Reading a file chunk by chunk in QT 4.3.3

I have following code in QT in

// myEditor.h
class myEditor : QScintilla {
    public:
        readFile();
};

#include "myEditor.h"
// myEditor.cc
myEditor::readFile() {
   FILE* fp = fopen("mynew.v","r"):
   QTextStream ts(fp, QIODevice::ReadOnly);
   /* reading the  text stream  buffer by buffer
   bufferSize is calculated using following formula
   2 to power(k) *  n  =  2 to power 31*
   where n is  size of each block in linux filesystem*/

   int bufferSize =(1024* 1024)/2;
   do {
      QString s = ts.read(bufferSize);
      append(s);
    } while(!ts.atEnd());
}

I calculated the bufferSize as per comments .It will be helpful if someone can review the code and let me know if there are issues.