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      1 // expanded-fst.h
      2 //
      3 // Licensed under the Apache License, Version 2.0 (the "License");
      4 // you may not use this file except in compliance with the License.
      5 // You may obtain a copy of the License at
      6 //
      7 //      http://www.apache.org/licenses/LICENSE-2.0
      8 //
      9 // Unless required by applicable law or agreed to in writing, software
     10 // distributed under the License is distributed on an "AS IS" BASIS,
     11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     12 // See the License for the specific language governing permissions and
     13 // limitations under the License.
     14 //
     15 //
     16 // \file
     17 // Generic FST augmented with state count - interface class definition.
     18 
     19 #ifndef FST_LIB_EXPANDED_FST_H__
     20 #define FST_LIB_EXPANDED_FST_H__
     21 
     22 #include "fst/lib/fst.h"
     23 
     24 namespace fst {
     25 
     26 // A generic FST plus state count.
     27 template <class A>
     28 class ExpandedFst : public Fst<A> {
     29  public:
     30   typedef A Arc;
     31   typedef typename A::StateId StateId;
     32 
     33   virtual StateId NumStates() const = 0;  // State count
     34 
     35   // Get a copy of this ExpandedFst.
     36   virtual ExpandedFst<A> *Copy() const = 0;
     37   // Read an ExpandedFst from an input stream; return NULL on error.
     38   static ExpandedFst<A> *Read(istream &strm, const FstReadOptions &opts) {
     39     FstReadOptions ropts(opts);
     40     FstHeader hdr;
     41     if (ropts.header)
     42       hdr = *opts.header;
     43     else {
     44       if (!hdr.Read(strm, opts.source))
     45         return 0;
     46       ropts.header = &hdr;
     47     }
     48     if (!(hdr.Properties() & kExpanded)) {
     49       LOG(ERROR) << "ExpandedFst::Read: Not an ExpandedFst: " << ropts.source;
     50       return 0;
     51     }
     52     FstRegister<A> *registr = FstRegister<A>::GetRegister();
     53     const typename FstRegister<A>::Reader reader =
     54       registr->GetReader(hdr.FstType());
     55     if (!reader) {
     56       LOG(ERROR) << "ExpandedFst::Read: Unknown FST type \"" << hdr.FstType()
     57                  << "\" (arc type = \"" << A::Type()
     58                  << "\"): " << ropts.source;
     59       return 0;
     60     }
     61     Fst<A> *fst = reader(strm, ropts);
     62     if (!fst) return 0;
     63     return down_cast<ExpandedFst<A> *>(fst);
     64   }
     65   // Read an ExpandedFst from a file; return NULL on error.
     66   static ExpandedFst<A> *Read(const string &filename) {
     67     ifstream strm(filename.c_str());
     68     if (!strm) {
     69       LOG(ERROR) << "ExpandedFst::Read: Can't open file: " << filename;
     70       return 0;
     71     }
     72     return Read(strm, FstReadOptions(filename));
     73   }
     74 };
     75 
     76 // A useful alias when using StdArc.
     77 typedef ExpandedFst<StdArc> StdExpandedFst;
     78 
     79 // Function to return the number of states in an FST, counting them
     80 // if necessary.
     81 template <class Arc>
     82 typename Arc::StateId CountStates(const Fst<Arc> &fst) {
     83   if (fst.Properties(kExpanded, false)) {
     84     const ExpandedFst<Arc> *efst = down_cast<const ExpandedFst<Arc> *>(&fst);
     85     return efst->NumStates();
     86   } else {
     87     typename Arc::StateId nstates = 0;
     88     for (StateIterator< Fst<Arc> > siter(fst); !siter.Done(); siter.Next())
     89       ++nstates;
     90     return nstates;
     91   }
     92 }
     93 
     94 }  // FST_LIB_FST_H__
     95 
     96 #endif  // FST_LIB_EXPANDED_FST_H__
     97