| // invert.h |
| |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| // |
| // Copyright 2005-2010 Google, Inc. |
| // Author: riley@google.com (Michael Riley) |
| // |
| // \file |
| // Functions and classes to invert an Fst. |
| |
| #ifndef FST_LIB_INVERT_H__ |
| #define FST_LIB_INVERT_H__ |
| |
| #include <fst/arc-map.h> |
| #include <fst/mutable-fst.h> |
| |
| |
| namespace fst { |
| |
| // Mapper to implement inversion of an arc. |
| template <class A> struct InvertMapper { |
| InvertMapper() {} |
| |
| A operator()(const A &arc) { |
| return A(arc.olabel, arc.ilabel, arc.weight, arc.nextstate); |
| } |
| |
| MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; } |
| |
| MapSymbolsAction InputSymbolsAction() const { return MAP_CLEAR_SYMBOLS; } |
| |
| MapSymbolsAction OutputSymbolsAction() const { return MAP_CLEAR_SYMBOLS;} |
| |
| uint64 Properties(uint64 props) { return InvertProperties(props); } |
| }; |
| |
| |
| // Inverts the transduction corresponding to an FST by exchanging the |
| // FST's input and output labels. This version modifies its input. |
| // |
| // Complexity: |
| // - Time: O(V + E) |
| // - Space: O(1) |
| // where V = # of states and E = # of arcs. |
| template<class Arc> inline |
| void Invert(MutableFst<Arc> *fst) { |
| SymbolTable *input = fst->InputSymbols() ? fst->InputSymbols()->Copy() : 0; |
| SymbolTable *output = fst->OutputSymbols() ? fst->OutputSymbols()->Copy() : 0; |
| ArcMap(fst, InvertMapper<Arc>()); |
| fst->SetInputSymbols(output); |
| fst->SetOutputSymbols(input); |
| delete input; |
| delete output; |
| } |
| |
| |
| // Inverts the transduction corresponding to an FST by exchanging the |
| // FST's input and output labels. This version is a delayed Fst. |
| // |
| // Complexity: |
| // - Time: O(v + e) |
| // - Space: O(1) |
| // where v = # of states visited, e = # of arcs visited. Constant |
| // time and to visit an input state or arc is assumed and exclusive |
| // of caching. |
| template <class A> |
| class InvertFst : public ArcMapFst<A, A, InvertMapper<A> > { |
| public: |
| typedef A Arc; |
| typedef InvertMapper<A> C; |
| typedef ArcMapFstImpl< A, A, InvertMapper<A> > Impl; |
| using ImplToFst<Impl>::GetImpl; |
| |
| explicit InvertFst(const Fst<A> &fst) : ArcMapFst<A, A, C>(fst, C()) { |
| GetImpl()->SetOutputSymbols(fst.InputSymbols()); |
| GetImpl()->SetInputSymbols(fst.OutputSymbols()); |
| } |
| |
| // See Fst<>::Copy() for doc. |
| InvertFst(const InvertFst<A> &fst, bool safe = false) |
| : ArcMapFst<A, A, C>(fst, safe) {} |
| |
| // Get a copy of this InvertFst. See Fst<>::Copy() for further doc. |
| virtual InvertFst<A> *Copy(bool safe = false) const { |
| return new InvertFst(*this, safe); |
| } |
| }; |
| |
| |
| // Specialization for InvertFst. |
| template <class A> |
| class StateIterator< InvertFst<A> > |
| : public StateIterator< ArcMapFst<A, A, InvertMapper<A> > > { |
| public: |
| explicit StateIterator(const InvertFst<A> &fst) |
| : StateIterator< ArcMapFst<A, A, InvertMapper<A> > >(fst) {} |
| }; |
| |
| |
| // Specialization for InvertFst. |
| template <class A> |
| class ArcIterator< InvertFst<A> > |
| : public ArcIterator< ArcMapFst<A, A, InvertMapper<A> > > { |
| public: |
| ArcIterator(const InvertFst<A> &fst, typename A::StateId s) |
| : ArcIterator< ArcMapFst<A, A, InvertMapper<A> > >(fst, s) {} |
| }; |
| |
| |
| // Useful alias when using StdArc. |
| typedef InvertFst<StdArc> StdInvertFst; |
| |
| } // namespace fst |
| |
| #endif // FST_LIB_INVERT_H__ |