Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 599 insertions, 0 deletions

diff --git a/third_party/rust/regex-automata/src/dfa/determinize.rs b/third_party/rust/regex-automata/src/dfa/determinize.rs
new file mode 100644
index 0000000000..19f99f5d64
--- /dev/null
+++ b/third_party/rust/regex-automata/src/dfa/determinize.rs
@@ -0,0 +1,599 @@
+use alloc::{collections::BTreeMap, vec::Vec};
+
+use crate::{
+    dfa::{
+        dense::{self, BuildError},
+        DEAD,
+    },
+    nfa::thompson,
+    util::{
+        self,
+        alphabet::{self, ByteSet},
+        determinize::{State, StateBuilderEmpty, StateBuilderNFA},
+        primitives::{PatternID, StateID},
+        search::{Anchored, MatchKind},
+        sparse_set::SparseSets,
+        start::Start,
+    },
+};
+
+/// A builder for configuring and running a DFA determinizer.
+#[derive(Clone, Debug)]
+pub(crate) struct Config {
+    match_kind: MatchKind,
+    quit: ByteSet,
+    dfa_size_limit: Option<usize>,
+    determinize_size_limit: Option<usize>,
+}
+
+impl Config {
+    /// Create a new default config for a determinizer. The determinizer may be
+    /// configured before calling `run`.
+    pub fn new() -> Config {
+        Config {
+            match_kind: MatchKind::LeftmostFirst,
+            quit: ByteSet::empty(),
+            dfa_size_limit: None,
+            determinize_size_limit: None,
+        }
+    }
+
+    /// Run determinization on the given NFA and write the resulting DFA into
+    /// the one given. The DFA given should be initialized but otherwise empty.
+    /// "Initialized" means that it is setup to handle the NFA's byte classes,
+    /// number of patterns and whether to build start states for each pattern.
+    pub fn run(
+        &self,
+        nfa: &thompson::NFA,
+        dfa: &mut dense::OwnedDFA,
+    ) -> Result<(), BuildError> {
+        let dead = State::dead();
+        let quit = State::dead();
+        let mut cache = StateMap::default();
+        // We only insert the dead state here since its representation is
+        // identical to the quit state. And we never want anything pointing
+        // to the quit state other than specific transitions derived from the
+        // determinizer's configured "quit" bytes.
+        //
+        // We do put the quit state into 'builder_states' below. This ensures
+        // that a proper DFA state ID is allocated for it, and that no other
+        // DFA state uses the "location after the DEAD state." That is, it
+        // is assumed that the quit state is always the state immediately
+        // following the DEAD state.
+        cache.insert(dead.clone(), DEAD);
+
+        let runner = Runner {
+            config: self.clone(),
+            nfa,
+            dfa,
+            builder_states: alloc::vec![dead, quit],
+            cache,
+            memory_usage_state: 0,
+            sparses: SparseSets::new(nfa.states().len()),
+            stack: alloc::vec![],
+            scratch_state_builder: StateBuilderEmpty::new(),
+        };
+        runner.run()
+    }
+
+    /// The match semantics to use for determinization.
+    ///
+    /// MatchKind::All corresponds to the standard textbook construction.
+    /// All possible match states are represented in the DFA.
+    /// MatchKind::LeftmostFirst permits greediness and otherwise tries to
+    /// simulate the match semantics of backtracking regex engines. Namely,
+    /// only a subset of match states are built, and dead states are used to
+    /// stop searches with an unanchored prefix.
+    ///
+    /// The default is MatchKind::LeftmostFirst.
+    pub fn match_kind(&mut self, kind: MatchKind) -> &mut Config {
+        self.match_kind = kind;
+        self
+    }
+
+    /// The set of bytes to use that will cause the DFA to enter a quit state,
+    /// stop searching and return an error. By default, this is empty.
+    pub fn quit(&mut self, set: ByteSet) -> &mut Config {
+        self.quit = set;
+        self
+    }
+
+    /// The limit, in bytes of the heap, that the DFA is permitted to use. This
+    /// does not include the auxiliary heap storage used by determinization.
+    pub fn dfa_size_limit(&mut self, bytes: Option<usize>) -> &mut Config {
+        self.dfa_size_limit = bytes;
+        self
+    }
+
+    /// The limit, in bytes of the heap, that determinization itself is allowed
+    /// to use. This does not include the size of the DFA being built.
+    pub fn determinize_size_limit(
+        &mut self,
+        bytes: Option<usize>,
+    ) -> &mut Config {
+        self.determinize_size_limit = bytes;
+        self
+    }
+}
+
+/// The actual implementation of determinization that converts an NFA to a DFA
+/// through powerset construction.
+///
+/// This determinizer roughly follows the typical powerset construction, where
+/// each DFA state is comprised of one or more NFA states. In the worst case,
+/// there is one DFA state for every possible combination of NFA states. In
+/// practice, this only happens in certain conditions, typically when there are
+/// bounded repetitions.
+///
+/// The main differences between this implementation and typical deteminization
+/// are that this implementation delays matches by one state and hackily makes
+/// look-around work. Comments below attempt to explain this.
+///
+/// The lifetime variable `'a` refers to the lifetime of the NFA or DFA,
+/// whichever is shorter.
+#[derive(Debug)]
+struct Runner<'a> {
+    /// The configuration used to initialize determinization.
+    config: Config,
+    /// The NFA we're converting into a DFA.
+    nfa: &'a thompson::NFA,
+    /// The DFA we're building.
+    dfa: &'a mut dense::OwnedDFA,
+    /// Each DFA state being built is defined as an *ordered* set of NFA
+    /// states, along with some meta facts about the ordered set of NFA states.
+    ///
+    /// This is never empty. The first state is always a dummy state such that
+    /// a state id == 0 corresponds to a dead state. The second state is always
+    /// the quit state.
+    ///
+    /// Why do we have states in both a `Vec` and in a cache map below?
+    /// Well, they serve two different roles based on access patterns.
+    /// `builder_states` is the canonical home of each state, and provides
+    /// constant random access by a DFA state's ID. The cache map below, on
+    /// the other hand, provides a quick way of searching for identical DFA
+    /// states by using the DFA state as a key in the map. Of course, we use
+    /// reference counting to avoid actually duplicating the state's data
+    /// itself. (Although this has never been benchmarked.) Note that the cache
+    /// map does not give us full minimization; it just lets us avoid some very
+    /// obvious redundant states.
+    ///
+    /// Note that the index into this Vec isn't quite the DFA's state ID.
+    /// Rather, it's just an index. To get the state ID, you have to multiply
+    /// it by the DFA's stride. That's done by self.dfa.from_index. And the
+    /// inverse is self.dfa.to_index.
+    ///
+    /// Moreover, DFA states don't usually retain the IDs assigned to them
+    /// by their position in this Vec. After determinization completes,
+    /// states are shuffled around to support other optimizations. See the
+    /// sibling 'special' module for more details on that. (The reason for
+    /// mentioning this is that if you print out the DFA for debugging during
+    /// determinization, and then print out the final DFA after it is fully
+    /// built, then the state IDs likely won't match up.)
+    builder_states: Vec<State>,
+    /// A cache of DFA states that already exist and can be easily looked up
+    /// via ordered sets of NFA states.
+    ///
+    /// See `builder_states` docs for why we store states in two different
+    /// ways.
+    cache: StateMap,
+    /// The memory usage, in bytes, used by builder_states and cache. We track
+    /// this as new states are added since states use a variable amount of
+    /// heap. Tracking this as we add states makes it possible to compute the
+    /// total amount of memory used by the determinizer in constant time.
+    memory_usage_state: usize,
+    /// A pair of sparse sets for tracking ordered sets of NFA state IDs.
+    /// These are reused throughout determinization. A bounded sparse set
+    /// gives us constant time insertion, membership testing and clearing.
+    sparses: SparseSets,
+    /// Scratch space for a stack of NFA states to visit, for depth first
+    /// visiting without recursion.
+    stack: Vec<StateID>,
+    /// Scratch space for storing an ordered sequence of NFA states, for
+    /// amortizing allocation. This is principally useful for when we avoid
+    /// adding a new DFA state since it already exists. In order to detect this
+    /// case though, we still need an ordered set of NFA state IDs. So we use
+    /// this space to stage that ordered set before we know whether we need to
+    /// create a new DFA state or not.
+    scratch_state_builder: StateBuilderEmpty,
+}
+
+/// A map from states to state identifiers. When using std, we use a standard
+/// hashmap, since it's a bit faster for this use case. (Other maps, like
+/// one's based on FNV, have not yet been benchmarked.)
+///
+/// The main purpose of this map is to reuse states where possible. This won't
+/// fully minimize the DFA, but it works well in a lot of cases.
+#[cfg(feature = "std")]
+type StateMap = std::collections::HashMap<State, StateID>;
+#[cfg(not(feature = "std"))]
+type StateMap = BTreeMap<State, StateID>;
+
+impl<'a> Runner<'a> {
+    /// Build the DFA. If there was a problem constructing the DFA (e.g., if
+    /// the chosen state identifier representation is too small), then an error
+    /// is returned.
+    fn run(mut self) -> Result<(), BuildError> {
+        if self.nfa.look_set_any().contains_word_unicode()
+            && !self.config.quit.contains_range(0x80, 0xFF)
+        {
+            return Err(BuildError::unsupported_dfa_word_boundary_unicode());
+        }
+
+        // A sequence of "representative" bytes drawn from each equivalence
+        // class. These representative bytes are fed to the NFA to compute
+        // state transitions. This allows us to avoid re-computing state
+        // transitions for bytes that are guaranteed to produce identical
+        // results. Since computing the representatives needs to do a little
+        // work, we do it once here because we'll be iterating over them a lot.
+        let representatives: Vec<alphabet::Unit> =
+            self.dfa.byte_classes().representatives(..).collect();
+        // The set of all DFA state IDs that still need to have their
+        // transitions set. We start by seeding this with all starting states.
+        let mut uncompiled = alloc::vec![];
+        self.add_all_starts(&mut uncompiled)?;
+        while let Some(dfa_id) = uncompiled.pop() {
+            for &unit in &representatives {
+                if unit.as_u8().map_or(false, |b| self.config.quit.contains(b))
+                {
+                    continue;
+                }
+                // In many cases, the state we transition to has already been
+                // computed. 'cached_state' will do the minimal amount of work
+                // to check this, and if it exists, immediately return an
+                // already existing state ID.
+                let (next_dfa_id, is_new) = self.cached_state(dfa_id, unit)?;
+                self.dfa.set_transition(dfa_id, unit, next_dfa_id);
+                // If the state ID we got back is newly created, then we need
+                // to compile it, so add it to our uncompiled frontier.
+                if is_new {
+                    uncompiled.push(next_dfa_id);
+                }
+            }
+        }
+        debug!(
+            "determinization complete, memory usage: {}, \
+             dense DFA size: {}, \
+             is reverse? {}",
+            self.memory_usage(),
+            self.dfa.memory_usage(),
+            self.nfa.is_reverse(),
+        );
+
+        // A map from DFA state ID to one or more NFA match IDs. Each NFA match
+        // ID corresponds to a distinct regex pattern that matches in the state
+        // corresponding to the key.
+        let mut matches: BTreeMap<StateID, Vec<PatternID>> = BTreeMap::new();
+        self.cache.clear();
+        #[cfg(feature = "logging")]
+        let mut total_pat_len = 0;
+        for (i, state) in self.builder_states.into_iter().enumerate() {
+            if let Some(pat_ids) = state.match_pattern_ids() {
+                let id = self.dfa.to_state_id(i);
+                log! {
+                    total_pat_len += pat_ids.len();
+                }
+                matches.insert(id, pat_ids);
+            }
+        }
+        log! {
+            use core::mem::size_of;
+            let per_elem = size_of::<StateID>() + size_of::<Vec<PatternID>>();
+            let pats = total_pat_len * size_of::<PatternID>();
+            let mem = (matches.len() * per_elem) + pats;
+            log::debug!("matches map built, memory usage: {}", mem);
+        }
+        // At this point, we shuffle the "special" states in the final DFA.
+        // This permits a DFA's match loop to detect a match condition (among
+        // other things) by merely inspecting the current state's identifier,
+        // and avoids the need for any additional auxiliary storage.
+        self.dfa.shuffle(matches)?;
+        Ok(())
+    }
+
+    /// Return the identifier for the next DFA state given an existing DFA
+    /// state and an input byte. If the next DFA state already exists, then
+    /// return its identifier from the cache. Otherwise, build the state, cache
+    /// it and return its identifier.
+    ///
+    /// This routine returns a boolean indicating whether a new state was
+    /// built. If a new state is built, then the caller needs to add it to its
+    /// frontier of uncompiled DFA states to compute transitions for.
+    fn cached_state(
+        &mut self,
+        dfa_id: StateID,
+        unit: alphabet::Unit,
+    ) -> Result<(StateID, bool), BuildError> {
+        // Compute the set of all reachable NFA states, including epsilons.
+        let empty_builder = self.get_state_builder();
+        let builder = util::determinize::next(
+            self.nfa,
+            self.config.match_kind,
+            &mut self.sparses,
+            &mut self.stack,
+            &self.builder_states[self.dfa.to_index(dfa_id)],
+            unit,
+            empty_builder,
+        );
+        self.maybe_add_state(builder)
+    }
+
+    /// Compute the set of DFA start states and add their identifiers in
+    /// 'dfa_state_ids' (no duplicates are added).
+    fn add_all_starts(
+        &mut self,
+        dfa_state_ids: &mut Vec<StateID>,
+    ) -> Result<(), BuildError> {
+        // These should be the first states added.
+        assert!(dfa_state_ids.is_empty());
+        // We only want to add (un)anchored starting states that is consistent
+        // with our DFA's configuration. Unconditionally adding both (although
+        // it is the default) can make DFAs quite a bit bigger.
+        if self.dfa.start_kind().has_unanchored() {
+            self.add_start_group(Anchored::No, dfa_state_ids)?;
+        }
+        if self.dfa.start_kind().has_anchored() {
+            self.add_start_group(Anchored::Yes, dfa_state_ids)?;
+        }
+        // I previously has an 'assert' here checking that either
+        // 'dfa_state_ids' was non-empty, or the NFA had zero patterns. But it
+        // turns out this isn't always true. For example, the NFA might have
+        // one or more patterns but where all such patterns are just 'fail'
+        // states. These will ultimately just compile down to DFA dead states,
+        // and since the dead state was added earlier, no new DFA states are
+        // added. And thus, it is valid and okay for 'dfa_state_ids' to be
+        // empty even if there are a non-zero number of patterns in the NFA.
+
+        // We only need to compute anchored start states for each pattern if it
+        // was requested to do so.
+        if self.dfa.starts_for_each_pattern() {
+            for pid in self.nfa.patterns() {
+                self.add_start_group(Anchored::Pattern(pid), dfa_state_ids)?;
+            }
+        }
+        Ok(())
+    }
+
+    /// Add a group of start states for the given match pattern ID. Any new
+    /// DFA states added are pushed on to 'dfa_state_ids'. (No duplicates are
+    /// pushed.)
+    ///
+    /// When pattern_id is None, then this will compile a group of unanchored
+    /// start states (if the DFA is unanchored). When the pattern_id is
+    /// present, then this will compile a group of anchored start states that
+    /// only match the given pattern.
+    ///
+    /// This panics if `anchored` corresponds to an invalid pattern ID.
+    fn add_start_group(
+        &mut self,
+        anchored: Anchored,
+        dfa_state_ids: &mut Vec<StateID>,
+    ) -> Result<(), BuildError> {
+        let nfa_start = match anchored {
+            Anchored::No => self.nfa.start_unanchored(),
+            Anchored::Yes => self.nfa.start_anchored(),
+            Anchored::Pattern(pid) => {
+                self.nfa.start_pattern(pid).expect("valid pattern ID")
+            }
+        };
+
+        // When compiling start states, we're careful not to build additional
+        // states that aren't necessary. For example, if the NFA has no word
+        // boundary assertion, then there's no reason to have distinct start
+        // states for 'NonWordByte' and 'WordByte' starting configurations.
+        // Instead, the 'WordByte' starting configuration can just point
+        // directly to the start state for the 'NonWordByte' config.
+        //
+        // Note though that we only need to care about assertions in the prefix
+        // of an NFA since this only concerns the starting states. (Actually,
+        // the most precisely thing we could do it is look at the prefix
+        // assertions of each pattern when 'anchored == Anchored::Pattern',
+        // and then only compile extra states if the prefix is non-empty.) But
+        // we settle for simplicity here instead of absolute minimalism. It is
+        // somewhat rare, after all, for multiple patterns in the same regex to
+        // have different prefix look-arounds.
+
+        let (id, is_new) =
+            self.add_one_start(nfa_start, Start::NonWordByte)?;
+        self.dfa.set_start_state(anchored, Start::NonWordByte, id);
+        if is_new {
+            dfa_state_ids.push(id);
+        }
+
+        if !self.nfa.look_set_prefix_any().contains_word() {
+            self.dfa.set_start_state(anchored, Start::WordByte, id);
+        } else {
+            let (id, is_new) =
+                self.add_one_start(nfa_start, Start::WordByte)?;
+            self.dfa.set_start_state(anchored, Start::WordByte, id);
+            if is_new {
+                dfa_state_ids.push(id);
+            }
+        }
+        if !self.nfa.look_set_prefix_any().contains_anchor() {
+            self.dfa.set_start_state(anchored, Start::Text, id);
+            self.dfa.set_start_state(anchored, Start::LineLF, id);
+            self.dfa.set_start_state(anchored, Start::LineCR, id);
+            self.dfa.set_start_state(
+                anchored,
+                Start::CustomLineTerminator,
+                id,
+            );
+        } else {
+            let (id, is_new) = self.add_one_start(nfa_start, Start::Text)?;
+            self.dfa.set_start_state(anchored, Start::Text, id);
+            if is_new {
+                dfa_state_ids.push(id);
+            }
+
+            let (id, is_new) = self.add_one_start(nfa_start, Start::LineLF)?;
+            self.dfa.set_start_state(anchored, Start::LineLF, id);
+            if is_new {
+                dfa_state_ids.push(id);
+            }
+
+            let (id, is_new) = self.add_one_start(nfa_start, Start::LineCR)?;
+            self.dfa.set_start_state(anchored, Start::LineCR, id);
+            if is_new {
+                dfa_state_ids.push(id);
+            }
+
+            let (id, is_new) =
+                self.add_one_start(nfa_start, Start::CustomLineTerminator)?;
+            self.dfa.set_start_state(
+                anchored,
+                Start::CustomLineTerminator,
+                id,
+            );
+            if is_new {
+                dfa_state_ids.push(id);
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Add a new DFA start state corresponding to the given starting NFA
+    /// state, and the starting search configuration. (The starting search
+    /// configuration essentially tells us which look-behind assertions are
+    /// true for this particular state.)
+    ///
+    /// The boolean returned indicates whether the state ID returned is a newly
+    /// created state, or a previously cached state.
+    fn add_one_start(
+        &mut self,
+        nfa_start: StateID,
+        start: Start,
+    ) -> Result<(StateID, bool), BuildError> {
+        // Compute the look-behind assertions that are true in this starting
+        // configuration, and the determine the epsilon closure. While
+        // computing the epsilon closure, we only follow condiional epsilon
+        // transitions that satisfy the look-behind assertions in 'look_have'.
+        let mut builder_matches = self.get_state_builder().into_matches();
+        util::determinize::set_lookbehind_from_start(
+            self.nfa,
+            &start,
+            &mut builder_matches,
+        );
+        self.sparses.set1.clear();
+        util::determinize::epsilon_closure(
+            self.nfa,
+            nfa_start,
+            builder_matches.look_have(),
+            &mut self.stack,
+            &mut self.sparses.set1,
+        );
+        let mut builder = builder_matches.into_nfa();
+        util::determinize::add_nfa_states(
+            &self.nfa,
+            &self.sparses.set1,
+            &mut builder,
+        );
+        self.maybe_add_state(builder)
+    }
+
+    /// Adds the given state to the DFA being built depending on whether it
+    /// already exists in this determinizer's cache.
+    ///
+    /// If it does exist, then the memory used by 'state' is put back into the
+    /// determinizer and the previously created state's ID is returned. (Along
+    /// with 'false', indicating that no new state was added.)
+    ///
+    /// If it does not exist, then the state is added to the DFA being built
+    /// and a fresh ID is allocated (if ID allocation fails, then an error is
+    /// returned) and returned. (Along with 'true', indicating that a new state
+    /// was added.)
+    fn maybe_add_state(
+        &mut self,
+        builder: StateBuilderNFA,
+    ) -> Result<(StateID, bool), BuildError> {
+        if let Some(&cached_id) = self.cache.get(builder.as_bytes()) {
+            // Since we have a cached state, put the constructed state's
+            // memory back into our scratch space, so that it can be reused.
+            self.put_state_builder(builder);
+            return Ok((cached_id, false));
+        }
+        self.add_state(builder).map(|sid| (sid, true))
+    }
+
+    /// Add the given state to the DFA and make it available in the cache.
+    ///
+    /// The state initially has no transitions. That is, it transitions to the
+    /// dead state for all possible inputs, and transitions to the quit state
+    /// for all quit bytes.
+    ///
+    /// If adding the state would exceed the maximum value for StateID, then an
+    /// error is returned.
+    fn add_state(
+        &mut self,
+        builder: StateBuilderNFA,
+    ) -> Result<StateID, BuildError> {
+        let id = self.dfa.add_empty_state()?;
+        if !self.config.quit.is_empty() {
+            for b in self.config.quit.iter() {
+                self.dfa.set_transition(
+                    id,
+                    alphabet::Unit::u8(b),
+                    self.dfa.quit_id(),
+                );
+            }
+        }
+        let state = builder.to_state();
+        // States use reference counting internally, so we only need to count
+        // their memory usage once.
+        self.memory_usage_state += state.memory_usage();
+        self.builder_states.push(state.clone());
+        self.cache.insert(state, id);
+        self.put_state_builder(builder);
+        if let Some(limit) = self.config.dfa_size_limit {
+            if self.dfa.memory_usage() > limit {
+                return Err(BuildError::dfa_exceeded_size_limit(limit));
+            }
+        }
+        if let Some(limit) = self.config.determinize_size_limit {
+            if self.memory_usage() > limit {
+                return Err(BuildError::determinize_exceeded_size_limit(
+                    limit,
+                ));
+            }
+        }
+        Ok(id)
+    }
+
+    /// Returns a state builder from this determinizer that might have existing
+    /// capacity. This helps avoid allocs in cases where a state is built that
+    /// turns out to already be cached.
+    ///
+    /// Callers must put the state builder back with 'put_state_builder',
+    /// otherwise the allocation reuse won't work.
+    fn get_state_builder(&mut self) -> StateBuilderEmpty {
+        core::mem::replace(
+            &mut self.scratch_state_builder,
+            StateBuilderEmpty::new(),
+        )
+    }
+
+    /// Puts the given state builder back into this determinizer for reuse.
+    ///
+    /// Note that building a 'State' from a builder always creates a new
+    /// alloc, so callers should always put the builder back.
+    fn put_state_builder(&mut self, builder: StateBuilderNFA) {
+        let _ = core::mem::replace(
+            &mut self.scratch_state_builder,
+            builder.clear(),
+        );
+    }
+
+    /// Return the memory usage, in bytes, of this determinizer at the current
+    /// point in time. This does not include memory used by the NFA or the
+    /// dense DFA itself.
+    fn memory_usage(&self) -> usize {
+        use core::mem::size_of;
+
+        self.builder_states.len() * size_of::<State>()
+        // Maps likely use more memory than this, but it's probably close.
+        + self.cache.len() * (size_of::<State>() + size_of::<StateID>())
+        + self.memory_usage_state
+        + self.stack.capacity() * size_of::<StateID>()
+        + self.scratch_state_builder.capacity()
+    }
+}