/usr/include/fst/symbol-table-ops.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 | // See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
#ifndef FST_LIB_SYMBOL_TABLE_OPS_H_
#define FST_LIB_SYMBOL_TABLE_OPS_H_
#include <string>
#include <unordered_set>
#include <vector>
#include <fst/fst.h>
#include <fst/symbol-table.h>
namespace fst {
// Returns a minimal symbol table containing only symbols referenced by the
// passed fst. Symbols preserve their original numbering, so fst does not
// require relabeling.
template <class Arc>
SymbolTable *PruneSymbolTable(const Fst<Arc> &fst, const SymbolTable &syms,
bool input) {
std::unordered_set<typename Arc::Label> seen;
seen.insert(0); // Always keep epsilon.
for (StateIterator<Fst<Arc>> siter(fst); !siter.Done(); siter.Next()) {
for (ArcIterator<Fst<Arc>> aiter(fst, siter.Value()); !aiter.Done();
aiter.Next()) {
const auto sym = (input) ? aiter.Value().ilabel : aiter.Value().olabel;
seen.insert(sym);
}
}
auto *pruned = new SymbolTable(syms.Name() + "_pruned");
for (SymbolTableIterator stiter(syms); !stiter.Done(); stiter.Next()) {
const auto label = stiter.Value();
if (seen.count(label)) pruned->AddSymbol(stiter.Symbol(), label);
}
return pruned;
}
// Relabels a symbol table to make it a contiguous mapping.
SymbolTable *CompactSymbolTable(const SymbolTable &syms);
// Merges two SymbolTables, all symbols from left will be merged into right
// with the same ids. Symbols in right that have conflicting ids with those
// in left will be assigned to value assigned from the left SymbolTable.
// The returned symbol table will never modify symbol assignments from the left
// side, but may do so on the right. If right_relabel_output is non-NULL, it
// will be assigned true if the symbols from the right table needed to be
// reassigned.
// A potential use case is to Compose two Fst's that have different symbol
// tables. You can reconcile them in the following way:
// Fst<Arc> a, b;
// bool relabel;
// std::unique_ptr<SymbolTable> bnew(MergeSymbolTable(a.OutputSymbols(),
// b.InputSymbols(), &relabel);
// if (relabel) {
// Relabel(b, bnew.get(), nullptr);
// }
// b.SetInputSymbols(bnew);
SymbolTable *MergeSymbolTable(const SymbolTable &left, const SymbolTable &right,
bool *right_relabel_output = nullptr);
// Read the symbol table from any Fst::Read()able file, without loading the
// corresponding Fst. Returns nullptr if the Fst does not contain a symbol
// table or the symbol table cannot be read.
SymbolTable *FstReadSymbols(const string &filename, bool input);
// Adds a contiguous range of symbols to a symbol table using a simple prefix
// for the string, returning false if the inserted symbol string clashes with
// any currently present.
bool AddAuxiliarySymbols(const string &prefix, int64 start_label,
int64 nlabels, SymbolTable *syms);
} // namespace fst
#endif // FST_LIB_SYMBOL_TABLE_OPS_H_
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