abstract-file-backed-feature-extractor.H

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#ifndef RERANKER_ABSTRACT_FILE_BACKED_FEATURE_EXTRACTOR_H_
#define RERANKER_ABSTRACT_FILE_BACKED_FEATURE_EXTRACTOR_H_

#include <iostream>
#include <fstream>

#include "tokenizer.H"
#include "feature-extractor.H"

namespace reranker {

using std::cout;
using std::istream;
using std::ifstream;

class AbstractFileBackedFeatureExtractor : public FeatureExtractor {
 public:
  AbstractFileBackedFeatureExtractor() : FeatureExtractor(), is_(NULL) {
  }
  virtual ~AbstractFileBackedFeatureExtractor() {
    delete is_;
  }

  virtual void RegisterInitializers(Initializers &initializers) {
    bool required = true;
    initializers.Add("filename", &filename_, required);
  }

  virtual void Init(const Environment *env, const string &arg) {
    delete is_;
    is_ = new ifstream(filename_.c_str());
  }

  virtual void Extract(Candidate &candidate,
                       FeatureVector<int,double> &features) = 0;

  virtual void ExtractSymbolic(Candidate &candidate,
                               FeatureVector<string,double> &symbolic_features)
  = 0;

  virtual void Reset() {
    delete is_;
    is_ = new ifstream(filename_.c_str());
  }


  virtual void Extract(CandidateSet &candidate_set) {
    for (CandidateSet::iterator it = candidate_set.begin();
         it != candidate_set.end();
         ++it) {
      Candidate &candidate = *(*it);
      ReadFromStream();
      Extract(candidate, candidate.mutable_features());
      ExtractSymbolic(candidate, candidate.mutable_symbolic_features());
    }
  }

  virtual long line_number() const { return line_number_; }

 protected:
  virtual void ReadFromStream() {
    // TODO(dbikel): Do error checking here for is_->good().
    //               Emit massive warnings when something goes wrong.
    // TODO(dbikel): Keep track of number of lines read.
    if (is_->good()) {
      getline(*is_, line_);
      ++line_number_;
    } else {
      cerr << "AbstractFileBackedFeatureExtractor: error: no more input\n"
           << "\t(number of lines read so far: " << line_number_ << ")" << endl;
    }
  }

  // data members
  string filename_;
  istream *is_;
  string line_;
  long line_number_;
  Tokenizer tokenizer_;
};

}  // namespace reranker

#endif