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Diffstat (limited to 'third_party/rust/regex-automata/src/meta/regex.rs')
| -rw-r--r-- | third_party/rust/regex-automata/src/meta/regex.rs | 3649 |
1 files changed, 3649 insertions, 0 deletions
diff --git a/third_party/rust/regex-automata/src/meta/regex.rs b/third_party/rust/regex-automata/src/meta/regex.rs new file mode 100644 index 0000000000..3a04b14d88 --- /dev/null +++ b/third_party/rust/regex-automata/src/meta/regex.rs @@ -0,0 +1,3649 @@ +use core::{ + borrow::Borrow, + panic::{RefUnwindSafe, UnwindSafe}, +}; + +use alloc::{boxed::Box, sync::Arc, vec, vec::Vec}; + +use regex_syntax::{ + ast, + hir::{self, Hir}, +}; + +use crate::{ + meta::{ + error::BuildError, + strategy::{self, Strategy}, + wrappers, + }, + nfa::thompson::WhichCaptures, + util::{ + captures::{Captures, GroupInfo}, + iter, + pool::{Pool, PoolGuard}, + prefilter::Prefilter, + primitives::{NonMaxUsize, PatternID}, + search::{HalfMatch, Input, Match, MatchKind, PatternSet, Span}, + }, +}; + +/// A type alias for our pool of meta::Cache that fixes the type parameters to +/// what we use for the meta regex below. +type CachePool = Pool<Cache, CachePoolFn>; + +/// Same as above, but for the guard returned by a pool. +type CachePoolGuard<'a> = PoolGuard<'a, Cache, CachePoolFn>; + +/// The type of the closure we use to create new caches. We need to spell out +/// all of the marker traits or else we risk leaking !MARKER impls. +type CachePoolFn = + Box<dyn Fn() -> Cache + Send + Sync + UnwindSafe + RefUnwindSafe>; + +/// A regex matcher that works by composing several other regex matchers +/// automatically. +/// +/// In effect, a meta regex papers over a lot of the quirks or performance +/// problems in each of the regex engines in this crate. Its goal is to provide +/// an infallible and simple API that "just does the right thing" in the common +/// case. +/// +/// A meta regex is the implementation of a `Regex` in the `regex` crate. +/// Indeed, the `regex` crate API is essentially just a light wrapper over +/// this type. This includes the `regex` crate's `RegexSet` API! +/// +/// # Composition +/// +/// This is called a "meta" matcher precisely because it uses other regex +/// matchers to provide a convenient high level regex API. Here are some +/// examples of how other regex matchers are composed: +/// +/// * When calling [`Regex::captures`], instead of immediately +/// running a slower but more capable regex engine like the +/// [`PikeVM`](crate::nfa::thompson::pikevm::PikeVM), the meta regex engine +/// will usually first look for the bounds of a match with a higher throughput +/// regex engine like a [lazy DFA](crate::hybrid). Only when a match is found +/// is a slower engine like `PikeVM` used to find the matching span for each +/// capture group. +/// * While higher throughout engines like the lazy DFA cannot handle +/// Unicode word boundaries in general, they can still be used on pure ASCII +/// haystacks by pretending that Unicode word boundaries are just plain ASCII +/// word boundaries. However, if a haystack is not ASCII, the meta regex engine +/// will automatically switch to a (possibly slower) regex engine that supports +/// Unicode word boundaries in general. +/// * In some cases where a regex pattern is just a simple literal or a small +/// set of literals, an actual regex engine won't be used at all. Instead, +/// substring or multi-substring search algorithms will be employed. +/// +/// There are many other forms of composition happening too, but the above +/// should give a general idea. In particular, it may perhaps be surprising +/// that *multiple* regex engines might get executed for a single search. That +/// is, the decision of what regex engine to use is not _just_ based on the +/// pattern, but also based on the dynamic execution of the search itself. +/// +/// The primary reason for this composition is performance. The fundamental +/// tension is that the faster engines tend to be less capable, and the more +/// capable engines tend to be slower. +/// +/// Note that the forms of composition that are allowed are determined by +/// compile time crate features and configuration. For example, if the `hybrid` +/// feature isn't enabled, or if [`Config::hybrid`] has been disabled, then the +/// meta regex engine will never use a lazy DFA. +/// +/// # Synchronization and cloning +/// +/// Most of the regex engines in this crate require some kind of mutable +/// "scratch" space to read and write from while performing a search. Since +/// a meta regex composes these regex engines, a meta regex also requires +/// mutable scratch space. This scratch space is called a [`Cache`]. +/// +/// Most regex engines _also_ usually have a read-only component, typically +/// a [Thompson `NFA`](crate::nfa::thompson::NFA). +/// +/// In order to make the `Regex` API convenient, most of the routines hide +/// the fact that a `Cache` is needed at all. To achieve this, a [memory +/// pool](crate::util::pool::Pool) is used internally to retrieve `Cache` +/// values in a thread safe way that also permits reuse. This in turn implies +/// that every such search call requires some form of synchronization. Usually +/// this synchronization is fast enough to not notice, but in some cases, it +/// can be a bottleneck. This typically occurs when all of the following are +/// true: +/// +/// * The same `Regex` is shared across multiple threads simultaneously, +/// usually via a [`util::lazy::Lazy`](crate::util::lazy::Lazy) or something +/// similar from the `once_cell` or `lazy_static` crates. +/// * The primary unit of work in each thread is a regex search. +/// * Searches are run on very short haystacks. +/// +/// This particular case can lead to high contention on the pool used by a +/// `Regex` internally, which can in turn increase latency to a noticeable +/// effect. This cost can be mitigated in one of the following ways: +/// +/// * Use a distinct copy of a `Regex` in each thread, usually by cloning it. +/// Cloning a `Regex` _does not_ do a deep copy of its read-only component. +/// But it does lead to each `Regex` having its own memory pool, which in +/// turn eliminates the problem of contention. In general, this technique should +/// not result in any additional memory usage when compared to sharing the same +/// `Regex` across multiple threads simultaneously. +/// * Use lower level APIs, like [`Regex::search_with`], which permit passing +/// a `Cache` explicitly. In this case, it is up to you to determine how best +/// to provide a `Cache`. For example, you might put a `Cache` in thread-local +/// storage if your use case allows for it. +/// +/// Overall, this is an issue that happens rarely in practice, but it can +/// happen. +/// +/// # Warning: spin-locks may be used in alloc-only mode +/// +/// When this crate is built without the `std` feature and the high level APIs +/// on a `Regex` are used, then a spin-lock will be used to synchronize access +/// to an internal pool of `Cache` values. This may be undesirable because +/// a spin-lock is [effectively impossible to implement correctly in user +/// space][spinlocks-are-bad]. That is, more concretely, the spin-lock could +/// result in a deadlock. +/// +/// [spinlocks-are-bad]: https://matklad.github.io/2020/01/02/spinlocks-considered-harmful.html +/// +/// If one wants to avoid the use of spin-locks when the `std` feature is +/// disabled, then you must use APIs that accept a `Cache` value explicitly. +/// For example, [`Regex::search_with`]. +/// +/// # Example +/// +/// ``` +/// use regex_automata::meta::Regex; +/// +/// let re = Regex::new(r"^[0-9]{4}-[0-9]{2}-[0-9]{2}$")?; +/// assert!(re.is_match("2010-03-14")); +/// +/// # Ok::<(), Box<dyn std::error::Error>>(()) +/// ``` +/// +/// # Example: anchored search +/// +/// This example shows how to use [`Input::anchored`] to run an anchored +/// search, even when the regex pattern itself isn't anchored. An anchored +/// search guarantees that if a match is found, then the start offset of the +/// match corresponds to the offset at which the search was started. +/// +/// ``` +/// use regex_automata::{meta::Regex, Anchored, Input, Match}; +/// +/// let re = Regex::new(r"\bfoo\b")?; +/// let input = Input::new("xx foo xx").range(3..).anchored(Anchored::Yes); +/// // The offsets are in terms of the original haystack. +/// assert_eq!(Some(Match::must(0, 3..6)), re.find(input)); +/// +/// // Notice that no match occurs here, because \b still takes the +/// // surrounding context into account, even if it means looking back +/// // before the start of your search. +/// let hay = "xxfoo xx"; +/// let input = Input::new(hay).range(2..).anchored(Anchored::Yes); +/// assert_eq!(None, re.find(input)); +/// // Indeed, you cannot achieve the above by simply slicing the +/// // haystack itself, since the regex engine can't see the +/// // surrounding context. This is why 'Input' permits setting +/// // the bounds of a search! +/// let input = Input::new(&hay[2..]).anchored(Anchored::Yes); +/// // WRONG! +/// assert_eq!(Some(Match::must(0, 0..3)), re.find(input)); +/// +/// # Ok::<(), Box<dyn std::error::Error>>(()) +/// ``` +/// +/// # Example: earliest search +/// +/// This example shows how to use [`Input::earliest`] to run a search that +/// might stop before finding the typical leftmost match. +/// +/// ``` +/// use regex_automata::{meta::Regex, Anchored, Input, Match}; +/// +/// let re = Regex::new(r"[a-z]{3}|b")?; +/// let input = Input::new("abc").earliest(true); +/// assert_eq!(Some(Match::must(0, 1..2)), re.find(input)); +/// +/// // Note that "earliest" isn't really a match semantic unto itself. +/// // Instead, it is merely an instruction to whatever regex engine +/// // gets used internally to quit as soon as it can. For example, +/// // this regex uses a different search technique, and winds up +/// // producing a different (but valid) match! +/// let re = Regex::new(r"abc|b")?; +/// let input = Input::new("abc").earliest(true); +/// assert_eq!(Some(Match::must(0, 0..3)), re.find(input)); +/// +/// # Ok::<(), Box<dyn std::error::Error>>(()) +/// ``` +/// +/// # Example: change the line terminator +/// +/// This example shows how to enable multi-line mode by default and change +/// the line terminator to the NUL byte: +/// +/// ``` +/// use regex_automata::{meta::Regex, util::syntax, Match}; +/// +/// let re = Regex::builder() +/// .syntax(syntax::Config::new().multi_line(true)) +/// .configure(Regex::config().line_terminator(b'\x00')) +/// .build(r"^foo$")?; +/// let hay = "\x00foo\x00"; +/// assert_eq!(Some(Match::must(0, 1..4)), re.find(hay)); +/// +/// # Ok::<(), Box<dyn std::error::Error>>(()) +/// ``` +#[derive(Debug)] +pub struct Regex { + /// The actual regex implementation. + imp: Arc<RegexI>, + /// A thread safe pool of caches. + /// + /// For the higher level search APIs, a `Cache` is automatically plucked + /// from this pool before running a search. The lower level `with` methods + /// permit the caller to provide their own cache, thereby bypassing + /// accesses to this pool. + /// + /// Note that we put this outside the `Arc` so that cloning a `Regex` + /// results in creating a fresh `CachePool`. This in turn permits callers + /// to clone regexes into separate threads where each such regex gets + /// the pool's "thread owner" optimization. Otherwise, if one shares the + /// `Regex` directly, then the pool will go through a slower mutex path for + /// all threads except for the "owner." + pool: CachePool, +} + +/// The internal implementation of `Regex`, split out so that it can be wrapped +/// in an `Arc`. +#[derive(Debug)] +struct RegexI { + /// The core matching engine. + /// + /// Why is this reference counted when RegexI is already wrapped in an Arc? + /// Well, we need to capture this in a closure to our `Pool` below in order + /// to create new `Cache` values when needed. So since it needs to be in + /// two places, we make it reference counted. + /// + /// We make `RegexI` itself reference counted too so that `Regex` itself + /// stays extremely small and very cheap to clone. + strat: Arc<dyn Strategy>, + /// Metadata about the regexes driving the strategy. The metadata is also + /// usually stored inside the strategy too, but we put it here as well + /// so that we can get quick access to it (without virtual calls) before + /// executing the regex engine. For example, we use this metadata to + /// detect a subset of cases where we know a match is impossible, and can + /// thus avoid calling into the strategy at all. + /// + /// Since `RegexInfo` is stored in multiple places, it is also reference + /// counted. + info: RegexInfo, +} + +/// Convenience constructors for a `Regex` using the default configuration. +impl Regex { + /// Builds a `Regex` from a single pattern string using the default + /// configuration. + /// + /// If there was a problem parsing the pattern or a problem turning it into + /// a regex matcher, then an error is returned. + /// + /// If you want to change the configuration of a `Regex`, use a [`Builder`] + /// with a [`Config`]. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Match}; + /// + /// let re = Regex::new(r"(?Rm)^foo$")?; + /// let hay = "\r\nfoo\r\n"; + /// assert_eq!(Some(Match::must(0, 2..5)), re.find(hay)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn new(pattern: &str) -> Result<Regex, BuildError> { + Regex::builder().build(pattern) + } + + /// Builds a `Regex` from many pattern strings using the default + /// configuration. + /// + /// If there was a problem parsing any of the patterns or a problem turning + /// them into a regex matcher, then an error is returned. + /// + /// If you want to change the configuration of a `Regex`, use a [`Builder`] + /// with a [`Config`]. + /// + /// # Example: simple lexer + /// + /// This simplistic example leverages the multi-pattern support to build a + /// simple little lexer. The pattern ID in the match tells you which regex + /// matched, which in turn might be used to map back to the "type" of the + /// token returned by the lexer. + /// + /// ``` + /// use regex_automata::{meta::Regex, Match}; + /// + /// let re = Regex::new_many(&[ + /// r"[[:space:]]", + /// r"[A-Za-z0-9][A-Za-z0-9_]+", + /// r"->", + /// r".", + /// ])?; + /// let haystack = "fn is_boss(bruce: i32, springsteen: String) -> bool;"; + /// let matches: Vec<Match> = re.find_iter(haystack).collect(); + /// assert_eq!(matches, vec![ + /// Match::must(1, 0..2), // 'fn' + /// Match::must(0, 2..3), // ' ' + /// Match::must(1, 3..10), // 'is_boss' + /// Match::must(3, 10..11), // '(' + /// Match::must(1, 11..16), // 'bruce' + /// Match::must(3, 16..17), // ':' + /// Match::must(0, 17..18), // ' ' + /// Match::must(1, 18..21), // 'i32' + /// Match::must(3, 21..22), // ',' + /// Match::must(0, 22..23), // ' ' + /// Match::must(1, 23..34), // 'springsteen' + /// Match::must(3, 34..35), // ':' + /// Match::must(0, 35..36), // ' ' + /// Match::must(1, 36..42), // 'String' + /// Match::must(3, 42..43), // ')' + /// Match::must(0, 43..44), // ' ' + /// Match::must(2, 44..46), // '->' + /// Match::must(0, 46..47), // ' ' + /// Match::must(1, 47..51), // 'bool' + /// Match::must(3, 51..52), // ';' + /// ]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// One can write a lexer like the above using a regex like + /// `(?P<space>[[:space:]])|(?P<ident>[A-Za-z0-9][A-Za-z0-9_]+)|...`, + /// but then you need to ask whether capture group matched to determine + /// which branch in the regex matched, and thus, which token the match + /// corresponds to. In contrast, the above example includes the pattern ID + /// in the match. There's no need to use capture groups at all. + /// + /// # Example: finding the pattern that caused an error + /// + /// When a syntax error occurs, it is possible to ask which pattern + /// caused the syntax error. + /// + /// ``` + /// use regex_automata::{meta::Regex, PatternID}; + /// + /// let err = Regex::new_many(&["a", "b", r"\p{Foo}", "c"]).unwrap_err(); + /// assert_eq!(Some(PatternID::must(2)), err.pattern()); + /// ``` + /// + /// # Example: zero patterns is valid + /// + /// Building a regex with zero patterns results in a regex that never + /// matches anything. Because this routine is generic, passing an empty + /// slice usually requires a turbo-fish (or something else to help type + /// inference). + /// + /// ``` + /// use regex_automata::{meta::Regex, util::syntax, Match}; + /// + /// let re = Regex::new_many::<&str>(&[])?; + /// assert_eq!(None, re.find("")); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn new_many<P: AsRef<str>>( + patterns: &[P], + ) -> Result<Regex, BuildError> { + Regex::builder().build_many(patterns) + } + + /// Return a default configuration for a `Regex`. + /// + /// This is a convenience routine to avoid needing to import the [`Config`] + /// type when customizing the construction of a `Regex`. + /// + /// # Example: lower the NFA size limit + /// + /// In some cases, the default size limit might be too big. The size limit + /// can be lowered, which will prevent large regex patterns from compiling. + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::meta::Regex; + /// + /// let result = Regex::builder() + /// .configure(Regex::config().nfa_size_limit(Some(20 * (1<<10)))) + /// // Not even 20KB is enough to build a single large Unicode class! + /// .build(r"\pL"); + /// assert!(result.is_err()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn config() -> Config { + Config::new() + } + + /// 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: change the line terminator + /// + /// This example shows how to enable multi-line mode by default and change + /// the line terminator to the NUL byte: + /// + /// ``` + /// use regex_automata::{meta::Regex, util::syntax, Match}; + /// + /// let re = Regex::builder() + /// .syntax(syntax::Config::new().multi_line(true)) + /// .configure(Regex::config().line_terminator(b'\x00')) + /// .build(r"^foo$")?; + /// let hay = "\x00foo\x00"; + /// assert_eq!(Some(Match::must(0, 1..4)), re.find(hay)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn builder() -> Builder { + Builder::new() + } +} + +/// High level convenience routines for using a regex to search a haystack. +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. (Consider how this might make + /// a difference given the regex `a+` on the haystack `aaaaaaaaaaaaaaa`. + /// This routine _may_ stop after it sees the first `a`, but routines like + /// `find` need to continue searching because `+` is greedy by default.) + /// + /// # Example + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new("foo[0-9]+bar")?; + /// + /// assert!(re.is_match("foo12345bar")); + /// assert!(!re.is_match("foobar")); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// # Example: consistency with search APIs + /// + /// `is_match` is guaranteed to return `true` whenever `find` returns a + /// match. This includes searches that are executed entirely within a + /// codepoint: + /// + /// ``` + /// use regex_automata::{meta::Regex, Input}; + /// + /// let re = Regex::new("a*")?; + /// + /// // This doesn't match because the default configuration bans empty + /// // matches from splitting a codepoint. + /// assert!(!re.is_match(Input::new("☃").span(1..2))); + /// assert_eq!(None, re.find(Input::new("☃").span(1..2))); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// Notice that when UTF-8 mode is disabled, then the above reports a + /// match because the restriction against zero-width matches that split a + /// codepoint has been lifted: + /// + /// ``` + /// use regex_automata::{meta::Regex, Input, Match}; + /// + /// let re = Regex::builder() + /// .configure(Regex::config().utf8_empty(false)) + /// .build("a*")?; + /// + /// assert!(re.is_match(Input::new("☃").span(1..2))); + /// assert_eq!( + /// Some(Match::must(0, 1..1)), + /// re.find(Input::new("☃").span(1..2)), + /// ); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// A similar idea applies when using line anchors with CRLF mode enabled, + /// which prevents them from matching between a `\r` and a `\n`. + /// + /// ``` + /// use regex_automata::{meta::Regex, Input, Match}; + /// + /// let re = Regex::new(r"(?Rm:$)")?; + /// assert!(!re.is_match(Input::new("\r\n").span(1..1))); + /// // A regular line anchor, which only considers \n as a + /// // line terminator, will match. + /// let re = Regex::new(r"(?m:$)")?; + /// assert!(re.is_match(Input::new("\r\n").span(1..1))); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn is_match<'h, I: Into<Input<'h>>>(&self, input: I) -> bool { + let input = input.into().earliest(true); + if self.imp.info.is_impossible(&input) { + return false; + } + let mut guard = self.pool.get(); + let result = self.imp.strat.is_match(&mut guard, &input); + // See 'Regex::search' for why we put the guard back explicitly. + PoolGuard::put(guard); + result + } + + /// Executes a leftmost search and returns the first match that is found, + /// if one exists. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Match}; + /// + /// let re = Regex::new("foo[0-9]+")?; + /// assert_eq!(Some(Match::must(0, 0..8)), re.find("foo12345")); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn find<'h, I: Into<Input<'h>>>(&self, input: I) -> Option<Match> { + self.search(&input.into()) + } + + /// Executes a leftmost forward search and writes the spans of capturing + /// groups that participated in a match into the provided [`Captures`] + /// value. If no match was found, then [`Captures::is_match`] is guaranteed + /// to return `false`. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Span}; + /// + /// let re = Regex::new(r"^([0-9]{4})-([0-9]{2})-([0-9]{2})$")?; + /// let mut caps = re.create_captures(); + /// + /// re.captures("2010-03-14", &mut caps); + /// assert!(caps.is_match()); + /// assert_eq!(Some(Span::from(0..4)), caps.get_group(1)); + /// assert_eq!(Some(Span::from(5..7)), caps.get_group(2)); + /// assert_eq!(Some(Span::from(8..10)), caps.get_group(3)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn captures<'h, I: Into<Input<'h>>>( + &self, + input: I, + caps: &mut Captures, + ) { + self.search_captures(&input.into(), caps) + } + + /// Returns an iterator over all non-overlapping leftmost matches in + /// the given haystack. If no match exists, then the iterator yields no + /// elements. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Match}; + /// + /// let re = Regex::new("foo[0-9]+")?; + /// let haystack = "foo1 foo12 foo123"; + /// let matches: Vec<Match> = re.find_iter(haystack).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, 'h, I: Into<Input<'h>>>( + &'r self, + input: I, + ) -> FindMatches<'r, 'h> { + let cache = self.pool.get(); + let it = iter::Searcher::new(input.into()); + FindMatches { re: self, cache, it } + } + + /// Returns an iterator over all non-overlapping `Captures` values. If no + /// match exists, then the iterator yields no elements. + /// + /// This yields the same matches as [`Regex::find_iter`], but it includes + /// the spans of all capturing groups that participate in each match. + /// + /// **Tip:** See [`util::iter::Searcher`](crate::util::iter::Searcher) for + /// how to correctly iterate over all matches in a haystack while avoiding + /// the creation of a new `Captures` value for every match. (Which you are + /// forced to do with an `Iterator`.) + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Span}; + /// + /// let re = Regex::new("foo(?P<numbers>[0-9]+)")?; + /// + /// let haystack = "foo1 foo12 foo123"; + /// let matches: Vec<Span> = re + /// .captures_iter(haystack) + /// // The unwrap is OK since 'numbers' matches if the pattern matches. + /// .map(|caps| caps.get_group_by_name("numbers").unwrap()) + /// .collect(); + /// assert_eq!(matches, vec![ + /// Span::from(3..4), + /// Span::from(8..10), + /// Span::from(14..17), + /// ]); + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn captures_iter<'r, 'h, I: Into<Input<'h>>>( + &'r self, + input: I, + ) -> CapturesMatches<'r, 'h> { + let cache = self.pool.get(); + let caps = self.create_captures(); + let it = iter::Searcher::new(input.into()); + CapturesMatches { re: self, cache, caps, it } + } + + /// Returns an iterator of spans of the haystack given, delimited by a + /// match of the regex. Namely, each element of the iterator corresponds to + /// a part of the haystack that *isn't* matched by the regular expression. + /// + /// # Example + /// + /// To split a string delimited by arbitrary amounts of spaces or tabs: + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r"[ \t]+")?; + /// let hay = "a b \t c\td e"; + /// let fields: Vec<&str> = re.split(hay).map(|span| &hay[span]).collect(); + /// assert_eq!(fields, vec!["a", "b", "c", "d", "e"]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// # Example: more cases + /// + /// Basic usage: + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r" ")?; + /// let hay = "Mary had a little lamb"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["Mary", "had", "a", "little", "lamb"]); + /// + /// let re = Regex::new(r"X")?; + /// let hay = ""; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec![""]); + /// + /// let re = Regex::new(r"X")?; + /// let hay = "lionXXtigerXleopard"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["lion", "", "tiger", "leopard"]); + /// + /// let re = Regex::new(r"::")?; + /// let hay = "lion::tiger::leopard"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["lion", "tiger", "leopard"]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// If a haystack contains multiple contiguous matches, you will end up + /// with empty spans yielded by the iterator: + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r"X")?; + /// let hay = "XXXXaXXbXc"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["", "", "", "", "a", "", "b", "c"]); + /// + /// let re = Regex::new(r"/")?; + /// let hay = "(///)"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["(", "", "", ")"]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// Separators at the start or end of a haystack are neighbored by empty + /// spans. + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r"0")?; + /// let hay = "010"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["", "1", ""]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// When the empty string is used as a regex, it splits at every valid + /// UTF-8 boundary by default (which includes the beginning and end of the + /// haystack): + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r"")?; + /// let hay = "rust"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["", "r", "u", "s", "t", ""]); + /// + /// // Splitting by an empty string is UTF-8 aware by default! + /// let re = Regex::new(r"")?; + /// let hay = "☃"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["", "☃", ""]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// But note that UTF-8 mode for empty strings can be disabled, which will + /// then result in a match at every byte offset in the haystack, + /// including between every UTF-8 code unit. + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::builder() + /// .configure(Regex::config().utf8_empty(false)) + /// .build(r"")?; + /// let hay = "☃".as_bytes(); + /// let got: Vec<&[u8]> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec![ + /// // Writing byte string slices is just brutal. The problem is that + /// // b"foo" has type &[u8; 3] instead of &[u8]. + /// &[][..], &[b'\xE2'][..], &[b'\x98'][..], &[b'\x83'][..], &[][..], + /// ]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// Contiguous separators (commonly shows up with whitespace), can lead to + /// possibly surprising behavior. For example, this code is correct: + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r" ")?; + /// let hay = " a b c"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["", "", "", "", "a", "", "b", "c"]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// It does *not* give you `["a", "b", "c"]`. For that behavior, you'd want + /// to match contiguous space characters: + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r" +")?; + /// let hay = " a b c"; + /// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect(); + /// // N.B. This does still include a leading empty span because ' +' + /// // matches at the beginning of the haystack. + /// assert_eq!(got, vec!["", "a", "b", "c"]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn split<'r, 'h, I: Into<Input<'h>>>( + &'r self, + input: I, + ) -> Split<'r, 'h> { + Split { finder: self.find_iter(input), last: 0 } + } + + /// Returns an iterator of at most `limit` spans of the haystack given, + /// delimited by a match of the regex. (A `limit` of `0` will return no + /// spans.) Namely, each element of the iterator corresponds to a part + /// of the haystack that *isn't* matched by the regular expression. The + /// remainder of the haystack that is not split will be the last element in + /// the iterator. + /// + /// # Example + /// + /// Get the first two words in some haystack: + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r"\W+").unwrap(); + /// let hay = "Hey! How are you?"; + /// let fields: Vec<&str> = + /// re.splitn(hay, 3).map(|span| &hay[span]).collect(); + /// assert_eq!(fields, vec!["Hey", "How", "are you?"]); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// # Examples: more cases + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r" ")?; + /// let hay = "Mary had a little lamb"; + /// let got: Vec<&str> = re.splitn(hay, 3).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["Mary", "had", "a little lamb"]); + /// + /// let re = Regex::new(r"X")?; + /// let hay = ""; + /// let got: Vec<&str> = re.splitn(hay, 3).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec![""]); + /// + /// let re = Regex::new(r"X")?; + /// let hay = "lionXXtigerXleopard"; + /// let got: Vec<&str> = re.splitn(hay, 3).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["lion", "", "tigerXleopard"]); + /// + /// let re = Regex::new(r"::")?; + /// let hay = "lion::tiger::leopard"; + /// let got: Vec<&str> = re.splitn(hay, 2).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["lion", "tiger::leopard"]); + /// + /// let re = Regex::new(r"X")?; + /// let hay = "abcXdef"; + /// let got: Vec<&str> = re.splitn(hay, 1).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["abcXdef"]); + /// + /// let re = Regex::new(r"X")?; + /// let hay = "abcdef"; + /// let got: Vec<&str> = re.splitn(hay, 2).map(|sp| &hay[sp]).collect(); + /// assert_eq!(got, vec!["abcdef"]); + /// + /// let re = Regex::new(r"X")?; + /// let hay = "abcXdef"; + /// let got: Vec<&str> = re.splitn(hay, 0).map(|sp| &hay[sp]).collect(); + /// assert!(got.is_empty()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn splitn<'r, 'h, I: Into<Input<'h>>>( + &'r self, + input: I, + limit: usize, + ) -> SplitN<'r, 'h> { + SplitN { splits: self.split(input), limit } + } +} + +/// Lower level search routines that give more control. +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, but it accepts a concrete `&Input` + /// instead of an `Into<Input>`. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Input, Match}; + /// + /// let re = Regex::new(r"Samwise|Sam")?; + /// let input = Input::new( + /// "one of the chief characters, Samwise the Brave", + /// ); + /// assert_eq!(Some(Match::must(0, 29..36)), re.search(&input)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn search(&self, input: &Input<'_>) -> Option<Match> { + if self.imp.info.is_impossible(input) { + return None; + } + let mut guard = self.pool.get(); + let result = self.imp.strat.search(&mut guard, input); + // We do this dance with the guard and explicitly put it back in the + // pool because it seems to result in better codegen. If we let the + // guard's Drop impl put it back in the pool, then functions like + // ptr::drop_in_place get called and they *don't* get inlined. This + // isn't usually a big deal, but in latency sensitive benchmarks the + // extra function call can matter. + // + // I used `rebar measure -f '^grep/every-line$' -e meta` to measure + // the effects here. + // + // Note that this doesn't eliminate the latency effects of using the + // pool. There is still some (minor) cost for the "thread owner" of the + // pool. (i.e., The thread that first calls a regex search routine.) + // However, for other threads using the regex, the pool access can be + // quite expensive as it goes through a mutex. Callers can avoid this + // by either cloning the Regex (which creates a distinct copy of the + // pool), or callers can use the lower level APIs that accept a 'Cache' + // directly and do their own handling. + PoolGuard::put(guard); + result + } + + /// Returns the end offset of the leftmost match. If no match exists, then + /// `None` is returned. + /// + /// This is distinct from [`Regex::search`] in that it only returns the end + /// of a match and not the start of the match. Depending on a variety of + /// implementation details, this _may_ permit the regex engine to do less + /// overall work. For example, if a DFA is being used to execute a search, + /// then the start of a match usually requires running a separate DFA in + /// reverse to the find the start of a match. If one only needs the end of + /// a match, then the separate reverse scan to find the start of a match + /// can be skipped. (Note that the reverse scan is avoided even when using + /// `Regex::search` when possible, for example, in the case of an anchored + /// search.) + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Input, HalfMatch}; + /// + /// let re = Regex::new(r"Samwise|Sam")?; + /// let input = Input::new( + /// "one of the chief characters, Samwise the Brave", + /// ); + /// assert_eq!(Some(HalfMatch::must(0, 36)), re.search_half(&input)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn search_half(&self, input: &Input<'_>) -> Option<HalfMatch> { + if self.imp.info.is_impossible(input) { + return None; + } + let mut guard = self.pool.get(); + let result = self.imp.strat.search_half(&mut guard, input); + // See 'Regex::search' for why we put the guard back explicitly. + PoolGuard::put(guard); + result + } + + /// Executes a leftmost forward search and writes the spans of capturing + /// groups that participated in a match into the provided [`Captures`] + /// value. If no match was found, then [`Captures::is_match`] is guaranteed + /// to return `false`. + /// + /// This is like [`Regex::captures`], but it accepts a concrete `&Input` + /// instead of an `Into<Input>`. + /// + /// # Example: specific pattern search + /// + /// This example shows how to build a multi-pattern `Regex` that permits + /// searching for specific patterns. + /// + /// ``` + /// use regex_automata::{ + /// meta::Regex, + /// Anchored, Match, PatternID, Input, + /// }; + /// + /// let re = Regex::new_many(&["[a-z0-9]{6}", "[a-z][a-z0-9]{5}"])?; + /// let mut caps = re.create_captures(); + /// let haystack = "foo123"; + /// + /// // Since we are using the default leftmost-first match and both + /// // patterns match at the same starting position, only the first pattern + /// // will be returned in this case when doing a search for any of the + /// // patterns. + /// let expected = Some(Match::must(0, 0..6)); + /// re.search_captures(&Input::new(haystack), &mut caps); + /// assert_eq!(expected, caps.get_match()); + /// + /// // But if we want to check whether some other pattern matches, then we + /// // can provide its pattern ID. + /// let expected = Some(Match::must(1, 0..6)); + /// let input = Input::new(haystack) + /// .anchored(Anchored::Pattern(PatternID::must(1))); + /// re.search_captures(&input, &mut caps); + /// assert_eq!(expected, caps.get_match()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// # Example: specifying the bounds of a search + /// + /// This example shows how providing the bounds of a search can produce + /// different results than simply sub-slicing the haystack. + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{meta::Regex, Match, Input}; + /// + /// let re = Regex::new(r"\b[0-9]{3}\b")?; + /// let mut caps = re.create_captures(); + /// let haystack = "foo123bar"; + /// + /// // Since we sub-slice the haystack, the search doesn't know about + /// // the larger context and assumes that `123` is surrounded by word + /// // boundaries. And of course, the match position is reported relative + /// // to the sub-slice as well, which means we get `0..3` instead of + /// // `3..6`. + /// let expected = Some(Match::must(0, 0..3)); + /// let input = Input::new(&haystack[3..6]); + /// re.search_captures(&input, &mut caps); + /// assert_eq!(expected, caps.get_match()); + /// + /// // But if we provide the bounds of the search within the context of the + /// // entire haystack, then the search can take the surrounding context + /// // into account. (And if we did find a match, it would be reported + /// // as a valid offset into `haystack` instead of its sub-slice.) + /// let expected = None; + /// let input = Input::new(haystack).range(3..6); + /// re.search_captures(&input, &mut caps); + /// assert_eq!(expected, caps.get_match()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn search_captures(&self, input: &Input<'_>, caps: &mut Captures) { + caps.set_pattern(None); + let pid = self.search_slots(input, caps.slots_mut()); + caps.set_pattern(pid); + } + + /// Executes a leftmost forward search and writes the spans of capturing + /// groups that participated in a match into the provided `slots`, and + /// returns the matching pattern ID. The contents of the slots for patterns + /// other than the matching pattern are unspecified. If no match was found, + /// then `None` is returned and the contents of `slots` is unspecified. + /// + /// This is like [`Regex::search`], but it accepts a raw slots slice + /// instead of a `Captures` value. This is useful in contexts where you + /// don't want or need to allocate a `Captures`. + /// + /// It is legal to pass _any_ number of slots to this routine. If the regex + /// engine would otherwise write a slot offset that doesn't fit in the + /// provided slice, then it is simply skipped. In general though, there are + /// usually three slice lengths you might want to use: + /// + /// * An empty slice, if you only care about which pattern matched. + /// * A slice with [`pattern_len() * 2`](Regex::pattern_len) slots, if you + /// only care about the overall match spans for each matching pattern. + /// * A slice with + /// [`slot_len()`](crate::util::captures::GroupInfo::slot_len) slots, which + /// permits recording match offsets for every capturing group in every + /// pattern. + /// + /// # Example + /// + /// This example shows how to find the overall match offsets in a + /// multi-pattern search without allocating a `Captures` value. Indeed, we + /// can put our slots right on the stack. + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{meta::Regex, PatternID, Input}; + /// + /// let re = Regex::new_many(&[ + /// r"\pL+", + /// r"\d+", + /// ])?; + /// let input = Input::new("!@#123"); + /// + /// // We only care about the overall match offsets here, so we just + /// // allocate two slots for each pattern. Each slot records the start + /// // and end of the match. + /// let mut slots = [None; 4]; + /// let pid = re.search_slots(&input, &mut slots); + /// assert_eq!(Some(PatternID::must(1)), pid); + /// + /// // The overall match offsets are always at 'pid * 2' and 'pid * 2 + 1'. + /// // See 'GroupInfo' for more details on the mapping between groups and + /// // slot indices. + /// let slot_start = pid.unwrap().as_usize() * 2; + /// let slot_end = slot_start + 1; + /// assert_eq!(Some(3), slots[slot_start].map(|s| s.get())); + /// assert_eq!(Some(6), slots[slot_end].map(|s| s.get())); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn search_slots( + &self, + input: &Input<'_>, + slots: &mut [Option<NonMaxUsize>], + ) -> Option<PatternID> { + if self.imp.info.is_impossible(input) { + return None; + } + let mut guard = self.pool.get(); + let result = self.imp.strat.search_slots(&mut guard, input, slots); + // See 'Regex::search' for why we put the guard back explicitly. + PoolGuard::put(guard); + result + } + + /// Writes the set of patterns that match anywhere in the given search + /// configuration to `patset`. If multiple patterns match at the same + /// position and this `Regex` was configured with [`MatchKind::All`] + /// semantics, then all matching patterns are written to the given set. + /// + /// Unless all of the patterns in this `Regex` are anchored, then generally + /// speaking, this will scan the entire haystack. + /// + /// This search routine *does not* clear the pattern set. This gives some + /// flexibility to the caller (e.g., running multiple searches with the + /// same pattern set), but does make the API bug-prone if you're reusing + /// the same pattern set for multiple searches but intended them to be + /// independent. + /// + /// If a pattern ID matched but the given `PatternSet` does not have + /// sufficient capacity to store it, then it is not inserted and silently + /// dropped. + /// + /// # Example + /// + /// This example shows how to find all matching patterns in a haystack, + /// even when some patterns match at the same position as other patterns. + /// It is important that we configure the `Regex` with [`MatchKind::All`] + /// semantics here, or else overlapping matches will not be reported. + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{meta::Regex, Input, MatchKind, PatternSet}; + /// + /// let patterns = &[ + /// r"\w+", r"\d+", r"\pL+", r"foo", r"bar", r"barfoo", r"foobar", + /// ]; + /// let re = Regex::builder() + /// .configure(Regex::config().match_kind(MatchKind::All)) + /// .build_many(patterns)?; + /// + /// let input = Input::new("foobar"); + /// let mut patset = PatternSet::new(re.pattern_len()); + /// re.which_overlapping_matches(&input, &mut patset); + /// let expected = vec![0, 2, 3, 4, 6]; + /// let got: Vec<usize> = patset.iter().map(|p| p.as_usize()).collect(); + /// assert_eq!(expected, got); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn which_overlapping_matches( + &self, + input: &Input<'_>, + patset: &mut PatternSet, + ) { + if self.imp.info.is_impossible(input) { + return; + } + let mut guard = self.pool.get(); + let result = self + .imp + .strat + .which_overlapping_matches(&mut guard, input, patset); + // See 'Regex::search' for why we put the guard back explicitly. + PoolGuard::put(guard); + result + } +} + +/// Lower level search routines that give more control, and require the caller +/// to provide an explicit [`Cache`] parameter. +impl Regex { + /// This is like [`Regex::search`], but requires the caller to + /// explicitly pass a [`Cache`]. + /// + /// # Why pass a `Cache` explicitly? + /// + /// Passing a `Cache` explicitly will bypass the use of an internal memory + /// pool used by `Regex` to get a `Cache` for a search. The use of this + /// pool can be slower in some cases when a `Regex` is used from multiple + /// threads simultaneously. Typically, performance only becomes an issue + /// when there is heavy contention, which in turn usually only occurs + /// when each thread's primary unit of work is a regex search on a small + /// haystack. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Input, Match}; + /// + /// let re = Regex::new(r"Samwise|Sam")?; + /// let mut cache = re.create_cache(); + /// let input = Input::new( + /// "one of the chief characters, Samwise the Brave", + /// ); + /// assert_eq!( + /// Some(Match::must(0, 29..36)), + /// re.search_with(&mut cache, &input), + /// ); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn search_with( + &self, + cache: &mut Cache, + input: &Input<'_>, + ) -> Option<Match> { + if self.imp.info.is_impossible(input) { + return None; + } + self.imp.strat.search(cache, input) + } + + /// This is like [`Regex::search_half`], but requires the caller to + /// explicitly pass a [`Cache`]. + /// + /// # Why pass a `Cache` explicitly? + /// + /// Passing a `Cache` explicitly will bypass the use of an internal memory + /// pool used by `Regex` to get a `Cache` for a search. The use of this + /// pool can be slower in some cases when a `Regex` is used from multiple + /// threads simultaneously. Typically, performance only becomes an issue + /// when there is heavy contention, which in turn usually only occurs + /// when each thread's primary unit of work is a regex search on a small + /// haystack. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Input, HalfMatch}; + /// + /// let re = Regex::new(r"Samwise|Sam")?; + /// let mut cache = re.create_cache(); + /// let input = Input::new( + /// "one of the chief characters, Samwise the Brave", + /// ); + /// assert_eq!( + /// Some(HalfMatch::must(0, 36)), + /// re.search_half_with(&mut cache, &input), + /// ); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn search_half_with( + &self, + cache: &mut Cache, + input: &Input<'_>, + ) -> Option<HalfMatch> { + if self.imp.info.is_impossible(input) { + return None; + } + self.imp.strat.search_half(cache, input) + } + + /// This is like [`Regex::search_captures`], but requires the caller to + /// explicitly pass a [`Cache`]. + /// + /// # Why pass a `Cache` explicitly? + /// + /// Passing a `Cache` explicitly will bypass the use of an internal memory + /// pool used by `Regex` to get a `Cache` for a search. The use of this + /// pool can be slower in some cases when a `Regex` is used from multiple + /// threads simultaneously. Typically, performance only becomes an issue + /// when there is heavy contention, which in turn usually only occurs + /// when each thread's primary unit of work is a regex search on a small + /// haystack. + /// + /// # Example: specific pattern search + /// + /// This example shows how to build a multi-pattern `Regex` that permits + /// searching for specific patterns. + /// + /// ``` + /// use regex_automata::{ + /// meta::Regex, + /// Anchored, Match, PatternID, Input, + /// }; + /// + /// let re = Regex::new_many(&["[a-z0-9]{6}", "[a-z][a-z0-9]{5}"])?; + /// let (mut cache, mut caps) = (re.create_cache(), re.create_captures()); + /// let haystack = "foo123"; + /// + /// // Since we are using the default leftmost-first match and both + /// // patterns match at the same starting position, only the first pattern + /// // will be returned in this case when doing a search for any of the + /// // patterns. + /// let expected = Some(Match::must(0, 0..6)); + /// re.search_captures_with(&mut cache, &Input::new(haystack), &mut caps); + /// assert_eq!(expected, caps.get_match()); + /// + /// // But if we want to check whether some other pattern matches, then we + /// // can provide its pattern ID. + /// let expected = Some(Match::must(1, 0..6)); + /// let input = Input::new(haystack) + /// .anchored(Anchored::Pattern(PatternID::must(1))); + /// re.search_captures_with(&mut cache, &input, &mut caps); + /// assert_eq!(expected, caps.get_match()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// # Example: specifying the bounds of a search + /// + /// This example shows how providing the bounds of a search can produce + /// different results than simply sub-slicing the haystack. + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{meta::Regex, Match, Input}; + /// + /// let re = Regex::new(r"\b[0-9]{3}\b")?; + /// let (mut cache, mut caps) = (re.create_cache(), re.create_captures()); + /// let haystack = "foo123bar"; + /// + /// // Since we sub-slice the haystack, the search doesn't know about + /// // the larger context and assumes that `123` is surrounded by word + /// // boundaries. And of course, the match position is reported relative + /// // to the sub-slice as well, which means we get `0..3` instead of + /// // `3..6`. + /// let expected = Some(Match::must(0, 0..3)); + /// let input = Input::new(&haystack[3..6]); + /// re.search_captures_with(&mut cache, &input, &mut caps); + /// assert_eq!(expected, caps.get_match()); + /// + /// // But if we provide the bounds of the search within the context of the + /// // entire haystack, then the search can take the surrounding context + /// // into account. (And if we did find a match, it would be reported + /// // as a valid offset into `haystack` instead of its sub-slice.) + /// let expected = None; + /// let input = Input::new(haystack).range(3..6); + /// re.search_captures_with(&mut cache, &input, &mut caps); + /// assert_eq!(expected, caps.get_match()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn search_captures_with( + &self, + cache: &mut Cache, + input: &Input<'_>, + caps: &mut Captures, + ) { + caps.set_pattern(None); + let pid = self.search_slots_with(cache, input, caps.slots_mut()); + caps.set_pattern(pid); + } + + /// This is like [`Regex::search_slots`], but requires the caller to + /// explicitly pass a [`Cache`]. + /// + /// # Why pass a `Cache` explicitly? + /// + /// Passing a `Cache` explicitly will bypass the use of an internal memory + /// pool used by `Regex` to get a `Cache` for a search. The use of this + /// pool can be slower in some cases when a `Regex` is used from multiple + /// threads simultaneously. Typically, performance only becomes an issue + /// when there is heavy contention, which in turn usually only occurs + /// when each thread's primary unit of work is a regex search on a small + /// haystack. + /// + /// # Example + /// + /// This example shows how to find the overall match offsets in a + /// multi-pattern search without allocating a `Captures` value. Indeed, we + /// can put our slots right on the stack. + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{meta::Regex, PatternID, Input}; + /// + /// let re = Regex::new_many(&[ + /// r"\pL+", + /// r"\d+", + /// ])?; + /// let mut cache = re.create_cache(); + /// let input = Input::new("!@#123"); + /// + /// // We only care about the overall match offsets here, so we just + /// // allocate two slots for each pattern. Each slot records the start + /// // and end of the match. + /// let mut slots = [None; 4]; + /// let pid = re.search_slots_with(&mut cache, &input, &mut slots); + /// assert_eq!(Some(PatternID::must(1)), pid); + /// + /// // The overall match offsets are always at 'pid * 2' and 'pid * 2 + 1'. + /// // See 'GroupInfo' for more details on the mapping between groups and + /// // slot indices. + /// let slot_start = pid.unwrap().as_usize() * 2; + /// let slot_end = slot_start + 1; + /// assert_eq!(Some(3), slots[slot_start].map(|s| s.get())); + /// assert_eq!(Some(6), slots[slot_end].map(|s| s.get())); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn search_slots_with( + &self, + cache: &mut Cache, + input: &Input<'_>, + slots: &mut [Option<NonMaxUsize>], + ) -> Option<PatternID> { + if self.imp.info.is_impossible(input) { + return None; + } + self.imp.strat.search_slots(cache, input, slots) + } + + /// This is like [`Regex::which_overlapping_matches`], but requires the + /// caller to explicitly pass a [`Cache`]. + /// + /// Passing a `Cache` explicitly will bypass the use of an internal memory + /// pool used by `Regex` to get a `Cache` for a search. The use of this + /// pool can be slower in some cases when a `Regex` is used from multiple + /// threads simultaneously. Typically, performance only becomes an issue + /// when there is heavy contention, which in turn usually only occurs + /// when each thread's primary unit of work is a regex search on a small + /// haystack. + /// + /// # Why pass a `Cache` explicitly? + /// + /// # Example + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{meta::Regex, Input, MatchKind, PatternSet}; + /// + /// let patterns = &[ + /// r"\w+", r"\d+", r"\pL+", r"foo", r"bar", r"barfoo", r"foobar", + /// ]; + /// let re = Regex::builder() + /// .configure(Regex::config().match_kind(MatchKind::All)) + /// .build_many(patterns)?; + /// let mut cache = re.create_cache(); + /// + /// let input = Input::new("foobar"); + /// let mut patset = PatternSet::new(re.pattern_len()); + /// re.which_overlapping_matches_with(&mut cache, &input, &mut patset); + /// let expected = vec![0, 2, 3, 4, 6]; + /// let got: Vec<usize> = patset.iter().map(|p| p.as_usize()).collect(); + /// assert_eq!(expected, got); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn which_overlapping_matches_with( + &self, + cache: &mut Cache, + input: &Input<'_>, + patset: &mut PatternSet, + ) { + if self.imp.info.is_impossible(input) { + return; + } + self.imp.strat.which_overlapping_matches(cache, input, patset) + } +} + +/// Various non-search routines for querying properties of a `Regex` and +/// convenience routines for creating [`Captures`] and [`Cache`] values. +impl Regex { + /// Creates a new object for recording capture group offsets. This is used + /// in search APIs like [`Regex::captures`] and [`Regex::search_captures`]. + /// + /// This is a convenience routine for + /// `Captures::all(re.group_info().clone())`. Callers may build other types + /// of `Captures` values that record less information (and thus require + /// less work from the regex engine) using [`Captures::matches`] and + /// [`Captures::empty`]. + /// + /// # Example + /// + /// This shows some alternatives to [`Regex::create_captures`]: + /// + /// ``` + /// use regex_automata::{ + /// meta::Regex, + /// util::captures::Captures, + /// Match, PatternID, Span, + /// }; + /// + /// let re = Regex::new(r"(?<first>[A-Z][a-z]+) (?<last>[A-Z][a-z]+)")?; + /// + /// // This is equivalent to Regex::create_captures. It stores matching + /// // offsets for all groups in the regex. + /// let mut all = Captures::all(re.group_info().clone()); + /// re.captures("Bruce Springsteen", &mut all); + /// assert_eq!(Some(Match::must(0, 0..17)), all.get_match()); + /// assert_eq!(Some(Span::from(0..5)), all.get_group_by_name("first")); + /// assert_eq!(Some(Span::from(6..17)), all.get_group_by_name("last")); + /// + /// // In this version, we only care about the implicit groups, which + /// // means offsets for the explicit groups will be unavailable. It can + /// // sometimes be faster to ask for fewer groups, since the underlying + /// // regex engine needs to do less work to keep track of them. + /// let mut matches = Captures::matches(re.group_info().clone()); + /// re.captures("Bruce Springsteen", &mut matches); + /// // We still get the overall match info. + /// assert_eq!(Some(Match::must(0, 0..17)), matches.get_match()); + /// // But now the explicit groups are unavailable. + /// assert_eq!(None, matches.get_group_by_name("first")); + /// assert_eq!(None, matches.get_group_by_name("last")); + /// + /// // Finally, in this version, we don't ask to keep track of offsets for + /// // *any* groups. All we get back is whether a match occurred, and if + /// // so, the ID of the pattern that matched. + /// let mut empty = Captures::empty(re.group_info().clone()); + /// re.captures("Bruce Springsteen", &mut empty); + /// // it's a match! + /// assert!(empty.is_match()); + /// // for pattern ID 0 + /// assert_eq!(Some(PatternID::ZERO), empty.pattern()); + /// // Match offsets are unavailable. + /// assert_eq!(None, empty.get_match()); + /// // And of course, explicit groups are unavailable too. + /// assert_eq!(None, empty.get_group_by_name("first")); + /// assert_eq!(None, empty.get_group_by_name("last")); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn create_captures(&self) -> Captures { + Captures::all(self.group_info().clone()) + } + + /// Creates a new cache for use with lower level search APIs like + /// [`Regex::search_with`]. + /// + /// 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`. + /// + /// This is a convenience routine for [`Cache::new`]. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Input, Match}; + /// + /// let re = Regex::new(r"(?-u)m\w+\s+m\w+")?; + /// let mut cache = re.create_cache(); + /// let input = Input::new("crazy janey and her mission man"); + /// assert_eq!( + /// Some(Match::must(0, 20..31)), + /// re.search_with(&mut cache, &input), + /// ); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn create_cache(&self) -> Cache { + self.imp.strat.create_cache() + } + + /// Returns the total number of patterns in this regex. + /// + /// The standard [`Regex::new`] constructor always results in a `Regex` + /// with a single pattern, but [`Regex::new_many`] permits building a + /// multi-pattern regex. + /// + /// A `Regex` guarantees that the maximum possible `PatternID` returned in + /// any match is `Regex::pattern_len() - 1`. In the case where the number + /// of patterns is `0`, a match is impossible. + /// + /// # Example + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let re = Regex::new(r"(?m)^[a-z]$")?; + /// assert_eq!(1, re.pattern_len()); + /// + /// let re = Regex::new_many::<&str>(&[])?; + /// assert_eq!(0, re.pattern_len()); + /// + /// let re = Regex::new_many(&["a", "b", "c"])?; + /// assert_eq!(3, re.pattern_len()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn pattern_len(&self) -> usize { + self.imp.info.pattern_len() + } + + /// Returns the total number of capturing groups. + /// + /// This includes the implicit capturing group corresponding to the + /// entire match. Therefore, the minimum value returned is `1`. + /// + /// # Example + /// + /// This shows a few patterns and how many capture groups they have. + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let len = |pattern| { + /// Regex::new(pattern).map(|re| re.captures_len()) + /// }; + /// + /// assert_eq!(1, len("a")?); + /// assert_eq!(2, len("(a)")?); + /// assert_eq!(3, len("(a)|(b)")?); + /// assert_eq!(5, len("(a)(b)|(c)(d)")?); + /// assert_eq!(2, len("(a)|b")?); + /// assert_eq!(2, len("a|(b)")?); + /// assert_eq!(2, len("(b)*")?); + /// assert_eq!(2, len("(b)+")?); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// # Example: multiple patterns + /// + /// This routine also works for multiple patterns. The total number is + /// the sum of the capture groups of each pattern. + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let len = |patterns| { + /// Regex::new_many(patterns).map(|re| re.captures_len()) + /// }; + /// + /// assert_eq!(2, len(&["a", "b"])?); + /// assert_eq!(4, len(&["(a)", "(b)"])?); + /// assert_eq!(6, len(&["(a)|(b)", "(c)|(d)"])?); + /// assert_eq!(8, len(&["(a)(b)|(c)(d)", "(x)(y)"])?); + /// assert_eq!(3, len(&["(a)", "b"])?); + /// assert_eq!(3, len(&["a", "(b)"])?); + /// assert_eq!(4, len(&["(a)", "(b)*"])?); + /// assert_eq!(4, len(&["(a)+", "(b)+"])?); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn captures_len(&self) -> usize { + self.imp + .info + .props_union() + .explicit_captures_len() + .saturating_add(self.pattern_len()) + } + + /// Returns the total number of capturing groups that appear in every + /// possible match. + /// + /// If the number of capture groups can vary depending on the match, then + /// this returns `None`. That is, a value is only returned when the number + /// of matching groups is invariant or "static." + /// + /// Note that like [`Regex::captures_len`], this **does** include the + /// implicit capturing group corresponding to the entire match. Therefore, + /// when a non-None value is returned, it is guaranteed to be at least `1`. + /// Stated differently, a return value of `Some(0)` is impossible. + /// + /// # Example + /// + /// This shows a few cases where a static number of capture groups is + /// available and a few cases where it is not. + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let len = |pattern| { + /// Regex::new(pattern).map(|re| re.static_captures_len()) + /// }; + /// + /// assert_eq!(Some(1), len("a")?); + /// assert_eq!(Some(2), len("(a)")?); + /// assert_eq!(Some(2), len("(a)|(b)")?); + /// assert_eq!(Some(3), len("(a)(b)|(c)(d)")?); + /// assert_eq!(None, len("(a)|b")?); + /// assert_eq!(None, len("a|(b)")?); + /// assert_eq!(None, len("(b)*")?); + /// assert_eq!(Some(2), len("(b)+")?); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// # Example: multiple patterns + /// + /// This property extends to regexes with multiple patterns as well. In + /// order for their to be a static number of capture groups in this case, + /// every pattern must have the same static number. + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// let len = |patterns| { + /// Regex::new_many(patterns).map(|re| re.static_captures_len()) + /// }; + /// + /// assert_eq!(Some(1), len(&["a", "b"])?); + /// assert_eq!(Some(2), len(&["(a)", "(b)"])?); + /// assert_eq!(Some(2), len(&["(a)|(b)", "(c)|(d)"])?); + /// assert_eq!(Some(3), len(&["(a)(b)|(c)(d)", "(x)(y)"])?); + /// assert_eq!(None, len(&["(a)", "b"])?); + /// assert_eq!(None, len(&["a", "(b)"])?); + /// assert_eq!(None, len(&["(a)", "(b)*"])?); + /// assert_eq!(Some(2), len(&["(a)+", "(b)+"])?); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn static_captures_len(&self) -> Option<usize> { + self.imp + .info + .props_union() + .static_explicit_captures_len() + .map(|len| len.saturating_add(1)) + } + + /// Return information about the capture groups in this `Regex`. + /// + /// A `GroupInfo` is an immutable object that can be cheaply cloned. It + /// is responsible for maintaining a mapping between the capture groups + /// in the concrete syntax of zero or more regex patterns and their + /// internal representation used by some of the regex matchers. It is also + /// responsible for maintaining a mapping between the name of each group + /// (if one exists) and its corresponding group index. + /// + /// A `GroupInfo` is ultimately what is used to build a [`Captures`] value, + /// which is some mutable space where group offsets are stored as a result + /// of a search. + /// + /// # Example + /// + /// This shows some alternatives to [`Regex::create_captures`]: + /// + /// ``` + /// use regex_automata::{ + /// meta::Regex, + /// util::captures::Captures, + /// Match, PatternID, Span, + /// }; + /// + /// let re = Regex::new(r"(?<first>[A-Z][a-z]+) (?<last>[A-Z][a-z]+)")?; + /// + /// // This is equivalent to Regex::create_captures. It stores matching + /// // offsets for all groups in the regex. + /// let mut all = Captures::all(re.group_info().clone()); + /// re.captures("Bruce Springsteen", &mut all); + /// assert_eq!(Some(Match::must(0, 0..17)), all.get_match()); + /// assert_eq!(Some(Span::from(0..5)), all.get_group_by_name("first")); + /// assert_eq!(Some(Span::from(6..17)), all.get_group_by_name("last")); + /// + /// // In this version, we only care about the implicit groups, which + /// // means offsets for the explicit groups will be unavailable. It can + /// // sometimes be faster to ask for fewer groups, since the underlying + /// // regex engine needs to do less work to keep track of them. + /// let mut matches = Captures::matches(re.group_info().clone()); + /// re.captures("Bruce Springsteen", &mut matches); + /// // We still get the overall match info. + /// assert_eq!(Some(Match::must(0, 0..17)), matches.get_match()); + /// // But now the explicit groups are unavailable. + /// assert_eq!(None, matches.get_group_by_name("first")); + /// assert_eq!(None, matches.get_group_by_name("last")); + /// + /// // Finally, in this version, we don't ask to keep track of offsets for + /// // *any* groups. All we get back is whether a match occurred, and if + /// // so, the ID of the pattern that matched. + /// let mut empty = Captures::empty(re.group_info().clone()); + /// re.captures("Bruce Springsteen", &mut empty); + /// // it's a match! + /// assert!(empty.is_match()); + /// // for pattern ID 0 + /// assert_eq!(Some(PatternID::ZERO), empty.pattern()); + /// // Match offsets are unavailable. + /// assert_eq!(None, empty.get_match()); + /// // And of course, explicit groups are unavailable too. + /// assert_eq!(None, empty.get_group_by_name("first")); + /// assert_eq!(None, empty.get_group_by_name("last")); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn group_info(&self) -> &GroupInfo { + self.imp.strat.group_info() + } + + /// Returns the configuration object used to build this `Regex`. + /// + /// If no configuration object was explicitly passed, then the + /// configuration returned represents the default. + #[inline] + pub fn get_config(&self) -> &Config { + self.imp.info.config() + } + + /// Returns true if this regex has a high chance of being "accelerated." + /// + /// The precise meaning of "accelerated" is specifically left unspecified, + /// but the general meaning is that the search is a high likelihood of + /// running faster than than a character-at-a-time loop inside a standard + /// regex engine. + /// + /// When a regex is accelerated, it is only a *probabilistic* claim. That + /// is, just because the regex is believed to be accelerated, that doesn't + /// mean it will definitely execute searches very fast. Similarly, if a + /// regex is *not* accelerated, that is also a probabilistic claim. That + /// is, a regex for which `is_accelerated` returns `false` could still run + /// searches more quickly than a regex for which `is_accelerated` returns + /// `true`. + /// + /// Whether a regex is marked as accelerated or not is dependent on + /// implementations details that may change in a semver compatible release. + /// That is, a regex that is accelerated in a `x.y.1` release might not be + /// accelerated in a `x.y.2` release. + /// + /// Basically, the value of acceleration boils down to a hedge: a hodge + /// podge of internal heuristics combine to make a probabilistic guess + /// that this regex search may run "fast." The value in knowing this from + /// a caller's perspective is that it may act as a signal that no further + /// work should be done to accelerate a search. For example, a grep-like + /// tool might try to do some extra work extracting literals from a regex + /// to create its own heuristic acceleration strategies. But it might + /// choose to defer to this crate's acceleration strategy if one exists. + /// This routine permits querying whether such a strategy is active for a + /// particular regex. + /// + /// # Example + /// + /// ``` + /// use regex_automata::meta::Regex; + /// + /// // A simple literal is very likely to be accelerated. + /// let re = Regex::new(r"foo")?; + /// assert!(re.is_accelerated()); + /// + /// // A regex with no literals is likely to not be accelerated. + /// let re = Regex::new(r"\w")?; + /// assert!(!re.is_accelerated()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + #[inline] + pub fn is_accelerated(&self) -> bool { + self.imp.strat.is_accelerated() + } + + /// Return the total approximate heap memory, in bytes, used by this `Regex`. + /// + /// Note that currently, there is no high level configuration for setting + /// a limit on the specific value returned by this routine. Instead, the + /// following routines can be used to control heap memory at a bit of a + /// lower level: + /// + /// * [`Config::nfa_size_limit`] controls how big _any_ of the NFAs are + /// allowed to be. + /// * [`Config::onepass_size_limit`] controls how big the one-pass DFA is + /// allowed to be. + /// * [`Config::hybrid_cache_capacity`] controls how much memory the lazy + /// DFA is permitted to allocate to store its transition table. + /// * [`Config::dfa_size_limit`] controls how big a fully compiled DFA is + /// allowed to be. + /// * [`Config::dfa_state_limit`] controls the conditions under which the + /// meta regex engine will even attempt to build a fully compiled DFA. + #[inline] + pub fn memory_usage(&self) -> usize { + self.imp.strat.memory_usage() + } +} + +impl Clone for Regex { + fn clone(&self) -> Regex { + let imp = Arc::clone(&self.imp); + let pool = { + let strat = Arc::clone(&imp.strat); + let create: CachePoolFn = Box::new(move || strat.create_cache()); + Pool::new(create) + }; + Regex { imp, pool } + } +} + +#[derive(Clone, Debug)] +pub(crate) struct RegexInfo(Arc<RegexInfoI>); + +#[derive(Clone, Debug)] +struct RegexInfoI { + config: Config, + props: Vec<hir::Properties>, + props_union: hir::Properties, +} + +impl RegexInfo { + fn new(config: Config, hirs: &[&Hir]) -> RegexInfo { + // Collect all of the properties from each of the HIRs, and also + // union them into one big set of properties representing all HIRs + // as if they were in one big alternation. + let mut props = vec![]; + for hir in hirs.iter() { + props.push(hir.properties().clone()); + } + let props_union = hir::Properties::union(&props); + + RegexInfo(Arc::new(RegexInfoI { config, props, props_union })) + } + + pub(crate) fn config(&self) -> &Config { + &self.0.config + } + + pub(crate) fn props(&self) -> &[hir::Properties] { + &self.0.props + } + + pub(crate) fn props_union(&self) -> &hir::Properties { + &self.0.props_union + } + + pub(crate) fn pattern_len(&self) -> usize { + self.props().len() + } + + pub(crate) fn memory_usage(&self) -> usize { + self.props().iter().map(|p| p.memory_usage()).sum::<usize>() + + self.props_union().memory_usage() + } + + /// Returns true when the search is guaranteed to be anchored. That is, + /// when a match is reported, its offset is guaranteed to correspond to + /// the start of the search. + /// + /// This includes returning true when `input` _isn't_ anchored but the + /// underlying regex is. + #[cfg_attr(feature = "perf-inline", inline(always))] + pub(crate) fn is_anchored_start(&self, input: &Input<'_>) -> bool { + input.get_anchored().is_anchored() || self.is_always_anchored_start() + } + + /// Returns true when this regex is always anchored to the start of a + /// search. And in particular, that regardless of an `Input` configuration, + /// if any match is reported it must start at `0`. + #[cfg_attr(feature = "perf-inline", inline(always))] + pub(crate) fn is_always_anchored_start(&self) -> bool { + use regex_syntax::hir::Look; + self.props_union().look_set_prefix().contains(Look::Start) + } + + /// Returns true when this regex is always anchored to the end of a + /// search. And in particular, that regardless of an `Input` configuration, + /// if any match is reported it must end at the end of the haystack. + #[cfg_attr(feature = "perf-inline", inline(always))] + pub(crate) fn is_always_anchored_end(&self) -> bool { + use regex_syntax::hir::Look; + self.props_union().look_set_suffix().contains(Look::End) + } + + /// Returns true if and only if it is known that a match is impossible + /// for the given input. This is useful for short-circuiting and avoiding + /// running the regex engine if it's known no match can be reported. + /// + /// Note that this doesn't necessarily detect every possible case. For + /// example, when `pattern_len() == 0`, a match is impossible, but that + /// case is so rare that it's fine to be handled by the regex engine + /// itself. That is, it's not worth the cost of adding it here in order to + /// make it a little faster. The reason is that this is called for every + /// search. so there is some cost to adding checks here. Arguably, some of + /// the checks that are here already probably shouldn't be here... + #[cfg_attr(feature = "perf-inline", inline(always))] + fn is_impossible(&self, input: &Input<'_>) -> bool { + // The underlying regex is anchored, so if we don't start the search + // at position 0, a match is impossible, because the anchor can only + // match at position 0. + if input.start() > 0 && self.is_always_anchored_start() { + return true; + } + // Same idea, but for the end anchor. + if input.end() < input.haystack().len() + && self.is_always_anchored_end() + { + return true; + } + // If the haystack is smaller than the minimum length required, then + // we know there can be no match. + let minlen = match self.props_union().minimum_len() { + None => return false, + Some(minlen) => minlen, + }; + if input.get_span().len() < minlen { + return true; + } + // Same idea as minimum, but for maximum. This is trickier. We can + // only apply the maximum when we know the entire span that we're + // searching *has* to match according to the regex (and possibly the + // input configuration). If we know there is too much for the regex + // to match, we can bail early. + // + // I don't think we can apply the maximum otherwise unfortunately. + if self.is_anchored_start(input) && self.is_always_anchored_end() { + let maxlen = match self.props_union().maximum_len() { + None => return false, + Some(maxlen) => maxlen, + }; + if input.get_span().len() > maxlen { + return true; + } + } + false + } +} + +/// An iterator over all non-overlapping matches. +/// +/// The iterator yields a [`Match`] value until no more matches could be found. +/// +/// The lifetime parameters are as follows: +/// +/// * `'r` represents the lifetime of the `Regex` that produced this iterator. +/// * `'h` represents the lifetime of the haystack being searched. +/// +/// This iterator can be created with the [`Regex::find_iter`] method. +#[derive(Debug)] +pub struct FindMatches<'r, 'h> { + re: &'r Regex, + cache: CachePoolGuard<'r>, + it: iter::Searcher<'h>, +} + +impl<'r, 'h> FindMatches<'r, 'h> { + /// Returns the `Regex` value that created this iterator. + #[inline] + pub fn regex(&self) -> &'r Regex { + self.re + } + + /// Returns the current `Input` associated with this iterator. + /// + /// The `start` position on the given `Input` may change during iteration, + /// but all other values are guaranteed to remain invariant. + #[inline] + pub fn input<'s>(&'s self) -> &'s Input<'h> { + self.it.input() + } +} + +impl<'r, 'h> Iterator for FindMatches<'r, 'h> { + type Item = Match; + + #[inline] + fn next(&mut self) -> Option<Match> { + let FindMatches { re, ref mut cache, ref mut it } = *self; + it.advance(|input| Ok(re.search_with(cache, input))) + } + + #[inline] + fn count(self) -> usize { + // If all we care about is a count of matches, then we only need to + // find the end position of each match. This can give us a 2x perf + // boost in some cases, because it avoids needing to do a reverse scan + // to find the start of a match. + let FindMatches { re, mut cache, it } = self; + // This does the deref for PoolGuard once instead of every iter. + let cache = &mut *cache; + it.into_half_matches_iter( + |input| Ok(re.search_half_with(cache, input)), + ) + .count() + } +} + +impl<'r, 'h> core::iter::FusedIterator for FindMatches<'r, 'h> {} + +/// An iterator over all non-overlapping leftmost matches with their capturing +/// groups. +/// +/// The iterator yields a [`Captures`] value until no more matches could be +/// found. +/// +/// The lifetime parameters are as follows: +/// +/// * `'r` represents the lifetime of the `Regex` that produced this iterator. +/// * `'h` represents the lifetime of the haystack being searched. +/// +/// This iterator can be created with the [`Regex::captures_iter`] method. +#[derive(Debug)] +pub struct CapturesMatches<'r, 'h> { + re: &'r Regex, + cache: CachePoolGuard<'r>, + caps: Captures, + it: iter::Searcher<'h>, +} + +impl<'r, 'h> CapturesMatches<'r, 'h> { + /// Returns the `Regex` value that created this iterator. + #[inline] + pub fn regex(&self) -> &'r Regex { + self.re + } + + /// Returns the current `Input` associated with this iterator. + /// + /// The `start` position on the given `Input` may change during iteration, + /// but all other values are guaranteed to remain invariant. + #[inline] + pub fn input<'s>(&'s self) -> &'s Input<'h> { + self.it.input() + } +} + +impl<'r, 'h> Iterator for CapturesMatches<'r, 'h> { + type Item = Captures; + + #[inline] + fn next(&mut self) -> Option<Captures> { + // Splitting 'self' apart seems necessary to appease borrowck. + let CapturesMatches { re, ref mut cache, ref mut caps, ref mut it } = + *self; + let _ = it.advance(|input| { + re.search_captures_with(cache, input, caps); + Ok(caps.get_match()) + }); + if caps.is_match() { + Some(caps.clone()) + } else { + None + } + } + + #[inline] + fn count(self) -> usize { + let CapturesMatches { re, mut cache, it, .. } = self; + // This does the deref for PoolGuard once instead of every iter. + let cache = &mut *cache; + it.into_half_matches_iter( + |input| Ok(re.search_half_with(cache, input)), + ) + .count() + } +} + +impl<'r, 'h> core::iter::FusedIterator for CapturesMatches<'r, 'h> {} + +/// Yields all substrings delimited by a regular expression match. +/// +/// The spans correspond to the offsets between matches. +/// +/// The lifetime parameters are as follows: +/// +/// * `'r` represents the lifetime of the `Regex` that produced this iterator. +/// * `'h` represents the lifetime of the haystack being searched. +/// +/// This iterator can be created with the [`Regex::split`] method. +#[derive(Debug)] +pub struct Split<'r, 'h> { + finder: FindMatches<'r, 'h>, + last: usize, +} + +impl<'r, 'h> Split<'r, 'h> { + /// Returns the current `Input` associated with this iterator. + /// + /// The `start` position on the given `Input` may change during iteration, + /// but all other values are guaranteed to remain invariant. + #[inline] + pub fn input<'s>(&'s self) -> &'s Input<'h> { + self.finder.input() + } +} + +impl<'r, 'h> Iterator for Split<'r, 'h> { + type Item = Span; + + fn next(&mut self) -> Option<Span> { + match self.finder.next() { + None => { + let len = self.finder.it.input().haystack().len(); + if self.last > len { + None + } else { + let span = Span::from(self.last..len); + self.last = len + 1; // Next call will return None + Some(span) + } + } + Some(m) => { + let span = Span::from(self.last..m.start()); + self.last = m.end(); + Some(span) + } + } + } +} + +impl<'r, 'h> core::iter::FusedIterator for Split<'r, 'h> {} + +/// Yields at most `N` spans delimited by a regular expression match. +/// +/// The spans correspond to the offsets between matches. The last span will be +/// whatever remains after splitting. +/// +/// The lifetime parameters are as follows: +/// +/// * `'r` represents the lifetime of the `Regex` that produced this iterator. +/// * `'h` represents the lifetime of the haystack being searched. +/// +/// This iterator can be created with the [`Regex::splitn`] method. +#[derive(Debug)] +pub struct SplitN<'r, 'h> { + splits: Split<'r, 'h>, + limit: usize, +} + +impl<'r, 'h> SplitN<'r, 'h> { + /// Returns the current `Input` associated with this iterator. + /// + /// The `start` position on the given `Input` may change during iteration, + /// but all other values are guaranteed to remain invariant. + #[inline] + pub fn input<'s>(&'s self) -> &'s Input<'h> { + self.splits.input() + } +} + +impl<'r, 'h> Iterator for SplitN<'r, 'h> { + type Item = Span; + + fn next(&mut self) -> Option<Span> { + if self.limit == 0 { + return None; + } + + self.limit -= 1; + if self.limit > 0 { + return self.splits.next(); + } + + let len = self.splits.finder.it.input().haystack().len(); + if self.splits.last > len { + // We've already returned all substrings. + None + } else { + // self.n == 0, so future calls will return None immediately + Some(Span::from(self.splits.last..len)) + } + } + + fn size_hint(&self) -> (usize, Option<usize>) { + (0, Some(self.limit)) + } +} + +impl<'r, 'h> core::iter::FusedIterator for SplitN<'r, 'h> {} + +/// Represents mutable scratch space used by regex engines during a search. +/// +/// Most of the regex engines in this crate require some kind of +/// mutable state in order to execute a search. This mutable state is +/// explicitly separated from the the core regex object (such as a +/// [`thompson::NFA`](crate::nfa::thompson::NFA)) so that the read-only regex +/// object can be shared across multiple threads simultaneously without any +/// synchronization. Conversely, a `Cache` must either be duplicated if using +/// the same `Regex` from multiple threads, or else there must be some kind of +/// synchronization that guarantees exclusive access while it's in use by one +/// thread. +/// +/// A `Regex` attempts to do this synchronization for you by using a thread +/// pool internally. Its size scales roughly with the number of simultaneous +/// regex searches. +/// +/// For cases where one does not want to rely on a `Regex`'s internal thread +/// pool, lower level routines such as [`Regex::search_with`] are provided +/// that permit callers to pass a `Cache` into the search routine explicitly. +/// +/// General advice is that the thread pool is often more than good enough. +/// However, it may be possible to observe the effects of its latency, +/// especially when searching many small haystacks from many threads +/// simultaneously. +/// +/// 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. +/// +/// # Example +/// +/// ``` +/// use regex_automata::{meta::Regex, Input, Match}; +/// +/// let re = Regex::new(r"(?-u)m\w+\s+m\w+")?; +/// let mut cache = re.create_cache(); +/// let input = Input::new("crazy janey and her mission man"); +/// assert_eq!( +/// Some(Match::must(0, 20..31)), +/// re.search_with(&mut cache, &input), +/// ); +/// +/// # Ok::<(), Box<dyn std::error::Error>>(()) +/// ``` +#[derive(Debug, Clone)] +pub struct Cache { + pub(crate) capmatches: Captures, + pub(crate) pikevm: wrappers::PikeVMCache, + pub(crate) backtrack: wrappers::BoundedBacktrackerCache, + pub(crate) onepass: wrappers::OnePassCache, + pub(crate) hybrid: wrappers::HybridCache, + pub(crate) revhybrid: wrappers::ReverseHybridCache, +} + +impl Cache { + /// Creates a new `Cache` for use with this 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 { + re.create_cache() + } + + /// Reset this cache such that it can be used for searching with the given + /// `Regex` (and only that `Regex`). + /// + /// A cache reset permits potentially reusing memory already allocated in + /// this cache with a different `Regex`. + /// + /// # 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::{meta::Regex, Match, Input}; + /// + /// 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.search_with(&mut cache, &Input::new("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.search_with(&mut cache, &Input::new("☃")), + /// ); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn reset(&mut self, re: &Regex) { + re.imp.strat.reset_cache(self) + } + + /// Returns the heap memory usage, in bytes, of this cache. + /// + /// 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 { + let mut bytes = 0; + bytes += self.pikevm.memory_usage(); + bytes += self.backtrack.memory_usage(); + bytes += self.onepass.memory_usage(); + bytes += self.hybrid.memory_usage(); + bytes += self.revhybrid.memory_usage(); + bytes + } +} + +/// An object describing the configuration of a `Regex`. +/// +/// This configuration only includes options for the +/// non-syntax behavior of a `Regex`, and can be applied via the +/// [`Builder::configure`] method. For configuring the syntax options, see +/// [`util::syntax::Config`](crate::util::syntax::Config). +/// +/// # Example: lower the NFA size limit +/// +/// In some cases, the default size limit might be too big. The size limit can +/// be lowered, which will prevent large regex patterns from compiling. +/// +/// ``` +/// # if cfg!(miri) { return Ok(()); } // miri takes too long +/// use regex_automata::meta::Regex; +/// +/// let result = Regex::builder() +/// .configure(Regex::config().nfa_size_limit(Some(20 * (1<<10)))) +/// // Not even 20KB is enough to build a single large Unicode class! +/// .build(r"\pL"); +/// assert!(result.is_err()); +/// +/// # Ok::<(), Box<dyn std::error::Error>>(()) +/// ``` +#[derive(Clone, Debug, Default)] +pub struct Config { + // As with other configuration types in this crate, we put all our knobs + // in options so that we can distinguish between "default" and "not set." + // This makes it possible to easily combine multiple configurations + // without default values overwriting explicitly specified values. See the + // 'overwrite' method. + // + // For docs on the fields below, see the corresponding method setters. + match_kind: Option<MatchKind>, + utf8_empty: Option<bool>, + autopre: Option<bool>, + pre: Option<Option<Prefilter>>, + which_captures: Option<WhichCaptures>, + nfa_size_limit: Option<Option<usize>>, + onepass_size_limit: Option<Option<usize>>, + hybrid_cache_capacity: Option<usize>, + hybrid: Option<bool>, + dfa: Option<bool>, + dfa_size_limit: Option<Option<usize>>, + dfa_state_limit: Option<Option<usize>>, + onepass: Option<bool>, + backtrack: Option<bool>, + byte_classes: Option<bool>, + line_terminator: Option<u8>, +} + +impl Config { + /// Create a new configuration object for a `Regex`. + pub fn new() -> Config { + Config::default() + } + + /// Set the match semantics for a `Regex`. + /// + /// The default value is [`MatchKind::LeftmostFirst`]. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Match, MatchKind}; + /// + /// // By default, leftmost-first semantics are used, which + /// // disambiguates matches at the same position by selecting + /// // the one that corresponds earlier in the pattern. + /// let re = Regex::new("sam|samwise")?; + /// assert_eq!(Some(Match::must(0, 0..3)), re.find("samwise")); + /// + /// // But with 'all' semantics, match priority is ignored + /// // and all match states are included. When coupled with + /// // a leftmost search, the search will report the last + /// // possible match. + /// let re = Regex::builder() + /// .configure(Regex::config().match_kind(MatchKind::All)) + /// .build("sam|samwise")?; + /// assert_eq!(Some(Match::must(0, 0..7)), re.find("samwise")); + /// // Beware that this can lead to skipping matches! + /// // Usually 'all' is used for anchored reverse searches + /// // only, or for overlapping searches. + /// assert_eq!(Some(Match::must(0, 4..11)), re.find("sam samwise")); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn match_kind(self, kind: MatchKind) -> Config { + Config { match_kind: Some(kind), ..self } + } + + /// Toggles whether empty matches are permitted to occur between the code + /// units of a UTF-8 encoded codepoint. + /// + /// This should generally be enabled when search a `&str` or anything that + /// you otherwise know is valid UTF-8. It should be disabled in all other + /// cases. Namely, if the haystack is not valid UTF-8 and this is enabled, + /// then behavior is unspecified. + /// + /// By default, this is enabled. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Match}; + /// + /// let re = Regex::new("")?; + /// let got: Vec<Match> = re.find_iter("☃").collect(); + /// // Matches only occur at the beginning and end of the snowman. + /// assert_eq!(got, vec![ + /// Match::must(0, 0..0), + /// Match::must(0, 3..3), + /// ]); + /// + /// let re = Regex::builder() + /// .configure(Regex::config().utf8_empty(false)) + /// .build("")?; + /// let got: Vec<Match> = re.find_iter("☃").collect(); + /// // Matches now occur at every position! + /// assert_eq!(got, vec![ + /// Match::must(0, 0..0), + /// Match::must(0, 1..1), + /// Match::must(0, 2..2), + /// Match::must(0, 3..3), + /// ]); + /// + /// Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn utf8_empty(self, yes: bool) -> Config { + Config { utf8_empty: Some(yes), ..self } + } + + /// Toggles whether automatic prefilter support is enabled. + /// + /// If this is disabled and [`Config::prefilter`] is not set, then the + /// meta regex engine will not use any prefilters. This can sometimes + /// be beneficial in cases where you know (or have measured) that the + /// prefilter leads to overall worse search performance. + /// + /// By default, this is enabled. + /// + /// # Example + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{meta::Regex, Match}; + /// + /// let re = Regex::builder() + /// .configure(Regex::config().auto_prefilter(false)) + /// .build(r"Bruce \w+")?; + /// let hay = "Hello Bruce Springsteen!"; + /// assert_eq!(Some(Match::must(0, 6..23)), re.find(hay)); + /// + /// Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn auto_prefilter(self, yes: bool) -> Config { + Config { autopre: Some(yes), ..self } + } + + /// Overrides and sets the prefilter to use inside a `Regex`. + /// + /// This permits one to forcefully set a prefilter in cases where the + /// caller knows better than whatever the automatic prefilter logic is + /// capable of. + /// + /// By default, this is set to `None` and an automatic prefilter will be + /// used if one could be built. (Assuming [`Config::auto_prefilter`] is + /// enabled, which it is by default.) + /// + /// # Example + /// + /// This example shows how to set your own prefilter. In the case of a + /// pattern like `Bruce \w+`, the automatic prefilter is likely to be + /// constructed in a way that it will look for occurrences of `Bruce `. + /// In most cases, this is the best choice. But in some cases, it may be + /// the case that running `memchr` on `B` is the best choice. One can + /// achieve that behavior by overriding the automatic prefilter logic + /// and providing a prefilter that just matches `B`. + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{ + /// meta::Regex, + /// util::prefilter::Prefilter, + /// Match, MatchKind, + /// }; + /// + /// let pre = Prefilter::new(MatchKind::LeftmostFirst, &["B"]) + /// .expect("a prefilter"); + /// let re = Regex::builder() + /// .configure(Regex::config().prefilter(Some(pre))) + /// .build(r"Bruce \w+")?; + /// let hay = "Hello Bruce Springsteen!"; + /// assert_eq!(Some(Match::must(0, 6..23)), re.find(hay)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// # Example: incorrect prefilters can lead to incorrect results! + /// + /// Be warned that setting an incorrect prefilter can lead to missed + /// matches. So if you use this option, ensure your prefilter can _never_ + /// report false negatives. (A false positive is, on the other hand, quite + /// okay and generally unavoidable.) + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::{ + /// meta::Regex, + /// util::prefilter::Prefilter, + /// Match, MatchKind, + /// }; + /// + /// let pre = Prefilter::new(MatchKind::LeftmostFirst, &["Z"]) + /// .expect("a prefilter"); + /// let re = Regex::builder() + /// .configure(Regex::config().prefilter(Some(pre))) + /// .build(r"Bruce \w+")?; + /// let hay = "Hello Bruce Springsteen!"; + /// // Oops! No match found, but there should be one! + /// assert_eq!(None, re.find(hay)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn prefilter(self, pre: Option<Prefilter>) -> Config { + Config { pre: Some(pre), ..self } + } + + /// Configures what kinds of groups are compiled as "capturing" in the + /// underlying regex engine. + /// + /// This is set to [`WhichCaptures::All`] by default. Callers may wish to + /// use [`WhichCaptures::Implicit`] in cases where one wants avoid the + /// overhead of capture states for explicit groups. + /// + /// Note that another approach to avoiding the overhead of capture groups + /// is by using non-capturing groups in the regex pattern. That is, + /// `(?:a)` instead of `(a)`. This option is useful when you can't control + /// the concrete syntax but know that you don't need the underlying capture + /// states. For example, using `WhichCaptures::Implicit` will behave as if + /// all explicit capturing groups in the pattern were non-capturing. + /// + /// Setting this to `WhichCaptures::None` is usually not the right thing to + /// do. When no capture states are compiled, some regex engines (such as + /// the `PikeVM`) won't be able to report match offsets. This will manifest + /// as no match being found. + /// + /// # Example + /// + /// This example demonstrates how the results of capture groups can change + /// based on this option. First we show the default (all capture groups in + /// the pattern are capturing): + /// + /// ``` + /// use regex_automata::{meta::Regex, Match, Span}; + /// + /// let re = Regex::new(r"foo([0-9]+)bar")?; + /// let hay = "foo123bar"; + /// + /// let mut caps = re.create_captures(); + /// re.captures(hay, &mut caps); + /// assert_eq!(Some(Span::from(0..9)), caps.get_group(0)); + /// assert_eq!(Some(Span::from(3..6)), caps.get_group(1)); + /// + /// Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + /// + /// And now we show the behavior when we only include implicit capture + /// groups. In this case, we can only find the overall match span, but the + /// spans of any other explicit group don't exist because they are treated + /// as non-capturing. (In effect, when `WhichCaptures::Implicit` is used, + /// there is no real point in using [`Regex::captures`] since it will never + /// be able to report more information than [`Regex::find`].) + /// + /// ``` + /// use regex_automata::{ + /// meta::Regex, + /// nfa::thompson::WhichCaptures, + /// Match, + /// Span, + /// }; + /// + /// let re = Regex::builder() + /// .configure(Regex::config().which_captures(WhichCaptures::Implicit)) + /// .build(r"foo([0-9]+)bar")?; + /// let hay = "foo123bar"; + /// + /// let mut caps = re.create_captures(); + /// re.captures(hay, &mut caps); + /// assert_eq!(Some(Span::from(0..9)), caps.get_group(0)); + /// assert_eq!(None, caps.get_group(1)); + /// + /// Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn which_captures(mut self, which_captures: WhichCaptures) -> Config { + self.which_captures = Some(which_captures); + self + } + + /// Sets the size limit, in bytes, to enforce on the construction of every + /// NFA build by the meta regex engine. + /// + /// Setting it to `None` disables the limit. This is not recommended if + /// you're compiling untrusted patterns. + /// + /// Note that this limit is applied to _each_ NFA built, and if any of + /// them excceed the limit, then construction will fail. This limit does + /// _not_ correspond to the total memory used by all NFAs in the meta regex + /// engine. + /// + /// This defaults to some reasonable number that permits most reasonable + /// patterns. + /// + /// # Example + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::meta::Regex; + /// + /// let result = Regex::builder() + /// .configure(Regex::config().nfa_size_limit(Some(20 * (1<<10)))) + /// // Not even 20KB is enough to build a single large Unicode class! + /// .build(r"\pL"); + /// assert!(result.is_err()); + /// + /// // But notice that building such a regex with the exact same limit + /// // can succeed depending on other aspects of the configuration. For + /// // example, a single *forward* NFA will (at time of writing) fit into + /// // the 20KB limit, but a *reverse* NFA of the same pattern will not. + /// // So if one configures a meta regex such that a reverse NFA is never + /// // needed and thus never built, then the 20KB limit will be enough for + /// // a pattern like \pL! + /// let result = Regex::builder() + /// .configure(Regex::config() + /// .nfa_size_limit(Some(20 * (1<<10))) + /// // The DFAs are the only thing that (currently) need a reverse + /// // NFA. So if both are disabled, the meta regex engine will + /// // skip building the reverse NFA. Note that this isn't an API + /// // guarantee. A future semver compatible version may introduce + /// // new use cases for a reverse NFA. + /// .hybrid(false) + /// .dfa(false) + /// ) + /// // Not even 20KB is enough to build a single large Unicode class! + /// .build(r"\pL"); + /// assert!(result.is_ok()); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn nfa_size_limit(self, limit: Option<usize>) -> Config { + Config { nfa_size_limit: Some(limit), ..self } + } + + /// Sets the size limit, in bytes, for the one-pass DFA. + /// + /// Setting it to `None` disables the limit. Disabling the limit is + /// strongly discouraged when compiling untrusted patterns. Even if the + /// patterns are trusted, it still may not be a good idea, since a one-pass + /// DFA can use a lot of memory. With that said, as the size of a regex + /// increases, the likelihood of it being one-pass likely decreases. + /// + /// This defaults to some reasonable number that permits most reasonable + /// one-pass patterns. + /// + /// # Example + /// + /// This shows how to set the one-pass DFA size limit. Note that since + /// a one-pass DFA is an optional component of the meta regex engine, + /// this size limit only impacts what is built internally and will never + /// determine whether a `Regex` itself fails to build. + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::meta::Regex; + /// + /// let result = Regex::builder() + /// .configure(Regex::config().onepass_size_limit(Some(2 * (1<<20)))) + /// .build(r"\pL{5}"); + /// assert!(result.is_ok()); + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn onepass_size_limit(self, limit: Option<usize>) -> Config { + Config { onepass_size_limit: Some(limit), ..self } + } + + /// Set the cache capacity, in bytes, for the lazy DFA. + /// + /// The cache capacity of the lazy DFA determines approximately how much + /// heap memory it is allowed to use to store its state transitions. The + /// state transitions are computed at search time, and if the cache fills + /// up it, it is cleared. At this point, any previously generated state + /// transitions are lost and are re-generated if they're needed again. + /// + /// This sort of cache filling and clearing works quite well _so long as + /// cache clearing happens infrequently_. If it happens too often, then the + /// meta regex engine will stop using the lazy DFA and switch over to a + /// different regex engine. + /// + /// In cases where the cache is cleared too often, it may be possible to + /// give the cache more space and reduce (or eliminate) how often it is + /// cleared. Similarly, sometimes a regex is so big that the lazy DFA isn't + /// used at all if its cache capacity isn't big enough. + /// + /// The capacity set here is a _limit_ on how much memory is used. The + /// actual memory used is only allocated as it's needed. + /// + /// Determining the right value for this is a little tricky and will likely + /// required some profiling. Enabling the `logging` feature and setting the + /// log level to `trace` will also tell you how often the cache is being + /// cleared. + /// + /// # Example + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::meta::Regex; + /// + /// let result = Regex::builder() + /// .configure(Regex::config().hybrid_cache_capacity(20 * (1<<20))) + /// .build(r"\pL{5}"); + /// assert!(result.is_ok()); + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn hybrid_cache_capacity(self, limit: usize) -> Config { + Config { hybrid_cache_capacity: Some(limit), ..self } + } + + /// Sets the size limit, in bytes, for heap memory used for a fully + /// compiled DFA. + /// + /// **NOTE:** If you increase this, you'll likely also need to increase + /// [`Config::dfa_state_limit`]. + /// + /// In contrast to the lazy DFA, building a full DFA requires computing + /// all of its state transitions up front. This can be a very expensive + /// process, and runs in worst case `2^n` time and space (where `n` is + /// proportional to the size of the regex). However, a full DFA unlocks + /// some additional optimization opportunities. + /// + /// Because full DFAs can be so expensive, the default limits for them are + /// incredibly small. Generally speaking, if your regex is moderately big + /// or if you're using Unicode features (`\w` is Unicode-aware by default + /// for example), then you can expect that the meta regex engine won't even + /// attempt to build a DFA for it. + /// + /// If this and [`Config::dfa_state_limit`] are set to `None`, then the + /// meta regex will not use any sort of limits when deciding whether to + /// build a DFA. This in turn makes construction of a `Regex` take + /// worst case exponential time and space. Even short patterns can result + /// in huge space blow ups. So it is strongly recommended to keep some kind + /// of limit set! + /// + /// The default is set to a small number that permits some simple regexes + /// to get compiled into DFAs in reasonable time. + /// + /// # Example + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::meta::Regex; + /// + /// let result = Regex::builder() + /// // 100MB is much bigger than the default. + /// .configure(Regex::config() + /// .dfa_size_limit(Some(100 * (1<<20))) + /// // We don't care about size too much here, so just + /// // remove the NFA state limit altogether. + /// .dfa_state_limit(None)) + /// .build(r"\pL{5}"); + /// assert!(result.is_ok()); + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn dfa_size_limit(self, limit: Option<usize>) -> Config { + Config { dfa_size_limit: Some(limit), ..self } + } + + /// Sets a limit on the total number of NFA states, beyond which, a full + /// DFA is not attempted to be compiled. + /// + /// This limit works in concert with [`Config::dfa_size_limit`]. Namely, + /// where as `Config::dfa_size_limit` is applied by attempting to construct + /// a DFA, this limit is used to avoid the attempt in the first place. This + /// is useful to avoid hefty initialization costs associated with building + /// a DFA for cases where it is obvious the DFA will ultimately be too big. + /// + /// By default, this is set to a very small number. + /// + /// # Example + /// + /// ``` + /// # if cfg!(miri) { return Ok(()); } // miri takes too long + /// use regex_automata::meta::Regex; + /// + /// let result = Regex::builder() + /// .configure(Regex::config() + /// // Sometimes the default state limit rejects DFAs even + /// // if they would fit in the size limit. Here, we disable + /// // the check on the number of NFA states and just rely on + /// // the size limit. + /// .dfa_state_limit(None)) + /// .build(r"(?-u)\w{30}"); + /// assert!(result.is_ok()); + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn dfa_state_limit(self, limit: Option<usize>) -> Config { + Config { dfa_state_limit: Some(limit), ..self } + } + + /// Whether to attempt to shrink the size of the alphabet for the regex + /// pattern or not. When enabled, the alphabet is shrunk into a set of + /// equivalence classes, where every byte in the same equivalence class + /// cannot discriminate between a match or non-match. + /// + /// **WARNING:** This is only useful for debugging DFAs. Disabling this + /// does not yield any speed advantages. Indeed, disabling it can result + /// in much higher memory usage. Disabling byte classes is useful for + /// debugging the actual generated transitions because it lets one see the + /// transitions defined on actual bytes instead of the equivalence classes. + /// + /// This option is enabled by default and should never be disabled unless + /// one is debugging the meta regex engine's internals. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, Match}; + /// + /// let re = Regex::builder() + /// .configure(Regex::config().byte_classes(false)) + /// .build(r"[a-z]+")?; + /// let hay = "!!quux!!"; + /// assert_eq!(Some(Match::must(0, 2..6)), re.find(hay)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn byte_classes(self, yes: bool) -> Config { + Config { byte_classes: Some(yes), ..self } + } + + /// Set the line terminator to be used by the `^` and `$` anchors in + /// multi-line mode. + /// + /// This option has no effect when CRLF mode is enabled. That is, + /// regardless of this setting, `(?Rm:^)` and `(?Rm:$)` will always treat + /// `\r` and `\n` as line terminators (and will never match between a `\r` + /// and a `\n`). + /// + /// By default, `\n` is the line terminator. + /// + /// **Warning**: This does not change the behavior of `.`. To do that, + /// you'll need to configure the syntax option + /// [`syntax::Config::line_terminator`](crate::util::syntax::Config::line_terminator) + /// in addition to this. Otherwise, `.` will continue to match any + /// character other than `\n`. + /// + /// # Example + /// + /// ``` + /// use regex_automata::{meta::Regex, util::syntax, Match}; + /// + /// let re = Regex::builder() + /// .syntax(syntax::Config::new().multi_line(true)) + /// .configure(Regex::config().line_terminator(b'\x00')) + /// .build(r"^foo$")?; + /// let hay = "\x00foo\x00"; + /// assert_eq!(Some(Match::must(0, 1..4)), re.find(hay)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn line_terminator(self, byte: u8) -> Config { + Config { line_terminator: Some(byte), ..self } + } + + /// Toggle whether the hybrid NFA/DFA (also known as the "lazy DFA") should + /// be available for use by the meta regex engine. + /// + /// Enabling this does not necessarily mean that the lazy DFA will + /// definitely be used. It just means that it will be _available_ for use + /// if the meta regex engine thinks it will be useful. + /// + /// When the `hybrid` crate feature is enabled, then this is enabled by + /// default. Otherwise, if the crate feature is disabled, then this is + /// always disabled, regardless of its setting by the caller. + pub fn hybrid(self, yes: bool) -> Config { + Config { hybrid: Some(yes), ..self } + } + + /// Toggle whether a fully compiled DFA should be available for use by the + /// meta regex engine. + /// + /// Enabling this does not necessarily mean that a DFA will definitely be + /// used. It just means that it will be _available_ for use if the meta + /// regex engine thinks it will be useful. + /// + /// When the `dfa-build` crate feature is enabled, then this is enabled by + /// default. Otherwise, if the crate feature is disabled, then this is + /// always disabled, regardless of its setting by the caller. + pub fn dfa(self, yes: bool) -> Config { + Config { dfa: Some(yes), ..self } + } + + /// Toggle whether a one-pass DFA should be available for use by the meta + /// regex engine. + /// + /// Enabling this does not necessarily mean that a one-pass DFA will + /// definitely be used. It just means that it will be _available_ for + /// use if the meta regex engine thinks it will be useful. (Indeed, a + /// one-pass DFA can only be used when the regex is one-pass. See the + /// [`dfa::onepass`](crate::dfa::onepass) module for more details.) + /// + /// When the `dfa-onepass` crate feature is enabled, then this is enabled + /// by default. Otherwise, if the crate feature is disabled, then this is + /// always disabled, regardless of its setting by the caller. + pub fn onepass(self, yes: bool) -> Config { + Config { onepass: Some(yes), ..self } + } + + /// Toggle whether a bounded backtracking regex engine should be available + /// for use by the meta regex engine. + /// + /// Enabling this does not necessarily mean that a bounded backtracker will + /// definitely be used. It just means that it will be _available_ for use + /// if the meta regex engine thinks it will be useful. + /// + /// When the `nfa-backtrack` crate feature is enabled, then this is enabled + /// by default. Otherwise, if the crate feature is disabled, then this is + /// always disabled, regardless of its setting by the caller. + pub fn backtrack(self, yes: bool) -> Config { + Config { backtrack: Some(yes), ..self } + } + + /// Returns the match kind on this configuration, as set by + /// [`Config::match_kind`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_match_kind(&self) -> MatchKind { + self.match_kind.unwrap_or(MatchKind::LeftmostFirst) + } + + /// Returns whether empty matches must fall on valid UTF-8 boundaries, as + /// set by [`Config::utf8_empty`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_utf8_empty(&self) -> bool { + self.utf8_empty.unwrap_or(true) + } + + /// Returns whether automatic prefilters are enabled, as set by + /// [`Config::auto_prefilter`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_auto_prefilter(&self) -> bool { + self.autopre.unwrap_or(true) + } + + /// Returns a manually set prefilter, if one was set by + /// [`Config::prefilter`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_prefilter(&self) -> Option<&Prefilter> { + self.pre.as_ref().unwrap_or(&None).as_ref() + } + + /// Returns the capture configuration, as set by + /// [`Config::which_captures`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_which_captures(&self) -> WhichCaptures { + self.which_captures.unwrap_or(WhichCaptures::All) + } + + /// Returns NFA size limit, as set by [`Config::nfa_size_limit`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_nfa_size_limit(&self) -> Option<usize> { + self.nfa_size_limit.unwrap_or(Some(10 * (1 << 20))) + } + + /// Returns one-pass DFA size limit, as set by + /// [`Config::onepass_size_limit`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_onepass_size_limit(&self) -> Option<usize> { + self.onepass_size_limit.unwrap_or(Some(1 * (1 << 20))) + } + + /// Returns hybrid NFA/DFA cache capacity, as set by + /// [`Config::hybrid_cache_capacity`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_hybrid_cache_capacity(&self) -> usize { + self.hybrid_cache_capacity.unwrap_or(2 * (1 << 20)) + } + + /// Returns DFA size limit, as set by [`Config::dfa_size_limit`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_dfa_size_limit(&self) -> Option<usize> { + // The default for this is VERY small because building a full DFA is + // ridiculously costly. But for regexes that are very small, it can be + // beneficial to use a full DFA. In particular, a full DFA can enable + // additional optimizations via something called "accelerated" states. + // Namely, when there's a state with only a few outgoing transitions, + // we can temporary suspend walking the transition table and use memchr + // for just those outgoing transitions to skip ahead very quickly. + // + // Generally speaking, if Unicode is enabled in your regex and you're + // using some kind of Unicode feature, then it's going to blow this + // size limit. Moreover, Unicode tends to defeat the "accelerated" + // state optimization too, so it's a double whammy. + // + // We also use a limit on the number of NFA states to avoid even + // starting the DFA construction process. Namely, DFA construction + // itself could make lots of initial allocs proportional to the size + // of the NFA, and if the NFA is large, it doesn't make sense to pay + // that cost if we know it's likely to be blown by a large margin. + self.dfa_size_limit.unwrap_or(Some(40 * (1 << 10))) + } + + /// Returns DFA size limit in terms of the number of states in the NFA, as + /// set by [`Config::dfa_state_limit`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_dfa_state_limit(&self) -> Option<usize> { + // Again, as with the size limit, we keep this very small. + self.dfa_state_limit.unwrap_or(Some(30)) + } + + /// Returns whether byte classes are enabled, as set by + /// [`Config::byte_classes`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_byte_classes(&self) -> bool { + self.byte_classes.unwrap_or(true) + } + + /// Returns the line terminator for this configuration, as set by + /// [`Config::line_terminator`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_line_terminator(&self) -> u8 { + self.line_terminator.unwrap_or(b'\n') + } + + /// Returns whether the hybrid NFA/DFA regex engine may be used, as set by + /// [`Config::hybrid`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_hybrid(&self) -> bool { + #[cfg(feature = "hybrid")] + { + self.hybrid.unwrap_or(true) + } + #[cfg(not(feature = "hybrid"))] + { + false + } + } + + /// Returns whether the DFA regex engine may be used, as set by + /// [`Config::dfa`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_dfa(&self) -> bool { + #[cfg(feature = "dfa-build")] + { + self.dfa.unwrap_or(true) + } + #[cfg(not(feature = "dfa-build"))] + { + false + } + } + + /// Returns whether the one-pass DFA regex engine may be used, as set by + /// [`Config::onepass`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_onepass(&self) -> bool { + #[cfg(feature = "dfa-onepass")] + { + self.onepass.unwrap_or(true) + } + #[cfg(not(feature = "dfa-onepass"))] + { + false + } + } + + /// Returns whether the bounded backtracking regex engine may be used, as + /// set by [`Config::backtrack`]. + /// + /// If it was not explicitly set, then a default value is returned. + pub fn get_backtrack(&self) -> bool { + #[cfg(feature = "nfa-backtrack")] + { + self.backtrack.unwrap_or(true) + } + #[cfg(not(feature = "nfa-backtrack"))] + { + false + } + } + + /// Overwrite the default configuration such that the options in `o` are + /// always used. If an option in `o` is not set, then the corresponding + /// option in `self` is used. If it's not set in `self` either, then it + /// remains not set. + pub(crate) fn overwrite(&self, o: Config) -> Config { + Config { + match_kind: o.match_kind.or(self.match_kind), + utf8_empty: o.utf8_empty.or(self.utf8_empty), + autopre: o.autopre.or(self.autopre), + pre: o.pre.or_else(|| self.pre.clone()), + which_captures: o.which_captures.or(self.which_captures), + nfa_size_limit: o.nfa_size_limit.or(self.nfa_size_limit), + onepass_size_limit: o + .onepass_size_limit + .or(self.onepass_size_limit), + hybrid_cache_capacity: o + .hybrid_cache_capacity + .or(self.hybrid_cache_capacity), + hybrid: o.hybrid.or(self.hybrid), + dfa: o.dfa.or(self.dfa), + dfa_size_limit: o.dfa_size_limit.or(self.dfa_size_limit), + dfa_state_limit: o.dfa_state_limit.or(self.dfa_state_limit), + onepass: o.onepass.or(self.onepass), + backtrack: o.backtrack.or(self.backtrack), + byte_classes: o.byte_classes.or(self.byte_classes), + line_terminator: o.line_terminator.or(self.line_terminator), + } + } +} + +/// A builder for configuring and constructing a `Regex`. +/// +/// The builder permits configuring two different aspects of a `Regex`: +/// +/// * [`Builder::configure`] will set high-level configuration options as +/// described by a [`Config`]. +/// * [`Builder::syntax`] will set the syntax level configuration options +/// as described by a [`util::syntax::Config`](crate::util::syntax::Config). +/// This only applies when building a `Regex` from pattern strings. +/// +/// Once configured, the builder can then be used to construct a `Regex` from +/// one of 4 different inputs: +/// +/// * [`Builder::build`] creates a regex from a single pattern string. +/// * [`Builder::build_many`] creates a regex from many pattern strings. +/// * [`Builder::build_from_hir`] creates a regex from a +/// [`regex-syntax::Hir`](Hir) expression. +/// * [`Builder::build_many_from_hir`] creates a regex from many +/// [`regex-syntax::Hir`](Hir) expressions. +/// +/// The latter two methods in particular provide a way to construct a fully +/// feature regular expression matcher directly from an `Hir` expression +/// without having to first convert it to a string. (This is in contrast to the +/// top-level `regex` crate which intentionally provides no such API in order +/// to avoid making `regex-syntax` a public dependency.) +/// +/// As a convenience, this builder may be created via [`Regex::builder`], which +/// may help avoid an extra import. +/// +/// # Example: change the line terminator +/// +/// This example shows how to enable multi-line mode by default and change the +/// line terminator to the NUL byte: +/// +/// ``` +/// use regex_automata::{meta::Regex, util::syntax, Match}; +/// +/// let re = Regex::builder() +/// .syntax(syntax::Config::new().multi_line(true)) +/// .configure(Regex::config().line_terminator(b'\x00')) +/// .build(r"^foo$")?; +/// let hay = "\x00foo\x00"; +/// assert_eq!(Some(Match::must(0, 1..4)), re.find(hay)); +/// +/// # Ok::<(), Box<dyn std::error::Error>>(()) +/// ``` +/// +/// # Example: disable UTF-8 requirement +/// +/// By default, regex patterns are required to match UTF-8. This includes +/// regex patterns that can produce matches of length zero. In the case of an +/// empty match, by default, matches will not appear between the code units of +/// a UTF-8 encoded codepoint. +/// +/// However, it can be useful to disable this requirement, particularly if +/// you're searching things like `&[u8]` that are not known to be valid UTF-8. +/// +/// ``` +/// use regex_automata::{meta::Regex, util::syntax, Match}; +/// +/// let mut builder = Regex::builder(); +/// // Disables the requirement that non-empty matches match UTF-8. +/// builder.syntax(syntax::Config::new().utf8(false)); +/// // Disables the requirement that empty matches match UTF-8 boundaries. +/// builder.configure(Regex::config().utf8_empty(false)); +/// +/// // We can match raw bytes via \xZZ syntax, but we need to disable +/// // Unicode mode to do that. We could disable it everywhere, or just +/// // selectively, as shown here. +/// let re = builder.build(r"(?-u:\xFF)foo(?-u:\xFF)")?; +/// let hay = b"\xFFfoo\xFF"; +/// assert_eq!(Some(Match::must(0, 0..5)), re.find(hay)); +/// +/// // We can also match between code units. +/// let re = builder.build(r"")?; +/// let hay = "☃"; +/// assert_eq!(re.find_iter(hay).collect::<Vec<Match>>(), vec![ +/// Match::must(0, 0..0), +/// Match::must(0, 1..1), +/// Match::must(0, 2..2), +/// Match::must(0, 3..3), +/// ]); +/// +/// # Ok::<(), Box<dyn std::error::Error>>(()) +/// ``` +#[derive(Clone, Debug)] +pub struct Builder { + config: Config, + ast: ast::parse::ParserBuilder, + hir: hir::translate::TranslatorBuilder, +} + +impl Builder { + /// Creates a new builder for configuring and constructing a [`Regex`]. + pub fn new() -> Builder { + Builder { + config: Config::default(), + ast: ast::parse::ParserBuilder::new(), + hir: hir::translate::TranslatorBuilder::new(), + } + } + + /// Builds a `Regex` from a single pattern string. + /// + /// If there was a problem parsing the pattern or a problem turning it into + /// a regex matcher, then an error is returned. + /// + /// # Example + /// + /// This example shows how to configure syntax options. + /// + /// ``` + /// use regex_automata::{meta::Regex, util::syntax, Match}; + /// + /// let re = Regex::builder() + /// .syntax(syntax::Config::new().crlf(true).multi_line(true)) + /// .build(r"^foo$")?; + /// let hay = "\r\nfoo\r\n"; + /// assert_eq!(Some(Match::must(0, 2..5)), re.find(hay)); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn build(&self, pattern: &str) -> Result<Regex, BuildError> { + self.build_many(&[pattern]) + } + + /// Builds a `Regex` from many pattern strings. + /// + /// If there was a problem parsing any of the patterns or a problem turning + /// them into a regex matcher, then an error is returned. + /// + /// # Example: finding the pattern that caused an error + /// + /// When a syntax error occurs, it is possible to ask which pattern + /// caused the syntax error. + /// + /// ``` + /// use regex_automata::{meta::Regex, PatternID}; + /// + /// let err = Regex::builder() + /// .build_many(&["a", "b", r"\p{Foo}", "c"]) + /// .unwrap_err(); + /// assert_eq!(Some(PatternID::must(2)), err.pattern()); + /// ``` + /// + /// # Example: zero patterns is valid + /// + /// Building a regex with zero patterns results in a regex that never + /// matches anything. Because this routine is generic, passing an empty + /// slice usually requires a turbo-fish (or something else to help type + /// inference). + /// + /// ``` + /// use regex_automata::{meta::Regex, util::syntax, Match}; + /// + /// let re = Regex::builder() + /// .build_many::<&str>(&[])?; + /// assert_eq!(None, re.find("")); + /// + /// # Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn build_many<P: AsRef<str>>( + &self, + patterns: &[P], + ) -> Result<Regex, BuildError> { + use crate::util::primitives::IteratorIndexExt; + log! { + debug!("building meta regex with {} patterns:", patterns.len()); + for (pid, p) in patterns.iter().with_pattern_ids() { + let p = p.as_ref(); + // We might split a grapheme with this truncation logic, but + // that's fine. We at least avoid splitting a codepoint. + let maxoff = p + .char_indices() + .map(|(i, ch)| i + ch.len_utf8()) + .take(1000) + .last() + .unwrap_or(0); + if maxoff < p.len() { + debug!("{:?}: {}[... snip ...]", pid, &p[..maxoff]); + } else { + debug!("{:?}: {}", pid, p); + } + } + } + let (mut asts, mut hirs) = (vec![], vec![]); + for (pid, p) in patterns.iter().with_pattern_ids() { + let ast = self + .ast + .build() + .parse(p.as_ref()) + .map_err(|err| BuildError::ast(pid, err))?; + asts.push(ast); + } + for ((pid, p), ast) in + patterns.iter().with_pattern_ids().zip(asts.iter()) + { + let hir = self + .hir + .build() + .translate(p.as_ref(), ast) + .map_err(|err| BuildError::hir(pid, err))?; + hirs.push(hir); + } + self.build_many_from_hir(&hirs) + } + + /// Builds a `Regex` directly from an `Hir` expression. + /// + /// This is useful if you needed to parse a pattern string into an `Hir` + /// for other reasons (such as analysis or transformations). This routine + /// permits building a `Regex` directly from the `Hir` expression instead + /// of first converting the `Hir` back to a pattern string. + /// + /// When using this method, any options set via [`Builder::syntax`] are + /// ignored. Namely, the syntax options only apply when parsing a pattern + /// string, which isn't relevant here. + /// + /// If there was a problem building the underlying regex matcher for the + /// given `Hir`, then an error is returned. + /// + /// # Example + /// + /// This example shows how one can hand-construct an `Hir` expression and + /// build a regex from it without doing any parsing at all. + /// + /// ``` + /// use { + /// regex_automata::{meta::Regex, Match}, + /// regex_syntax::hir::{Hir, Look}, + /// }; + /// + /// // (?Rm)^foo$ + /// let hir = Hir::concat(vec![ + /// Hir::look(Look::StartCRLF), + /// Hir::literal("foo".as_bytes()), + /// Hir::look(Look::EndCRLF), + /// ]); + /// let re = Regex::builder() + /// .build_from_hir(&hir)?; + /// let hay = "\r\nfoo\r\n"; + /// assert_eq!(Some(Match::must(0, 2..5)), re.find(hay)); + /// + /// Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn build_from_hir(&self, hir: &Hir) -> Result<Regex, BuildError> { + self.build_many_from_hir(&[hir]) + } + + /// Builds a `Regex` directly from many `Hir` expressions. + /// + /// This is useful if you needed to parse pattern strings into `Hir` + /// expressions for other reasons (such as analysis or transformations). + /// This routine permits building a `Regex` directly from the `Hir` + /// expressions instead of first converting the `Hir` expressions back to + /// pattern strings. + /// + /// When using this method, any options set via [`Builder::syntax`] are + /// ignored. Namely, the syntax options only apply when parsing a pattern + /// string, which isn't relevant here. + /// + /// If there was a problem building the underlying regex matcher for the + /// given `Hir` expressions, then an error is returned. + /// + /// Note that unlike [`Builder::build_many`], this can only fail as a + /// result of building the underlying matcher. In that case, there is + /// no single `Hir` expression that can be isolated as a reason for the + /// failure. So if this routine fails, it's not possible to determine which + /// `Hir` expression caused the failure. + /// + /// # Example + /// + /// This example shows how one can hand-construct multiple `Hir` + /// expressions and build a single regex from them without doing any + /// parsing at all. + /// + /// ``` + /// use { + /// regex_automata::{meta::Regex, Match}, + /// regex_syntax::hir::{Hir, Look}, + /// }; + /// + /// // (?Rm)^foo$ + /// let hir1 = Hir::concat(vec![ + /// Hir::look(Look::StartCRLF), + /// Hir::literal("foo".as_bytes()), + /// Hir::look(Look::EndCRLF), + /// ]); + /// // (?Rm)^bar$ + /// let hir2 = Hir::concat(vec![ + /// Hir::look(Look::StartCRLF), + /// Hir::literal("bar".as_bytes()), + /// Hir::look(Look::EndCRLF), + /// ]); + /// let re = Regex::builder() + /// .build_many_from_hir(&[&hir1, &hir2])?; + /// let hay = "\r\nfoo\r\nbar"; + /// let got: Vec<Match> = re.find_iter(hay).collect(); + /// let expected = vec![ + /// Match::must(0, 2..5), + /// Match::must(1, 7..10), + /// ]; + /// assert_eq!(expected, got); + /// + /// Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn build_many_from_hir<H: Borrow<Hir>>( + &self, + hirs: &[H], + ) -> Result<Regex, BuildError> { + let config = self.config.clone(); + // We collect the HIRs into a vec so we can write internal routines + // with '&[&Hir]'. i.e., Don't use generics everywhere to keep code + // bloat down.. + let hirs: Vec<&Hir> = hirs.iter().map(|hir| hir.borrow()).collect(); + let info = RegexInfo::new(config, &hirs); + let strat = strategy::new(&info, &hirs)?; + let pool = { + let strat = Arc::clone(&strat); + let create: CachePoolFn = Box::new(move || strat.create_cache()); + Pool::new(create) + }; + Ok(Regex { imp: Arc::new(RegexI { strat, info }), pool }) + } + + /// Configure the behavior of a `Regex`. + /// + /// This configuration controls non-syntax options related to the behavior + /// of a `Regex`. This includes things like whether empty matches can split + /// a codepoint, prefilters, line terminators and a long list of options + /// for configuring which regex engines the meta regex engine will be able + /// to use internally. + /// + /// # Example + /// + /// This example shows how to disable UTF-8 empty mode. This will permit + /// empty matches to occur between the UTF-8 encoding of a codepoint. + /// + /// ``` + /// use regex_automata::{meta::Regex, Match}; + /// + /// let re = Regex::new("")?; + /// let got: Vec<Match> = re.find_iter("☃").collect(); + /// // Matches only occur at the beginning and end of the snowman. + /// assert_eq!(got, vec![ + /// Match::must(0, 0..0), + /// Match::must(0, 3..3), + /// ]); + /// + /// let re = Regex::builder() + /// .configure(Regex::config().utf8_empty(false)) + /// .build("")?; + /// let got: Vec<Match> = re.find_iter("☃").collect(); + /// // Matches now occur at every position! + /// assert_eq!(got, vec![ + /// Match::must(0, 0..0), + /// Match::must(0, 1..1), + /// Match::must(0, 2..2), + /// Match::must(0, 3..3), + /// ]); + /// + /// Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn configure(&mut self, config: Config) -> &mut Builder { + self.config = self.config.overwrite(config); + self + } + + /// Configure the syntax options when parsing a pattern string while + /// building a `Regex`. + /// + /// These options _only_ apply when [`Builder::build`] or [`Builder::build_many`] + /// are used. The other build methods accept `Hir` values, which have + /// already been parsed. + /// + /// # Example + /// + /// This example shows how to enable case insensitive mode. + /// + /// ``` + /// use regex_automata::{meta::Regex, util::syntax, Match}; + /// + /// let re = Regex::builder() + /// .syntax(syntax::Config::new().case_insensitive(true)) + /// .build(r"δ")?; + /// assert_eq!(Some(Match::must(0, 0..2)), re.find(r"Δ")); + /// + /// Ok::<(), Box<dyn std::error::Error>>(()) + /// ``` + pub fn syntax( + &mut self, + config: crate::util::syntax::Config, + ) -> &mut Builder { + config.apply_ast(&mut self.ast); + config.apply_hir(&mut self.hir); + self + } +} + +#[cfg(test)] +mod tests { + use super::*; + + // I found this in the course of building out the benchmark suite for + // rebar. + #[test] + fn regression() { + env_logger::init(); + + let re = Regex::new(r"[a-zA-Z]+ing").unwrap(); + assert_eq!(1, re.find_iter("tingling").count()); + } +} |