rem: unsigned char val = aStr[i] - ' ';
add: val = aStr[i] - ' ';
context: QCString encryptStr(const QCString& aStr){  uint i,len = aStr.length();  QCString result;  for (i=0; i<len; i++)  {    unsigned char val = aStr[i] - ' ';    val = (255-' ') - val;    result += (val + ' ');  }  return result;}