| /*! |
| An NFA backed bounded backtracker for executing regex searches with capturing |
| groups. |
| |
| This module provides a [`BoundedBacktracker`] that works by simulating an NFA |
| using the classical backtracking algorithm with a twist: it avoids redoing |
| work that it has done before and thereby avoids worst case exponential time. |
| In exchange, it can only be used on "short" haystacks. Its advantage is that |
| is can be faster than the [`PikeVM`](thompson::pikevm::PikeVM) in many cases |
| because it does less book-keeping. |
| */ |
| |
| use alloc::{vec, vec::Vec}; |
| |
| use crate::{ |
| nfa::thompson::{self, BuildError, State, NFA}, |
| util::{ |
| captures::Captures, |
| empty, iter, |
| prefilter::Prefilter, |
| primitives::{NonMaxUsize, PatternID, SmallIndex, StateID}, |
| search::{Anchored, HalfMatch, Input, Match, MatchError, Span}, |
| }, |
| }; |
| |
| /// Returns the minimum visited capacity for the given haystack. |
| /// |
| /// This function can be used as the argument to [`Config::visited_capacity`] |
| /// in order to guarantee that a backtracking search for the given `input` |
| /// won't return an error when using a [`BoundedBacktracker`] built from the |
| /// given `NFA`. |
| /// |
| /// This routine exists primarily as a way to test that the bounded backtracker |
| /// works correctly when its capacity is set to the smallest possible amount. |
| /// Still, it may be useful in cases where you know you want to use the bounded |
| /// backtracker for a specific input, and just need to know what visited |
| /// capacity to provide to make it work. |
| /// |
| /// Be warned that this number could be quite large as it is multiplicative in |
| /// the size the given NFA and haystack. |
| pub fn min_visited_capacity(nfa: &NFA, input: &Input<'_>) -> usize { |
| div_ceil(nfa.states().len() * (input.get_span().len() + 1), 8) |
| } |
| |
| /// The configuration used for building a bounded backtracker. |
| /// |
| /// A bounded backtracker configuration is a simple data object that is |
| /// typically used with [`Builder::configure`]. |
| #[derive(Clone, Debug, Default)] |
| pub struct Config { |
| pre: Option<Option<Prefilter>>, |
| visited_capacity: Option<usize>, |
| } |
| |
| impl Config { |
| /// Return a new default regex configuration. |
| pub fn new() -> Config { |
| Config::default() |
| } |
| |
| /// Set a prefilter to be used whenever a start state is entered. |
| /// |
| /// A [`Prefilter`] in this context is meant to accelerate searches by |
| /// looking for literal prefixes that every match for the corresponding |
| /// pattern (or patterns) must start with. Once a prefilter produces a |
| /// match, the underlying search routine continues on to try and confirm |
| /// the match. |
| /// |
| /// Be warned that setting a prefilter does not guarantee that the search |
| /// will be faster. While it's usually a good bet, if the prefilter |
| /// produces a lot of false positive candidates (i.e., positions matched |
| /// by the prefilter but not by the regex), then the overall result can |
| /// be slower than if you had just executed the regex engine without any |
| /// prefilters. |
| /// |
| /// By default no prefilter is set. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// util::prefilter::Prefilter, |
| /// Input, Match, MatchKind, |
| /// }; |
| /// |
| /// let pre = Prefilter::new(MatchKind::LeftmostFirst, &["foo", "bar"]); |
| /// let re = BoundedBacktracker::builder() |
| /// .configure(BoundedBacktracker::config().prefilter(pre)) |
| /// .build(r"(foo|bar)[a-z]+")?; |
| /// let mut cache = re.create_cache(); |
| /// let input = Input::new("foo1 barfox bar"); |
| /// assert_eq!( |
| /// Some(Match::must(0, 5..11)), |
| /// re.try_find(&mut cache, input)?, |
| /// ); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| /// |
| /// Be warned though that an incorrect prefilter can lead to incorrect |
| /// results! |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// util::prefilter::Prefilter, |
| /// Input, HalfMatch, MatchKind, |
| /// }; |
| /// |
| /// let pre = Prefilter::new(MatchKind::LeftmostFirst, &["foo", "car"]); |
| /// let re = BoundedBacktracker::builder() |
| /// .configure(BoundedBacktracker::config().prefilter(pre)) |
| /// .build(r"(foo|bar)[a-z]+")?; |
| /// let mut cache = re.create_cache(); |
| /// let input = Input::new("foo1 barfox bar"); |
| /// // No match reported even though there clearly is one! |
| /// assert_eq!(None, re.try_find(&mut cache, input)?); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn prefilter(mut self, pre: Option<Prefilter>) -> Config { |
| self.pre = Some(pre); |
| self |
| } |
| |
| /// Set the visited capacity used to bound backtracking. |
| /// |
| /// The visited capacity represents the amount of heap memory (in bytes) to |
| /// allocate toward tracking which parts of the backtracking search have |
| /// been done before. The heap memory needed for any particular search is |
| /// proportional to `haystack.len() * nfa.states().len()`, which an be |
| /// quite large. Therefore, the bounded backtracker is typically only able |
| /// to run on shorter haystacks. |
| /// |
| /// For a given regex, increasing the visited capacity means that the |
| /// maximum haystack length that can be searched is increased. The |
| /// [`BoundedBacktracker::max_haystack_len`] method returns that maximum. |
| /// |
| /// The default capacity is a reasonable but empirically chosen size. |
| /// |
| /// # Example |
| /// |
| /// As with other regex engines, Unicode is what tends to make the bounded |
| /// backtracker less useful by making the maximum haystack length quite |
| /// small. If necessary, increasing the visited capacity using this routine |
| /// will increase the maximum haystack length at the cost of using more |
| /// memory. |
| /// |
| /// Note though that the specific maximum values here are not an API |
| /// guarantee. The default visited capacity is subject to change and not |
| /// covered by semver. |
| /// |
| /// ``` |
| /// # if cfg!(miri) { return Ok(()); } // miri takes too long |
| /// use regex_automata::nfa::thompson::backtrack::BoundedBacktracker; |
| /// |
| /// // Unicode inflates the size of the underlying NFA quite a bit, and |
| /// // thus means that the backtracker can only handle smaller haystacks, |
| /// // assuming that the visited capacity remains unchanged. |
| /// let re = BoundedBacktracker::new(r"\w+")?; |
| /// assert!(re.max_haystack_len() <= 7_000); |
| /// // But we can increase the visited capacity to handle bigger haystacks! |
| /// let re = BoundedBacktracker::builder() |
| /// .configure(BoundedBacktracker::config().visited_capacity(1<<20)) |
| /// .build(r"\w+")?; |
| /// assert!(re.max_haystack_len() >= 25_000); |
| /// assert!(re.max_haystack_len() <= 28_000); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn visited_capacity(mut self, capacity: usize) -> Config { |
| self.visited_capacity = Some(capacity); |
| self |
| } |
| |
| /// Returns the prefilter set in this configuration, if one at all. |
| pub fn get_prefilter(&self) -> Option<&Prefilter> { |
| self.pre.as_ref().unwrap_or(&None).as_ref() |
| } |
| |
| /// Returns the configured visited capacity. |
| /// |
| /// Note that the actual capacity used may be slightly bigger than the |
| /// configured capacity. |
| pub fn get_visited_capacity(&self) -> usize { |
| const DEFAULT: usize = 256 * (1 << 10); // 256 KB |
| self.visited_capacity.unwrap_or(DEFAULT) |
| } |
| |
| /// 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 { |
| pre: o.pre.or_else(|| self.pre.clone()), |
| visited_capacity: o.visited_capacity.or(self.visited_capacity), |
| } |
| } |
| } |
| |
| /// A builder for a bounded backtracker. |
| /// |
| /// This builder permits configuring options for the syntax of a pattern, the |
| /// NFA construction and the `BoundedBacktracker` construction. This builder |
| /// is different from a general purpose regex builder in that it permits fine |
| /// grain configuration of the construction process. The trade off for this is |
| /// complexity, and the possibility of setting a configuration that might not |
| /// make sense. For example, there are two different UTF-8 modes: |
| /// |
| /// * [`syntax::Config::utf8`](crate::util::syntax::Config::utf8) controls |
| /// whether the pattern itself can contain sub-expressions that match invalid |
| /// UTF-8. |
| /// * [`thompson::Config::utf8`] controls how the regex iterators themselves |
| /// advance the starting position of the next search when a match with zero |
| /// length is found. |
| /// |
| /// Generally speaking, callers will want to either enable all of these or |
| /// disable all of these. |
| /// |
| /// # Example |
| /// |
| /// This example shows how to disable UTF-8 mode in the syntax and the regex |
| /// itself. This is generally what you want for matching on arbitrary bytes. |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::{self, backtrack::BoundedBacktracker}, |
| /// util::syntax, |
| /// Match, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::builder() |
| /// .syntax(syntax::Config::new().utf8(false)) |
| /// .thompson(thompson::Config::new().utf8(false)) |
| /// .build(r"foo(?-u:[^b])ar.*")?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// let haystack = b"\xFEfoo\xFFarzz\xE2\x98\xFF\n"; |
| /// let expected = Some(Ok(Match::must(0, 1..9))); |
| /// let got = re.try_find_iter(&mut cache, haystack).next(); |
| /// assert_eq!(expected, got); |
| /// // Notice that `(?-u:[^b])` matches invalid UTF-8, |
| /// // but the subsequent `.*` does not! Disabling UTF-8 |
| /// // on the syntax permits this. |
| /// // |
| /// // N.B. This example does not show the impact of |
| /// // disabling UTF-8 mode on a BoundedBacktracker Config, since that |
| /// // only impacts regexes that can produce matches of |
| /// // length 0. |
| /// assert_eq!(b"foo\xFFarzz", &haystack[got.unwrap()?.range()]); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[derive(Clone, Debug)] |
| pub struct Builder { |
| config: Config, |
| #[cfg(feature = "syntax")] |
| thompson: thompson::Compiler, |
| } |
| |
| impl Builder { |
| /// Create a new BoundedBacktracker builder with its default configuration. |
| pub fn new() -> Builder { |
| Builder { |
| config: Config::default(), |
| #[cfg(feature = "syntax")] |
| thompson: thompson::Compiler::new(), |
| } |
| } |
| |
| /// Build a `BoundedBacktracker` from the given pattern. |
| /// |
| /// If there was a problem parsing or compiling the pattern, then an error |
| /// is returned. |
| #[cfg(feature = "syntax")] |
| pub fn build( |
| &self, |
| pattern: &str, |
| ) -> Result<BoundedBacktracker, BuildError> { |
| self.build_many(&[pattern]) |
| } |
| |
| /// Build a `BoundedBacktracker` from the given patterns. |
| #[cfg(feature = "syntax")] |
| pub fn build_many<P: AsRef<str>>( |
| &self, |
| patterns: &[P], |
| ) -> Result<BoundedBacktracker, BuildError> { |
| let nfa = self.thompson.build_many(patterns)?; |
| self.build_from_nfa(nfa) |
| } |
| |
| /// Build a `BoundedBacktracker` directly from its NFA. |
| /// |
| /// Note that when using this method, any configuration that applies to the |
| /// construction of the NFA itself will of course be ignored, since the NFA |
| /// given here is already built. |
| pub fn build_from_nfa( |
| &self, |
| nfa: NFA, |
| ) -> Result<BoundedBacktracker, BuildError> { |
| nfa.look_set_any().available().map_err(BuildError::word)?; |
| Ok(BoundedBacktracker { config: self.config.clone(), nfa }) |
| } |
| |
| /// Apply the given `BoundedBacktracker` configuration options to this |
| /// builder. |
| pub fn configure(&mut self, config: Config) -> &mut Builder { |
| self.config = self.config.overwrite(config); |
| self |
| } |
| |
| /// Set the syntax configuration for this builder using |
| /// [`syntax::Config`](crate::util::syntax::Config). |
| /// |
| /// This permits setting things like case insensitivity, Unicode and multi |
| /// line mode. |
| /// |
| /// These settings only apply when constructing a `BoundedBacktracker` |
| /// directly from a pattern. |
| #[cfg(feature = "syntax")] |
| pub fn syntax( |
| &mut self, |
| config: crate::util::syntax::Config, |
| ) -> &mut Builder { |
| self.thompson.syntax(config); |
| self |
| } |
| |
| /// Set the Thompson NFA configuration for this builder using |
| /// [`nfa::thompson::Config`](crate::nfa::thompson::Config). |
| /// |
| /// This permits setting things like if additional time should be spent |
| /// shrinking the size of the NFA. |
| /// |
| /// These settings only apply when constructing a `BoundedBacktracker` |
| /// directly from a pattern. |
| #[cfg(feature = "syntax")] |
| pub fn thompson(&mut self, config: thompson::Config) -> &mut Builder { |
| self.thompson.configure(config); |
| self |
| } |
| } |
| |
| /// A backtracking regex engine that bounds its execution to avoid exponential |
| /// blow-up. |
| /// |
| /// This regex engine only implements leftmost-first match semantics and |
| /// only supports leftmost searches. It effectively does the same thing as a |
| /// [`PikeVM`](thompson::pikevm::PikeVM), but typically does it faster because |
| /// it doesn't have to worry about copying capturing group spans for most NFA |
| /// states. Instead, the backtracker can maintain one set of captures (provided |
| /// by the caller) and never needs to copy them. In exchange, the backtracker |
| /// bounds itself to ensure it doesn't exhibit worst case exponential time. |
| /// This results in the backtracker only being able to handle short haystacks |
| /// given reasonable memory usage. |
| /// |
| /// # Searches may return an error! |
| /// |
| /// By design, this backtracking regex engine is bounded. This bound is |
| /// implemented by not visiting any combination of NFA state ID and position |
| /// in a haystack more than once. Thus, the total memory required to bound |
| /// backtracking is proportional to `haystack.len() * nfa.states().len()`. |
| /// This can obviously get quite large, since large haystacks aren't terribly |
| /// uncommon. To avoid using exorbitant memory, the capacity is bounded by |
| /// a fixed limit set via [`Config::visited_capacity`]. Thus, if the total |
| /// capacity required for a particular regex and a haystack exceeds this |
| /// capacity, then the search routine will return an error. |
| /// |
| /// Unlike other regex engines that may return an error at search time (like |
| /// the DFA or the hybrid NFA/DFA), there is no way to guarantee that a bounded |
| /// backtracker will work for every haystack. Therefore, this regex engine |
| /// _only_ exposes fallible search routines to avoid the footgun of panicking |
| /// when running a search on a haystack that is too big. |
| /// |
| /// If one wants to use the fallible search APIs without handling the |
| /// error, the only way to guarantee an error won't occur from the |
| /// haystack length is to ensure the haystack length does not exceed |
| /// [`BoundedBacktracker::max_haystack_len`]. |
| /// |
| /// # Example: Unicode word boundaries |
| /// |
| /// This example shows that the bounded backtracker implements Unicode word |
| /// boundaries correctly by default. |
| /// |
| /// ``` |
| /// # if cfg!(miri) { return Ok(()); } // miri takes too long |
| /// use regex_automata::{nfa::thompson::backtrack::BoundedBacktracker, Match}; |
| /// |
| /// let re = BoundedBacktracker::new(r"\b\w+\b")?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// let mut it = re.try_find_iter(&mut cache, "Шерлок Холмс"); |
| /// assert_eq!(Some(Ok(Match::must(0, 0..12))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 13..23))), it.next()); |
| /// assert_eq!(None, it.next()); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| /// |
| /// # Example: multiple regex patterns |
| /// |
| /// The bounded backtracker supports searching for multiple patterns |
| /// simultaneously, just like other regex engines. Note though that because it |
| /// uses a backtracking strategy, this regex engine is unlikely to scale well |
| /// as more patterns are added. But then again, as more patterns are added, the |
| /// maximum haystack length allowed will also shorten (assuming the visited |
| /// capacity remains invariant). |
| /// |
| /// ``` |
| /// use regex_automata::{nfa::thompson::backtrack::BoundedBacktracker, Match}; |
| /// |
| /// let re = BoundedBacktracker::new_many(&["[a-z]+", "[0-9]+"])?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// let mut it = re.try_find_iter(&mut cache, "abc 1 foo 4567 0 quux"); |
| /// assert_eq!(Some(Ok(Match::must(0, 0..3))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(1, 4..5))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 6..9))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(1, 10..14))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(1, 15..16))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 17..21))), it.next()); |
| /// assert_eq!(None, it.next()); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[derive(Clone, Debug)] |
| pub struct BoundedBacktracker { |
| config: Config, |
| nfa: NFA, |
| } |
| |
| impl BoundedBacktracker { |
| /// Parse the given regular expression using the default configuration and |
| /// return the corresponding `BoundedBacktracker`. |
| /// |
| /// If you want a non-default configuration, then use the [`Builder`] to |
| /// set your own configuration. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::new("foo[0-9]+bar")?; |
| /// let mut cache = re.create_cache(); |
| /// assert_eq!( |
| /// Some(Ok(Match::must(0, 3..14))), |
| /// re.try_find_iter(&mut cache, "zzzfoo12345barzzz").next(), |
| /// ); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[cfg(feature = "syntax")] |
| pub fn new(pattern: &str) -> Result<BoundedBacktracker, BuildError> { |
| BoundedBacktracker::builder().build(pattern) |
| } |
| |
| /// Like `new`, but parses multiple patterns into a single "multi regex." |
| /// This similarly uses the default regex configuration. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::new_many(&["[a-z]+", "[0-9]+"])?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// let mut it = re.try_find_iter(&mut cache, "abc 1 foo 4567 0 quux"); |
| /// assert_eq!(Some(Ok(Match::must(0, 0..3))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(1, 4..5))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 6..9))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(1, 10..14))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(1, 15..16))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 17..21))), it.next()); |
| /// assert_eq!(None, it.next()); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[cfg(feature = "syntax")] |
| pub fn new_many<P: AsRef<str>>( |
| patterns: &[P], |
| ) -> Result<BoundedBacktracker, BuildError> { |
| BoundedBacktracker::builder().build_many(patterns) |
| } |
| |
| /// # Example |
| /// |
| /// This shows how to hand assemble a regular expression via its HIR, |
| /// compile an NFA from it and build a BoundedBacktracker from the NFA. |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::{NFA, backtrack::BoundedBacktracker}, |
| /// Match, |
| /// }; |
| /// use regex_syntax::hir::{Hir, Class, ClassBytes, ClassBytesRange}; |
| /// |
| /// let hir = Hir::class(Class::Bytes(ClassBytes::new(vec![ |
| /// ClassBytesRange::new(b'0', b'9'), |
| /// ClassBytesRange::new(b'A', b'Z'), |
| /// ClassBytesRange::new(b'_', b'_'), |
| /// ClassBytesRange::new(b'a', b'z'), |
| /// ]))); |
| /// |
| /// let config = NFA::config().nfa_size_limit(Some(1_000)); |
| /// let nfa = NFA::compiler().configure(config).build_from_hir(&hir)?; |
| /// |
| /// let re = BoundedBacktracker::new_from_nfa(nfa)?; |
| /// let (mut cache, mut caps) = (re.create_cache(), re.create_captures()); |
| /// let expected = Some(Match::must(0, 3..4)); |
| /// re.try_captures(&mut cache, "!@#A#@!", &mut caps)?; |
| /// assert_eq!(expected, caps.get_match()); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn new_from_nfa(nfa: NFA) -> Result<BoundedBacktracker, BuildError> { |
| BoundedBacktracker::builder().build_from_nfa(nfa) |
| } |
| |
| /// Create a new `BoundedBacktracker` that matches every input. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::always_match()?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// let expected = Some(Ok(Match::must(0, 0..0))); |
| /// assert_eq!(expected, re.try_find_iter(&mut cache, "").next()); |
| /// assert_eq!(expected, re.try_find_iter(&mut cache, "foo").next()); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn always_match() -> Result<BoundedBacktracker, BuildError> { |
| let nfa = thompson::NFA::always_match(); |
| BoundedBacktracker::new_from_nfa(nfa) |
| } |
| |
| /// Create a new `BoundedBacktracker` that never matches any input. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::nfa::thompson::backtrack::BoundedBacktracker; |
| /// |
| /// let re = BoundedBacktracker::never_match()?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// assert_eq!(None, re.try_find_iter(&mut cache, "").next()); |
| /// assert_eq!(None, re.try_find_iter(&mut cache, "foo").next()); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn never_match() -> Result<BoundedBacktracker, BuildError> { |
| let nfa = thompson::NFA::never_match(); |
| BoundedBacktracker::new_from_nfa(nfa) |
| } |
| |
| /// Return a default configuration for a `BoundedBacktracker`. |
| /// |
| /// This is a convenience routine to avoid needing to import the `Config` |
| /// type when customizing the construction of a `BoundedBacktracker`. |
| /// |
| /// # Example |
| /// |
| /// This example shows how to disable UTF-8 mode. When UTF-8 mode is |
| /// disabled, zero-width matches that split a codepoint are allowed. |
| /// Otherwise they are never reported. |
| /// |
| /// In the code below, notice that `""` is permitted to match positions |
| /// that split the encoding of a codepoint. |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::{self, backtrack::BoundedBacktracker}, |
| /// Match, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::builder() |
| /// .thompson(thompson::Config::new().utf8(false)) |
| /// .build(r"")?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// let haystack = "a☃z"; |
| /// let mut it = re.try_find_iter(&mut cache, haystack); |
| /// assert_eq!(Some(Ok(Match::must(0, 0..0))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 1..1))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 2..2))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 3..3))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 4..4))), it.next()); |
| /// assert_eq!(Some(Ok(Match::must(0, 5..5))), it.next()); |
| /// assert_eq!(None, it.next()); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn config() -> Config { |
| Config::new() |
| } |
| |
| /// Return a builder for configuring the construction of a |
| /// `BoundedBacktracker`. |
| /// |
| /// This is a convenience routine to avoid needing to import the |
| /// [`Builder`] type in common cases. |
| /// |
| /// # Example |
| /// |
| /// This example shows how to use the builder to disable UTF-8 mode |
| /// everywhere. |
| /// |
| /// ``` |
| /// # if cfg!(miri) { return Ok(()); } // miri takes too long |
| /// use regex_automata::{ |
| /// nfa::thompson::{self, backtrack::BoundedBacktracker}, |
| /// util::syntax, |
| /// Match, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::builder() |
| /// .syntax(syntax::Config::new().utf8(false)) |
| /// .thompson(thompson::Config::new().utf8(false)) |
| /// .build(r"foo(?-u:[^b])ar.*")?; |
| /// let (mut cache, mut caps) = (re.create_cache(), re.create_captures()); |
| /// |
| /// let haystack = b"\xFEfoo\xFFarzz\xE2\x98\xFF\n"; |
| /// let expected = Some(Match::must(0, 1..9)); |
| /// re.try_captures(&mut cache, haystack, &mut caps)?; |
| /// assert_eq!(expected, caps.get_match()); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn builder() -> Builder { |
| Builder::new() |
| } |
| |
| /// Create a new cache for this regex. |
| /// |
| /// The cache returned should only be used for searches for this |
| /// regex. If you want to reuse the cache for another regex, then you |
| /// must call [`Cache::reset`] with that regex (or, equivalently, |
| /// [`BoundedBacktracker::reset_cache`]). |
| pub fn create_cache(&self) -> Cache { |
| Cache::new(self) |
| } |
| |
| /// Create a new empty set of capturing groups that is guaranteed to be |
| /// valid for the search APIs on this `BoundedBacktracker`. |
| /// |
| /// A `Captures` value created for a specific `BoundedBacktracker` cannot |
| /// be used with any other `BoundedBacktracker`. |
| /// |
| /// This is a convenience function for [`Captures::all`]. See the |
| /// [`Captures`] documentation for an explanation of its alternative |
| /// constructors that permit the `BoundedBacktracker` to do less work |
| /// during a search, and thus might make it faster. |
| pub fn create_captures(&self) -> Captures { |
| Captures::all(self.get_nfa().group_info().clone()) |
| } |
| |
| /// Reset the given cache such that it can be used for searching with the |
| /// this `BoundedBacktracker` (and only this `BoundedBacktracker`). |
| /// |
| /// A cache reset permits reusing memory already allocated in this cache |
| /// with a different `BoundedBacktracker`. |
| /// |
| /// # Example |
| /// |
| /// This shows how to re-purpose a cache for use with a different |
| /// `BoundedBacktracker`. |
| /// |
| /// ``` |
| /// # if cfg!(miri) { return Ok(()); } // miri takes too long |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, |
| /// }; |
| /// |
| /// let re1 = BoundedBacktracker::new(r"\w")?; |
| /// let re2 = BoundedBacktracker::new(r"\W")?; |
| /// |
| /// let mut cache = re1.create_cache(); |
| /// assert_eq!( |
| /// Some(Ok(Match::must(0, 0..2))), |
| /// re1.try_find_iter(&mut cache, "Δ").next(), |
| /// ); |
| /// |
| /// // 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 BoundedBacktracker 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(Ok(Match::must(0, 0..3))), |
| /// re2.try_find_iter(&mut cache, "☃").next(), |
| /// ); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn reset_cache(&self, cache: &mut Cache) { |
| cache.reset(self); |
| } |
| |
| /// Returns the total number of patterns compiled into this |
| /// `BoundedBacktracker`. |
| /// |
| /// In the case of a `BoundedBacktracker` that contains no patterns, this |
| /// returns `0`. |
| /// |
| /// # Example |
| /// |
| /// This example shows the pattern length for a `BoundedBacktracker` that |
| /// never matches: |
| /// |
| /// ``` |
| /// use regex_automata::nfa::thompson::backtrack::BoundedBacktracker; |
| /// |
| /// let re = BoundedBacktracker::never_match()?; |
| /// assert_eq!(re.pattern_len(), 0); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| /// |
| /// And another example for a `BoundedBacktracker` that matches at every |
| /// position: |
| /// |
| /// ``` |
| /// use regex_automata::nfa::thompson::backtrack::BoundedBacktracker; |
| /// |
| /// let re = BoundedBacktracker::always_match()?; |
| /// assert_eq!(re.pattern_len(), 1); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| /// |
| /// And finally, a `BoundedBacktracker` that was constructed from multiple |
| /// patterns: |
| /// |
| /// ``` |
| /// use regex_automata::nfa::thompson::backtrack::BoundedBacktracker; |
| /// |
| /// let re = BoundedBacktracker::new_many(&["[0-9]+", "[a-z]+", "[A-Z]+"])?; |
| /// assert_eq!(re.pattern_len(), 3); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn pattern_len(&self) -> usize { |
| self.nfa.pattern_len() |
| } |
| |
| /// Return the config for this `BoundedBacktracker`. |
| #[inline] |
| pub fn get_config(&self) -> &Config { |
| &self.config |
| } |
| |
| /// Returns a reference to the underlying NFA. |
| #[inline] |
| pub fn get_nfa(&self) -> &NFA { |
| &self.nfa |
| } |
| |
| /// Returns the maximum haystack length supported by this backtracker. |
| /// |
| /// This routine is a function of both [`Config::visited_capacity`] and the |
| /// internal size of the backtracker's NFA. |
| /// |
| /// # Example |
| /// |
| /// This example shows how the maximum haystack length can vary depending |
| /// on the size of the regex itself. Note though that the specific maximum |
| /// values here are not an API guarantee. The default visited capacity is |
| /// subject to change and not covered by semver. |
| /// |
| /// ``` |
| /// # if cfg!(miri) { return Ok(()); } // miri takes too long |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, MatchError, |
| /// }; |
| /// |
| /// // If you're only using ASCII, you get a big budget. |
| /// let re = BoundedBacktracker::new(r"(?-u)\w+")?; |
| /// let mut cache = re.create_cache(); |
| /// assert_eq!(re.max_haystack_len(), 299_592); |
| /// // Things work up to the max. |
| /// let mut haystack = "a".repeat(299_592); |
| /// let expected = Some(Ok(Match::must(0, 0..299_592))); |
| /// assert_eq!(expected, re.try_find_iter(&mut cache, &haystack).next()); |
| /// // But you'll get an error if you provide a haystack that's too big. |
| /// // Notice that we use the 'try_find_iter' routine instead, which |
| /// // yields Result<Match, MatchError> instead of Match. |
| /// haystack.push('a'); |
| /// let expected = Some(Err(MatchError::haystack_too_long(299_593))); |
| /// assert_eq!(expected, re.try_find_iter(&mut cache, &haystack).next()); |
| /// |
| /// // Unicode inflates the size of the underlying NFA quite a bit, and |
| /// // thus means that the backtracker can only handle smaller haystacks, |
| /// // assuming that the visited capacity remains unchanged. |
| /// let re = BoundedBacktracker::new(r"\w+")?; |
| /// assert!(re.max_haystack_len() <= 7_000); |
| /// // But we can increase the visited capacity to handle bigger haystacks! |
| /// let re = BoundedBacktracker::builder() |
| /// .configure(BoundedBacktracker::config().visited_capacity(1<<20)) |
| /// .build(r"\w+")?; |
| /// assert!(re.max_haystack_len() >= 25_000); |
| /// assert!(re.max_haystack_len() <= 28_000); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[inline] |
| pub fn max_haystack_len(&self) -> usize { |
| // The capacity given in the config is "bytes of heap memory," but the |
| // capacity we use here is "number of bits." So convert the capacity in |
| // bytes to the capacity in bits. |
| let capacity = 8 * self.get_config().get_visited_capacity(); |
| let blocks = div_ceil(capacity, Visited::BLOCK_SIZE); |
| let real_capacity = blocks.saturating_mul(Visited::BLOCK_SIZE); |
| // It's possible for `real_capacity` to be smaller than the number of |
| // NFA states for particularly large regexes, so we saturate towards |
| // zero. |
| (real_capacity / self.nfa.states().len()).saturating_sub(1) |
| } |
| } |
| |
| impl BoundedBacktracker { |
| /// Returns true if and only if this regex matches the given haystack. |
| /// |
| /// In the case of a backtracking regex engine, and unlike most other |
| /// regex engines in this crate, short circuiting isn't practical. However, |
| /// this routine may still be faster because it instructs backtracking to |
| /// not keep track of any capturing groups. |
| /// |
| /// # Errors |
| /// |
| /// This routine only errors if the search could not complete. For this |
| /// backtracking regex engine, this only occurs when the haystack length |
| /// exceeds [`BoundedBacktracker::max_haystack_len`]. |
| /// |
| /// When a search cannot complete, callers cannot know whether a match |
| /// exists or not. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::nfa::thompson::backtrack::BoundedBacktracker; |
| /// |
| /// let re = BoundedBacktracker::new("foo[0-9]+bar")?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// assert!(re.try_is_match(&mut cache, "foo12345bar")?); |
| /// assert!(!re.try_is_match(&mut cache, "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::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Input, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::new("a*")?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// assert!(!re.try_is_match(&mut cache, 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::{ |
| /// nfa::thompson::{backtrack::BoundedBacktracker, NFA}, |
| /// Input, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::builder() |
| /// .thompson(NFA::config().utf8(false)) |
| /// .build("a*")?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// assert!(re.try_is_match(&mut cache, Input::new("☃").span(1..2))?); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[inline] |
| pub fn try_is_match<'h, I: Into<Input<'h>>>( |
| &self, |
| cache: &mut Cache, |
| input: I, |
| ) -> Result<bool, MatchError> { |
| let input = input.into().earliest(true); |
| self.try_search_slots(cache, &input, &mut []).map(|pid| pid.is_some()) |
| } |
| |
| /// Executes a leftmost forward search and returns a `Match` if one exists. |
| /// |
| /// This routine only includes the overall match span. To get |
| /// access to the individual spans of each capturing group, use |
| /// [`BoundedBacktracker::try_captures`]. |
| /// |
| /// # Errors |
| /// |
| /// This routine only errors if the search could not complete. For this |
| /// backtracking regex engine, this only occurs when the haystack length |
| /// exceeds [`BoundedBacktracker::max_haystack_len`]. |
| /// |
| /// When a search cannot complete, callers cannot know whether a match |
| /// exists or not. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::new("foo[0-9]+")?; |
| /// let mut cache = re.create_cache(); |
| /// let expected = Match::must(0, 0..8); |
| /// assert_eq!(Some(expected), re.try_find(&mut cache, "foo12345")?); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[inline] |
| pub fn try_find<'h, I: Into<Input<'h>>>( |
| &self, |
| cache: &mut Cache, |
| input: I, |
| ) -> Result<Option<Match>, MatchError> { |
| let input = input.into(); |
| if self.get_nfa().pattern_len() == 1 { |
| let mut slots = [None, None]; |
| let pid = match self.try_search_slots(cache, &input, &mut slots)? { |
| None => return Ok(None), |
| Some(pid) => pid, |
| }; |
| let start = match slots[0] { |
| None => return Ok(None), |
| Some(s) => s.get(), |
| }; |
| let end = match slots[1] { |
| None => return Ok(None), |
| Some(s) => s.get(), |
| }; |
| return Ok(Some(Match::new(pid, Span { start, end }))); |
| } |
| let ginfo = self.get_nfa().group_info(); |
| let slots_len = ginfo.implicit_slot_len(); |
| let mut slots = vec![None; slots_len]; |
| let pid = match self.try_search_slots(cache, &input, &mut slots)? { |
| None => return Ok(None), |
| Some(pid) => pid, |
| }; |
| let start = match slots[pid.as_usize() * 2] { |
| None => return Ok(None), |
| Some(s) => s.get(), |
| }; |
| let end = match slots[pid.as_usize() * 2 + 1] { |
| None => return Ok(None), |
| Some(s) => s.get(), |
| }; |
| Ok(Some(Match::new(pid, Span { start, end }))) |
| } |
| |
| /// 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`. |
| /// |
| /// # Errors |
| /// |
| /// This routine only errors if the search could not complete. For this |
| /// backtracking regex engine, this only occurs when the haystack length |
| /// exceeds [`BoundedBacktracker::max_haystack_len`]. |
| /// |
| /// When a search cannot complete, callers cannot know whether a match |
| /// exists or not. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Span, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::new( |
| /// r"^([0-9]{4})-([0-9]{2})-([0-9]{2})$", |
| /// )?; |
| /// let (mut cache, mut caps) = (re.create_cache(), re.create_captures()); |
| /// |
| /// re.try_captures(&mut cache, "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 try_captures<'h, I: Into<Input<'h>>>( |
| &self, |
| cache: &mut Cache, |
| input: I, |
| caps: &mut Captures, |
| ) -> Result<(), MatchError> { |
| self.try_search(cache, &input.into(), caps) |
| } |
| |
| /// Returns an iterator over all non-overlapping leftmost matches in the |
| /// given bytes. If no match exists, then the iterator yields no elements. |
| /// |
| /// If the regex engine returns an error at any point, then the iterator |
| /// will yield that error. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, MatchError, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::new("foo[0-9]+")?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// let text = "foo1 foo12 foo123"; |
| /// let result: Result<Vec<Match>, MatchError> = re |
| /// .try_find_iter(&mut cache, text) |
| /// .collect(); |
| /// let matches = result?; |
| /// 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 try_find_iter<'r, 'c, 'h, I: Into<Input<'h>>>( |
| &'r self, |
| cache: &'c mut Cache, |
| input: I, |
| ) -> TryFindMatches<'r, 'c, 'h> { |
| let caps = Captures::matches(self.get_nfa().group_info().clone()); |
| let it = iter::Searcher::new(input.into()); |
| TryFindMatches { re: self, cache, caps, 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 [`BoundedBacktracker::try_find_iter`], |
| /// but it includes the spans of all capturing groups that participate in |
| /// each match. |
| /// |
| /// If the regex engine returns an error at any point, then the iterator |
| /// will yield that error. |
| /// |
| /// **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::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Span, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::new("foo(?P<numbers>[0-9]+)")?; |
| /// let mut cache = re.create_cache(); |
| /// |
| /// let text = "foo1 foo12 foo123"; |
| /// let mut spans = vec![]; |
| /// for result in re.try_captures_iter(&mut cache, text) { |
| /// let caps = result?; |
| /// // The unwrap is OK since 'numbers' matches if the pattern matches. |
| /// spans.push(caps.get_group_by_name("numbers").unwrap()); |
| /// } |
| /// assert_eq!(spans, vec![ |
| /// Span::from(3..4), |
| /// Span::from(8..10), |
| /// Span::from(14..17), |
| /// ]); |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[inline] |
| pub fn try_captures_iter<'r, 'c, 'h, I: Into<Input<'h>>>( |
| &'r self, |
| cache: &'c mut Cache, |
| input: I, |
| ) -> TryCapturesMatches<'r, 'c, 'h> { |
| let caps = self.create_captures(); |
| let it = iter::Searcher::new(input.into()); |
| TryCapturesMatches { re: self, cache, caps, it } |
| } |
| } |
| |
| impl BoundedBacktracker { |
| /// 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 [`BoundedBacktracker::try_captures`], but it accepts a |
| /// concrete `&Input` instead of an `Into<Input>`. |
| /// |
| /// # Errors |
| /// |
| /// This routine only errors if the search could not complete. For this |
| /// backtracking regex engine, this only occurs when the haystack length |
| /// exceeds [`BoundedBacktracker::max_haystack_len`]. |
| /// |
| /// When a search cannot complete, callers cannot know whether a match |
| /// exists or not. |
| /// |
| /// # Example: specific pattern search |
| /// |
| /// This example shows how to build a multi bounded backtracker that |
| /// permits searching for specific patterns. |
| /// |
| /// ``` |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Anchored, Input, Match, PatternID, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::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.try_search(&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.try_search(&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::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, Input, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::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)); |
| /// re.try_search(&mut cache, &Input::new(&haystack[3..6]), &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; |
| /// re.try_search( |
| /// &mut cache, &Input::new(haystack).range(3..6), &mut caps, |
| /// )?; |
| /// assert_eq!(expected, caps.get_match()); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| #[inline] |
| pub fn try_search( |
| &self, |
| cache: &mut Cache, |
| input: &Input<'_>, |
| caps: &mut Captures, |
| ) -> Result<(), MatchError> { |
| caps.set_pattern(None); |
| let pid = self.try_search_slots(cache, input, caps.slots_mut())?; |
| caps.set_pattern(pid); |
| Ok(()) |
| } |
| |
| /// 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 all `slots` is unspecified. |
| /// |
| /// This is like [`BoundedBacktracker::try_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`](crate::nfa::thompson::NFA::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. |
| /// |
| /// # Errors |
| /// |
| /// This routine only errors if the search could not complete. For this |
| /// backtracking regex engine, this only occurs when the haystack length |
| /// exceeds [`BoundedBacktracker::max_haystack_len`]. |
| /// |
| /// When a search cannot complete, callers cannot know whether a match |
| /// exists or not. |
| /// |
| /// # 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::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// PatternID, Input, |
| /// }; |
| /// |
| /// let re = BoundedBacktracker::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.try_search_slots(&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 try_search_slots( |
| &self, |
| cache: &mut Cache, |
| input: &Input<'_>, |
| slots: &mut [Option<NonMaxUsize>], |
| ) -> Result<Option<PatternID>, MatchError> { |
| let utf8empty = self.get_nfa().has_empty() && self.get_nfa().is_utf8(); |
| if !utf8empty { |
| let maybe_hm = self.try_search_slots_imp(cache, input, slots)?; |
| return Ok(maybe_hm.map(|hm| hm.pattern())); |
| } |
| // See PikeVM::try_search_slots for why we do this. |
| let min = self.get_nfa().group_info().implicit_slot_len(); |
| if slots.len() >= min { |
| let maybe_hm = self.try_search_slots_imp(cache, input, slots)?; |
| return Ok(maybe_hm.map(|hm| hm.pattern())); |
| } |
| if self.get_nfa().pattern_len() == 1 { |
| let mut enough = [None, None]; |
| let got = self.try_search_slots_imp(cache, input, &mut enough)?; |
| // This is OK because we know `enough_slots` is strictly bigger |
| // than `slots`, otherwise this special case isn't reached. |
| slots.copy_from_slice(&enough[..slots.len()]); |
| return Ok(got.map(|hm| hm.pattern())); |
| } |
| let mut enough = vec![None; min]; |
| let got = self.try_search_slots_imp(cache, input, &mut enough)?; |
| // This is OK because we know `enough_slots` is strictly bigger than |
| // `slots`, otherwise this special case isn't reached. |
| slots.copy_from_slice(&enough[..slots.len()]); |
| Ok(got.map(|hm| hm.pattern())) |
| } |
| |
| /// This is the actual implementation of `try_search_slots_imp` that |
| /// doesn't account for the special case when 1) the NFA has UTF-8 mode |
| /// enabled, 2) the NFA can match the empty string and 3) the caller has |
| /// provided an insufficient number of slots to record match offsets. |
| #[inline(never)] |
| fn try_search_slots_imp( |
| &self, |
| cache: &mut Cache, |
| input: &Input<'_>, |
| slots: &mut [Option<NonMaxUsize>], |
| ) -> Result<Option<HalfMatch>, MatchError> { |
| let utf8empty = self.get_nfa().has_empty() && self.get_nfa().is_utf8(); |
| let hm = match self.search_imp(cache, input, slots)? { |
| None => return Ok(None), |
| Some(hm) if !utf8empty => return Ok(Some(hm)), |
| Some(hm) => hm, |
| }; |
| empty::skip_splits_fwd(input, hm, hm.offset(), |input| { |
| Ok(self |
| .search_imp(cache, input, slots)? |
| .map(|hm| (hm, hm.offset()))) |
| }) |
| } |
| |
| /// The implementation of standard leftmost backtracking search. |
| /// |
| /// Capturing group spans are written to 'caps', but only if requested. |
| /// 'caps' can be one of three things: 1) totally empty, in which case, we |
| /// only report the pattern that matched or 2) only has slots for recording |
| /// the overall match offsets for any pattern or 3) has all slots available |
| /// for recording the spans of any groups participating in a match. |
| fn search_imp( |
| &self, |
| cache: &mut Cache, |
| input: &Input<'_>, |
| slots: &mut [Option<NonMaxUsize>], |
| ) -> Result<Option<HalfMatch>, MatchError> { |
| // Unlike in the PikeVM, we write our capturing group spans directly |
| // into the caller's captures groups. So we have to make sure we're |
| // starting with a blank slate first. In the PikeVM, we avoid this |
| // by construction: the spans that are copied to every slot in the |
| // 'Captures' value already account for presence/absence. In this |
| // backtracker, we write directly into the caller provided slots, where |
| // as in the PikeVM, we write into scratch space first and only copy |
| // them to the caller provided slots when a match is found. |
| for slot in slots.iter_mut() { |
| *slot = None; |
| } |
| cache.setup_search(&self, input)?; |
| if input.is_done() { |
| return Ok(None); |
| } |
| let (anchored, start_id) = match input.get_anchored() { |
| // Only way we're unanchored is if both the caller asked for an |
| // unanchored search *and* the pattern is itself not anchored. |
| Anchored::No => ( |
| self.nfa.is_always_start_anchored(), |
| // We always use the anchored starting state here, even if |
| // doing an unanchored search. The "unanchored" part of it is |
| // implemented in the loop below, by simply trying the next |
| // byte offset if the previous backtracking exploration failed. |
| self.nfa.start_anchored(), |
| ), |
| Anchored::Yes => (true, self.nfa.start_anchored()), |
| Anchored::Pattern(pid) => match self.nfa.start_pattern(pid) { |
| None => return Ok(None), |
| Some(sid) => (true, sid), |
| }, |
| }; |
| if anchored { |
| let at = input.start(); |
| return Ok(self.backtrack(cache, input, at, start_id, slots)); |
| } |
| let pre = self.get_config().get_prefilter(); |
| let mut at = input.start(); |
| while at <= input.end() { |
| if let Some(ref pre) = pre { |
| let span = Span::from(at..input.end()); |
| match pre.find(input.haystack(), span) { |
| None => break, |
| Some(ref span) => at = span.start, |
| } |
| } |
| if let Some(hm) = self.backtrack(cache, input, at, start_id, slots) |
| { |
| return Ok(Some(hm)); |
| } |
| at += 1; |
| } |
| Ok(None) |
| } |
| |
| /// Look for a match starting at `at` in `input` and write the matching |
| /// pattern ID and group spans to `caps`. The search uses `start_id` as its |
| /// starting state in the underlying NFA. |
| /// |
| /// If no match was found, then the caller should increment `at` and try |
| /// at the next position. |
| #[cfg_attr(feature = "perf-inline", inline(always))] |
| fn backtrack( |
| &self, |
| cache: &mut Cache, |
| input: &Input<'_>, |
| at: usize, |
| start_id: StateID, |
| slots: &mut [Option<NonMaxUsize>], |
| ) -> Option<HalfMatch> { |
| cache.stack.push(Frame::Step { sid: start_id, at }); |
| while let Some(frame) = cache.stack.pop() { |
| match frame { |
| Frame::Step { sid, at } => { |
| if let Some(hm) = self.step(cache, input, sid, at, slots) { |
| return Some(hm); |
| } |
| } |
| Frame::RestoreCapture { slot, offset } => { |
| slots[slot] = offset; |
| } |
| } |
| } |
| None |
| } |
| |
| // LAMENTATION: The actual backtracking search is implemented in about |
| // 75 lines below. Yet this file is over 2,000 lines long. What have I |
| // done? |
| |
| /// Execute a "step" in the backtracing algorithm. |
| /// |
| /// A "step" is somewhat of a misnomer, because this routine keeps going |
| /// until it either runs out of things to try or fins a match. In the |
| /// former case, it may have pushed some things on to the backtracking |
| /// stack, in which case, those will be tried next as part of the |
| /// 'backtrack' routine above. |
| #[cfg_attr(feature = "perf-inline", inline(always))] |
| fn step( |
| &self, |
| cache: &mut Cache, |
| input: &Input<'_>, |
| mut sid: StateID, |
| mut at: usize, |
| slots: &mut [Option<NonMaxUsize>], |
| ) -> Option<HalfMatch> { |
| loop { |
| if !cache.visited.insert(sid, at - input.start()) { |
| return None; |
| } |
| match *self.nfa.state(sid) { |
| State::ByteRange { ref trans } => { |
| // Why do we need this? Unlike other regex engines in this |
| // crate, the backtracker can steam roll ahead in the |
| // haystack outside of the main loop over the bytes in the |
| // haystack. While 'trans.matches()' below handles the case |
| // of 'at' being out of bounds of 'input.haystack()', we |
| // also need to handle the case of 'at' going out of bounds |
| // of the span the caller asked to search. |
| // |
| // We should perhaps make the 'trans.matches()' API accept |
| // an '&Input' instead of a '&[u8]'. Or at least, add a new |
| // API that does it. |
| if at >= input.end() { |
| return None; |
| } |
| if !trans.matches(input.haystack(), at) { |
| return None; |
| } |
| sid = trans.next; |
| at += 1; |
| } |
| State::Sparse(ref sparse) => { |
| if at >= input.end() { |
| return None; |
| } |
| sid = sparse.matches(input.haystack(), at)?; |
| at += 1; |
| } |
| State::Dense(ref dense) => { |
| if at >= input.end() { |
| return None; |
| } |
| sid = dense.matches(input.haystack(), at)?; |
| at += 1; |
| } |
| State::Look { look, next } => { |
| // OK because we don't permit building a searcher with a |
| // Unicode word boundary if the requisite Unicode data is |
| // unavailable. |
| if !self.nfa.look_matcher().matches_inline( |
| look, |
| input.haystack(), |
| at, |
| ) { |
| return None; |
| } |
| sid = next; |
| } |
| State::Union { ref alternates } => { |
| sid = match alternates.get(0) { |
| None => return None, |
| Some(&sid) => sid, |
| }; |
| cache.stack.extend( |
| alternates[1..] |
| .iter() |
| .copied() |
| .rev() |
| .map(|sid| Frame::Step { sid, at }), |
| ); |
| } |
| State::BinaryUnion { alt1, alt2 } => { |
| sid = alt1; |
| cache.stack.push(Frame::Step { sid: alt2, at }); |
| } |
| State::Capture { next, slot, .. } => { |
| if slot.as_usize() < slots.len() { |
| cache.stack.push(Frame::RestoreCapture { |
| slot, |
| offset: slots[slot], |
| }); |
| slots[slot] = NonMaxUsize::new(at); |
| } |
| sid = next; |
| } |
| State::Fail => return None, |
| State::Match { pattern_id } => { |
| return Some(HalfMatch::new(pattern_id, at)); |
| } |
| } |
| } |
| } |
| } |
| |
| /// An iterator over all non-overlapping matches for a fallible search. |
| /// |
| /// The iterator yields a `Result<Match, MatchError` value until no more |
| /// matches could be found. |
| /// |
| /// The lifetime parameters are as follows: |
| /// |
| /// * `'r` represents the lifetime of the BoundedBacktracker. |
| /// * `'c` represents the lifetime of the BoundedBacktracker's cache. |
| /// * `'h` represents the lifetime of the haystack being searched. |
| /// |
| /// This iterator can be created with the [`BoundedBacktracker::try_find_iter`] |
| /// method. |
| #[derive(Debug)] |
| pub struct TryFindMatches<'r, 'c, 'h> { |
| re: &'r BoundedBacktracker, |
| cache: &'c mut Cache, |
| caps: Captures, |
| it: iter::Searcher<'h>, |
| } |
| |
| impl<'r, 'c, 'h> Iterator for TryFindMatches<'r, 'c, 'h> { |
| type Item = Result<Match, MatchError>; |
| |
| #[inline] |
| fn next(&mut self) -> Option<Result<Match, MatchError>> { |
| // Splitting 'self' apart seems necessary to appease borrowck. |
| let TryFindMatches { re, ref mut cache, ref mut caps, ref mut it } = |
| *self; |
| it.try_advance(|input| { |
| re.try_search(cache, input, caps)?; |
| Ok(caps.get_match()) |
| }) |
| .transpose() |
| } |
| } |
| |
| /// An iterator over all non-overlapping leftmost matches, with their capturing |
| /// groups, for a fallible search. |
| /// |
| /// The iterator yields a `Result<Captures, MatchError>` value until no more |
| /// matches could be found. |
| /// |
| /// The lifetime parameters are as follows: |
| /// |
| /// * `'r` represents the lifetime of the BoundedBacktracker. |
| /// * `'c` represents the lifetime of the BoundedBacktracker's cache. |
| /// * `'h` represents the lifetime of the haystack being searched. |
| /// |
| /// This iterator can be created with the |
| /// [`BoundedBacktracker::try_captures_iter`] method. |
| #[derive(Debug)] |
| pub struct TryCapturesMatches<'r, 'c, 'h> { |
| re: &'r BoundedBacktracker, |
| cache: &'c mut Cache, |
| caps: Captures, |
| it: iter::Searcher<'h>, |
| } |
| |
| impl<'r, 'c, 'h> Iterator for TryCapturesMatches<'r, 'c, 'h> { |
| type Item = Result<Captures, MatchError>; |
| |
| #[inline] |
| fn next(&mut self) -> Option<Result<Captures, MatchError>> { |
| // Splitting 'self' apart seems necessary to appease borrowck. |
| let TryCapturesMatches { re, ref mut cache, ref mut caps, ref mut it } = |
| *self; |
| let _ = it |
| .try_advance(|input| { |
| re.try_search(cache, input, caps)?; |
| Ok(caps.get_match()) |
| }) |
| .transpose()?; |
| if caps.is_match() { |
| Some(Ok(caps.clone())) |
| } else { |
| None |
| } |
| } |
| } |
| |
| /// A cache represents mutable state that a [`BoundedBacktracker`] requires |
| /// during a search. |
| /// |
| /// For a given [`BoundedBacktracker`], its corresponding cache may be created |
| /// either via [`BoundedBacktracker::create_cache`], or via [`Cache::new`]. |
| /// They are equivalent in every way, except the former does not require |
| /// explicitly importing `Cache`. |
| /// |
| /// A particular `Cache` is coupled with the [`BoundedBacktracker`] from which |
| /// it was created. It may only be used with that `BoundedBacktracker`. A cache |
| /// and its allocations may be re-purposed via [`Cache::reset`], in which case, |
| /// it can only be used with the new `BoundedBacktracker` (and not the old |
| /// one). |
| #[derive(Clone, Debug)] |
| pub struct Cache { |
| /// Stack used on the heap for doing backtracking instead of the |
| /// traditional recursive approach. We don't want recursion because then |
| /// we're likely to hit a stack overflow for bigger regexes. |
| stack: Vec<Frame>, |
| /// The set of (StateID, HaystackOffset) pairs that have been visited |
| /// by the backtracker within a single search. If such a pair has been |
| /// visited, then we avoid doing the work for that pair again. This is |
| /// what "bounds" the backtracking and prevents it from having worst case |
| /// exponential time. |
| visited: Visited, |
| } |
| |
| impl Cache { |
| /// Create a new [`BoundedBacktracker`] cache. |
| /// |
| /// A potentially more convenient routine to create a cache is |
| /// [`BoundedBacktracker::create_cache`], as it does not require also |
| /// importing the `Cache` type. |
| /// |
| /// If you want to reuse the returned `Cache` with some other |
| /// `BoundedBacktracker`, then you must call [`Cache::reset`] with the |
| /// desired `BoundedBacktracker`. |
| pub fn new(re: &BoundedBacktracker) -> Cache { |
| Cache { stack: vec![], visited: Visited::new(re) } |
| } |
| |
| /// Reset this cache such that it can be used for searching with different |
| /// [`BoundedBacktracker`]. |
| /// |
| /// A cache reset permits reusing memory already allocated in this cache |
| /// with a different `BoundedBacktracker`. |
| /// |
| /// # Example |
| /// |
| /// This shows how to re-purpose a cache for use with a different |
| /// `BoundedBacktracker`. |
| /// |
| /// ``` |
| /// # if cfg!(miri) { return Ok(()); } // miri takes too long |
| /// use regex_automata::{ |
| /// nfa::thompson::backtrack::BoundedBacktracker, |
| /// Match, |
| /// }; |
| /// |
| /// let re1 = BoundedBacktracker::new(r"\w")?; |
| /// let re2 = BoundedBacktracker::new(r"\W")?; |
| /// |
| /// let mut cache = re1.create_cache(); |
| /// assert_eq!( |
| /// Some(Ok(Match::must(0, 0..2))), |
| /// re1.try_find_iter(&mut cache, "Δ").next(), |
| /// ); |
| /// |
| /// // 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 BoundedBacktracker 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(Ok(Match::must(0, 0..3))), |
| /// re2.try_find_iter(&mut cache, "☃").next(), |
| /// ); |
| /// |
| /// # Ok::<(), Box<dyn std::error::Error>>(()) |
| /// ``` |
| pub fn reset(&mut self, re: &BoundedBacktracker) { |
| self.visited.reset(re); |
| } |
| |
| /// 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 { |
| self.stack.len() * core::mem::size_of::<Frame>() |
| + self.visited.memory_usage() |
| } |
| |
| /// Clears this cache. This should be called at the start of every search |
| /// to ensure we start with a clean slate. |
| /// |
| /// This also sets the length of the capturing groups used in the current |
| /// search. This permits an optimization where by 'SlotTable::for_state' |
| /// only returns the number of slots equivalent to the number of slots |
| /// given in the 'Captures' value. This may be less than the total number |
| /// of possible slots, e.g., when one only wants to track overall match |
| /// offsets. This in turn permits less copying of capturing group spans |
| /// in the BoundedBacktracker. |
| fn setup_search( |
| &mut self, |
| re: &BoundedBacktracker, |
| input: &Input<'_>, |
| ) -> Result<(), MatchError> { |
| self.stack.clear(); |
| self.visited.setup_search(re, input)?; |
| Ok(()) |
| } |
| } |
| |
| /// Represents a stack frame on the heap while doing backtracking. |
| /// |
| /// Instead of using explicit recursion for backtracking, we use a stack on |
| /// the heap to keep track of things that we want to explore if the current |
| /// backtracking branch turns out to not lead to a match. |
| #[derive(Clone, Debug)] |
| enum Frame { |
| /// Look for a match starting at `sid` and the given position in the |
| /// haystack. |
| Step { sid: StateID, at: usize }, |
| /// Reset the given `slot` to the given `offset` (which might be `None`). |
| /// This effectively gives a "scope" to capturing groups, such that an |
| /// offset for a particular group only gets returned if the match goes |
| /// through that capturing group. If backtracking ends up going down a |
| /// different branch that results in a different offset (or perhaps none at |
| /// all), then this "restore capture" frame will cause the offset to get |
| /// reset. |
| RestoreCapture { slot: SmallIndex, offset: Option<NonMaxUsize> }, |
| } |
| |
| /// A bitset that keeps track of whether a particular (StateID, offset) has |
| /// been considered during backtracking. If it has already been visited, then |
| /// backtracking skips it. This is what gives backtracking its "bound." |
| #[derive(Clone, Debug)] |
| struct Visited { |
| /// The actual underlying bitset. Each element in the bitset corresponds |
| /// to a particular (StateID, offset) pair. States correspond to the rows |
| /// and the offsets correspond to the columns. |
| /// |
| /// If our underlying NFA has N states and the haystack we're searching |
| /// has M bytes, then we have N*(M+1) entries in our bitset table. The |
| /// M+1 occurs because our matches are delayed by one byte (to support |
| /// look-around), and so we need to handle the end position itself rather |
| /// than stopping just before the end. (If there is no end position, then |
| /// it's treated as "end-of-input," which is matched by things like '$'.) |
| /// |
| /// Given BITS=N*(M+1), we wind up with div_ceil(BITS, sizeof(usize)) |
| /// blocks. |
| /// |
| /// We use 'usize' to represent our blocks because it makes some of the |
| /// arithmetic in 'insert' a bit nicer. For example, if we used 'u32' for |
| /// our block, we'd either need to cast u32s to usizes or usizes to u32s. |
| bitset: Vec<usize>, |
| /// The stride represents one plus length of the haystack we're searching |
| /// (as described above). The stride must be initialized for each search. |
| stride: usize, |
| } |
| |
| impl Visited { |
| /// The size of each block, in bits. |
| const BLOCK_SIZE: usize = 8 * core::mem::size_of::<usize>(); |
| |
| /// Create a new visited set for the given backtracker. |
| /// |
| /// The set is ready to use, but must be setup at the beginning of each |
| /// search by calling `setup_search`. |
| fn new(re: &BoundedBacktracker) -> Visited { |
| let mut visited = Visited { bitset: vec![], stride: 0 }; |
| visited.reset(re); |
| visited |
| } |
| |
| /// Insert the given (StateID, offset) pair into this set. If it already |
| /// exists, then this is a no-op and it returns false. Otherwise this |
| /// returns true. |
| fn insert(&mut self, sid: StateID, at: usize) -> bool { |
| let table_index = sid.as_usize() * self.stride + at; |
| let block_index = table_index / Visited::BLOCK_SIZE; |
| let bit = table_index % Visited::BLOCK_SIZE; |
| let block_with_bit = 1 << bit; |
| if self.bitset[block_index] & block_with_bit != 0 { |
| return false; |
| } |
| self.bitset[block_index] |= block_with_bit; |
| true |
| } |
| |
| /// Reset this visited set to work with the given bounded backtracker. |
| fn reset(&mut self, _: &BoundedBacktracker) { |
| self.bitset.truncate(0); |
| } |
| |
| /// Setup this visited set to work for a search using the given NFA |
| /// and input configuration. The NFA must be the same NFA used by the |
| /// BoundedBacktracker given to Visited::reset. Failing to call this might |
| /// result in panics or silently incorrect search behavior. |
| fn setup_search( |
| &mut self, |
| re: &BoundedBacktracker, |
| input: &Input<'_>, |
| ) -> Result<(), MatchError> { |
| // Our haystack length is only the length of the span of the entire |
| // haystack that we'll be searching. |
| let haylen = input.get_span().len(); |
| let err = || MatchError::haystack_too_long(haylen); |
| // Our stride is one more than the length of the input because our main |
| // search loop includes the position at input.end(). (And it does this |
| // because matches are delayed by one byte to account for look-around.) |
| self.stride = haylen + 1; |
| let needed_capacity = |
| match re.get_nfa().states().len().checked_mul(self.stride) { |
| None => return Err(err()), |
| Some(capacity) => capacity, |
| }; |
| let max_capacity = 8 * re.get_config().get_visited_capacity(); |
| if needed_capacity > max_capacity { |
| return Err(err()); |
| } |
| let needed_blocks = div_ceil(needed_capacity, Visited::BLOCK_SIZE); |
| self.bitset.truncate(needed_blocks); |
| for block in self.bitset.iter_mut() { |
| *block = 0; |
| } |
| if needed_blocks > self.bitset.len() { |
| self.bitset.resize(needed_blocks, 0); |
| } |
| Ok(()) |
| } |
| |
| /// Return the heap memory usage, in bytes, of this visited set. |
| fn memory_usage(&self) -> usize { |
| self.bitset.len() * core::mem::size_of::<usize>() |
| } |
| } |
| |
| /// Integer division, but rounds up instead of down. |
| fn div_ceil(lhs: usize, rhs: usize) -> usize { |
| if lhs % rhs == 0 { |
| lhs / rhs |
| } else { |
| (lhs / rhs) + 1 |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| |
| // This is a regression test for the maximum haystack length computation. |
| // Previously, it assumed that the total capacity of the backtracker's |
| // bitset would always be greater than the number of NFA states. But there |
| // is of course no guarantee that this is true. This regression test |
| // ensures that not only does `max_haystack_len` not panic, but that it |
| // should return `0`. |
| #[cfg(feature = "syntax")] |
| #[test] |
| fn max_haystack_len_overflow() { |
| let re = BoundedBacktracker::builder() |
| .configure(BoundedBacktracker::config().visited_capacity(10)) |
| .build(r"[0-9A-Za-z]{100}") |
| .unwrap(); |
| assert_eq!(0, re.max_haystack_len()); |
| } |
| } |