
10#[derive(Clone, Debug)]
11pub struct Error {
12 kind: ErrorKind,
13}
14
15/// The kind of error that occurred.
16#[derive(Clone, Debug)]
17pub enum ErrorKind {
18 /// An error that occurred while parsing a regular expression. Note that
19 /// this error may be printed over multiple lines, and is generally
20 /// intended to be end user readable on its own.
21 Syntax(String),
22 /// An error that occurred because an unsupported regex feature was used.
23 /// The message string describes which unsupported feature was used.
24 ///
25 /// The primary regex features that are unsupported are those that require
26 /// look-around, such as the `^` and `$` anchors and the word boundary
27 /// assertion `\b`. These may be supported in the future.
28 Unsupported(String),
29 /// An error that occurred when attempting to serialize a DFA to bytes.
30 Serialize(String),
31 /// An error that occurs when constructing a DFA would require the use of
32 /// a state ID that overflows the chosen state ID representation. For
33 /// example, if one is using `u8` for state IDs and builds a DFA with
34 /// 257 states, then the last state's ID will be `256` which cannot be
35 /// represented with `u8`.
36 ///
37 /// Typically, this error occurs in the determinization process of building
38 /// a DFA (the conversion step from NFA to DFA). It can also occur when
39 /// trying to build a smaller DFA from an existing one.
40 StateIDOverflow {
41 /// The maximum possible state ID.
42 max: usize,
43 },
44 /// An error that occurs when premultiplication of state IDs is requested,
45 /// but doing so would overflow the chosen state ID representation.
46 ///
47 /// When `max == requested_max`, then the state ID would overflow `usize`.
48 PremultiplyOverflow {
49 /// The maximum possible state id.
50 max: usize,
51 /// The maximum ID required by premultiplication.
52 requested_max: usize,
53 },
54}
55
56impl Error {
57 /// Return the kind of this error.
58 pub fn kind(&self) -> &ErrorKind {
59 &self.kind
60 }
61
62 pub(crate) fn syntax(err: regex_syntax::Error) -> Error {
63 Error { kind: ErrorKind::Syntax(err.to_string()) }
64 }
65
66 pub(crate) fn unsupported_anchor() -> Error {
67 let msg = r"anchors such as ^, $, \A and \z are not supported";
68 Error { kind: ErrorKind::Unsupported(msg.to_string()) }
69 }
70
71 pub(crate) fn unsupported_word() -> Error {
72 let msg = r"word boundary assertions (\b and \B) are not supported";
73 Error { kind: ErrorKind::Unsupported(msg.to_string()) }
74 }
75
76 pub(crate) fn unsupported_longest_match() -> Error {
77 let msg = "unachored searches with longest match \
78 semantics are not supported";
79 Error { kind: ErrorKind::Unsupported(msg.to_string()) }
80 }
81
82 pub(crate) fn serialize(message: &str) -> Error {
83 Error { kind: ErrorKind::Serialize(message.to_string()) }
84 }
85
86 pub(crate) fn state_id_overflow(max: usize) -> Error {
87 Error { kind: ErrorKind::StateIDOverflow { max } }
88 }
89
90 pub(crate) fn premultiply_overflow(
91 max: usize,
92 requested_max: usize,
93 ) -> Error {
94 Error { kind: ErrorKind::PremultiplyOverflow { max, requested_max } }
95 }
96}
97
98impl error::Error for Error {
99 fn description(&self) -> &str {
100 match self.kind {
101 ErrorKind::Syntax(_) => "syntax error",
102 ErrorKind::Unsupported(_) => "unsupported syntax",
103 ErrorKind::Serialize(_) => "serialization error",
104 ErrorKind::StateIDOverflow { .. } => {
105 "state id representation too small"
106 }
107 ErrorKind::PremultiplyOverflow { .. } => {
108 "state id representation too small for premultiplication"
109 }
110 }
111 }
112}
113
114impl fmt::Display for Error {
115 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
116 match self.kind {
117 ErrorKind::Syntax(ref msg) => write!(f, "{}", msg),
118 ErrorKind::Unsupported(ref msg) => write!(f, "{}", msg),
119 ErrorKind::Serialize(ref msg) => {
120 write!(f, "DFA serialization error: {}", msg)
121 }
122 ErrorKind::StateIDOverflow { max } => write!(
123 f,
124 "building the DFA failed because it required building \
125 more states that can be identified, where the maximum \
126 ID for the chosen representation is {}",
127 max,
128 ),
129 ErrorKind::PremultiplyOverflow { max, requested_max } => {
130 if max == requested_max {
131 write!(
132 f,
133 "premultiplication of states requires the ability to \
134 represent a state ID greater than what can fit on \
135 this platform's usize, which is {}",
136 ::std::usize::MAX,
137 )
138 } else {
139 write!(
140 f,
141 "premultiplication of states requires the ability to \
142 represent at least a state ID of {}, but the chosen \
143 representation only permits a maximum state ID of {}",
144 requested_max, max,
145 )
146 }
147 }
148 }
149 }
150}
151