xapian-core/backends/positionlist.h

   1 /** @file positionlist.h
   2  * @brief Abstract base class for iterating term positions in a document.
   3  */
   4 /* Copyright (C) 2007,2010,2017 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_POSITIONLIST_H
  22 #define XAPIAN_INCLUDED_POSITIONLIST_H
  23
  24 #include <xapian/intrusive_ptr.h>
  25 #include <xapian/positioniterator.h>
  26 #include <xapian/types.h>
  27
  28 namespace Xapian {
  29
  30 /// Abstract base class for iterating term positions in a document.
  31 class PositionIterator::Internal : public Xapian::Internal::intrusive_base
  32 {
  33     /// Don't allow assignment.
  34     void operator=(const Internal &) = delete;
  35
  36     /// Don't allow copying.
  37     Internal(const Internal &) = delete;
  38
  39   protected:
  40     /// Only constructable as a base class for derived classes.
  41     Internal() { }
  42
  43   public:
  44     /** We have virtual methods and want to be able to delete derived classes
  45      *  using a pointer to the base class, so we need a virtual destructor.
  46      */
  47     virtual ~Internal() { }
  48
  49     /// Return approximate size of this positionlist.
  50     virtual Xapian::termcount get_approx_size() const = 0;
  51
  52     /// Return the current position.
  53     virtual Xapian::termpos get_position() const = 0;
  54
  55     /** Advance to the next entry in the positionlist.
  56      *
  57      *  The list starts before the first entry, so next() or skip_to() must be
  58      *  called before get_position().
  59      *
  60      *  @return true if we're on a valid entry; false if we've reached the end
  61      *          of the list.
  62      */
  63     virtual bool next() = 0;
  64
  65     /** Skip forward to the specified position.
  66      *
  67      *  If the specified position isn't in the list, position ourselves on the
  68      *  first entry after it.
  69      *
  70      *  @return true if we're on a valid entry; false if we've reached the end
  71      *          of the list.
  72      */
  73     virtual bool skip_to(Xapian::termpos termpos) = 0;
  74 };
  75
  76 }
  77
  78 typedef Xapian::PositionIterator::Internal PositionList;
  79
  80 #endif // XAPIAN_INCLUDED_POSITIONLIST_H