File indexing completed on 2023-05-30 11:30:51

 /**
  * Copyright (C) 2003 Maksim Orlovich <maksim.orlovich@kdemail.net>
  *
  * This program is free software; you can redistribute it and/or modify it under
  * the terms of the GNU General Public License as published by the Free Software
  * Foundation; either version 2 of the License, or (at your option) any later
  * version.
  *
  * This program is distributed in the hope that it will be useful, but WITHOUT ANY
  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
  * PARTICULAR PURPOSE. See the GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License along with
  * this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 #include "stringshare.h"
 
 #include <QHash>
 
 const int SIZE = 8191;
 
 static unsigned num_attempts = 0;
 static unsigned num_hits     = 0;
 
 /**
  * We store the strings in a simple direct-mapped (i.e. no collision handling,
  * just replace) hash, which contain strings or null objects. This costs only
  * 4 bytes per slot on 32-bit archs, so with the default constant size we only
  * really use 40K or so.
  *
  * The end result is that many strings end up pointing to the same underlying data
  * object, instead of each one having its own little copy.
  *
  * More importantly, the way the tryShare function is coded ensures that
  * most-recently inserted text stays in the cache, which gives a better chance
  * of continuing to share data. (Even if something old ("foo") that was shared
  * gets kicked out, all the other "foo"s will still be sharing each other's
  * data.
  */
 
 struct StringShare::Data
 {
     QString  qstringHash [SIZE];
 };
 
 StringShare::Data* StringShare::data()
 {
     static Data *data = new Data;
     return data;
 }
 
 QString StringShare::tryShare(const QString& in)
 {
     uint index = qHash(in) % SIZE;
 
     num_attempts++;
 
     Data* dat = data();
     if (dat->qstringHash[index] == in) {
         // Match
         num_hits++;
         return dat->qstringHash[index];
     } else {
         // Else replace whatever was there before
         dat->qstringHash[index] = in;
         return in;
     }
 }
 
 unsigned StringShare::numHits()
 {
     return num_hits;
 }
 
 unsigned StringShare::numAttempts()
 {
     return num_attempts;
 }
 
 // vim: set et sw=4 tw=0 sta: