Initial import of regex-automata-0.1.9.
Bug: 155309706
Change-Id: I20031167cbe49d12754936285a0781eb7a3b8bfd
diff --git a/src/regex.rs b/src/regex.rs
new file mode 100644
index 0000000..47e1c58
--- /dev/null
+++ b/src/regex.rs
@@ -0,0 +1,771 @@
+#[cfg(feature = "std")]
+use dense::{self, DenseDFA};
+use dfa::DFA;
+#[cfg(feature = "std")]
+use error::Result;
+#[cfg(feature = "std")]
+use sparse::SparseDFA;
+#[cfg(feature = "std")]
+use state_id::StateID;
+
+/// A regular expression that uses deterministic finite automata for fast
+/// searching.
+///
+/// A regular expression is comprised of two DFAs, a "forward" DFA and a
+/// "reverse" DFA. The forward DFA is responsible for detecting the end of a
+/// match while the reverse DFA is responsible for detecting the start of a
+/// match. Thus, in order to find the bounds of any given match, a forward
+/// search must first be run followed by a reverse search. A match found by
+/// the forward DFA guarantees that the reverse DFA will also find a match.
+///
+/// The type of the DFA used by a `Regex` corresponds to the `D` type
+/// parameter, which must satisfy the [`DFA`](trait.DFA.html) trait. Typically,
+/// `D` is either a [`DenseDFA`](enum.DenseDFA.html) or a
+/// [`SparseDFA`](enum.SparseDFA.html), where dense DFAs use more memory but
+/// search faster, while sparse DFAs use less memory but search more slowly.
+///
+/// By default, a regex's DFA type parameter is set to
+/// `DenseDFA<Vec<usize>, usize>`. For most in-memory work loads, this is the
+/// most convenient type that gives the best search performance.
+///
+/// # Sparse DFAs
+///
+/// Since a `Regex` is generic over the `DFA` trait, it can be used with any
+/// kind of DFA. While this crate constructs dense DFAs by default, it is easy
+/// enough to build corresponding sparse DFAs, and then build a regex from
+/// them:
+///
+/// ```
+/// use regex_automata::Regex;
+///
+/// # fn example() -> Result<(), regex_automata::Error> {
+/// // First, build a regex that uses dense DFAs.
+/// let dense_re = Regex::new("foo[0-9]+")?;
+///
+/// // Second, build sparse DFAs from the forward and reverse dense DFAs.
+/// let fwd = dense_re.forward().to_sparse()?;
+/// let rev = dense_re.reverse().to_sparse()?;
+///
+/// // Third, build a new regex from the constituent sparse DFAs.
+/// let sparse_re = Regex::from_dfas(fwd, rev);
+///
+/// // A regex that uses sparse DFAs can be used just like with dense DFAs.
+/// assert_eq!(true, sparse_re.is_match(b"foo123"));
+/// # Ok(()) }; example().unwrap()
+/// ```
+#[cfg(feature = "std")]
+#[derive(Clone, Debug)]
+pub struct Regex<D: DFA = DenseDFA<Vec<usize>, usize>> {
+ forward: D,
+ reverse: D,
+}
+
+/// A regular expression that uses deterministic finite automata for fast
+/// searching.
+///
+/// A regular expression is comprised of two DFAs, a "forward" DFA and a
+/// "reverse" DFA. The forward DFA is responsible for detecting the end of a
+/// match while the reverse DFA is responsible for detecting the start of a
+/// match. Thus, in order to find the bounds of any given match, a forward
+/// search must first be run followed by a reverse search. A match found by
+/// the forward DFA guarantees that the reverse DFA will also find a match.
+///
+/// The type of the DFA used by a `Regex` corresponds to the `D` type
+/// parameter, which must satisfy the [`DFA`](trait.DFA.html) trait. Typically,
+/// `D` is either a [`DenseDFA`](enum.DenseDFA.html) or a
+/// [`SparseDFA`](enum.SparseDFA.html), where dense DFAs use more memory but
+/// search faster, while sparse DFAs use less memory but search more slowly.
+///
+/// When using this crate without the standard library, the `Regex` type has
+/// no default type parameter.
+///
+/// # Sparse DFAs
+///
+/// Since a `Regex` is generic over the `DFA` trait, it can be used with any
+/// kind of DFA. While this crate constructs dense DFAs by default, it is easy
+/// enough to build corresponding sparse DFAs, and then build a regex from
+/// them:
+///
+/// ```
+/// use regex_automata::Regex;
+///
+/// # fn example() -> Result<(), regex_automata::Error> {
+/// // First, build a regex that uses dense DFAs.
+/// let dense_re = Regex::new("foo[0-9]+")?;
+///
+/// // Second, build sparse DFAs from the forward and reverse dense DFAs.
+/// let fwd = dense_re.forward().to_sparse()?;
+/// let rev = dense_re.reverse().to_sparse()?;
+///
+/// // Third, build a new regex from the constituent sparse DFAs.
+/// let sparse_re = Regex::from_dfas(fwd, rev);
+///
+/// // A regex that uses sparse DFAs can be used just like with dense DFAs.
+/// assert_eq!(true, sparse_re.is_match(b"foo123"));
+/// # Ok(()) }; example().unwrap()
+/// ```
+#[cfg(not(feature = "std"))]
+#[derive(Clone, Debug)]
+pub struct Regex<D> {
+ forward: D,
+ reverse: D,
+}
+
+#[cfg(feature = "std")]
+impl Regex {
+ /// Parse the given regular expression using a default configuration and
+ /// return the corresponding regex.
+ ///
+ /// The default configuration uses `usize` for state IDs, premultiplies
+ /// them and reduces the alphabet size by splitting bytes into equivalence
+ /// classes. The underlying DFAs are *not* minimized.
+ ///
+ /// If you want a non-default configuration, then use the
+ /// [`RegexBuilder`](struct.RegexBuilder.html)
+ /// to set your own configuration.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let re = Regex::new("foo[0-9]+bar")?;
+ /// assert_eq!(Some((3, 14)), re.find(b"zzzfoo12345barzzz"));
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ pub fn new(pattern: &str) -> Result<Regex> {
+ RegexBuilder::new().build(pattern)
+ }
+}
+
+#[cfg(feature = "std")]
+impl Regex<SparseDFA<Vec<u8>, usize>> {
+ /// Parse the given regular expression using a default configuration and
+ /// return the corresponding regex using sparse DFAs.
+ ///
+ /// The default configuration uses `usize` for state IDs, reduces the
+ /// alphabet size by splitting bytes into equivalence classes. The
+ /// underlying DFAs are *not* minimized.
+ ///
+ /// If you want a non-default configuration, then use the
+ /// [`RegexBuilder`](struct.RegexBuilder.html)
+ /// to set your own configuration.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let re = Regex::new_sparse("foo[0-9]+bar")?;
+ /// assert_eq!(Some((3, 14)), re.find(b"zzzfoo12345barzzz"));
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ pub fn new_sparse(
+ pattern: &str,
+ ) -> Result<Regex<SparseDFA<Vec<u8>, usize>>> {
+ RegexBuilder::new().build_sparse(pattern)
+ }
+}
+
+impl<D: DFA> Regex<D> {
+ /// Returns true if and only if the given bytes match.
+ ///
+ /// This routine may short circuit if it knows that scanning future input
+ /// will never lead to a different result. In particular, if the underlying
+ /// DFA enters a match state or a dead state, then this routine will return
+ /// `true` or `false`, respectively, without inspecting any future input.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let re = Regex::new("foo[0-9]+bar")?;
+ /// assert_eq!(true, re.is_match(b"foo12345bar"));
+ /// assert_eq!(false, re.is_match(b"foobar"));
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ pub fn is_match(&self, input: &[u8]) -> bool {
+ self.is_match_at(input, 0)
+ }
+
+ /// Returns the first position at which a match is found.
+ ///
+ /// This routine stops scanning input in precisely the same circumstances
+ /// as `is_match`. The key difference is that this routine returns the
+ /// position at which it stopped scanning input if and only if a match
+ /// was found. If no match is found, then `None` is returned.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let re = Regex::new("foo[0-9]+")?;
+ /// assert_eq!(Some(4), re.shortest_match(b"foo12345"));
+ ///
+ /// // Normally, the end of the leftmost first match here would be 3,
+ /// // but the shortest match semantics detect a match earlier.
+ /// let re = Regex::new("abc|a")?;
+ /// assert_eq!(Some(1), re.shortest_match(b"abc"));
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ pub fn shortest_match(&self, input: &[u8]) -> Option<usize> {
+ self.shortest_match_at(input, 0)
+ }
+
+ /// Returns the start and end offset of the leftmost first match. If no
+ /// match exists, then `None` is returned.
+ ///
+ /// The "leftmost first" match corresponds to the match with the smallest
+ /// starting offset, but where the end offset is determined by preferring
+ /// earlier branches in the original regular expression. For example,
+ /// `Sam|Samwise` will match `Sam` in `Samwise`, but `Samwise|Sam` will
+ /// match `Samwise` in `Samwise`.
+ ///
+ /// Generally speaking, the "leftmost first" match is how most backtracking
+ /// regular expressions tend to work. This is in contrast to POSIX-style
+ /// regular expressions that yield "leftmost longest" matches. Namely,
+ /// both `Sam|Samwise` and `Samwise|Sam` match `Samwise` when using
+ /// leftmost longest semantics.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let re = Regex::new("foo[0-9]+")?;
+ /// assert_eq!(Some((3, 11)), re.find(b"zzzfoo12345zzz"));
+ ///
+ /// // Even though a match is found after reading the first byte (`a`),
+ /// // the leftmost first match semantics demand that we find the earliest
+ /// // match that prefers earlier parts of the pattern over latter parts.
+ /// let re = Regex::new("abc|a")?;
+ /// assert_eq!(Some((0, 3)), re.find(b"abc"));
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ pub fn find(&self, input: &[u8]) -> Option<(usize, usize)> {
+ self.find_at(input, 0)
+ }
+
+ /// Returns the same as `is_match`, but starts the search at the given
+ /// offset.
+ ///
+ /// The significance of the starting point is that it takes the surrounding
+ /// context into consideration. For example, if the DFA is anchored, then
+ /// a match can only occur when `start == 0`.
+ pub fn is_match_at(&self, input: &[u8], start: usize) -> bool {
+ self.forward().is_match_at(input, start)
+ }
+
+ /// Returns the same as `shortest_match`, but starts the search at the
+ /// given offset.
+ ///
+ /// The significance of the starting point is that it takes the surrounding
+ /// context into consideration. For example, if the DFA is anchored, then
+ /// a match can only occur when `start == 0`.
+ pub fn shortest_match_at(
+ &self,
+ input: &[u8],
+ start: usize,
+ ) -> Option<usize> {
+ self.forward().shortest_match_at(input, start)
+ }
+
+ /// Returns the same as `find`, but starts the search at the given
+ /// offset.
+ ///
+ /// The significance of the starting point is that it takes the surrounding
+ /// context into consideration. For example, if the DFA is anchored, then
+ /// a match can only occur when `start == 0`.
+ pub fn find_at(
+ &self,
+ input: &[u8],
+ start: usize,
+ ) -> Option<(usize, usize)> {
+ let end = match self.forward().find_at(input, start) {
+ None => return None,
+ Some(end) => end,
+ };
+ let start = self
+ .reverse()
+ .rfind(&input[start..end])
+ .map(|i| start + i)
+ .expect("reverse search must match if forward search does");
+ Some((start, end))
+ }
+
+ /// Returns an iterator over all non-overlapping leftmost first matches
+ /// in the given bytes. If no match exists, then the iterator yields no
+ /// elements.
+ ///
+ /// Note that if the regex can match the empty string, then it is
+ /// possible for the iterator to yield a zero-width match at a location
+ /// that is not a valid UTF-8 boundary (for example, between the code units
+ /// of a UTF-8 encoded codepoint). This can happen regardless of whether
+ /// [`allow_invalid_utf8`](struct.RegexBuilder.html#method.allow_invalid_utf8)
+ /// was enabled or not.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let re = Regex::new("foo[0-9]+")?;
+ /// let text = b"foo1 foo12 foo123";
+ /// let matches: Vec<(usize, usize)> = re.find_iter(text).collect();
+ /// assert_eq!(matches, vec![(0, 4), (5, 10), (11, 17)]);
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ pub fn find_iter<'r, 't>(&'r self, input: &'t [u8]) -> Matches<'r, 't, D> {
+ Matches::new(self, input)
+ }
+
+ /// Build a new regex from its constituent forward and reverse DFAs.
+ ///
+ /// This is useful when deserializing a regex from some arbitrary
+ /// memory region. This is also useful for building regexes from other
+ /// types of DFAs.
+ ///
+ /// # Example
+ ///
+ /// This example is a bit a contrived. The usual use of these methods
+ /// would involve serializing `initial_re` somewhere and then deserializing
+ /// it later to build a regex.
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let initial_re = Regex::new("foo[0-9]+")?;
+ /// assert_eq!(true, initial_re.is_match(b"foo123"));
+ ///
+ /// let (fwd, rev) = (initial_re.forward(), initial_re.reverse());
+ /// let re = Regex::from_dfas(fwd, rev);
+ /// assert_eq!(true, re.is_match(b"foo123"));
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ ///
+ /// This example shows how you might build smaller DFAs, and then use those
+ /// smaller DFAs to build a new regex.
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let initial_re = Regex::new("foo[0-9]+")?;
+ /// assert_eq!(true, initial_re.is_match(b"foo123"));
+ ///
+ /// let fwd = initial_re.forward().to_u16()?;
+ /// let rev = initial_re.reverse().to_u16()?;
+ /// let re = Regex::from_dfas(fwd, rev);
+ /// assert_eq!(true, re.is_match(b"foo123"));
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ ///
+ /// This example shows how to build a `Regex` that uses sparse DFAs instead
+ /// of dense DFAs:
+ ///
+ /// ```
+ /// use regex_automata::Regex;
+ ///
+ /// # fn example() -> Result<(), regex_automata::Error> {
+ /// let initial_re = Regex::new("foo[0-9]+")?;
+ /// assert_eq!(true, initial_re.is_match(b"foo123"));
+ ///
+ /// let fwd = initial_re.forward().to_sparse()?;
+ /// let rev = initial_re.reverse().to_sparse()?;
+ /// let re = Regex::from_dfas(fwd, rev);
+ /// assert_eq!(true, re.is_match(b"foo123"));
+ /// # Ok(()) }; example().unwrap()
+ /// ```
+ pub fn from_dfas(forward: D, reverse: D) -> Regex<D> {
+ Regex { forward, reverse }
+ }
+
+ /// Return the underlying DFA responsible for forward matching.
+ pub fn forward(&self) -> &D {
+ &self.forward
+ }
+
+ /// Return the underlying DFA responsible for reverse matching.
+ pub fn reverse(&self) -> &D {
+ &self.reverse
+ }
+}
+
+/// An iterator over all non-overlapping matches for a particular search.
+///
+/// The iterator yields a `(usize, usize)` value until no more matches could be
+/// found. The first `usize` is the start of the match (inclusive) while the
+/// second `usize` is the end of the match (exclusive).
+///
+/// `S` is the type used to represent state identifiers in the underlying
+/// regex. The lifetime variables are as follows:
+///
+/// * `'r` is the lifetime of the regular expression value itself.
+/// * `'t` is the lifetime of the text being searched.
+#[derive(Clone, Debug)]
+pub struct Matches<'r, 't, D: DFA + 'r> {
+ re: &'r Regex<D>,
+ text: &'t [u8],
+ last_end: usize,
+ last_match: Option<usize>,
+}
+
+impl<'r, 't, D: DFA> Matches<'r, 't, D> {
+ fn new(re: &'r Regex<D>, text: &'t [u8]) -> Matches<'r, 't, D> {
+ Matches { re, text, last_end: 0, last_match: None }
+ }
+}
+
+impl<'r, 't, D: DFA> Iterator for Matches<'r, 't, D> {
+ type Item = (usize, usize);
+
+ fn next(&mut self) -> Option<(usize, usize)> {
+ if self.last_end > self.text.len() {
+ return None;
+ }
+ let (s, e) = match self.re.find_at(self.text, self.last_end) {
+ None => return None,
+ Some((s, e)) => (s, e),
+ };
+ if s == e {
+ // This is an empty match. To ensure we make progress, start
+ // the next search at the smallest possible starting position
+ // of the next match following this one.
+ self.last_end = e + 1;
+ // Don't accept empty matches immediately following a match.
+ // Just move on to the next match.
+ if Some(e) == self.last_match {
+ return self.next();
+ }
+ } else {
+ self.last_end = e;
+ }
+ self.last_match = Some(e);
+ Some((s, e))
+ }
+}
+
+/// A builder for a regex based on deterministic finite automatons.
+///
+/// This builder permits configuring several aspects of the construction
+/// process such as case insensitivity, Unicode support and various options
+/// that impact the size of the underlying DFAs. In some cases, options (like
+/// performing DFA minimization) can come with a substantial additional cost.
+///
+/// This builder generally constructs two DFAs, where one is responsible for
+/// finding the end of a match and the other is responsible for finding the
+/// start of a match. If you only need to detect whether something matched,
+/// or only the end of a match, then you should use a
+/// [`dense::Builder`](dense/struct.Builder.html)
+/// to construct a single DFA, which is cheaper than building two DFAs.
+#[cfg(feature = "std")]
+#[derive(Clone, Debug)]
+pub struct RegexBuilder {
+ dfa: dense::Builder,
+}
+
+#[cfg(feature = "std")]
+impl RegexBuilder {
+ /// Create a new regex builder with the default configuration.
+ pub fn new() -> RegexBuilder {
+ RegexBuilder { dfa: dense::Builder::new() }
+ }
+
+ /// Build a regex from the given pattern.
+ ///
+ /// If there was a problem parsing or compiling the pattern, then an error
+ /// is returned.
+ pub fn build(&self, pattern: &str) -> Result<Regex> {
+ self.build_with_size::<usize>(pattern)
+ }
+
+ /// Build a regex from the given pattern using sparse DFAs.
+ ///
+ /// If there was a problem parsing or compiling the pattern, then an error
+ /// is returned.
+ pub fn build_sparse(
+ &self,
+ pattern: &str,
+ ) -> Result<Regex<SparseDFA<Vec<u8>, usize>>> {
+ self.build_with_size_sparse::<usize>(pattern)
+ }
+
+ /// Build a regex from the given pattern using a specific representation
+ /// for the underlying DFA state IDs.
+ ///
+ /// If there was a problem parsing or compiling the pattern, then an error
+ /// is returned.
+ ///
+ /// The representation of state IDs is determined by the `S` type
+ /// parameter. In general, `S` is usually one of `u8`, `u16`, `u32`, `u64`
+ /// or `usize`, where `usize` is the default used for `build`. The purpose
+ /// of specifying a representation for state IDs is to reduce the memory
+ /// footprint of the underlying DFAs.
+ ///
+ /// When using this routine, the chosen state ID representation will be
+ /// used throughout determinization and minimization, if minimization was
+ /// requested. Even if the minimized DFAs can fit into the chosen state ID
+ /// representation but the initial determinized DFA cannot, then this will
+ /// still return an error. To get a minimized DFA with a smaller state ID
+ /// representation, first build it with a bigger state ID representation,
+ /// and then shrink the sizes of the DFAs using one of its conversion
+ /// routines, such as [`DenseDFA::to_u16`](enum.DenseDFA.html#method.to_u16).
+ /// Finally, reconstitute the regex via
+ /// [`Regex::from_dfa`](struct.Regex.html#method.from_dfa).
+ pub fn build_with_size<S: StateID>(
+ &self,
+ pattern: &str,
+ ) -> Result<Regex<DenseDFA<Vec<S>, S>>> {
+ let forward = self.dfa.build_with_size(pattern)?;
+ let reverse = self
+ .dfa
+ .clone()
+ .anchored(true)
+ .reverse(true)
+ .longest_match(true)
+ .build_with_size(pattern)?;
+ Ok(Regex::from_dfas(forward, reverse))
+ }
+
+ /// Build a regex from the given pattern using a specific representation
+ /// for the underlying DFA state IDs using sparse DFAs.
+ pub fn build_with_size_sparse<S: StateID>(
+ &self,
+ pattern: &str,
+ ) -> Result<Regex<SparseDFA<Vec<u8>, S>>> {
+ let re = self.build_with_size(pattern)?;
+ let fwd = re.forward().to_sparse()?;
+ let rev = re.reverse().to_sparse()?;
+ Ok(Regex::from_dfas(fwd, rev))
+ }
+
+ /// Set whether matching must be anchored at the beginning of the input.
+ ///
+ /// When enabled, a match must begin at the start of the input. When
+ /// disabled, the regex will act as if the pattern started with a `.*?`,
+ /// which enables a match to appear anywhere.
+ ///
+ /// By default this is disabled.
+ pub fn anchored(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.anchored(yes);
+ self
+ }
+
+ /// Enable or disable the case insensitive flag by default.
+ ///
+ /// By default this is disabled. It may alternatively be selectively
+ /// enabled in the regular expression itself via the `i` flag.
+ pub fn case_insensitive(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.case_insensitive(yes);
+ self
+ }
+
+ /// Enable verbose mode in the regular expression.
+ ///
+ /// When enabled, verbose mode permits insigificant whitespace in many
+ /// places in the regular expression, as well as comments. Comments are
+ /// started using `#` and continue until the end of the line.
+ ///
+ /// By default, this is disabled. It may be selectively enabled in the
+ /// regular expression by using the `x` flag regardless of this setting.
+ pub fn ignore_whitespace(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.ignore_whitespace(yes);
+ self
+ }
+
+ /// Enable or disable the "dot matches any character" flag by default.
+ ///
+ /// By default this is disabled. It may alternatively be selectively
+ /// enabled in the regular expression itself via the `s` flag.
+ pub fn dot_matches_new_line(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.dot_matches_new_line(yes);
+ self
+ }
+
+ /// Enable or disable the "swap greed" flag by default.
+ ///
+ /// By default this is disabled. It may alternatively be selectively
+ /// enabled in the regular expression itself via the `U` flag.
+ pub fn swap_greed(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.swap_greed(yes);
+ self
+ }
+
+ /// Enable or disable the Unicode flag (`u`) by default.
+ ///
+ /// By default this is **enabled**. It may alternatively be selectively
+ /// disabled in the regular expression itself via the `u` flag.
+ ///
+ /// Note that unless `allow_invalid_utf8` is enabled (it's disabled by
+ /// default), a regular expression will fail to parse if Unicode mode is
+ /// disabled and a sub-expression could possibly match invalid UTF-8.
+ pub fn unicode(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.unicode(yes);
+ self
+ }
+
+ /// When enabled, the builder will permit the construction of a regular
+ /// expression that may match invalid UTF-8.
+ ///
+ /// When disabled (the default), the builder is guaranteed to produce a
+ /// regex that will only ever match valid UTF-8 (otherwise, the builder
+ /// will return an error).
+ pub fn allow_invalid_utf8(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.allow_invalid_utf8(yes);
+ self
+ }
+
+ /// Set the nesting limit used for the regular expression parser.
+ ///
+ /// The nesting limit controls how deep the abstract syntax tree is allowed
+ /// to be. If the AST exceeds the given limit (e.g., with too many nested
+ /// groups), then an error is returned by the parser.
+ ///
+ /// The purpose of this limit is to act as a heuristic to prevent stack
+ /// overflow when building a finite automaton from a regular expression's
+ /// abstract syntax tree. In particular, construction currently uses
+ /// recursion. In the future, the implementation may stop using recursion
+ /// and this option will no longer be necessary.
+ ///
+ /// This limit is not checked until the entire AST is parsed. Therefore,
+ /// if callers want to put a limit on the amount of heap space used, then
+ /// they should impose a limit on the length, in bytes, of the concrete
+ /// pattern string. In particular, this is viable since the parser will
+ /// limit itself to heap space proportional to the lenth of the pattern
+ /// string.
+ ///
+ /// Note that a nest limit of `0` will return a nest limit error for most
+ /// patterns but not all. For example, a nest limit of `0` permits `a` but
+ /// not `ab`, since `ab` requires a concatenation AST item, which results
+ /// in a nest depth of `1`. In general, a nest limit is not something that
+ /// manifests in an obvious way in the concrete syntax, therefore, it
+ /// should not be used in a granular way.
+ pub fn nest_limit(&mut self, limit: u32) -> &mut RegexBuilder {
+ self.dfa.nest_limit(limit);
+ self
+ }
+
+ /// Minimize the underlying DFAs.
+ ///
+ /// When enabled, the DFAs powering the resulting regex will be minimized
+ /// such that it is as small as possible.
+ ///
+ /// Whether one enables minimization or not depends on the types of costs
+ /// you're willing to pay and how much you care about its benefits. In
+ /// particular, minimization has worst case `O(n*k*logn)` time and `O(k*n)`
+ /// space, where `n` is the number of DFA states and `k` is the alphabet
+ /// size. In practice, minimization can be quite costly in terms of both
+ /// space and time, so it should only be done if you're willing to wait
+ /// longer to produce a DFA. In general, you might want a minimal DFA in
+ /// the following circumstances:
+ ///
+ /// 1. You would like to optimize for the size of the automaton. This can
+ /// manifest in one of two ways. Firstly, if you're converting the
+ /// DFA into Rust code (or a table embedded in the code), then a minimal
+ /// DFA will translate into a corresponding reduction in code size, and
+ /// thus, also the final compiled binary size. Secondly, if you are
+ /// building many DFAs and putting them on the heap, you'll be able to
+ /// fit more if they are smaller. Note though that building a minimal
+ /// DFA itself requires additional space; you only realize the space
+ /// savings once the minimal DFA is constructed (at which point, the
+ /// space used for minimization is freed).
+ /// 2. You've observed that a smaller DFA results in faster match
+ /// performance. Naively, this isn't guaranteed since there is no
+ /// inherent difference between matching with a bigger-than-minimal
+ /// DFA and a minimal DFA. However, a smaller DFA may make use of your
+ /// CPU's cache more efficiently.
+ /// 3. You are trying to establish an equivalence between regular
+ /// languages. The standard method for this is to build a minimal DFA
+ /// for each language and then compare them. If the DFAs are equivalent
+ /// (up to state renaming), then the languages are equivalent.
+ ///
+ /// This option is disabled by default.
+ pub fn minimize(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.minimize(yes);
+ self
+ }
+
+ /// Premultiply state identifiers in the underlying DFA transition tables.
+ ///
+ /// When enabled, state identifiers are premultiplied to point to their
+ /// corresponding row in the DFA's transition table. That is, given the
+ /// `i`th state, its corresponding premultiplied identifier is `i * k`
+ /// where `k` is the alphabet size of the DFA. (The alphabet size is at
+ /// most 256, but is in practice smaller if byte classes is enabled.)
+ ///
+ /// When state identifiers are not premultiplied, then the identifier of
+ /// the `i`th state is `i`.
+ ///
+ /// The advantage of premultiplying state identifiers is that is saves
+ /// a multiplication instruction per byte when searching with the DFA.
+ /// This has been observed to lead to a 20% performance benefit in
+ /// micro-benchmarks.
+ ///
+ /// The primary disadvantage of premultiplying state identifiers is
+ /// that they require a larger integer size to represent. For example,
+ /// if your DFA has 200 states, then its premultiplied form requires
+ /// 16 bits to represent every possible state identifier, where as its
+ /// non-premultiplied form only requires 8 bits.
+ ///
+ /// This option is enabled by default.
+ pub fn premultiply(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.premultiply(yes);
+ self
+ }
+
+ /// Shrink the size of the underlying DFA alphabet by mapping bytes to
+ /// their equivalence classes.
+ ///
+ /// When enabled, each DFA will use a map from all possible bytes to their
+ /// corresponding equivalence class. Each equivalence class represents a
+ /// set of bytes that does not discriminate between a match and a non-match
+ /// in the DFA. For example, the pattern `[ab]+` has at least two
+ /// equivalence classes: a set containing `a` and `b` and a set containing
+ /// every byte except for `a` and `b`. `a` and `b` are in the same
+ /// equivalence classes because they never discriminate between a match
+ /// and a non-match.
+ ///
+ /// The advantage of this map is that the size of the transition table can
+ /// be reduced drastically from `#states * 256 * sizeof(id)` to
+ /// `#states * k * sizeof(id)` where `k` is the number of equivalence
+ /// classes. As a result, total space usage can decrease substantially.
+ /// Moreover, since a smaller alphabet is used, compilation becomes faster
+ /// as well.
+ ///
+ /// The disadvantage of this map is that every byte searched must be
+ /// passed through this map before it can be used to determine the next
+ /// transition. This has a small match time performance cost.
+ ///
+ /// This option is enabled by default.
+ pub fn byte_classes(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.byte_classes(yes);
+ self
+ }
+
+ /// Apply best effort heuristics to shrink the NFA at the expense of more
+ /// time/memory.
+ ///
+ /// This may be exposed in the future, but for now is exported for use in
+ /// the `regex-automata-debug` tool.
+ #[doc(hidden)]
+ pub fn shrink(&mut self, yes: bool) -> &mut RegexBuilder {
+ self.dfa.shrink(yes);
+ self
+ }
+}
+
+#[cfg(feature = "std")]
+impl Default for RegexBuilder {
+ fn default() -> RegexBuilder {
+ RegexBuilder::new()
+ }
+}