I have a such peace of code.

thread that reeds the file

Qt Code: 
  1. #include <QThread>
  2. #include <QString>
  3. class openner : public QThread
  4. {
  5. 	Q_OBJECT
  6.  
  7. public:	
  8. 	openner(QString);
  9. 	~openner();
  10. 	void run();
  11. private:
  12. 	QString file;
  13. signals:
  14. 	void onStart(int);
  15. 	void on(int);
  16. 	void onEnd(int);
  17. };
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Qt Code: 
  1. #include "openner.h"
  2. #include <QFile>
  3. #include <QTextStream>
  4. openner::openner(QString f)
  5. 	: QThread(0)
  6. {
  7. 	file=f;
  8. }
  9. void openner::run()
  10. {
  11. 	QString str;
  12. 	QFile f(file);	
  13. 	f.open(QIODevice::ReadOnly | QIODevice::Text);		
  14. 	QTextStream in(&f);
  15. 	emit onStart(f.size());
  16. 	while(!in.atEnd())
  17. 	{
  18. 		str=in.readLine();		
  19. 		emit on(in.pos());
  20. 	}
  21. 	emit onEnd(f.size());
  22. 	f.close();
  23. }
  24. openner::~openner()
  25. {
  26.  
  27. }
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main form

Qt Code: 
  1. #include <QtGui/QMainWindow>
  2. #include <QProgressBar>
  3. #include "openner.h"
  4. class progressTest : public QMainWindow
  5. {
  6. 	Q_OBJECT
  7. private:
  8. 	openner *o;
  10. public:
  11. 	progressTest(QWidget *parent = 0, Qt::WFlags flags = 0);
  12. 	~progressTest();
  13. protected slots:
  14. 	void onStart(int);
  15. 	void onProgres(int);
  16. 	void onEnd(int);
  17. };
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Qt Code: 
  1. #include "progresstest.h"
  2.  
  3. progressTest::progressTest(QWidget *parent, Qt::WFlags flags)
  4. 	: QMainWindow(parent, flags)
  5. {
  6. 	pb=new QProgressBar(this);
  7. 	pb->resize(200,20);
  8. 	o=new openner("C:\\projects\\umc\\UMC_invoice_.28532.00.00.100000_id_0793918_part_1.csv");
  9. 	QObject::connect(o,SIGNAL(onStart(int)),this,SLOT(onStart(int)));
  10. 	QObject::connect(o,SIGNAL(on(int)),this,SLOT(onProgres(int)));
  11. 	QObject::connect(o,SIGNAL(onEnd(int)),this,SLOT(onEnd(int)));
  12. 	o->start();
  13. }
  14. void progressTest::onStart(int m)
  15. {	
  16. 	pb->setMaximum(m);
  17.  
  18. }
  19. void progressTest::onProgres(int l)
  20. {
  21. 	pb->setValue(l);
  22. }
  23. void progressTest::onEnd(int l)
  24. {	
  25. 	pb->setValue(0);
  26. }
  27. progressTest::~progressTest()
  28. {
  29.  
  30. }
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When I use my program with emit on(in.pos()); then it takes for about three hours to read file. But then I use it without emit on(in.pos()); file is read in the minutes. the size of file is 3000 kb
How the emit of signal can be optimised?
OS - windows XP
IDE - Microsoft Visual Studio 2008?