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// concat.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 compute the concat of two FSTs.
#ifndef FST_LIB_CONCAT_H__
#define FST_LIB_CONCAT_H__
#include <vector>
using std::vector;
#include <algorithm>
#include <fst/mutable-fst.h>
#include <fst/rational.h>
namespace fst {
// Computes the concatenation (product) of two FSTs. If FST1
// transduces string x to y with weight a and FST2 transduces string w
// to v with weight b, then their concatenation transduces string xw
// to yv with Times(a, b).
//
// This version modifies its MutableFst argument (in first position).
//
// Complexity:
// - Time: O(V1 + V2 + E2)
// - Space: O(V1 + V2 + E2)
// where Vi = # of states and Ei = # of arcs of the ith FST.
//
template<class Arc>
void Concat(MutableFst<Arc> *fst1, const Fst<Arc> &fst2) {
typedef typename Arc::StateId StateId;
typedef typename Arc::Label Label;
typedef typename Arc::Weight Weight;
// TODO(riley): restore when voice actions issues fixed
// Check that the symbol table are compatible
if (!CompatSymbols(fst1->InputSymbols(), fst2.InputSymbols()) ||
!CompatSymbols(fst1->OutputSymbols(), fst2.OutputSymbols())) {
LOG(ERROR) << "Concat: input/output symbol tables of 1st argument "
<< "do not match input/output symbol tables of 2nd argument";
// fst1->SetProperties(kError, kError);
// return;
}
uint64 props1 = fst1->Properties(kFstProperties, false);
uint64 props2 = fst2.Properties(kFstProperties, false);
StateId start1 = fst1->Start();
if (start1 == kNoStateId) {
if (props2 & kError) fst1->SetProperties(kError, kError);
return;
}
StateId numstates1 = fst1->NumStates();
if (fst2.Properties(kExpanded, false))
fst1->ReserveStates(numstates1 + CountStates(fst2));
for (StateIterator< Fst<Arc> > siter2(fst2);
!siter2.Done();
siter2.Next()) {
StateId s1 = fst1->AddState();
StateId s2 = siter2.Value();
fst1->SetFinal(s1, fst2.Final(s2));
fst1->ReserveArcs(s1, fst2.NumArcs(s2));
for (ArcIterator< Fst<Arc> > aiter(fst2, s2);
!aiter.Done();
aiter.Next()) {
Arc arc = aiter.Value();
arc.nextstate += numstates1;
fst1->AddArc(s1, arc);
}
}
StateId start2 = fst2.Start();
for (StateId s1 = 0; s1 < numstates1; ++s1) {
Weight final = fst1->Final(s1);
if (final != Weight::Zero()) {
fst1->SetFinal(s1, Weight::Zero());
if (start2 != kNoStateId)
fst1->AddArc(s1, Arc(0, 0, final, start2 + numstates1));
}
}
if (start2 != kNoStateId)
fst1->SetProperties(ConcatProperties(props1, props2), kFstProperties);
}
// Computes the concatentation of two FSTs. This version modifies its
// MutableFst argument (in second position).
//
// Complexity:
// - Time: O(V1 + E1)
// - Space: O(V1 + E1)
// where Vi = # of states and Ei = # of arcs of the ith FST.
//
template<class Arc>
void Concat(const Fst<Arc> &fst1, MutableFst<Arc> *fst2) {
typedef typename Arc::StateId StateId;
typedef typename Arc::Label Label;
typedef typename Arc::Weight Weight;
// Check that the symbol table are compatible
if (!CompatSymbols(fst1.InputSymbols(), fst2->InputSymbols()) ||
!CompatSymbols(fst1.OutputSymbols(), fst2->OutputSymbols())) {
LOG(ERROR) << "Concat: input/output symbol tables of 1st argument "
<< "do not match input/output symbol tables of 2nd argument";
// fst2->SetProperties(kError, kError);
// return;
}
uint64 props1 = fst1.Properties(kFstProperties, false);
uint64 props2 = fst2->Properties(kFstProperties, false);
StateId start2 = fst2->Start();
if (start2 == kNoStateId) {
if (props1 & kError) fst2->SetProperties(kError, kError);
return;
}
StateId numstates2 = fst2->NumStates();
if (fst1.Properties(kExpanded, false))
fst2->ReserveStates(numstates2 + CountStates(fst1));
for (StateIterator< Fst<Arc> > siter(fst1);
!siter.Done();
siter.Next()) {
StateId s1 = siter.Value();
StateId s2 = fst2->AddState();
Weight final = fst1.Final(s1);
fst2->ReserveArcs(s2, fst1.NumArcs(s1) + (final != Weight::Zero() ? 1 : 0));
if (final != Weight::Zero())
fst2->AddArc(s2, Arc(0, 0, final, start2));
for (ArcIterator< Fst<Arc> > aiter(fst1, s1);
!aiter.Done();
aiter.Next()) {
Arc arc = aiter.Value();
arc.nextstate += numstates2;
fst2->AddArc(s2, arc);
}
}
StateId start1 = fst1.Start();
fst2->SetStart(start1 == kNoStateId ? fst2->AddState() : start1 + numstates2);
if (start1 != kNoStateId)
fst2->SetProperties(ConcatProperties(props1, props2), kFstProperties);
}
// Computes the concatentation of two FSTs. This version modifies its
// RationalFst input (in first position).
template<class Arc>
void Concat(RationalFst<Arc> *fst1, const Fst<Arc> &fst2) {
fst1->GetImpl()->AddConcat(fst2, true);
}
// Computes the concatentation of two FSTs. This version modifies its
// RationalFst input (in second position).
template<class Arc>
void Concat(const Fst<Arc> &fst1, RationalFst<Arc> *fst2) {
fst2->GetImpl()->AddConcat(fst1, false);
}
typedef RationalFstOptions ConcatFstOptions;
// Computes the concatenation (product) of two FSTs; this version is a
// delayed Fst. If FST1 transduces string x to y with weight a and FST2
// transduces string w to v with weight b, then their concatenation
// transduces string xw to yv with Times(a, b).
//
// Complexity:
// - Time: O(v1 + e1 + v2 + e2),
// - Space: O(v1 + v2)
// where vi = # of states visited and ei = # of arcs visited of the
// ith FST. Constant time and space to visit an input state or arc is
// assumed and exclusive of caching.
template <class A>
class ConcatFst : public RationalFst<A> {
public:
using ImplToFst< RationalFstImpl<A> >::GetImpl;
typedef A Arc;
typedef typename A::Weight Weight;
typedef typename A::StateId StateId;
ConcatFst(const Fst<A> &fst1, const Fst<A> &fst2) {
GetImpl()->InitConcat(fst1, fst2);
}
ConcatFst(const Fst<A> &fst1, const Fst<A> &fst2,
const ConcatFstOptions &opts) : RationalFst<A>(opts) {
GetImpl()->InitConcat(fst1, fst2);
}
// See Fst<>::Copy() for doc.
ConcatFst(const ConcatFst<A> &fst, bool safe = false)
: RationalFst<A>(fst, safe) {}
// Get a copy of this ConcatFst. See Fst<>::Copy() for further doc.
virtual ConcatFst<A> *Copy(bool safe = false) const {
return new ConcatFst<A>(*this, safe);
}
};
// Specialization for ConcatFst.
template <class A>
class StateIterator< ConcatFst<A> > : public StateIterator< RationalFst<A> > {
public:
explicit StateIterator(const ConcatFst<A> &fst)
: StateIterator< RationalFst<A> >(fst) {}
};
// Specialization for ConcatFst.
template <class A>
class ArcIterator< ConcatFst<A> > : public ArcIterator< RationalFst<A> > {
public:
typedef typename A::StateId StateId;
ArcIterator(const ConcatFst<A> &fst, StateId s)
: ArcIterator< RationalFst<A> >(fst, s) {}
};
// Useful alias when using StdArc.
typedef ConcatFst<StdArc> StdConcatFst;
} // namespace fst
#endif // FST_LIB_CONCAT_H__
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