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Diffstat (limited to 'vendor/regex-automata/src/nfa/compiler.rs')
| -rw-r--r-- | vendor/regex-automata/src/nfa/compiler.rs | 1193 |
1 files changed, 1193 insertions, 0 deletions
diff --git a/vendor/regex-automata/src/nfa/compiler.rs b/vendor/regex-automata/src/nfa/compiler.rs new file mode 100644 index 000000000..d9b3945b3 --- /dev/null +++ b/vendor/regex-automata/src/nfa/compiler.rs @@ -0,0 +1,1193 @@ +// This module provides an NFA compiler using Thompson's construction +// algorithm. The compiler takes a regex-syntax::Hir as input and emits an NFA +// graph as output. The NFA graph is structured in a way that permits it to be +// executed by a virtual machine and also used to efficiently build a DFA. +// +// The compiler deals with a slightly expanded set of NFA states that notably +// includes an empty node that has exactly one epsilon transition to the next +// state. In other words, it's a "goto" instruction if one views Thompson's NFA +// as a set of bytecode instructions. These goto instructions are removed in +// a subsequent phase before returning the NFA to the caller. The purpose of +// these empty nodes is that they make the construction algorithm substantially +// simpler to implement. We remove them before returning to the caller because +// they can represent substantial overhead when traversing the NFA graph +// (either while searching using the NFA directly or while building a DFA). +// +// In the future, it would be nice to provide a Glushkov compiler as well, +// as it would work well as a bit-parallel NFA for smaller regexes. But +// the Thompson construction is one I'm more familiar with and seems more +// straight-forward to deal with when it comes to large Unicode character +// classes. +// +// Internally, the compiler uses interior mutability to improve composition +// in the face of the borrow checker. In particular, we'd really like to be +// able to write things like this: +// +// self.c_concat(exprs.iter().map(|e| self.c(e))) +// +// Which elegantly uses iterators to build up a sequence of compiled regex +// sub-expressions and then hands it off to the concatenating compiler +// routine. Without interior mutability, the borrow checker won't let us +// borrow `self` mutably both inside and outside the closure at the same +// time. + +use std::cell::RefCell; +use std::mem; + +use regex_syntax::hir::{self, Hir, HirKind}; +use regex_syntax::utf8::{Utf8Range, Utf8Sequences}; + +use classes::ByteClassSet; +use error::{Error, Result}; +use nfa::map::{Utf8BoundedMap, Utf8SuffixKey, Utf8SuffixMap}; +use nfa::range_trie::RangeTrie; +use nfa::{State, StateID, Transition, NFA}; + +/// Config knobs for the NFA compiler. See the builder's methods for more +/// docs on each one. +#[derive(Clone, Copy, Debug)] +struct Config { + anchored: bool, + allow_invalid_utf8: bool, + reverse: bool, + shrink: bool, +} + +impl Default for Config { + fn default() -> Config { + Config { + anchored: false, + allow_invalid_utf8: false, + reverse: false, + shrink: true, + } + } +} + +/// A builder for compiling an NFA. +#[derive(Clone, Debug)] +pub struct Builder { + config: Config, +} + +impl Builder { + /// Create a new NFA builder with its default configuration. + pub fn new() -> Builder { + Builder { config: Config::default() } + } + + /// Compile the given high level intermediate representation of a regular + /// expression into an NFA. + /// + /// If there was a problem building the NFA, then an error is returned. + /// For example, if the regex uses unsupported features (such as zero-width + /// assertions), then an error is returned. + pub fn build(&self, expr: &Hir) -> Result<NFA> { + let mut nfa = NFA::always_match(); + self.build_with(&mut Compiler::new(), &mut nfa, expr)?; + Ok(nfa) + } + + /// Compile the given high level intermediate representation of a regular + /// expression into the NFA given using the given compiler. Callers may + /// prefer this over `build` if they would like to reuse allocations while + /// compiling many regular expressions. + /// + /// On success, the given NFA is completely overwritten with the NFA + /// produced by the compiler. + /// + /// If there was a problem building the NFA, then an error is returned. For + /// example, if the regex uses unsupported features (such as zero-width + /// assertions), then an error is returned. When an error is returned, + /// the contents of `nfa` are unspecified and should not be relied upon. + /// However, it can still be reused in subsequent calls to this method. + pub fn build_with( + &self, + compiler: &mut Compiler, + nfa: &mut NFA, + expr: &Hir, + ) -> Result<()> { + compiler.clear(); + compiler.configure(self.config); + compiler.compile(nfa, expr) + } + + /// Set whether matching must be anchored at the beginning of the input. + /// + /// When enabled, a match must begin at the start of the input. When + /// disabled, the NFA will act as if the pattern started with a `.*?`, + /// which enables a match to appear anywhere. + /// + /// By default this is disabled. + pub fn anchored(&mut self, yes: bool) -> &mut Builder { + self.config.anchored = yes; + self + } + + /// When enabled, the builder will permit the construction of an NFA that + /// may match invalid UTF-8. + /// + /// When disabled (the default), the builder is guaranteed to produce a + /// regex that will only ever match valid UTF-8 (otherwise, the builder + /// will return an error). + pub fn allow_invalid_utf8(&mut self, yes: bool) -> &mut Builder { + self.config.allow_invalid_utf8 = yes; + self + } + + /// Reverse the NFA. + /// + /// A NFA reversal is performed by reversing all of the concatenated + /// sub-expressions in the original pattern, recursively. The resulting + /// NFA can be used to match the pattern starting from the end of a string + /// instead of the beginning of a string. + /// + /// Reversing the NFA is useful for building a reverse DFA, which is most + /// useful for finding the start of a match. + pub fn reverse(&mut self, yes: bool) -> &mut Builder { + self.config.reverse = yes; + self + } + + /// Apply best effort heuristics to shrink the NFA at the expense of more + /// time/memory. + /// + /// This is enabled by default. Generally speaking, if one is using an NFA + /// to compile DFA, then the extra time used to shrink the NFA will be + /// more than made up for during DFA construction (potentially by a lot). + /// In other words, enabling this can substantially decrease the overall + /// amount of time it takes to build a DFA. + /// + /// The only reason to disable this if you want to compile an NFA and start + /// using it as quickly as possible without needing to build a DFA. + pub fn shrink(&mut self, yes: bool) -> &mut Builder { + self.config.shrink = yes; + self + } +} + +/// A compiler that converts a regex abstract syntax to an NFA via Thompson's +/// construction. Namely, this compiler permits epsilon transitions between +/// states. +/// +/// Users of this crate cannot use a compiler directly. Instead, all one can +/// do is create one and use it via the +/// [`Builder::build_with`](struct.Builder.html#method.build_with) +/// method. This permits callers to reuse compilers in order to amortize +/// allocations. +#[derive(Clone, Debug)] +pub struct Compiler { + /// The set of compiled NFA states. Once a state is compiled, it is + /// assigned a state ID equivalent to its index in this list. Subsequent + /// compilation can modify previous states by adding new transitions. + states: RefCell<Vec<CState>>, + /// The configuration from the builder. + config: Config, + /// State used for compiling character classes to UTF-8 byte automata. + /// State is not retained between character class compilations. This just + /// serves to amortize allocation to the extent possible. + utf8_state: RefCell<Utf8State>, + /// State used for arranging character classes in reverse into a trie. + trie_state: RefCell<RangeTrie>, + /// State used for caching common suffixes when compiling reverse UTF-8 + /// automata (for Unicode character classes). + utf8_suffix: RefCell<Utf8SuffixMap>, + /// A map used to re-map state IDs when translating the compiler's internal + /// NFA state representation to the external NFA representation. + remap: RefCell<Vec<StateID>>, + /// A set of compiler internal state IDs that correspond to states that are + /// exclusively epsilon transitions, i.e., goto instructions, combined with + /// the state that they point to. This is used to record said states while + /// transforming the compiler's internal NFA representation to the external + /// form. + empties: RefCell<Vec<(StateID, StateID)>>, +} + +/// A compiler intermediate state representation for an NFA that is only used +/// during compilation. Once compilation is done, `CState`s are converted to +/// `State`s, which have a much simpler representation. +#[derive(Clone, Debug, Eq, PartialEq)] +enum CState { + /// An empty state whose only purpose is to forward the automaton to + /// another state via en epsilon transition. These are useful during + /// compilation but are otherwise removed at the end. + Empty { next: StateID }, + /// A state that only transitions to `next` if the current input byte is + /// in the range `[start, end]` (inclusive on both ends). + Range { range: Transition }, + /// A state with possibly many transitions, represented in a sparse + /// fashion. Transitions are ordered lexicographically by input range. + /// As such, this may only be used when every transition has equal + /// priority. (In practice, this is only used for encoding large UTF-8 + /// automata.) + Sparse { ranges: Vec<Transition> }, + /// An alternation such that there exists an epsilon transition to all + /// states in `alternates`, where matches found via earlier transitions + /// are preferred over later transitions. + Union { alternates: Vec<StateID> }, + /// An alternation such that there exists an epsilon transition to all + /// states in `alternates`, where matches found via later transitions + /// are preferred over earlier transitions. + /// + /// This "reverse" state exists for convenience during compilation that + /// permits easy construction of non-greedy combinations of NFA states. + /// At the end of compilation, Union and UnionReverse states are merged + /// into one Union type of state, where the latter has its epsilon + /// transitions reversed to reflect the priority inversion. + UnionReverse { alternates: Vec<StateID> }, + /// A match state. There is exactly one such occurrence of this state in + /// an NFA. + Match, +} + +/// A value that represents the result of compiling a sub-expression of a +/// regex's HIR. Specifically, this represents a sub-graph of the NFA that +/// has an initial state at `start` and a final state at `end`. +#[derive(Clone, Copy, Debug)] +pub struct ThompsonRef { + start: StateID, + end: StateID, +} + +impl Compiler { + /// Create a new compiler. + pub fn new() -> Compiler { + Compiler { + states: RefCell::new(vec![]), + config: Config::default(), + utf8_state: RefCell::new(Utf8State::new()), + trie_state: RefCell::new(RangeTrie::new()), + utf8_suffix: RefCell::new(Utf8SuffixMap::new(1000)), + remap: RefCell::new(vec![]), + empties: RefCell::new(vec![]), + } + } + + /// Clear any memory used by this compiler such that it is ready to compile + /// a new regex. + /// + /// It is preferrable to reuse a compiler if possible in order to reuse + /// allocations. + fn clear(&self) { + self.states.borrow_mut().clear(); + // We don't need to clear anything else since they are cleared on + // their own and only when they are used. + } + + /// Configure this compiler from the builder's knobs. + /// + /// The compiler is always reconfigured by the builder before using it to + /// build an NFA. + fn configure(&mut self, config: Config) { + self.config = config; + } + + /// Convert the current intermediate NFA to its final compiled form. + fn compile(&self, nfa: &mut NFA, expr: &Hir) -> Result<()> { + nfa.anchored = self.config.anchored; + + let mut start = self.add_empty(); + if !nfa.anchored { + let compiled = if self.config.allow_invalid_utf8 { + self.c_unanchored_prefix_invalid_utf8()? + } else { + self.c_unanchored_prefix_valid_utf8()? + }; + self.patch(start, compiled.start); + start = compiled.end; + } + let compiled = self.c(&expr)?; + let match_id = self.add_match(); + self.patch(start, compiled.start); + self.patch(compiled.end, match_id); + self.finish(nfa); + Ok(()) + } + + /// Finishes the compilation process and populates the provide NFA with + /// the final graph. + fn finish(&self, nfa: &mut NFA) { + let mut bstates = self.states.borrow_mut(); + let mut remap = self.remap.borrow_mut(); + remap.resize(bstates.len(), 0); + let mut empties = self.empties.borrow_mut(); + empties.clear(); + + // We don't reuse allocations here becuase this is what we're + // returning. + nfa.states.clear(); + let mut byteset = ByteClassSet::new(); + + // The idea here is to convert our intermediate states to their final + // form. The only real complexity here is the process of converting + // transitions, which are expressed in terms of state IDs. The new + // set of states will be smaller because of partial epsilon removal, + // so the state IDs will not be the same. + for (id, bstate) in bstates.iter_mut().enumerate() { + match *bstate { + CState::Empty { next } => { + // Since we're removing empty states, we need to handle + // them later since we don't yet know which new state this + // empty state will be mapped to. + empties.push((id, next)); + } + CState::Range { ref range } => { + remap[id] = nfa.states.len(); + byteset.set_range(range.start, range.end); + nfa.states.push(State::Range { range: range.clone() }); + } + CState::Sparse { ref mut ranges } => { + remap[id] = nfa.states.len(); + + let ranges = mem::replace(ranges, vec![]); + for r in &ranges { + byteset.set_range(r.start, r.end); + } + nfa.states.push(State::Sparse { + ranges: ranges.into_boxed_slice(), + }); + } + CState::Union { ref mut alternates } => { + remap[id] = nfa.states.len(); + + let alternates = mem::replace(alternates, vec![]); + nfa.states.push(State::Union { + alternates: alternates.into_boxed_slice(), + }); + } + CState::UnionReverse { ref mut alternates } => { + remap[id] = nfa.states.len(); + + let mut alternates = mem::replace(alternates, vec![]); + alternates.reverse(); + nfa.states.push(State::Union { + alternates: alternates.into_boxed_slice(), + }); + } + CState::Match => { + remap[id] = nfa.states.len(); + nfa.states.push(State::Match); + } + } + } + for &(empty_id, mut empty_next) in empties.iter() { + // empty states can point to other empty states, forming a chain. + // So we must follow the chain until the end, which must end at + // a non-empty state, and therefore, a state that is correctly + // remapped. We are guaranteed to terminate because our compiler + // never builds a loop among empty states. + while let CState::Empty { next } = bstates[empty_next] { + empty_next = next; + } + remap[empty_id] = remap[empty_next]; + } + for state in &mut nfa.states { + state.remap(&remap); + } + // The compiler always begins the NFA at the first state. + nfa.start = remap[0]; + nfa.byte_classes = byteset.byte_classes(); + } + + fn c(&self, expr: &Hir) -> Result<ThompsonRef> { + match *expr.kind() { + HirKind::Empty => { + let id = self.add_empty(); + Ok(ThompsonRef { start: id, end: id }) + } + HirKind::Literal(hir::Literal::Unicode(ch)) => { + let mut buf = [0; 4]; + let it = ch + .encode_utf8(&mut buf) + .as_bytes() + .iter() + .map(|&b| Ok(self.c_range(b, b))); + self.c_concat(it) + } + HirKind::Literal(hir::Literal::Byte(b)) => Ok(self.c_range(b, b)), + HirKind::Class(hir::Class::Bytes(ref cls)) => { + self.c_byte_class(cls) + } + HirKind::Class(hir::Class::Unicode(ref cls)) => { + self.c_unicode_class(cls) + } + HirKind::Repetition(ref rep) => self.c_repetition(rep), + HirKind::Group(ref group) => self.c(&*group.hir), + HirKind::Concat(ref exprs) => { + self.c_concat(exprs.iter().map(|e| self.c(e))) + } + HirKind::Alternation(ref exprs) => { + self.c_alternation(exprs.iter().map(|e| self.c(e))) + } + HirKind::Anchor(_) => Err(Error::unsupported_anchor()), + HirKind::WordBoundary(_) => Err(Error::unsupported_word()), + } + } + + fn c_concat<I>(&self, mut it: I) -> Result<ThompsonRef> + where + I: DoubleEndedIterator<Item = Result<ThompsonRef>>, + { + let first = + if self.config.reverse { it.next_back() } else { it.next() }; + let ThompsonRef { start, mut end } = match first { + Some(result) => result?, + None => return Ok(self.c_empty()), + }; + loop { + let next = + if self.config.reverse { it.next_back() } else { it.next() }; + let compiled = match next { + Some(result) => result?, + None => break, + }; + self.patch(end, compiled.start); + end = compiled.end; + } + Ok(ThompsonRef { start, end }) + } + + fn c_alternation<I>(&self, mut it: I) -> Result<ThompsonRef> + where + I: Iterator<Item = Result<ThompsonRef>>, + { + let first = it.next().expect("alternations must be non-empty")?; + let second = match it.next() { + None => return Ok(first), + Some(result) => result?, + }; + + let union = self.add_union(); + let end = self.add_empty(); + self.patch(union, first.start); + self.patch(first.end, end); + self.patch(union, second.start); + self.patch(second.end, end); + for result in it { + let compiled = result?; + self.patch(union, compiled.start); + self.patch(compiled.end, end); + } + Ok(ThompsonRef { start: union, end }) + } + + fn c_repetition(&self, rep: &hir::Repetition) -> Result<ThompsonRef> { + match rep.kind { + hir::RepetitionKind::ZeroOrOne => { + self.c_zero_or_one(&rep.hir, rep.greedy) + } + hir::RepetitionKind::ZeroOrMore => { + self.c_at_least(&rep.hir, rep.greedy, 0) + } + hir::RepetitionKind::OneOrMore => { + self.c_at_least(&rep.hir, rep.greedy, 1) + } + hir::RepetitionKind::Range(ref rng) => match *rng { + hir::RepetitionRange::Exactly(count) => { + self.c_exactly(&rep.hir, count) + } + hir::RepetitionRange::AtLeast(m) => { + self.c_at_least(&rep.hir, rep.greedy, m) + } + hir::RepetitionRange::Bounded(min, max) => { + self.c_bounded(&rep.hir, rep.greedy, min, max) + } + }, + } + } + + fn c_bounded( + &self, + expr: &Hir, + greedy: bool, + min: u32, + max: u32, + ) -> Result<ThompsonRef> { + let prefix = self.c_exactly(expr, min)?; + if min == max { + return Ok(prefix); + } + + // It is tempting here to compile the rest here as a concatenation + // of zero-or-one matches. i.e., for `a{2,5}`, compile it as if it + // were `aaa?a?a?`. The problem here is that it leads to this program: + // + // >000000: 61 => 01 + // 000001: 61 => 02 + // 000002: alt(03, 04) + // 000003: 61 => 04 + // 000004: alt(05, 06) + // 000005: 61 => 06 + // 000006: alt(07, 08) + // 000007: 61 => 08 + // 000008: MATCH + // + // And effectively, once you hit state 2, the epsilon closure will + // include states 3, 5, 5, 6, 7 and 8, which is quite a bit. It is + // better to instead compile it like so: + // + // >000000: 61 => 01 + // 000001: 61 => 02 + // 000002: alt(03, 08) + // 000003: 61 => 04 + // 000004: alt(05, 08) + // 000005: 61 => 06 + // 000006: alt(07, 08) + // 000007: 61 => 08 + // 000008: MATCH + // + // So that the epsilon closure of state 2 is now just 3 and 8. + let empty = self.add_empty(); + let mut prev_end = prefix.end; + for _ in min..max { + let union = if greedy { + self.add_union() + } else { + self.add_reverse_union() + }; + let compiled = self.c(expr)?; + self.patch(prev_end, union); + self.patch(union, compiled.start); + self.patch(union, empty); + prev_end = compiled.end; + } + self.patch(prev_end, empty); + Ok(ThompsonRef { start: prefix.start, end: empty }) + } + + fn c_at_least( + &self, + expr: &Hir, + greedy: bool, + n: u32, + ) -> Result<ThompsonRef> { + if n == 0 { + let union = if greedy { + self.add_union() + } else { + self.add_reverse_union() + }; + let compiled = self.c(expr)?; + self.patch(union, compiled.start); + self.patch(compiled.end, union); + Ok(ThompsonRef { start: union, end: union }) + } else if n == 1 { + let compiled = self.c(expr)?; + let union = if greedy { + self.add_union() + } else { + self.add_reverse_union() + }; + self.patch(compiled.end, union); + self.patch(union, compiled.start); + Ok(ThompsonRef { start: compiled.start, end: union }) + } else { + let prefix = self.c_exactly(expr, n - 1)?; + let last = self.c(expr)?; + let union = if greedy { + self.add_union() + } else { + self.add_reverse_union() + }; + self.patch(prefix.end, last.start); + self.patch(last.end, union); + self.patch(union, last.start); + Ok(ThompsonRef { start: prefix.start, end: union }) + } + } + + fn c_zero_or_one(&self, expr: &Hir, greedy: bool) -> Result<ThompsonRef> { + let union = + if greedy { self.add_union() } else { self.add_reverse_union() }; + let compiled = self.c(expr)?; + let empty = self.add_empty(); + self.patch(union, compiled.start); + self.patch(union, empty); + self.patch(compiled.end, empty); + Ok(ThompsonRef { start: union, end: empty }) + } + + fn c_exactly(&self, expr: &Hir, n: u32) -> Result<ThompsonRef> { + let it = (0..n).map(|_| self.c(expr)); + self.c_concat(it) + } + + fn c_byte_class(&self, cls: &hir::ClassBytes) -> Result<ThompsonRef> { + let end = self.add_empty(); + let mut trans = Vec::with_capacity(cls.ranges().len()); + for r in cls.iter() { + trans.push(Transition { + start: r.start(), + end: r.end(), + next: end, + }); + } + Ok(ThompsonRef { start: self.add_sparse(trans), end }) + } + + fn c_unicode_class(&self, cls: &hir::ClassUnicode) -> Result<ThompsonRef> { + // If all we have are ASCII ranges wrapped in a Unicode package, then + // there is zero reason to bring out the big guns. We can fit all ASCII + // ranges within a single sparse transition. + if cls.is_all_ascii() { + let end = self.add_empty(); + let mut trans = Vec::with_capacity(cls.ranges().len()); + for r in cls.iter() { + assert!(r.start() <= '\x7F'); + assert!(r.end() <= '\x7F'); + trans.push(Transition { + start: r.start() as u8, + end: r.end() as u8, + next: end, + }); + } + Ok(ThompsonRef { start: self.add_sparse(trans), end }) + } else if self.config.reverse { + if !self.config.shrink { + // When we don't want to spend the extra time shrinking, we + // compile the UTF-8 automaton in reverse using something like + // the "naive" approach, but will attempt to re-use common + // suffixes. + self.c_unicode_class_reverse_with_suffix(cls) + } else { + // When we want to shrink our NFA for reverse UTF-8 automata, + // we cannot feed UTF-8 sequences directly to the UTF-8 + // compiler, since the UTF-8 compiler requires all sequences + // to be lexicographically sorted. Instead, we organize our + // sequences into a range trie, which can then output our + // sequences in the correct order. Unfortunately, building the + // range trie is fairly expensive (but not nearly as expensive + // as building a DFA). Hence the reason why the 'shrink' option + // exists, so that this path can be toggled off. + let mut trie = self.trie_state.borrow_mut(); + trie.clear(); + + for rng in cls.iter() { + for mut seq in Utf8Sequences::new(rng.start(), rng.end()) { + seq.reverse(); + trie.insert(seq.as_slice()); + } + } + let mut utf8_state = self.utf8_state.borrow_mut(); + let mut utf8c = Utf8Compiler::new(self, &mut *utf8_state); + trie.iter(|seq| { + utf8c.add(&seq); + }); + Ok(utf8c.finish()) + } + } else { + // In the forward direction, we always shrink our UTF-8 automata + // because we can stream it right into the UTF-8 compiler. There + // is almost no downside (in either memory or time) to using this + // approach. + let mut utf8_state = self.utf8_state.borrow_mut(); + let mut utf8c = Utf8Compiler::new(self, &mut *utf8_state); + for rng in cls.iter() { + for seq in Utf8Sequences::new(rng.start(), rng.end()) { + utf8c.add(seq.as_slice()); + } + } + Ok(utf8c.finish()) + } + + // For reference, the code below is the "naive" version of compiling a + // UTF-8 automaton. It is deliciously simple (and works for both the + // forward and reverse cases), but will unfortunately produce very + // large NFAs. When compiling a forward automaton, the size difference + // can sometimes be an order of magnitude. For example, the '\w' regex + // will generate about ~3000 NFA states using the naive approach below, + // but only 283 states when using the approach above. This is because + // the approach above actually compiles a *minimal* (or near minimal, + // because of the bounded hashmap) UTF-8 automaton. + // + // The code below is kept as a reference point in order to make it + // easier to understand the higher level goal here. + /* + let it = cls + .iter() + .flat_map(|rng| Utf8Sequences::new(rng.start(), rng.end())) + .map(|seq| { + let it = seq + .as_slice() + .iter() + .map(|rng| Ok(self.c_range(rng.start, rng.end))); + self.c_concat(it) + }); + self.c_alternation(it); + */ + } + + fn c_unicode_class_reverse_with_suffix( + &self, + cls: &hir::ClassUnicode, + ) -> Result<ThompsonRef> { + // N.B. It would likely be better to cache common *prefixes* in the + // reverse direction, but it's not quite clear how to do that. The + // advantage of caching suffixes is that it does give us a win, and + // has a very small additional overhead. + let mut cache = self.utf8_suffix.borrow_mut(); + cache.clear(); + + let union = self.add_union(); + let alt_end = self.add_empty(); + for urng in cls.iter() { + for seq in Utf8Sequences::new(urng.start(), urng.end()) { + let mut end = alt_end; + for brng in seq.as_slice() { + let key = Utf8SuffixKey { + from: end, + start: brng.start, + end: brng.end, + }; + let hash = cache.hash(&key); + if let Some(id) = cache.get(&key, hash) { + end = id; + continue; + } + + let compiled = self.c_range(brng.start, brng.end); + self.patch(compiled.end, end); + end = compiled.start; + cache.set(key, hash, end); + } + self.patch(union, end); + } + } + Ok(ThompsonRef { start: union, end: alt_end }) + } + + fn c_range(&self, start: u8, end: u8) -> ThompsonRef { + let id = self.add_range(start, end); + ThompsonRef { start: id, end: id } + } + + fn c_empty(&self) -> ThompsonRef { + let id = self.add_empty(); + ThompsonRef { start: id, end: id } + } + + fn c_unanchored_prefix_valid_utf8(&self) -> Result<ThompsonRef> { + self.c(&Hir::repetition(hir::Repetition { + kind: hir::RepetitionKind::ZeroOrMore, + greedy: false, + hir: Box::new(Hir::any(false)), + })) + } + + fn c_unanchored_prefix_invalid_utf8(&self) -> Result<ThompsonRef> { + self.c(&Hir::repetition(hir::Repetition { + kind: hir::RepetitionKind::ZeroOrMore, + greedy: false, + hir: Box::new(Hir::any(true)), + })) + } + + fn patch(&self, from: StateID, to: StateID) { + match self.states.borrow_mut()[from] { + CState::Empty { ref mut next } => { + *next = to; + } + CState::Range { ref mut range } => { + range.next = to; + } + CState::Sparse { .. } => { + panic!("cannot patch from a sparse NFA state") + } + CState::Union { ref mut alternates } => { + alternates.push(to); + } + CState::UnionReverse { ref mut alternates } => { + alternates.push(to); + } + CState::Match => {} + } + } + + fn add_empty(&self) -> StateID { + let id = self.states.borrow().len(); + self.states.borrow_mut().push(CState::Empty { next: 0 }); + id + } + + fn add_range(&self, start: u8, end: u8) -> StateID { + let id = self.states.borrow().len(); + let trans = Transition { start, end, next: 0 }; + let state = CState::Range { range: trans }; + self.states.borrow_mut().push(state); + id + } + + fn add_sparse(&self, ranges: Vec<Transition>) -> StateID { + if ranges.len() == 1 { + let id = self.states.borrow().len(); + let state = CState::Range { range: ranges[0] }; + self.states.borrow_mut().push(state); + return id; + } + let id = self.states.borrow().len(); + let state = CState::Sparse { ranges }; + self.states.borrow_mut().push(state); + id + } + + fn add_union(&self) -> StateID { + let id = self.states.borrow().len(); + let state = CState::Union { alternates: vec![] }; + self.states.borrow_mut().push(state); + id + } + + fn add_reverse_union(&self) -> StateID { + let id = self.states.borrow().len(); + let state = CState::UnionReverse { alternates: vec![] }; + self.states.borrow_mut().push(state); + id + } + + fn add_match(&self) -> StateID { + let id = self.states.borrow().len(); + self.states.borrow_mut().push(CState::Match); + id + } +} + +#[derive(Debug)] +struct Utf8Compiler<'a> { + nfac: &'a Compiler, + state: &'a mut Utf8State, + target: StateID, +} + +#[derive(Clone, Debug)] +struct Utf8State { + compiled: Utf8BoundedMap, + uncompiled: Vec<Utf8Node>, +} + +#[derive(Clone, Debug)] +struct Utf8Node { + trans: Vec<Transition>, + last: Option<Utf8LastTransition>, +} + +#[derive(Clone, Debug)] +struct Utf8LastTransition { + start: u8, + end: u8, +} + +impl Utf8State { + fn new() -> Utf8State { + Utf8State { compiled: Utf8BoundedMap::new(5000), uncompiled: vec![] } + } + + fn clear(&mut self) { + self.compiled.clear(); + self.uncompiled.clear(); + } +} + +impl<'a> Utf8Compiler<'a> { + fn new(nfac: &'a Compiler, state: &'a mut Utf8State) -> Utf8Compiler<'a> { + let target = nfac.add_empty(); + state.clear(); + let mut utf8c = Utf8Compiler { nfac, state, target }; + utf8c.add_empty(); + utf8c + } + + fn finish(&mut self) -> ThompsonRef { + self.compile_from(0); + let node = self.pop_root(); + let start = self.compile(node); + ThompsonRef { start, end: self.target } + } + + fn add(&mut self, ranges: &[Utf8Range]) { + let prefix_len = ranges + .iter() + .zip(&self.state.uncompiled) + .take_while(|&(range, node)| { + node.last.as_ref().map_or(false, |t| { + (t.start, t.end) == (range.start, range.end) + }) + }) + .count(); + assert!(prefix_len < ranges.len()); + self.compile_from(prefix_len); + self.add_suffix(&ranges[prefix_len..]); + } + + fn compile_from(&mut self, from: usize) { + let mut next = self.target; + while from + 1 < self.state.uncompiled.len() { + let node = self.pop_freeze(next); + next = self.compile(node); + } + self.top_last_freeze(next); + } + + fn compile(&mut self, node: Vec<Transition>) -> StateID { + let hash = self.state.compiled.hash(&node); + if let Some(id) = self.state.compiled.get(&node, hash) { + return id; + } + let id = self.nfac.add_sparse(node.clone()); + self.state.compiled.set(node, hash, id); + id + } + + fn add_suffix(&mut self, ranges: &[Utf8Range]) { + assert!(!ranges.is_empty()); + let last = self + .state + .uncompiled + .len() + .checked_sub(1) + .expect("non-empty nodes"); + assert!(self.state.uncompiled[last].last.is_none()); + self.state.uncompiled[last].last = Some(Utf8LastTransition { + start: ranges[0].start, + end: ranges[0].end, + }); + for r in &ranges[1..] { + self.state.uncompiled.push(Utf8Node { + trans: vec![], + last: Some(Utf8LastTransition { start: r.start, end: r.end }), + }); + } + } + + fn add_empty(&mut self) { + self.state.uncompiled.push(Utf8Node { trans: vec![], last: None }); + } + + fn pop_freeze(&mut self, next: StateID) -> Vec<Transition> { + let mut uncompiled = self.state.uncompiled.pop().unwrap(); + uncompiled.set_last_transition(next); + uncompiled.trans + } + + fn pop_root(&mut self) -> Vec<Transition> { + assert_eq!(self.state.uncompiled.len(), 1); + assert!(self.state.uncompiled[0].last.is_none()); + self.state.uncompiled.pop().expect("non-empty nodes").trans + } + + fn top_last_freeze(&mut self, next: StateID) { + let last = self + .state + .uncompiled + .len() + .checked_sub(1) + .expect("non-empty nodes"); + self.state.uncompiled[last].set_last_transition(next); + } +} + +impl Utf8Node { + fn set_last_transition(&mut self, next: StateID) { + if let Some(last) = self.last.take() { + self.trans.push(Transition { + start: last.start, + end: last.end, + next, + }); + } + } +} + +#[cfg(test)] +mod tests { + use regex_syntax::hir::Hir; + use regex_syntax::ParserBuilder; + + use super::{Builder, State, StateID, Transition, NFA}; + + fn parse(pattern: &str) -> Hir { + ParserBuilder::new().build().parse(pattern).unwrap() + } + + fn build(pattern: &str) -> NFA { + Builder::new().anchored(true).build(&parse(pattern)).unwrap() + } + + fn s_byte(byte: u8, next: StateID) -> State { + let trans = Transition { start: byte, end: byte, next }; + State::Range { range: trans } + } + + fn s_range(start: u8, end: u8, next: StateID) -> State { + let trans = Transition { start, end, next }; + State::Range { range: trans } + } + + fn s_sparse(ranges: &[(u8, u8, StateID)]) -> State { + let ranges = ranges + .iter() + .map(|&(start, end, next)| Transition { start, end, next }) + .collect(); + State::Sparse { ranges } + } + + fn s_union(alts: &[StateID]) -> State { + State::Union { alternates: alts.to_vec().into_boxed_slice() } + } + + fn s_match() -> State { + State::Match + } + + #[test] + fn errors() { + // unsupported anchors + assert!(Builder::new().build(&parse(r"^")).is_err()); + assert!(Builder::new().build(&parse(r"$")).is_err()); + assert!(Builder::new().build(&parse(r"\A")).is_err()); + assert!(Builder::new().build(&parse(r"\z")).is_err()); + + // unsupported word boundaries + assert!(Builder::new().build(&parse(r"\b")).is_err()); + assert!(Builder::new().build(&parse(r"\B")).is_err()); + assert!(Builder::new().build(&parse(r"(?-u)\b")).is_err()); + } + + // Test that building an unanchored NFA has an appropriate `.*?` prefix. + #[test] + fn compile_unanchored_prefix() { + // When the machine can only match valid UTF-8. + let nfa = Builder::new().anchored(false).build(&parse(r"a")).unwrap(); + // There should be many states since the `.` in `.*?` matches any + // Unicode scalar value. + assert_eq!(11, nfa.len()); + assert_eq!(nfa.states[10], s_match()); + assert_eq!(nfa.states[9], s_byte(b'a', 10)); + + // When the machine can match invalid UTF-8. + let nfa = Builder::new() + .anchored(false) + .allow_invalid_utf8(true) + .build(&parse(r"a")) + .unwrap(); + assert_eq!( + nfa.states, + &[ + s_union(&[2, 1]), + s_range(0, 255, 0), + s_byte(b'a', 3), + s_match(), + ] + ); + } + + #[test] + fn compile_empty() { + assert_eq!(build("").states, &[s_match(),]); + } + + #[test] + fn compile_literal() { + assert_eq!(build("a").states, &[s_byte(b'a', 1), s_match(),]); + assert_eq!( + build("ab").states, + &[s_byte(b'a', 1), s_byte(b'b', 2), s_match(),] + ); + assert_eq!( + build("ā").states, + &[s_byte(0xE2, 1), s_byte(0x98, 2), s_byte(0x83, 3), s_match(),] + ); + + // Check that non-UTF-8 literals work. + let hir = ParserBuilder::new() + .allow_invalid_utf8(true) + .build() + .parse(r"(?-u)\xFF") + .unwrap(); + let nfa = Builder::new() + .anchored(true) + .allow_invalid_utf8(true) + .build(&hir) + .unwrap(); + assert_eq!(nfa.states, &[s_byte(b'\xFF', 1), s_match(),]); + } + + #[test] + fn compile_class() { + assert_eq!( + build(r"[a-z]").states, + &[s_range(b'a', b'z', 1), s_match(),] + ); + assert_eq!( + build(r"[x-za-c]").states, + &[s_sparse(&[(b'a', b'c', 1), (b'x', b'z', 1)]), s_match()] + ); + assert_eq!( + build(r"[\u03B1-\u03B4]").states, + &[s_range(0xB1, 0xB4, 2), s_byte(0xCE, 0), s_match()] + ); + assert_eq!( + build(r"[\u03B1-\u03B4\u{1F919}-\u{1F91E}]").states, + &[ + s_range(0xB1, 0xB4, 5), + s_range(0x99, 0x9E, 5), + s_byte(0xA4, 1), + s_byte(0x9F, 2), + s_sparse(&[(0xCE, 0xCE, 0), (0xF0, 0xF0, 3)]), + s_match(), + ] + ); + assert_eq!( + build(r"[a-zā]").states, + &[ + s_byte(0x83, 3), + s_byte(0x98, 0), + s_sparse(&[(b'a', b'z', 3), (0xE2, 0xE2, 1)]), + s_match(), + ] + ); + } + + #[test] + fn compile_repetition() { + assert_eq!( + build(r"a?").states, + &[s_union(&[1, 2]), s_byte(b'a', 2), s_match(),] + ); + assert_eq!( + build(r"a??").states, + &[s_union(&[2, 1]), s_byte(b'a', 2), s_match(),] + ); + } + + #[test] + fn compile_group() { + assert_eq!( + build(r"ab+").states, + &[s_byte(b'a', 1), s_byte(b'b', 2), s_union(&[1, 3]), s_match(),] + ); + assert_eq!( + build(r"(ab)").states, + &[s_byte(b'a', 1), s_byte(b'b', 2), s_match(),] + ); + assert_eq!( + build(r"(ab)+").states, + &[s_byte(b'a', 1), s_byte(b'b', 2), s_union(&[0, 3]), s_match(),] + ); + } + + #[test] + fn compile_alternation() { + assert_eq!( + build(r"a|b").states, + &[s_byte(b'a', 3), s_byte(b'b', 3), s_union(&[0, 1]), s_match(),] + ); + assert_eq!( + build(r"|b").states, + &[s_byte(b'b', 2), s_union(&[2, 0]), s_match(),] + ); + assert_eq!( + build(r"a|").states, + &[s_byte(b'a', 2), s_union(&[0, 2]), s_match(),] + ); + } +} |