search.hxx

// search.hxx: this file is part of the Vaucanson project.
//
// Vaucanson, a generic library for finite state machines.
//
// Copyright (C) 2001, 2002, 2003, 2004, 2005 The Vaucanson Group.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// The complete GNU General Public Licence Notice can be found as the
// `COPYING' file in the root directory.
//
// The Vaucanson Group consists of people listed in the `AUTHORS' file.
//
#ifndef VCSN_ALGORITHMS_SEARCH_HXX
# define VCSN_ALGORITHMS_SEARCH_HXX

# include <vaucanson/algorithms/search.hh>

# include <vaucanson/misc/window.hh>
# include <vaucanson/misc/bitset.hh>

# include <vector>

namespace vcsn {

  template <class InputIterator, class FoundFunctor, class Series, class T>
  void
  search(const Element<Automata<Series>, T>& a,
         const InputIterator& begin,
         const InputIterator& end,
         typename Element<Automata<Series>, T>::letter_t eol,
         FoundFunctor& f)
  {
    FindBestSearch::search(a, begin, end, eol, f);
  }

  template <class InputIterator, class FoundFunctor, class Series, class T>
  void
  FindBestSearch::search(const Element<Automata<Series>, T>& a,
                         const InputIterator& begin,
                         const InputIterator& end,
                         typename Element<Automata<Series>, T>::
                         letter_t eol,
                         FoundFunctor& f)
  {
    WindowedBackSearch::search(a, begin, end, eol, f);
  }

  template <class Series, class T, class StatesSet>
  static
  unsigned int
  compute_distances(const Element<Automata<Series>, T>& a,
                    std::vector<StatesSet>& distances)
  {
    precondition(a.initial().size() > 0);
    precondition(a.final().size() > 0);
    precondition(distances.size() == 0);

    // Typedefs.
    typedef typename vcsn::Element<Automata<Series>, T> automaton_t;
    AUTOMATON_TYPES(automaton_t);

    // Code.
    StatesSet           s_new (a.states().max() + 1);
    StatesSet           s_old (a.states().max() + 1);
    unsigned int        i = 0;

    s_old.insert(a.initial().begin(), a.initial().end());
    for (bool get_out = false; !get_out; ++i)
      {
        s_new.clear();
        distances.push_back(s_old);
        if (i > 0)
          distances[i].insert(distances[i - 1].begin(),
                              distances[i - 1].end());
        for (typename StatesSet::const_iterator s = s_old.begin();
             s != s_old.end();
             ++s)
          {
            if (a.is_final(*s))
              // FIXME: Could be optimized with a return i, but code
              // is easier to read this way.
              get_out = true;
            a.deltac(s_new, *s, delta_kind::states());
          }
        std::swap(s_new, s_old);
      }

    postcondition(i == distances.size());
    return i - 1;
  }

  template <class InputIterator, class Series, class T, class StatesSet>
  static
  std::pair<bool, unsigned int>
  window_backsearch(const utility::Window<InputIterator,
                    typename Element<Automata<Series>, T>::letter_t>& w,
                    const Element<Automata<Series>, T>& a,
                    const std::vector<StatesSet>& distances)
  {
    precondition(w.size() > 0);

    // Typedefs.
    typedef typename vcsn::Element<Automata<Series>, T>         automaton_t;
    AUTOMATON_TYPES(automaton_t);
    AUTOMATON_FREEMONOID_TYPES(automaton_t);
    typedef typename utility::Window<InputIterator, letter_t>   window_t;
    typedef typename window_t::length_t                         length_t;
    typedef utility::Bitset                                     bitset_t;

    // Code.
    bitset_t    s_new (a.states().max() + 1);
    bitset_t    s_old (a.states().max() + 1);
    int         pos = w.size();
    length_t    critpos = pos;

    s_old.insert(distances[pos].begin(), distances[pos].end());
    while ((--pos >= 0) && !s_old.empty())
      {
        s_new.clear();
        for (bitset_t::const_iterator s = s_old.begin(); s != s_old.end(); ++s)
          if (distances[pos + 1].find(*s) != distances[pos + 1].end())
            {
              if (a.is_initial(*s))
                critpos = pos + 1;
              a.letter_rdeltac(s_new, *s, w[pos], delta_kind::states());
            }
        std::swap(s_new, s_old);
      }
    if (pos < 0)
      for (bitset_t::const_iterator s = s_old.begin(); s != s_old.end(); ++s)
        if (a.is_initial(*s))
          return std::make_pair(true, critpos);
    return std::make_pair(false, critpos);
  }

  template <class InputIterator, class FoundFunctor, class Series, class T>
  static
  InputIterator
  confirm_and_report_match(const utility::Window<InputIterator,
                           typename Element<Automata<Series>, T>::letter_t>& w,
                           const Element<Automata<Series>, T>& a,
                           FoundFunctor& f)
  {
    // Typedefs.
    typedef typename vcsn::Element<Automata<Series>, T>         automaton_t;
    AUTOMATON_TYPES(automaton_t);
    AUTOMATON_FREEMONOID_TYPES(automaton_t);
    typedef typename utility::Window<InputIterator, letter_t>   window_t;
    typedef typename window_t::length_t                         length_t;
    typedef typename window_t::iterator_t                       iterator_t;
    typedef utility::Bitset                                     bitset_t;

    // Code.
    bitset_t    s_old (a.states().max() + 1);
    bitset_t    s_new (a.states().max() + 1);
    iterator_t  pos = w.stream();
    iterator_t  last = pos;

    s_old.insert(a.initial().begin(), a.initial().end());
    while (!s_old.empty() && (*pos != w.eol_value()))
      {
        s_new.clear();
        for (bitset_t::const_iterator s = s_old.begin(); s != s_old.end(); ++s)
          {
            if (a.is_final(*s))
              last = pos - 1;
            a.letter_deltac(s_new, *s, *pos, delta_kind::states());
          }
        std::swap(s_old, s_new);
        ++pos;
      }
    for (bitset_t::const_iterator s = s_old.begin(); s != s_old.end(); ++s)
      if (a.is_final(*s))
        last = pos - 1;
    if (last != pos)
      return f(w.begin(), w.stream(), last);
    else
      return w.stream();
  }

  template <class InputIterator, class FoundFunctor, class Series, class T>
  void
  WindowedBackSearch::search(const Element<Automata<Series>, T>& a,
                             const InputIterator& begin,
                             const InputIterator& end,
                             typename Element<Automata<Series>, T>::
                             letter_t eol,
                             FoundFunctor& f)
  {
    // Typedefs.
    typedef typename vcsn::Element<Automata<Series>, T>         automaton_t;
    AUTOMATON_TYPES(automaton_t);
    AUTOMATON_FREEMONOID_TYPES(automaton_t);
    typedef typename utility::Window<InputIterator, letter_t>   window_t;
    typedef typename window_t::length_t                         length_t;
    typedef utility::Bitset                                     bitset_t;

    // Code.
    std::vector<bitset_t>       distances;
    length_t                    wl = compute_distances(a, distances);

    if (wl == 0)
      warning("Search match every position in the stream, ignored.");
    else
      {
        window_t                w (begin, end, eol, wl);
        InputIterator           it;

        while (!w.eof())
          {
            if (w.size() != wl)
              w.shift();
            else
              {
                std::pair<bool, length_t> p =
                  window_backsearch(w, a, distances);
                if (p.first &&
                    (it = confirm_and_report_match(w, a, f)) != w.stream())
                  w.moveto(it);
                else
                  w.shift(p.second);
              }
          }
      }
  }

} // vcsn

#endif // ! VCSN_ALGORITHMS_SEARCH_HXX

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