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AlphanumComparer.h
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AlphanumComparer.h
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#ifndef ALPHANUMCOMPARER_H
#define ALPHANUMCOMPARER_H
/*!
* \brief Natural (alpha-num) sorting
* \author Litkevich Yuriy
* \see http://www.forum.crossplatform.ru/index.php?showtopic=6244&st=0&p=44752&#entry44752
*/
#include <QString>
class AlphanumComparer
{
public:
static bool lessThan(const QString &s1, const QString &s2)
{
return compare( s1, s2 ) < 0 ;
}
private:
/*!
* \fn compare - compare two strings
* \param l - left sring.
* \param r - right string.
*
* \return
* l<r - result less than zero;
* l>r - result more than zero;
* l=r - result is zero.
*/
static int compare(QString l, QString r)
{
enum Mode { STRING, NUMBER } mode = STRING;
int size;
if ( l.size() < r.size() )
size = l.size();
else
size = r.size();
int i = 0;
// runing throught both strings to position "size-1"
while( i < size) {
if ( mode == STRING ) {
QChar lchar, rchar;
bool ldigit, rdigit;
while( i < size ) {
lchar = l.at( i );
rchar = r.at( i );
ldigit = lchar.isDigit();
rdigit = rchar.isDigit();
// if both simbols is numbers, using numbers state
if ( ldigit && rdigit ) {
mode = NUMBER;
break;
}
if ( ldigit ) return -1;
if ( rdigit ) return +1;
// both simbols are letters
if ( lchar < rchar ) return -1;
if ( lchar > rchar ) return +1;
// simbols are equal
i++;
}
} else { //mode == NUMBER
unsigned long long lnum = 0, rnum = 0;
int li = i, ri = i; // local indexes
int ld = 0, rd = 0; // numbers
// make left number
while ( li < l.size() ) {
ld = l.at( li ).digitValue();
if ( ld < 0 ) break;
lnum = lnum*10 + ld;
li++;
}
// make right number
while( ri < r.size() ) {
rd = r.at( ri ).digitValue();
if ( rd < 0 ) break;
rnum = rnum*10 + rd;
ri++;
}
long long delta = lnum - rnum;
if ( delta ) return delta;
// numbers are equal
mode = STRING;
if ( li <= ri )
i=li;
else
i=ri;
}
}
// this is for situation when both strings to position "size-1" equals
if ( i < r.size() ) return -1;
if (i < l.size() ) return +1;
// strings are full equal
return 0;
}
};
#endif // ALPHANUMCOMPARER_H