Initial import of regex-automata-0.1.9.
Bug: 155309706
Change-Id: I20031167cbe49d12754936285a0781eb7a3b8bfd
diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..70fe436
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,150 @@
+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,
+ )
+ }
+ }
+ }
+ }
+}