ParameterCollector.h

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// -*- C++ -*-
//
//

// class ParameterCollector provides a tool to parse blocks of PSets
// like "PythiaParameters" where one can list blocks of vstrings to be
// parsed inside another vstring named "parameterSets".  It is also
// extended to allow nesting of blocks using "+block" statements
// (something which is heavily used for Herwig++).
// arbitrary vstring blocks can also be explicitly retrieved by name.

#ifndef gen_ParameterCollector_h
#define gen_ParameterCollector_h

#include <ostream>
#include <vector>
#include <string>
#include <map>

#include <boost/iterator/iterator_facade.hpp>

#include "FWCore/ParameterSet/interface/ParameterSet.h"

namespace gen {

  class ParameterCollector {
  public:
    ParameterCollector();
    ParameterCollector(const edm::ParameterSet &pset);
    ~ParameterCollector();

    // this iterator makes begin()/end() look like it was
    // looping over a simple vector<string>

    class const_iterator
        : public boost::iterator_facade<const_iterator, const std::string, boost::forward_traversal_tag> {
    public:
      const_iterator() : collector_(nullptr), dump_(nullptr) {}

    protected:
      friend class ParameterCollector;

      inline const_iterator(const ParameterCollector *collector,
                            std::vector<std::string>::const_iterator begin,
                            std::vector<std::string>::const_iterator end,
                            bool special = false,
                            std::ostream *dump = nullptr);

    private:
      friend class boost::iterator_core_access;

      void increment();
      const std::string &dereference() const { return cache_; }
      bool equal(const const_iterator &other) const { return iter_ == other.iter_; }

      void next();

      typedef std::pair<std::vector<std::string>::const_iterator, std::vector<std::string>::const_iterator> IterPair;

      const ParameterCollector *collector_;
      std::ostream *dump_;
      bool special_;
      std::vector<IterPair> iter_;
      std::string cache_;
    };

    // start iterating over blocks listed in "parameterSets"
    const_iterator begin() const;
    const_iterator begin(std::ostream &dump) const;

    // start iterating over contents of this particular vstring block
    const_iterator begin(const std::string &block) const;
    const_iterator begin(const std::string &block, std::ostream &dump) const;

    // the iterator to mark the end of a loop
    const_iterator end() const { return const_iterator(); }

    // this replaces ${...} with environment variables
    // needed for ThePEG because you need full path to repository
    static std::string resolve(const std::string &line);

  private:
    friend class const_iterator;

    std::map<std::string, std::vector<std::string> > contents_;
  };

}  // namespace gen

#endif  // gen_ParameterCollector_h