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use std::error;
use std::fmt;
use std::result;
use regex_syntax;
pub type Result<T> = result::Result<T, Error>;
/// An error that occurred during the construction of a DFA.
#[derive(Clone, Debug)]
pub struct Error {
kind: ErrorKind,
}
/// The kind of error that occurred.
#[derive(Clone, Debug)]
pub enum ErrorKind {
/// An error that occurred while parsing a regular expression. Note that
/// this error may be printed over multiple lines, and is generally
/// intended to be end user readable on its own.
Syntax(String),
/// An error that occurred because an unsupported regex feature was used.
/// The message string describes which unsupported feature was used.
///
/// The primary regex features that are unsupported are those that require
/// look-around, such as the `^` and `$` anchors and the word boundary
/// assertion `\b`. These may be supported in the future.
Unsupported(String),
/// An error that occurred when attempting to serialize a DFA to bytes.
Serialize(String),
/// An error that occurs when constructing a DFA would require the use of
/// a state ID that overflows the chosen state ID representation. For
/// example, if one is using `u8` for state IDs and builds a DFA with
/// 257 states, then the last state's ID will be `256` which cannot be
/// represented with `u8`.
///
/// Typically, this error occurs in the determinization process of building
/// a DFA (the conversion step from NFA to DFA). It can also occur when
/// trying to build a smaller DFA from an existing one.
StateIDOverflow {
/// The maximum possible state ID.
max: usize,
},
/// An error that occurs when premultiplication of state IDs is requested,
/// but doing so would overflow the chosen state ID representation.
///
/// When `max == requested_max`, then the state ID would overflow `usize`.
PremultiplyOverflow {
/// The maximum possible state id.
max: usize,
/// The maximum ID required by premultiplication.
requested_max: usize,
}
}
impl Error {
/// Return the kind of this error.
pub fn kind(&self) -> &ErrorKind {
&self.kind
}
pub(crate) fn syntax(err: regex_syntax::Error) -> Error {
Error { kind: ErrorKind::Syntax(err.to_string()) }
}
pub(crate) fn unsupported_anchor() -> Error {
let msg = r"anchors such as ^, $, \A and \z are not supported";
Error { kind: ErrorKind::Unsupported(msg.to_string()) }
}
pub(crate) fn unsupported_word() -> Error {
let msg = r"word boundary assertions (\b and \B) are not supported";
Error { kind: ErrorKind::Unsupported(msg.to_string()) }
}
pub(crate) fn unsupported_longest_match() -> Error {
let msg = "unachored searches with longest match \
semantics are not supported";
Error { kind: ErrorKind::Unsupported(msg.to_string()) }
}
pub(crate) fn serialize(message: &str) -> Error {
Error { kind: ErrorKind::Serialize(message.to_string()) }
}
pub(crate) fn state_id_overflow(max: usize) -> Error {
Error { kind: ErrorKind::StateIDOverflow { max } }
}
pub(crate) fn premultiply_overflow(
max: usize,
requested_max: usize,
) -> Error {
Error { kind: ErrorKind::PremultiplyOverflow { max, requested_max } }
}
}
impl error::Error for Error {
fn description(&self) -> &str {
match self.kind {
ErrorKind::Syntax(_) => "syntax error",
ErrorKind::Unsupported(_) => "unsupported syntax",
ErrorKind::Serialize(_) => "serialization error",
ErrorKind::StateIDOverflow { .. } => {
"state id representation too small"
}
ErrorKind::PremultiplyOverflow { .. } => {
"state id representation too small for premultiplication"
}
}
}
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.kind {
ErrorKind::Syntax(ref msg) => write!(f, "{}", msg),
ErrorKind::Unsupported(ref msg) => write!(f, "{}", msg),
ErrorKind::Serialize(ref msg) => {
write!(f, "DFA serialization error: {}", msg)
}
ErrorKind::StateIDOverflow { max } => {
write!(
f,
"building the DFA failed because it required building \
more states that can be identified, where the maximum \
ID for the chosen representation is {}",
max,
)
}
ErrorKind::PremultiplyOverflow { max, requested_max } => {
if max == requested_max {
write!(
f,
"premultiplication of states requires the ability to \
represent a state ID greater than what can fit on \
this platform's usize, which is {}",
::std::usize::MAX,
)
} else {
write!(
f,
"premultiplication of states requires the ability to \
represent at least a state ID of {}, but the chosen \
representation only permits a maximum state ID of {}",
requested_max, max,
)
}
}
}
}
}