Binary file I/O, weird problem

[brixton]

Hello,
I've got the following code:

 wxString path = filepath;
 wxString newpath = filepath;
 fstream f(path.Append("/tests/tests.bin"), ios::in | ios::binary);
 fstream fnew(newpath.Append("/tests/temp.bin"), ios::out | ios::binary);
 Test* transferTest = new Test();
 int thisSize = sizeof(Test);
 bool success = false;
 bool toBeDeleted = false;
 int testNo = 1;
 if (f)
 {
  f.seekg(0, ios::beg);
  fnew.seekp(0, ios::beg);
  while (testNo <= noOfTests)
  {
   toBeDeleted = false;
   for (int i = 0; i < noOfSelectedRows; i++)
   {
    int row = selectedRows[i];
    if (testNo == row)
    {
     toBeDeleted = true;
    }
   }
   if (!toBeDeleted)
   {
    f.read(reinterpret_cast<char *>(transferTest), thisSize);
    fnew.write(reinterpret_cast<char *>(transferTest), thisSize);
    fnew.seekp(testNo*thisSize, ios::beg);
   }
   f.seekg(testNo*thisSize, ios::beg);
   testNo++;
  }
  success = true;
  f.close();
  fnew.close();
  remove(path.c_str());
  rename(newpath.c_str(), path.c_str());
 }
 delete transferTest;

Essentially, what I have is a binary file with objects of the class Test. Trough a list in my GUI I make it possible to delete objects from this bunch. And it works fine as long as I delete one or more objects at the end of the file. However if I try to delete an object in the middle of the bunch, there becomes a "hole" in the "temp.bin" file and it keeps on writing the rest of the objects perfectly fine. So the file gets the exact same size as before.
I've been staring at this for a while now and I really can't see why it doesn't work the way I want it to, so hopefully someone can help :)
Thanks in advance!

[Banfa]

I am going to take a stab in the dark and guess that the whole in your new file appears at the location after the entry to be deleted.

The problem is this line of code

    fnew.seekp(testNo*thisSize, ios::beg);

It sets the file pointer for the new file based on the current test not the number of tests that have been written to the file.

In theory this seekp (and the seekg at line 31) are just not required, a file is read or written sequencially you only need to seek if you want to move the file pointer to an out of sequence position.

[newb16]

 f.seekg(testNo*thisSize, ios::beg); 
 testNo++; 
 

You apply this with incrementing testNo each iteration, whether item was written or not. Write function should handle seek after write automatically, try to comment out all seek()'s.
Btw, writing classes ( unless they are POD objects ) as memory snapshot is no a good idea.