/*!
A lazy DFA backed `Regex`.
This module provides a [`Regex`] backed by a lazy DFA. A `Regex` implements
convenience routines you might have come to expect, such as finding a match
and iterating over all non-overlapping matches. This `Regex` type is limited
in its capabilities to what a lazy DFA can provide. Therefore, APIs involving
capturing groups, for example, are not provided.
Internally, a `Regex` is composed of two DFAs. One is a "forward" DFA that
finds the end offset of a match, where as the other is a "reverse" DFA that
find the start offset of a match.
See the [parent module](crate::hybrid) for examples.
*/
use crate::{
hybrid::{
dfa::{self, DFA},
error::BuildError,
},
nfa::thompson,
util::{
iter,
search::{Anchored, Input, Match, MatchError, MatchKind},
},
};
/// A regular expression that uses hybrid NFA/DFAs (also called "lazy DFAs")
/// for searching.
///
/// A regular expression is comprised of two lazy 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.
///
/// # Fallibility
///
/// Most of the search routines defined on this type will _panic_ when the
/// underlying search fails. This might be because the DFA gave up because it
/// saw a quit byte, whether configured explicitly or via heuristic Unicode
/// word boundary support, although neither are enabled by default. It might
/// also fail if the underlying DFA determines it isn't making effective use of
/// the cache (which also never happens by default). Or it might fail because
/// an invalid `Input` configuration is given, for example, with an unsupported
/// [`Anchored`] mode.
///
/// If you need to handle these error cases instead of allowing them to trigger
/// a panic, then the lower level [`Regex::try_search`] provides a fallible API
/// that never panics.
///
/// # Example
///
/// This example shows how to cause a search to terminate if it sees a
/// `\n` byte, and handle the error returned. This could be useful if, for
/// example, you wanted to prevent a user supplied pattern from matching
/// across a line boundary.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{hybrid::{dfa, regex::Regex}, Input, MatchError};
///
/// let re = Regex::builder()
/// .dfa(dfa::Config::new().quit(b'\n', true))
/// .build(r"foo\p{any}+bar")?;
/// let mut cache = re.create_cache();
///
/// let input = Input::new("foo\nbar");
/// // Normally this would produce a match, since \p{any} contains '\n'.
/// // But since we instructed the automaton to enter a quit state if a
/// // '\n' is observed, this produces a match error instead.
/// let expected = MatchError::quit(b'\n', 3);
/// let got = re.try_search(&mut cache, &input).unwrap_err();
/// assert_eq!(expected, got);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[derive(Debug)]
pub struct Regex {
/// The forward lazy DFA. This can only find the end of a match.
forward: DFA,
/// The reverse lazy DFA. This can only find the start of a match.
///
/// This is built with 'all' match semantics (instead of leftmost-first)
/// so that it always finds the longest possible match (which corresponds
/// to the leftmost starting position). It is also compiled as an anchored
/// matcher and has 'starts_for_each_pattern' enabled. Including starting
/// states for each pattern is necessary to ensure that we only look for
/// matches of a pattern that matched in the forward direction. Otherwise,
/// we might wind up finding the "leftmost" starting position of a totally
/// different pattern!
reverse: DFA,
}
/// Convenience routines for regex and cache construction.
impl Regex {
/// Parse the given regular expression using the default configuration and
/// return the corresponding regex.
///
/// If you want a non-default configuration, then use the [`Builder`] to
/// set your own configuration.
///
/// # Example
///
/// ```
/// use regex_automata::{hybrid::regex::Regex, Match};
///
/// let re = Regex::new("foo[0-9]+bar")?;
/// let mut cache = re.create_cache();
/// assert_eq!(
/// Some(Match::must(0, 3..14)),
/// re.find(&mut cache, "zzzfoo12345barzzz"),
/// );
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[cfg(feature = "syntax")]
pub fn new(pattern: &str) -> Result<Regex, BuildError> {
Regex::builder().build(pattern)
}
/// Like `new`, but parses multiple patterns into a single "multi regex."
/// This similarly uses the default regex configuration.
///
/// # Example
///
/// ```
/// use regex_automata::{hybrid::regex::Regex, Match};
///
/// let re = Regex::new_many(&["[a-z]+", "[0-9]+"])?;
/// let mut cache = re.create_cache();
///
/// let mut it = re.find_iter(&mut cache, "abc 1 foo 4567 0 quux");
/// assert_eq!(Some(Match::must(0, 0..3)), it.next());
/// assert_eq!(Some(Match::must(1, 4..5)), it.next());
/// assert_eq!(Some(Match::must(0, 6..9)), it.next());
/// assert_eq!(Some(Match::must(1, 10..14)), it.next());
/// assert_eq!(Some(Match::must(1, 15..16)), it.next());
/// assert_eq!(Some(Match::must(0, 17..21)), it.next());
/// assert_eq!(None, it.next());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[cfg(feature = "syntax")]
pub fn new_many<P: AsRef<str>>(
patterns: &[P],
) -> Result<Regex, BuildError> {
Regex::builder().build_many(patterns)
}
/// Return a builder for configuring the construction of a `Regex`.
///
/// This is a convenience routine to avoid needing to import the
/// [`Builder`] type in common cases.
///
/// # Example
///
/// This example shows how to use the builder to disable UTF-8 mode
/// everywhere.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{
/// hybrid::regex::Regex, nfa::thompson, util::syntax, Match,
/// };
///
/// let re = Regex::builder()
/// .syntax(syntax::Config::new().utf8(false))
/// .thompson(thompson::Config::new().utf8(false))
/// .build(r"foo(?-u:[^b])ar.*")?;
/// let mut cache = re.create_cache();
///
/// let haystack = b"\xFEfoo\xFFarzz\xE2\x98\xFF\n";
/// let expected = Some(Match::must(0, 1..9));
/// let got = re.find(&mut cache, haystack);
/// assert_eq!(expected, got);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn builder() -> Builder {
Builder::new()
}
/// Create a new cache for this `Regex`.
///
/// The cache returned should only be used for searches for this
/// `Regex`. If you want to reuse the cache for another `Regex`, then
/// you must call [`Cache::reset`] with that `Regex` (or, equivalently,
/// [`Regex::reset_cache`]).
pub fn create_cache(&self) -> Cache {
Cache::new(self)
}
/// Reset the given cache such that it can be used for searching with the
/// this `Regex` (and only this `Regex`).
///
/// A cache reset permits reusing memory already allocated in this cache
/// with a different `Regex`.
///
/// Resetting a cache sets its "clear count" to 0. This is relevant if the
/// `Regex` has been configured to "give up" after it has cleared the cache
/// a certain number of times.
///
/// # Example
///
/// This shows how to re-purpose a cache for use with a different `Regex`.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{hybrid::regex::Regex, Match};
///
/// let re1 = Regex::new(r"\w")?;
/// let re2 = Regex::new(r"\W")?;
///
/// let mut cache = re1.create_cache();
/// assert_eq!(
/// Some(Match::must(0, 0..2)),
/// re1.find(&mut cache, "Δ"),
/// );
///
/// // Using 'cache' with re2 is not allowed. It may result in panics or
/// // incorrect results. In order to re-purpose the cache, we must reset
/// // it with the Regex we'd like to use it with.
/// //
/// // Similarly, after this reset, using the cache with 're1' is also not
/// // allowed.
/// re2.reset_cache(&mut cache);
/// assert_eq!(
/// Some(Match::must(0, 0..3)),
/// re2.find(&mut cache, "☃"),
/// );
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn reset_cache(&self, cache: &mut Cache) {
self.forward().reset_cache(&mut cache.forward);
self.reverse().reset_cache(&mut cache.reverse);
}
}
/// Standard infallible search routines for finding and iterating over matches.
impl Regex {
/// Returns true if and only if this regex matches the given haystack.
///
/// 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.
///
/// # Panics
///
/// This routine panics if the search could not complete. This can occur
/// in a number of circumstances:
///
/// * The configuration of the lazy DFA may permit it to "quit" the search.
/// For example, setting quit bytes or enabling heuristic support for
/// Unicode word boundaries. The default configuration does not enable any
/// option that could result in the lazy DFA quitting.
/// * The configuration of the lazy DFA may also permit it to "give up"
/// on a search if it makes ineffective use of its transition table
/// cache. The default configuration does not enable this by default,
/// although it is typically a good idea to.
/// * When the provided `Input` configuration is not supported. For
/// example, by providing an unsupported anchor mode.
///
/// When a search panics, callers cannot know whether a match exists or
/// not.
///
/// Use [`Regex::try_search`] if you want to handle these error conditions.
///
/// # Example
///
/// ```
/// use regex_automata::hybrid::regex::Regex;
///
/// let re = Regex::new("foo[0-9]+bar")?;
/// let mut cache = re.create_cache();
///
/// assert!(re.is_match(&mut cache, "foo12345bar"));
/// assert!(!re.is_match(&mut cache, "foobar"));
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn is_match<'h, I: Into<Input<'h>>>(
&self,
cache: &mut Cache,
input: I,
) -> bool {
// Not only can we do an "earliest" search, but we can avoid doing a
// reverse scan too.
self.forward()
.try_search_fwd(&mut cache.forward, &input.into().earliest(true))
.unwrap()
.is_some()
}
/// Returns the start and end offset of the leftmost match. If no match
/// exists, then `None` is returned.
///
/// # Panics
///
/// This routine panics if the search could not complete. This can occur
/// in a number of circumstances:
///
/// * The configuration of the lazy DFA may permit it to "quit" the search.
/// For example, setting quit bytes or enabling heuristic support for
/// Unicode word boundaries. The default configuration does not enable any
/// option that could result in the lazy DFA quitting.
/// * The configuration of the lazy DFA may also permit it to "give up"
/// on a search if it makes ineffective use of its transition table
/// cache. The default configuration does not enable this by default,
/// although it is typically a good idea to.
/// * When the provided `Input` configuration is not supported. For
/// example, by providing an unsupported anchor mode.
///
/// When a search panics, callers cannot know whether a match exists or
/// not.
///
/// Use [`Regex::try_search`] if you want to handle these error conditions.
///
/// # Example
///
/// ```
/// use regex_automata::{Match, hybrid::regex::Regex};
///
/// let re = Regex::new("foo[0-9]+")?;
/// let mut cache = re.create_cache();
/// assert_eq!(
/// Some(Match::must(0, 3..11)),
/// re.find(&mut cache, "zzzfoo12345zzz"),
/// );
///
/// // Even though a match is found after reading the first byte (`a`),
/// // the default 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")?;
/// let mut cache = re.create_cache();
/// assert_eq!(Some(Match::must(0, 0..3)), re.find(&mut cache, "abc"));
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn find<'h, I: Into<Input<'h>>>(
&self,
cache: &mut Cache,
input: I,
) -> Option<Match> {
self.try_search(cache, &input.into()).unwrap()
}
/// Returns an iterator over all non-overlapping leftmost matches in the
/// given bytes. If no match exists, then the iterator yields no elements.
///
/// # Panics
///
/// This routine panics if the search could not complete. This can occur
/// in a number of circumstances:
///
/// * The configuration of the lazy DFA may permit it to "quit" the search.
/// For example, setting quit bytes or enabling heuristic support for
/// Unicode word boundaries. The default configuration does not enable any
/// option that could result in the lazy DFA quitting.
/// * The configuration of the lazy DFA may also permit it to "give up"
/// on a search if it makes ineffective use of its transition table
/// cache. The default configuration does not enable this by default,
/// although it is typically a good idea to.
/// * When the provided `Input` configuration is not supported. For
/// example, by providing an unsupported anchor mode.
///
/// When a search panics, callers cannot know whether a match exists or
/// not.
///
/// The above conditions also apply to the iterator returned as well. For
/// example, if the lazy DFA gives up or quits during a search using this
/// method, then a panic will occur during iteration.
///
/// Use [`Regex::try_search`] with [`util::iter::Searcher`](iter::Searcher)
/// if you want to handle these error conditions.
///
/// # Example
///
/// ```
/// use regex_automata::{hybrid::regex::Regex, Match};
///
/// let re = Regex::new("foo[0-9]+")?;
/// let mut cache = re.create_cache();
///
/// let text = "foo1 foo12 foo123";
/// let matches: Vec<Match> = re.find_iter(&mut cache, text).collect();
/// assert_eq!(matches, vec![
/// Match::must(0, 0..4),
/// Match::must(0, 5..10),
/// Match::must(0, 11..17),
/// ]);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn find_iter<'r, 'c, 'h, I: Into<Input<'h>>>(
&'r self,
cache: &'c mut Cache,
input: I,
) -> FindMatches<'r, 'c, 'h> {
let it = iter::Searcher::new(input.into());
FindMatches { re: self, cache, it }
}
}
/// Lower level "search" primitives that accept a `&Input` for cheap reuse
/// and return an error if one occurs instead of panicking.
impl Regex {
/// Returns the start and end offset of the leftmost match. If no match
/// exists, then `None` is returned.
///
/// This is like [`Regex::find`] but with two differences:
///
/// 1. It is not generic over `Into<Input>` and instead accepts a
/// `&Input`. This permits reusing the same `Input` for multiple searches
/// without needing to create a new one. This _may_ help with latency.
/// 2. It returns an error if the search could not complete where as
/// [`Regex::find`] will panic.
///
/// # Errors
///
/// This routine errors if the search could not complete. This can occur
/// in a number of circumstances:
///
/// * The configuration of the lazy DFA may permit it to "quit" the search.
/// For example, setting quit bytes or enabling heuristic support for
/// Unicode word boundaries. The default configuration does not enable any
/// option that could result in the lazy DFA quitting.
/// * The configuration of the lazy DFA may also permit it to "give up"
/// on a search if it makes ineffective use of its transition table
/// cache. The default configuration does not enable this by default,
/// although it is typically a good idea to.
/// * When the provided `Input` configuration is not supported. For
/// example, by providing an unsupported anchor mode.
///
/// When a search returns an error, callers cannot know whether a match
/// exists or not.
#[inline]
pub fn try_search(
&self,
cache: &mut Cache,
input: &Input<'_>,
) -> Result<Option<Match>, MatchError> {
let (fcache, rcache) = (&mut cache.forward, &mut cache.reverse);
let end = match self.forward().try_search_fwd(fcache, input)? {
None => return Ok(None),
Some(end) => end,
};
// This special cases an empty match at the beginning of the search. If
// our end matches our start, then since a reverse DFA can't match past
// the start, it must follow that our starting position is also our end
// position. So short circuit and skip the reverse search.
if input.start() == end.offset() {
return Ok(Some(Match::new(
end.pattern(),
end.offset()..end.offset(),
)));
}
// We can also skip the reverse search if we know our search was
// anchored. This occurs either when the input config is anchored or
// when we know the regex itself is anchored. In this case, we know the
// start of the match, if one is found, must be the start of the
// search.
if self.is_anchored(input) {
return Ok(Some(Match::new(
end.pattern(),
input.start()..end.offset(),
)));
}
// N.B. I have tentatively convinced myself that it isn't necessary
// to specify the specific pattern for the reverse search since the
// reverse search will always find the same pattern to match as the
// forward search. But I lack a rigorous proof. Why not just provide
// the pattern anyway? Well, if it is needed, then leaving it out
// gives us a chance to find a witness. (Also, if we don't need to
// specify the pattern, then we don't need to build the reverse DFA
// with 'starts_for_each_pattern' enabled. It doesn't matter too much
// for the lazy DFA, but does make the overall DFA bigger.)
//
// We also need to be careful to disable 'earliest' for the reverse
// search, since it could be enabled for the forward search. In the
// reverse case, to satisfy "leftmost" criteria, we need to match as
// much as we can. We also need to be careful to make the search
// anchored. We don't want the reverse search to report any matches
// other than the one beginning at the end of our forward search.
let revsearch = input
.clone()
.span(input.start()..end.offset())
.anchored(Anchored::Yes)
.earliest(false);
let start = self
.reverse()
.try_search_rev(rcache, &revsearch)?
.expect("reverse search must match if forward search does");
debug_assert_eq!(
start.pattern(),
end.pattern(),
"forward and reverse search must match same pattern",
);
debug_assert!(start.offset() <= end.offset());
Ok(Some(Match::new(end.pattern(), start.offset()..end.offset())))
}
/// Returns true if either the given input specifies an anchored search
/// or if the underlying NFA is always anchored.
fn is_anchored(&self, input: &Input<'_>) -> bool {
match input.get_anchored() {
Anchored::No => {
self.forward().get_nfa().is_always_start_anchored()
}
Anchored::Yes | Anchored::Pattern(_) => true,
}
}
}
/// Non-search APIs for querying information about the regex and setting a
/// prefilter.
impl Regex {
/// Return the underlying lazy DFA responsible for forward matching.
///
/// This is useful for accessing the underlying lazy DFA and using it
/// directly if the situation calls for it.
pub fn forward(&self) -> &DFA {
&self.forward
}
/// Return the underlying lazy DFA responsible for reverse matching.
///
/// This is useful for accessing the underlying lazy DFA and using it
/// directly if the situation calls for it.
pub fn reverse(&self) -> &DFA {
&self.reverse
}
/// Returns the total number of patterns matched by this regex.
///
/// # Example
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::hybrid::regex::Regex;
///
/// let re = Regex::new_many(&[r"[a-z]+", r"[0-9]+", r"\w+"])?;
/// assert_eq!(3, re.pattern_len());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn pattern_len(&self) -> usize {
assert_eq!(self.forward().pattern_len(), self.reverse().pattern_len());
self.forward().pattern_len()
}
}
/// An iterator over all non-overlapping matches for an infallible search.
///
/// The iterator yields a [`Match`] value until no more matches could be found.
/// If the underlying regex engine returns an error, then a panic occurs.
///
/// The lifetime parameters are as follows:
///
/// * `'r` represents the lifetime of the regex object.
/// * `'h` represents the lifetime of the haystack being searched.
/// * `'c` represents the lifetime of the regex cache.
///
/// This iterator can be created with the [`Regex::find_iter`] method.
#[derive(Debug)]
pub struct FindMatches<'r, 'c, 'h> {
re: &'r Regex,
cache: &'c mut Cache,
it: iter::Searcher<'h>,
}
impl<'r, 'c, 'h> Iterator for FindMatches<'r, 'c, 'h> {
type Item = Match;
#[inline]
fn next(&mut self) -> Option<Match> {
let FindMatches { re, ref mut cache, ref mut it } = *self;
it.advance(|input| re.try_search(cache, input))
}
}
/// A cache represents a partially computed forward and reverse DFA.
///
/// A cache is the key component that differentiates a classical DFA and a
/// hybrid NFA/DFA (also called a "lazy DFA"). Where a classical DFA builds a
/// complete transition table that can handle all possible inputs, a hybrid
/// NFA/DFA starts with an empty transition table and builds only the parts
/// required during search. The parts that are built are stored in a cache. For
/// this reason, a cache is a required parameter for nearly every operation on
/// a [`Regex`].
///
/// Caches can be created from their corresponding `Regex` via
/// [`Regex::create_cache`]. A cache can only be used with either the `Regex`
/// that created it, or the `Regex` that was most recently used to reset it
/// with [`Cache::reset`]. Using a cache with any other `Regex` may result in
/// panics or incorrect results.
#[derive(Debug, Clone)]
pub struct Cache {
forward: dfa::Cache,
reverse: dfa::Cache,
}
impl Cache {
/// Create a new cache for the given `Regex`.
///
/// The cache returned should only be used for searches for the given
/// `Regex`. If you want to reuse the cache for another `Regex`, then you
/// must call [`Cache::reset`] with that `Regex`.
pub fn new(re: &Regex) -> Cache {
let forward = dfa::Cache::new(re.forward());
let reverse = dfa::Cache::new(re.reverse());
Cache { forward, reverse }
}
/// Reset this cache such that it can be used for searching with the given
/// `Regex` (and only that `Regex`).
///
/// A cache reset permits reusing memory already allocated in this cache
/// with a different `Regex`.
///
/// Resetting a cache sets its "clear count" to 0. This is relevant if the
/// `Regex` has been configured to "give up" after it has cleared the cache
/// a certain number of times.
///
/// # Example
///
/// This shows how to re-purpose a cache for use with a different `Regex`.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{hybrid::regex::Regex, Match};
///
/// let re1 = Regex::new(r"\w")?;
/// let re2 = Regex::new(r"\W")?;
///
/// let mut cache = re1.create_cache();
/// assert_eq!(
/// Some(Match::must(0, 0..2)),
/// re1.find(&mut cache, "Δ"),
/// );
///
/// // Using 'cache' with re2 is not allowed. It may result in panics or
/// // incorrect results. In order to re-purpose the cache, we must reset
/// // it with the Regex we'd like to use it with.
/// //
/// // Similarly, after this reset, using the cache with 're1' is also not
/// // allowed.
/// cache.reset(&re2);
/// assert_eq!(
/// Some(Match::must(0, 0..3)),
/// re2.find(&mut cache, "☃"),
/// );
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn reset(&mut self, re: &Regex) {
self.forward.reset(re.forward());
self.reverse.reset(re.reverse());
}
/// Return a reference to the forward cache.
pub fn forward(&mut self) -> &dfa::Cache {
&self.forward
}
/// Return a reference to the reverse cache.
pub fn reverse(&mut self) -> &dfa::Cache {
&self.reverse
}
/// Return a mutable reference to the forward cache.
///
/// If you need mutable references to both the forward and reverse caches,
/// then use [`Cache::as_parts_mut`].
pub fn forward_mut(&mut self) -> &mut dfa::Cache {
&mut self.forward
}
/// Return a mutable reference to the reverse cache.
///
/// If you need mutable references to both the forward and reverse caches,
/// then use [`Cache::as_parts_mut`].
pub fn reverse_mut(&mut self) -> &mut dfa::Cache {
&mut self.reverse
}
/// Return references to the forward and reverse caches, respectively.
pub fn as_parts(&self) -> (&dfa::Cache, &dfa::Cache) {
(&self.forward, &self.reverse)
}
/// Return mutable references to the forward and reverse caches,
/// respectively.
pub fn as_parts_mut(&mut self) -> (&mut dfa::Cache, &mut dfa::Cache) {
(&mut self.forward, &mut self.reverse)
}
/// Returns the heap memory usage, in bytes, as a sum of the forward and
/// reverse lazy DFA caches.
///
/// This does **not** include the stack size used up by this cache. To
/// compute that, use `std::mem::size_of::<Cache>()`.
pub fn memory_usage(&self) -> usize {
self.forward.memory_usage() + self.reverse.memory_usage()
}
}
/// A builder for a regex based on a hybrid NFA/DFA.
///
/// This builder permits configuring options for the syntax of a pattern, the
/// NFA construction, the lazy DFA construction and finally the regex searching
/// itself. This builder is different from a general purpose regex builder
/// in that it permits fine grain configuration of the construction process.
/// The trade off for this is complexity, and the possibility of setting a
/// configuration that might not make sense. For example, there are two
/// different UTF-8 modes:
///
/// * [`syntax::Config::utf8`](crate::util::syntax::Config::utf8) controls
/// whether the pattern itself can contain sub-expressions that match invalid
/// UTF-8.
/// * [`thompson::Config::utf8`] controls how the regex iterators themselves
/// advance the starting position of the next search when a match with zero
/// length is found.
///
/// Generally speaking, callers will want to either enable all of these or
/// disable all of these.
///
/// Internally, building a regex requires building two hybrid NFA/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 [`dfa::Builder`] to construct a single hybrid NFA/DFA, which is cheaper
/// than building two of them.
///
/// # Example
///
/// This example shows how to disable UTF-8 mode in the syntax and the regex
/// itself. This is generally what you want for matching on arbitrary bytes.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{
/// hybrid::regex::Regex, nfa::thompson, util::syntax, Match,
/// };
///
/// let re = Regex::builder()
/// .syntax(syntax::Config::new().utf8(false))
/// .thompson(thompson::Config::new().utf8(false))
/// .build(r"foo(?-u:[^b])ar.*")?;
/// let mut cache = re.create_cache();
///
/// let haystack = b"\xFEfoo\xFFarzz\xE2\x98\xFF\n";
/// let expected = Some(Match::must(0, 1..9));
/// let got = re.find(&mut cache, haystack);
/// assert_eq!(expected, got);
/// // Notice that `(?-u:[^b])` matches invalid UTF-8,
/// // but the subsequent `.*` does not! Disabling UTF-8
/// // on the syntax permits this.
/// assert_eq!(b"foo\xFFarzz", &haystack[got.unwrap().range()]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[derive(Clone, Debug)]
pub struct Builder {
dfa: dfa::Builder,
}
impl Builder {
/// Create a new regex builder with the default configuration.
pub fn new() -> Builder {
Builder { dfa: DFA::builder() }
}
/// Build a regex from the given pattern.
///
/// If there was a problem parsing or compiling the pattern, then an error
/// is returned.
#[cfg(feature = "syntax")]
pub fn build(&self, pattern: &str) -> Result<Regex, BuildError> {
self.build_many(&[pattern])
}
/// Build a regex from the given patterns.
#[cfg(feature = "syntax")]
pub fn build_many<P: AsRef<str>>(
&self,
patterns: &[P],
) -> Result<Regex, BuildError> {
let forward = self.dfa.build_many(patterns)?;
let reverse = self
.dfa
.clone()
.configure(
DFA::config()
.prefilter(None)
.specialize_start_states(false)
.match_kind(MatchKind::All),
)
.thompson(thompson::Config::new().reverse(true))
.build_many(patterns)?;
Ok(self.build_from_dfas(forward, reverse))
}
/// Build a regex from its component forward and reverse hybrid NFA/DFAs.
///
/// This is useful when you've built a forward and reverse lazy DFA
/// separately, and want to combine them into a single regex. Once build,
/// the individual DFAs given can still be accessed via [`Regex::forward`]
/// and [`Regex::reverse`].
///
/// It is important that the reverse lazy DFA be compiled under the
/// following conditions:
///
/// * It should use [`MatchKind::All`] semantics.
/// * It should match in reverse.
/// * Otherwise, its configuration should match the forward DFA.
///
/// If these conditions aren't satisfied, then the behavior of searches is
/// unspecified.
///
/// Note that when using this constructor, no configuration is applied.
/// Since this routine provides the DFAs to the builder, there is no
/// opportunity to apply other configuration options.
///
/// # Example
///
/// This shows how to build individual lazy forward and reverse DFAs, and
/// then combine them into a single `Regex`.
///
/// ```
/// use regex_automata::{
/// hybrid::{dfa::DFA, regex::Regex},
/// nfa::thompson,
/// MatchKind,
/// };
///
/// let fwd = DFA::new(r"foo[0-9]+")?;
/// let rev = DFA::builder()
/// .configure(DFA::config().match_kind(MatchKind::All))
/// .thompson(thompson::Config::new().reverse(true))
/// .build(r"foo[0-9]+")?;
///
/// let re = Regex::builder().build_from_dfas(fwd, rev);
/// let mut cache = re.create_cache();
/// assert_eq!(true, re.is_match(&mut cache, "foo123"));
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn build_from_dfas(&self, forward: DFA, reverse: DFA) -> Regex {
Regex { forward, reverse }
}
/// Set the syntax configuration for this builder using
/// [`syntax::Config`](crate::util::syntax::Config).
///
/// This permits setting things like case insensitivity, Unicode and multi
/// line mode.
#[cfg(feature = "syntax")]
pub fn syntax(
&mut self,
config: crate::util::syntax::Config,
) -> &mut Builder {
self.dfa.syntax(config);
self
}
/// Set the Thompson NFA configuration for this builder using
/// [`nfa::thompson::Config`](thompson::Config).
///
/// This permits setting things like whether additional time should be
/// spent shrinking the size of the NFA.
#[cfg(feature = "syntax")]
pub fn thompson(&mut self, config: thompson::Config) -> &mut Builder {
self.dfa.thompson(config);
self
}
/// Set the lazy DFA compilation configuration for this builder using
/// [`dfa::Config`](dfa::Config).
///
/// This permits setting things like whether Unicode word boundaries should
/// be heuristically supported or settings how the behavior of the cache.
pub fn dfa(&mut self, config: dfa::Config) -> &mut Builder {
self.dfa.configure(config);
self
}
}
impl Default for Builder {
fn default() -> Builder {
Builder::new()
}
}
