Reading mid part of file

I've been using vb6 to print a block of data from the middle of a file. ...

Dim Chunk As String * 100
Open files(i) For Binary As #ff1
MyLen = LOF(ff1)
Get #ff1, MyLen / 2, Chunk
For i = 1 To 100
f = Asc(Mid(ff, i, 1))
Debug.Print Right("00" & Hex(f), 2); " ";
next
Close # ff1

... I would like to now use this in VS keeping the same output

  Using fs As New FileStream(filePath, FileMode.Open, FileAccess.Read)
      ' Get the total length of the file
      Dim fileLength As Long = fs.Length

      ' Calculate the midpoint (VB6 was using LOF/2, the equivalent to fileLength / 2 in VB.NET ?)
      Dim midpoint As Long = fileLength \ 2

      ' Read a block of bytes starting from the midpoint
      ' read 100 bytes 
      Dim buffer(99) As Byte
      fs.Seek(midpoint, SeekOrigin.Begin) ' Move to midpoint
      fs.Read(buffer, 0, buffer.Length)

      ' Print the read bytes in hex 
      For Each b As Byte In buffer
          Debug.Write(b.ToString("X2") & " ")
      Next
      Debug.WriteLine("")

  End Using

There are about 200 files, some which have matched, but never all.

The Mid starting point is non-consistent.

Some factors may be (but cannot confirm or find a pattern)

VS file read is 0-Based and VB6 is 1-based

LOF/2 can often be a non integer

Can anyone suggest why the midpoint isn't consistent and the same for both procedures?

Answer

In VB6 you should use chunk instead of ff - I haven't run your code, but using ff should not work. Do this in VB6:

f = Asc(Mid(chunk, i, 1))

If the file length is odd, VB6 will start one byte later than VB.NET, due to 1-indexed vs 0-indexed. To get the same result, do this in VB.NET:

Dim midpoint As Long = (fileLength + 1) \ 2

You use two different methods of division to calculate the midpoint, floating point division (/) and integer division (\). You should use integer division in both languages, for what you are trying to achieve.

And in VB6 you don't print a newline after the loop, before you close the file, like you do in VB.NET. Add this line before you close the file to VB6:

Debug.Print ""

I'd also check if the length of the file is one or zero bytes long; and print nothing if that's the case.