how to sort strings in vb

Question

I am stuck with this problem. I am using Visual Studio Express 2013 (is that VB.NET?) and this is the task I would like to perform: I have a .txt file formatted like this (many more lines):

b2 a9 9c b4 d2 d3 52 02 da d2 e2 a2 c2 34 b2 a4 25 1c cb 52
00 00 00 00 00 00 00 00 00 00 04 c6 a2 10 a2 aa 5a 96 12 35 00 00 00 00 00 00 00 00 00 00 04 ae a5 9b 53 6c 15 56 56 d2 a1 54 55 b4 a6 ba a8 aa a6 b9 a8 44 94 69 5e d1 17 6a 56 9a 0b a7 29 49
69 d2 14 11 a1 78 41 d0 a4 54 41 51 1c 94 c1 24 a8 2a 71 14 50 14 04 b5 45 31 00 00 00 00 00 00 00 00 00 00

They are HEX values, I need to find repeating patterns. The pattern can be 2, 3, 4 or 5 bytes long, but for the moment it's ok to do it only with fixed size (ie only 2 bytes pattern). I want to populate a SortedDictionary with (Hex pattern, Repetition) I tried SortedDictionary and Dictionary, same issue. I have tested it for 10 lines or so step-by-step F11 debug and it works ok. However if I run the application with a 120 lines text file (which is small compared to what I want to do), it just hangs. The maximum number of elements in the dictionary would be 256*256, is it too much? What then with 3,4 or 5 bytes? It's not only a matter of time, the debugger raises an exception because the process doesn't end in 60 seconds. Is there a more clever way of doing what I want to do?

    Dim BytesList As New SortedDictionary(Of String, Integer)
    Dim line As String = ""
    Dim CurrentString As String
    Dim ByteLen As Byte

    For ByteLen = 2 To 2 'to do: ideally repeat for ByteLen = 2,3,4,5
        Using sr As StreamReader = New StreamReader(path & LOGFILENAME,False)
            Do
                line = line & sr.ReadLine()
                line = line.Replace(Chr(32), "") 'remove unwanted chars from line
                line = line.Replace(Chr(10), "")
                line = line.Replace(Chr(13), "")
                While (line.Length > ByteLen * 2)
                    CurrentString = line.Substring(0, ByteLen * 2)
                    line = line.Substring(2, line.Length - 2)
                    Try
                        BytesList.Add(CurrentString, 1)     'insert found address
                    Catch
                        BytesList(CurrentString) = BytesList(CurrentString) + 1 ' if string is already present, increment value
                    End Try
                End While
            Loop Until line Is Nothing
        End Using
    Next ByteLen
End Sub

Thanks in advance to everyone who helps!

Answer 1

If you intend to find repeated single bytes (hex-digit pairs) such as 00 00 00 00 then something like this would work:

Dim pattern As String = "(?<bh>\d\d )(\k<bh>)+"
Dim rx As New Regex(pattern)
Dim match = rx.Match("00 00 00 00 00 00 00 00 00 00 04 c6 a2 10 a2 aa 5a 96 12 35 00 00 00 00 00 00 00 00 00 00 04 ae a5 9b 53 6c 15 56 56 d2 a1 54 55 b4 a6 ba a8 aa a6 b9 a8 44 94 69 5e d1 17 6a 56 9a 0b a7 29 49 ")
While match.Success
    Debug.WriteLine("'{0}' found at position {1}", match.Value, match.Index)
    match = match.NextMatch()
End While

results

'00 00 00 00 00 00 00 00 00 00 ' found at 0
'00 00 00 00 00 00 00 00 00 00 ' found at 60
'56 56 ' found at 111

That's only for a single line (your 2nd line of your sample input), but you can easily expand that to work over each of the lines from the file.