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// arcsort.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 sort arcs in an FST.
#ifndef FST_LIB_ARCSORT_H__
#define FST_LIB_ARCSORT_H__
#include <algorithm>
#include <string>
#include <vector>
using std::vector;
#include <fst/cache.h>
#include <fst/state-map.h>
#include <fst/test-properties.h>
namespace fst {
template <class Arc, class Compare>
class ArcSortMapper {
public:
typedef Arc FromArc;
typedef Arc ToArc;
typedef typename Arc::StateId StateId;
typedef typename Arc::Weight Weight;
ArcSortMapper(const Fst<Arc> &fst, const Compare &comp)
: fst_(fst), comp_(comp), i_(0) {}
// Allows updating Fst argument; pass only if changed.
ArcSortMapper(const ArcSortMapper<Arc, Compare> &mapper,
const Fst<Arc> *fst = 0)
: fst_(fst ? *fst : mapper.fst_), comp_(mapper.comp_), i_(0) {}
StateId Start() { return fst_.Start(); }
Weight Final(StateId s) const { return fst_.Final(s); }
void SetState(StateId s) {
i_ = 0;
arcs_.clear();
arcs_.reserve(fst_.NumArcs(s));
for (ArcIterator< Fst<Arc> > aiter(fst_, s); !aiter.Done(); aiter.Next())
arcs_.push_back(aiter.Value());
sort(arcs_.begin(), arcs_.end(), comp_);
}
bool Done() const { return i_ >= arcs_.size(); }
const Arc &Value() const { return arcs_[i_]; }
void Next() { ++i_; }
MapSymbolsAction InputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
MapSymbolsAction OutputSymbolsAction() const { return MAP_COPY_SYMBOLS; }
uint64 Properties(uint64 props) const { return comp_.Properties(props); }
private:
const Fst<Arc> &fst_;
const Compare &comp_;
vector<Arc> arcs_;
ssize_t i_; // current arc position
void operator=(const ArcSortMapper<Arc, Compare> &); // disallow
};
// Sorts the arcs in an FST according to function object 'comp' of
// type Compare. This version modifies its input. Comparison function
// objects ILabelCompare and OLabelCompare are provived by the
// library. In general, Compare must meet the requirements for an STL
// sort comparision function object. It must also have a member
// Properties(uint64) that specifies the known properties of the
// sorted FST; it takes as argument the input FST's known properties
// before the sort.
//
// Complexity:
// - Time: O(V D log D)
// - Space: O(D)
// where V = # of states and D = maximum out-degree.
template<class Arc, class Compare>
void ArcSort(MutableFst<Arc> *fst, Compare comp) {
ArcSortMapper<Arc, Compare> mapper(*fst, comp);
StateMap(fst, mapper);
}
typedef CacheOptions ArcSortFstOptions;
// Sorts the arcs in an FST according to function object 'comp' of
// type Compare. This version is a delayed Fst. Comparsion function
// objects ILabelCompare and OLabelCompare are provided by the
// library. In general, Compare must meet the requirements for an STL
// comparision function object (e.g. as used for STL sort). It must
// also have a member Properties(uint64) that specifies the known
// properties of the sorted FST; it takes as argument the input FST's
// known properties.
//
// Complexity:
// - Time: O(v d log d)
// - Space: O(d)
// where v = # of states visited, d = maximum out-degree of states
// visited. Constant time and space to visit an input state is assumed
// and exclusive of caching.
template <class A, class C>
class ArcSortFst : public StateMapFst<A, A, ArcSortMapper<A, C> > {
public:
typedef A Arc;
typedef ArcSortMapper<A, C> M;
ArcSortFst(const Fst<A> &fst, const C &comp)
: StateMapFst<A, A, M>(fst, ArcSortMapper<A, C>(fst, comp)) {}
ArcSortFst(const Fst<A> &fst, const C &comp, const ArcSortFstOptions &opts)
: StateMapFst<A, A, M>(fst, ArcSortMapper<A, C>(fst, comp), opts) {}
// See Fst<>::Copy() for doc.
ArcSortFst(const ArcSortFst<A, C> &fst, bool safe = false)
: StateMapFst<A, A, M>(fst, safe) {}
// Get a copy of this ArcSortFst. See Fst<>::Copy() for further doc.
virtual ArcSortFst<A, C> *Copy(bool safe = false) const {
return new ArcSortFst(*this, safe);
}
};
// Specialization for ArcSortFst.
template <class A, class C>
class StateIterator< ArcSortFst<A, C> >
: public StateIterator< StateMapFst<A, A, ArcSortMapper<A, C> > > {
public:
explicit StateIterator(const ArcSortFst<A, C> &fst)
: StateIterator< StateMapFst<A, A, ArcSortMapper<A, C> > >(fst) {}
};
// Specialization for ArcSortFst.
template <class A, class C>
class ArcIterator< ArcSortFst<A, C> >
: public ArcIterator< StateMapFst<A, A, ArcSortMapper<A, C> > > {
public:
ArcIterator(const ArcSortFst<A, C> &fst, typename A::StateId s)
: ArcIterator< StateMapFst<A, A, ArcSortMapper<A, C> > >(fst, s) {}
};
// Compare class for comparing input labels of arcs.
template<class A> class ILabelCompare {
public:
bool operator() (A arc1, A arc2) const {
return arc1.ilabel < arc2.ilabel;
}
uint64 Properties(uint64 props) const {
return (props & kArcSortProperties) | kILabelSorted |
(props & kAcceptor ? kOLabelSorted : 0);
}
};
// Compare class for comparing output labels of arcs.
template<class A> class OLabelCompare {
public:
bool operator() (const A &arc1, const A &arc2) const {
return arc1.olabel < arc2.olabel;
}
uint64 Properties(uint64 props) const {
return (props & kArcSortProperties) | kOLabelSorted |
(props & kAcceptor ? kILabelSorted : 0);
}
};
// Useful aliases when using StdArc.
template<class C> class StdArcSortFst : public ArcSortFst<StdArc, C> {
public:
typedef StdArc Arc;
typedef C Compare;
};
typedef ILabelCompare<StdArc> StdILabelCompare;
typedef OLabelCompare<StdArc> StdOLabelCompare;
} // namespace fst
#endif // FST_LIB_ARCSORT_H__
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