xapian-core/api/emptypostlist.h

   1 /** @file emptypostlist.h
   2  * @brief A PostList which contains no entries.
   3  */
   4 /* Copyright (C) 2009,2011,2015 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of the
   9  * License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #ifndef XAPIAN_INCLUDED_EMPTYPOSTLIST_H
  22 #define XAPIAN_INCLUDED_EMPTYPOSTLIST_H
  23
  24 #include "postlist.h"
  25
  26 /// A PostList which contains no entries.
  27 class EmptyPostList : public PostList {
  28     /// Don't allow assignment.
  29     void operator=(const EmptyPostList &);
  30
  31     /// Don't allow copying.
  32     EmptyPostList(const EmptyPostList &);
  33
  34   public:
  35     /// Constructor.
  36     EmptyPostList() { }
  37
  38     Xapian::doccount get_termfreq_min() const;
  39     Xapian::doccount get_termfreq_max() const;
  40     Xapian::doccount get_termfreq_est() const;
  41
  42     TermFreqs get_termfreq_est_using_stats(const Xapian::Weight::Internal &) const;
  43
  44     double get_maxweight() const;
  45     Xapian::docid get_docid() const;
  46     Xapian::termcount get_doclength() const;
  47     Xapian::termcount get_unique_terms() const;
  48     double get_weight() const;
  49     bool at_end() const;
  50     double recalc_maxweight();
  51
  52     PostList * next(double w_min);
  53     PostList * skip_to(Xapian::docid, double w_min);
  54
  55     std::string get_description() const;
  56 };
  57
  58 #endif // XAPIAN_INCLUDED_EMPTYPOSTLIST_H