xapian-core/api/terminfo.cc

   1 /** @file terminfo.cc
   2  * @brief Metadata for a term in a document
   3  */
   4 /* Copyright 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 #include <config.h>
  22
  23 #include "terminfo.h"
  24
  25 #include "omassert.h"
  26
  27 bool
  28 TermInfo::add_position(Xapian::termcount wdf_inc, Xapian::termpos termpos)
  29 {
  30     if (rare(deleted)) {
  31         wdf = wdf_inc;
  32         deleted = false;
  33         positions.push_back(termpos);
  34         return true;
  35     }
  36
  37     wdf += wdf_inc;
  38
  39     // Optimise the common case of adding positions in ascending order.
  40     if (positions.empty() || termpos > positions.back()) {
  41         positions.push_back(termpos);
  42         return false;
  43     }
  44
  45     // We keep positions sorted, so use lower_bound() which can binary chop to
  46     // find the entry.
  47     auto i = lower_bound(positions.cbegin(), positions.cend(), termpos);
  48     // Add unless termpos is already in the list.
  49     if (i == positions.cend() || *i != termpos) {
  50         positions.insert(i, termpos);
  51     }
  52     return false;
  53 }
  54
  55 bool
  56 TermInfo::remove_position(Xapian::termpos termpos)
  57 {
  58     Assert(!deleted);
  59
  60     if (rare(positions.empty()))
  61         return false;
  62
  63     // Special case removing the final position, which we can handle in O(1).
  64     if (positions.back() == termpos) {
  65         positions.pop_back();
  66         return true;
  67     }
  68
  69     // We keep positions sorted, so use lower_bound() which can binary chop to
  70     // find the entry.
  71     auto i = lower_bound(positions.cbegin(), positions.cend(), termpos);
  72     if (i == positions.cend() || *i != termpos) {
  73         // Not there.
  74         return false;
  75     }
  76     positions.erase(i);
  77     return true;
  78 }