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/**
* 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:
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