xapian-core/api/documentterm.h

   1 /** @file documentterm.h
   2  * @brief internal class representing a term in a modified document
   3  */
   4 /* Copyright 1999,2000,2001 BrightStation PLC
   5  * Copyright 2002 Ananova Ltd
   6  * Copyright 2003,2007 Olly Betts
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of the
  11  * License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  21  * USA
  22  */
  23
  24 #ifndef OM_HGUARD_DOCUMENTTERM_H
  25 #define OM_HGUARD_DOCUMENTTERM_H
  26
  27 #include "debuglog.h"
  28
  29 #include <string>
  30 #include <vector>
  31
  32 #include <xapian/types.h>
  33
  34 using namespace std;
  35
  36 /// A term in a document.
  37 class OmDocumentTerm {
  38     public:
  39     /** Make a new term.
  40      *
  41      *  @param wdf_   Initial wdf.
  42      */
  43     explicit OmDocumentTerm(Xapian::termcount wdf_)
  44         : wdf(wdf_)
  45     {
  46         LOGCALL_CTOR(DB, "OmDocumentTerm", wdf_);
  47     }
  48
  49     /** Within document frequency of the term.
  50      *  This is the number of occurrences of the term in the document.
  51      */
  52     Xapian::termcount wdf;
  53
  54     typedef vector<Xapian::termpos> term_positions;
  55
  56     /** Positional information.
  57      *
  58      *  This is a list of positions at which the term occurs in the
  59      *  document. The list is in strictly increasing order of term
  60      *  position.
  61      *
  62      *  The positions start at 1.
  63      *
  64      *  Note that, even if positional information is present, the WDF might
  65      *  not be equal to the length of the position list, since a term might
  66      *  occur multiple times at a single position, but will only have one
  67      *  entry in the position list for each position.
  68      */
  69     term_positions positions;
  70
  71     /** Add a position to the position list.
  72      *
  73      *  This adds an entry to the list of positions, unless
  74      *  there is already one for the specified position.
  75      *
  76      *  This does not change the value of the wdf.
  77      *
  78      *  @param tpos The position within the document at which the term
  79      *              occurs.
  80      */
  81     void add_position(Xapian::termpos tpos);
  82
  83     /** Remove an entry from the position list.
  84      *
  85      *  This removes an entry from the list of positions.
  86      *
  87      *  This does not change the value of the wdf.
  88      *
  89      *  @exception Xapian::InvalidArgumentError is thrown if the position does
  90      *  not occur in the position list.
  91      */
  92     void remove_position(Xapian::termpos tpos);
  93
  94     /// Increase the wdf
  95     void inc_wdf(Xapian::termcount inc) { wdf += inc; }
  96
  97     /// Decrease the wdf
  98     void dec_wdf(Xapian::termcount dec) {
  99         if (wdf <= dec) {
 100             wdf = 0;
 101         } else {
 102             wdf -= dec;
 103         }
 104     }
 105
 106     /// Get the wdf
 107     Xapian::termcount get_wdf() const { return wdf; }
 108
 109     /// Return a string describing this object.
 110     string get_description() const;
 111 };
 112
 113 #endif // OM_HGUARD_DOCUMENTTERM_H