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/***************************************************************************
begin : Sat Oct 25 2003
copyright : (C) 2003 by Maksim Orlovich
email : 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. *
* *
***************************************************************************/
#include <QHash>
#include "stringshare.h"
const int SIZE = 5003;
StringShare::Data* StringShare::s_data = 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()
{
if (!s_data)
s_data = new Data;
return s_data;
}
QString StringShare::tryShare(const QString& in)
{
uint index = qHash(in) % SIZE;
Data* dat = data();
if (dat->qstringHash[index] == in) //Match
return dat->qstringHash[index];
else
{
//Else replace whatever was there before
dat->qstringHash[index] = in;
return in;
}
}
// vim: set et sw=4 tw=0 sta:
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