xapian-core/expand/ortermlist.h

   1 /** @file
   2  * @brief Merge two TermList objects using an OR operation.
   3  */
   4 /* Copyright (C) 2007,2010 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_ORTERMLIST_H
  22 #define XAPIAN_INCLUDED_ORTERMLIST_H
  23
  24 #include "api/termlist.h"
  25
  26 namespace Xapian {
  27 namespace Internal {
  28 class ExpandStats;
  29 }
  30 }
  31
  32 class OrTermList : public TermList {
  33   protected:
  34     /// The two TermList objects we're merging.
  35     TermList *left, *right;
  36
  37     /** The current term for left and right respectively.
  38      *
  39      *  Until next() is first called, these will be empty strings.  Once next()
  40      *  has been called, they won't be empty (since the empty string isn't a
  41      *  valid term).
  42      */
  43     std::string left_current, right_current;
  44
  45     /// Check that next() has already been called.
  46     void check_started() const;
  47
  48   public:
  49     OrTermList(TermList * left_, TermList * right_)
  50         : left(left_), right(right_) { }
  51
  52     ~OrTermList();
  53
  54     Xapian::termcount get_approx_size() const;
  55
  56     void accumulate_stats(Xapian::Internal::ExpandStats & stats) const;
  57
  58     std::string get_termname() const;
  59
  60     Xapian::termcount get_wdf() const;
  61
  62     Xapian::doccount get_termfreq() const;
  63
  64     TermList *next();
  65
  66     TermList * skip_to(const std::string & term);
  67
  68     bool at_end() const;
  69
  70     Xapian::termcount positionlist_count() const;
  71
  72     Xapian::PositionIterator positionlist_begin() const;
  73 };
  74
  75 /** A termlist which ORs two termlists together, adding term frequencies.
  76  *
  77  *  This termlist is just like OrTermList, but adds the term frequencies of
  78  *  terms which appear in both sublists together, rather than asserting that the
  79  *  frequencies are equal.  This is appropriate for spelling termlists.
  80  */
  81 class FreqAdderOrTermList : public OrTermList {
  82   public:
  83     FreqAdderOrTermList(TermList * left_, TermList * right_)
  84             : OrTermList(left_, right_)
  85     { }
  86
  87     Xapian::doccount get_termfreq() const;
  88 };
  89
  90 #endif // XAPIAN_INCLUDED_ORTERMLIST_H