[RESOLVED] Help with Function

I found this code and I think it could be useful for some members. The code search for the specified bytes in jpg file and when first match is founded msgbox gives you position of the bytes in the file and Function stops.

Code:

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Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim B() As Byte = My.Computer.FileSystem.ReadAllBytes("C:\users\Public\SIMG1374.jpg")
        Dim C() As Byte = {164, 114, 78, 88, 245, 164, 83, 158, 43}
        Dim P As Integer = ByteMatch(B, C)
        If P = -1 Then MsgBox("No Match") Else MsgBox("Matched at " & P.ToString)
    End Sub
    Function ByteMatch(ByVal Source As Byte(), ByVal Match As Byte()) As Integer
        For I As Integer = 0 To Source.Count - 1
            Dim Matched As Boolean = False
            If Match(0) = Source(I) Then
                For J As Integer = 1 To Match.Count - 1
                    Matched = True
                    If Match(J) <> Source(I + J) Then
                        Matched = False
                        Exit For
                    End If
                    If Matched Then Return I
                    Exit For
                Next J
            End If
        Next I
        Return -1
    End Function
End Class

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Now, because I am newbie to VB I have one question. How can I change the Function so that Function search the whole file for all byte matches ?
Thanks in advance

it already does that.

Not quite, it will stop when it finds a match. I would suggest adding a third input, which is startingPoint. Then change this line:

For I As Integer = 0 To Source.Count - 1

to

For I As Integer = startingPoint To Source.Count - 1

Then, you start it out by passing in 0 as the startingPoint, and if it returns something other than -1, you call the method again passing in that number +1 as the new startingPoint.

Quote:

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Originally Posted by vb_ftw

it already does that.

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I've tested the code and as I already said when function finds the first match it stops so if file (jpg in this case) contains several byte arrays - C() - you're searching for (say 4) msgbox(s) will display only position of first match not all 4 of them.

This is the line that is causing it to stop after the first match

Code:

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If Matched Then Return I

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You can either solve it the way I suggested, or you can change it to return a List (of Integer), and rather than calling Return I, you would simply add I to the list, then at the end of the function return the list. It would look like this:

Code:

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Function ByteMatch(ByVal Source As Byte(), ByVal Match As Byte()) As List (of Integer)
        Dim ret As New List(of Integer)
        For I As Integer = 0 To Source.Count - 1
            Dim Matched As Boolean = False
            If Match(0) = Source(I) Then
                For J As Integer = 1 To Match.Count - 1
                    Matched = True
                    If Match(J) <> Source(I + J) Then
                        Matched = False
                        Exit For
                    End If
                    If Matched Then
                    ret.Add(I)
                    End If
                Next J
            End If
        Next I
        Return ret
    End Function

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Thank you for your replies Shaggy but I still didn't make it work. Is it possible to add Function result you provided to ListBox and how (if possible)? I would be very grateful if you can provide me some code with StartingPoint you're talking about in your post.
Thanks.

Like this:-

vbnet Code:

For Each i As Integer In ByteMatch(src, match)
            ListBox1.Items.Add(i)
        Next

Is there an Items.AddRange?

Ya, I tried that but AddRange takes a ListBox.ObjectCollection object and not an array as you would expect.

I have managed to display Function result in Listbox. Let me just say when I run the code I got duplicate values in the listbox so I've added a Sub to remove duplicates from the listbox and finally I have what I was looking for.
Thank you for helping me solve this problem.