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// complement.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
// Class to complement an Fst.
#ifndef FST_LIB_COMPLEMENT_H__
#define FST_LIB_COMPLEMENT_H__
#include <algorithm>
#include <string>
#include <vector>
using std::vector;
#include <fst/fst.h>
#include <fst/test-properties.h>
namespace fst {
template <class A> class ComplementFst;
// Implementation of delayed ComplementFst. The algorithm used
// completes the (deterministic) FSA and then exchanges final and
// non-final states. Completion, i.e. ensuring that all labels can be
// read from every state, is accomplished by using RHO labels, which
// match all labels that are otherwise not found leaving a state. The
// first state in the output is reserved to be a new state that is the
// destination of all RHO labels. Each remaining output state s
// corresponds to input state s - 1. The first arc in the output at
// these states is the rho label, the remaining arcs correspond to the
// input arcs.
template <class A>
class ComplementFstImpl : public FstImpl<A> {
public:
using FstImpl<A>::SetType;
using FstImpl<A>::SetProperties;
using FstImpl<A>::SetInputSymbols;
using FstImpl<A>::SetOutputSymbols;
friend class StateIterator< ComplementFst<A> >;
friend class ArcIterator< ComplementFst<A> >;
typedef A Arc;
typedef typename A::Label Label;
typedef typename A::Weight Weight;
typedef typename A::StateId StateId;
explicit ComplementFstImpl(const Fst<A> &fst) : fst_(fst.Copy()) {
SetType("complement");
uint64 props = fst.Properties(kILabelSorted, false);
SetProperties(ComplementProperties(props), kCopyProperties);
SetInputSymbols(fst.InputSymbols());
SetOutputSymbols(fst.OutputSymbols());
}
ComplementFstImpl(const ComplementFstImpl<A> &impl)
: fst_(impl.fst_->Copy()) {
SetType("complement");
SetProperties(impl.Properties(), kCopyProperties);
SetInputSymbols(impl.InputSymbols());
SetOutputSymbols(impl.OutputSymbols());
}
~ComplementFstImpl() { delete fst_; }
StateId Start() const {
if (Properties(kError))
return kNoStateId;
StateId start = fst_->Start();
if (start != kNoStateId)
return start + 1;
else
return 0;
}
// Exchange final and non-final states; make rho destination state final.
Weight Final(StateId s) const {
if (s == 0 || fst_->Final(s - 1) == Weight::Zero())
return Weight::One();
else
return Weight::Zero();
}
size_t NumArcs(StateId s) const {
if (s == 0)
return 1;
else
return fst_->NumArcs(s - 1) + 1;
}
size_t NumInputEpsilons(StateId s) const {
return s == 0 ? 0 : fst_->NumInputEpsilons(s - 1);
}
size_t NumOutputEpsilons(StateId s) const {
return s == 0 ? 0 : fst_->NumOutputEpsilons(s - 1);
}
uint64 Properties() const { return Properties(kFstProperties); }
// Set error if found; return FST impl properties.
uint64 Properties(uint64 mask) const {
if ((mask & kError) && fst_->Properties(kError, false))
SetProperties(kError, kError);
return FstImpl<Arc>::Properties(mask);
}
private:
const Fst<A> *fst_;
void operator=(const ComplementFstImpl<A> &fst); // Disallow
};
// Complements an automaton. This is a library-internal operation that
// introduces a (negative) 'rho' label; use Difference/DifferenceFst in
// user code, which will not see this label. This version is a delayed Fst.
//
// This class attaches interface to implementation and handles
// reference counting, delegating most methods to ImplToFst.
template <class A>
class ComplementFst : public ImplToFst< ComplementFstImpl<A> > {
public:
friend class StateIterator< ComplementFst<A> >;
friend class ArcIterator< ComplementFst<A> >;
using ImplToFst< ComplementFstImpl<A> >::GetImpl;
typedef A Arc;
typedef typename A::StateId StateId;
typedef typename A::Label Label;
typedef ComplementFstImpl<A> Impl;
explicit ComplementFst(const Fst<A> &fst)
: ImplToFst<Impl>(new Impl(fst)) {
uint64 props = kUnweighted | kNoEpsilons | kIDeterministic | kAcceptor;
if (fst.Properties(props, true) != props) {
FSTERROR() << "ComplementFst: argument not an unweighted "
<< "epsilon-free deterministic acceptor";
GetImpl()->SetProperties(kError, kError);
}
}
// See Fst<>::Copy() for doc.
ComplementFst(const ComplementFst<A> &fst, bool safe = false)
: ImplToFst<Impl>(fst, safe) {}
// Get a copy of this ComplementFst. See Fst<>::Copy() for further doc.
virtual ComplementFst<A> *Copy(bool safe = false) const {
return new ComplementFst<A>(*this, safe);
}
virtual inline void InitStateIterator(StateIteratorData<A> *data) const;
virtual inline void InitArcIterator(StateId s,
ArcIteratorData<A> *data) const;
// Label that represents the rho transition.
// We use a negative value, which is thus private to the library and
// which will preserve FST label sort order.
static const Label kRhoLabel = -2;
private:
// Makes visible to friends.
Impl *GetImpl() const { return ImplToFst<Impl>::GetImpl(); }
void operator=(const ComplementFst<A> &fst); // disallow
};
template <class A> const typename A::Label ComplementFst<A>::kRhoLabel;
// Specialization for ComplementFst.
template <class A>
class StateIterator< ComplementFst<A> > : public StateIteratorBase<A> {
public:
typedef typename A::StateId StateId;
typedef typename A::Label Label;
explicit StateIterator(const ComplementFst<A> &fst)
: siter_(*fst.GetImpl()->fst_), s_(0) {
}
bool Done() const { return s_ > 0 && siter_.Done(); }
StateId Value() const { return s_; }
void Next() {
if (s_ != 0)
siter_.Next();
++s_;
}
void Reset() {
siter_.Reset();
s_ = 0;
}
private:
// This allows base class virtual access to non-virtual derived-
// class members of the same name. It makes the derived class more
// efficient to use but unsafe to further derive.
virtual bool Done_() const { return Done(); }
virtual StateId Value_() const { return Value(); }
virtual void Next_() { Next(); }
virtual void Reset_() { Reset(); }
StateIterator< Fst<A> > siter_;
StateId s_;
DISALLOW_COPY_AND_ASSIGN(StateIterator);
};
// Specialization for ComplementFst.
template <class A>
class ArcIterator< ComplementFst<A> > : public ArcIteratorBase<A> {
public:
typedef typename A::StateId StateId;
typedef typename A::Label Label;
typedef typename A::Weight Weight;
ArcIterator(const ComplementFst<A> &fst, StateId s)
: aiter_(0), s_(s), pos_(0) {
if (s_ != 0)
aiter_ = new ArcIterator< Fst<A> >(*fst.GetImpl()->fst_, s - 1);
}
virtual ~ArcIterator() { delete aiter_; }
bool Done() const {
if (s_ != 0)
return pos_ > 0 && aiter_->Done();
else
return pos_ > 0;
}
// Adds the rho label to the rho destination state.
const A& Value() const {
if (pos_ == 0) {
arc_.ilabel = arc_.olabel = ComplementFst<A>::kRhoLabel;
arc_.weight = Weight::One();
arc_.nextstate = 0;
} else {
arc_ = aiter_->Value();
++arc_.nextstate;
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