This file is indexed.

/usr/include/fst/state-reachable.h is in libfst-dev 1.6.3-2.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
//
// Class to determine whether a given (final) state can be reached from some
// other given state.

#ifndef FST_LIB_STATE_REACHABLE_H_
#define FST_LIB_STATE_REACHABLE_H_

#include <vector>

#include <fst/log.h>

#include <fst/connect.h>
#include <fst/dfs-visit.h>
#include <fst/fst.h>
#include <fst/interval-set.h>
#include <fst/vector-fst.h>


namespace fst {

// Computes the (final) states reachable from a given state in an FST. After
// this visitor has been called, a final state f can be reached from a state
// s iff (*isets)[s].Member(state2index[f]) is true, where (*isets[s]) is a
// set of half-open inteval of final state indices and state2index[f] maps from
// a final state to its index. If state2index is empty, it is filled-in with
// suitable indices. If it is non-empty, those indices are used; in this case,
// the final states must have out-degree 0.
template <class Arc, class I = typename Arc::StateId, class S = IntervalSet<I>>
class IntervalReachVisitor {
 public:
  using Label = typename Arc::Label;
  using StateId = typename Arc::StateId;
  using Weight = typename Arc::Weight;

  using Index = I;
  using ISet = S;
  using Interval = typename ISet::Interval;

  IntervalReachVisitor(const Fst<Arc> &fst, std::vector<S> *isets,
                       std::vector<Index> *state2index)
      : fst_(fst),
        isets_(isets),
        state2index_(state2index),
        index_(state2index->empty() ? 1 : -1),
        error_(false) {
    isets_->clear();
  }

  void InitVisit(const Fst<Arc> &) { error_ = false; }

  bool InitState(StateId s, StateId r) {
    while (isets_->size() <= s) isets_->push_back(S());
    while (state2index_->size() <= s) state2index_->push_back(-1);
    if (fst_.Final(s) != Weight::Zero()) {
      // Create tree interval.
      auto *intervals = (*isets_)[s].MutableIntervals();
      if (index_ < 0) {  // Uses state2index_ map to set index.
        if (fst_.NumArcs(s) > 0) {
          FSTERROR() << "IntervalReachVisitor: state2index map must be empty "
                     << "for this FST";
          error_ = true;
          return false;
        }
        const auto index = (*state2index_)[s];
        if (index < 0) {
          FSTERROR() << "IntervalReachVisitor: state2index map incomplete";
          error_ = true;
          return false;
        }
        intervals->push_back(Interval(index, index + 1));
      } else {  // Use pre-order index.
        intervals->push_back(Interval(index_, index_ + 1));
        (*state2index_)[s] = index_++;
      }
    }
    return true;
  }

  constexpr bool TreeArc(StateId, const Arc &) const { return true; }

  bool BackArc(StateId s, const Arc &arc) {
    FSTERROR() << "IntervalReachVisitor: Cyclic input";
    error_ = true;
    return false;
  }

  bool ForwardOrCrossArc(StateId s, const Arc &arc) {
    // Non-tree interval.
    (*isets_)[s].Union((*isets_)[arc.nextstate]);
    return true;
  }

  void FinishState(StateId s, StateId p, const Arc *) {
    if (index_ >= 0 && fst_.Final(s) != Weight::Zero()) {
      auto *intervals = (*isets_)[s].MutableIntervals();
      (*intervals)[0].end = index_;  // Updates tree interval end.
    }
    (*isets_)[s].Normalize();
    if (p != kNoStateId) {
      (*isets_)[p].Union((*isets_)[s]);  // Propagates intervals to parent.
    }
  }

  void FinishVisit() {}

  bool Error() const { return error_; }

 private:
  const Fst<Arc> &fst_;
  std::vector<ISet> *isets_;
  std::vector<Index> *state2index_;
  Index index_;
  bool error_;
};

// Tests reachability of final states from a given state. To test for
// reachability from a state s, first do SetState(s). Then a final state f can
// be reached from state s of FST iff Reach(f) is true. The input can be cyclic,
// but no cycle may contain a final state.
template <class Arc, class I = typename Arc::StateId, class S = IntervalSet<I>>
class StateReachable {
 public:
  using Label = typename Arc::Label;
  using StateId = typename Arc::StateId;
  using Weight = typename Arc::Weight;

  using Index = I;
  using ISet = S;
  using Interval = typename ISet::Interval;

  explicit StateReachable(const Fst<Arc> &fst) : error_(false) {
    if (fst.Properties(kAcyclic, true)) {
      AcyclicStateReachable(fst);
    } else {
      CyclicStateReachable(fst);
    }
  }

  explicit StateReachable(const StateReachable<Arc> &reachable) {
    FSTERROR() << "Copy constructor for state reachable class "
               << "not implemented.";
    error_ = true;
  }

  // Sets current state.
  void SetState(StateId s) { s_ = s; }

  // Can reach this final state from current state?
  bool Reach(StateId s) {
    if (s >= state2index_.size()) return false;
    const auto i = state2index_[s];
    if (i < 0) {
      FSTERROR() << "StateReachable: State non-final: " << s;
      error_ = true;
      return false;
    }
    return isets_[s_].Member(i);
  }

  // Access to the state-to-index mapping. Unassigned states have index -1.
  std::vector<Index> &State2Index() { return state2index_; }

  // Access to the interval sets. These specify the reachability to the final
  // states as intervals of the final state indices.
  const std::vector<ISet> &IntervalSets() { return isets_; }

  bool Error() const { return error_; }

 private:
  void AcyclicStateReachable(const Fst<Arc> &fst) {
    IntervalReachVisitor<Arc, StateId, ISet> reach_visitor(fst, &isets_,
                                                           &state2index_);
    DfsVisit(fst, &reach_visitor);
    if (reach_visitor.Error()) error_ = true;
  }

  void CyclicStateReachable(const Fst<Arc> &fst) {
    // Finds state reachability on the acyclic condensation FST.
    VectorFst<Arc> cfst;
    std::vector<StateId> scc;
    Condense(fst, &cfst, &scc);
    StateReachable reachable(cfst);
    if (reachable.Error()) {
      error_ = true;
      return;
    }
    // Gets the number of states per SCC.
    std::vector<size_t> nscc;
    for (StateId s = 0; s < scc.size(); ++s) {
      const auto c = scc[s];
      while (c >= nscc.size()) nscc.push_back(0);
      ++nscc[c];
    }
    // Constructs the interval sets and state index mapping for the original
    // FST from the condensation FST.
    state2index_.resize(scc.size(), -1);
    isets_.resize(scc.size());
    for (StateId s = 0; s < scc.size(); ++s) {
      const auto c = scc[s];
      isets_[s] = reachable.IntervalSets()[c];
      state2index_[s] = reachable.State2Index()[c];
      // Checks that each final state in an input FST is not contained in a
      // cycle (i.e., not in a non-trivial SCC).
      if (cfst.Final(c) != Weight::Zero() && nscc[c] > 1) {
        FSTERROR() << "StateReachable: Final state contained in a cycle";
        error_ = true;
        return;
      }
    }
  }

  StateId s_;                       // Current state.
  std::vector<ISet> isets_;         // Interval sets per state.
  std::vector<Index> state2index_;  // Finds index for a final state.
  bool error_;

  StateReachable &operator=(const StateReachable &) = delete;
};

}  // namespace fst

#endif  // FST_LIB_STATE_REACHABLE_H_