Can you search a array for another array?

[CrystalAnnoysMe]

I need to search a Byte array for the existence of another Byte array. The first array is large, about 30,000 bytes and the second varies but is usually between 300 and 500 bytes. I need to know the start position of the second array inside the first. For example if these were the arrays:

Array 1     Array 2
00
34
00
23              23
00              00
64              64
00              00
41              41
00
45
92
33

I would need to know the start position is 3. I COULD do something horribly painful like:

        For x = 0 To UBound(Array1)
            If Array1(x) = Array2(0) And Array1(x + 1) = Array2(1) And Array1(x + 2) = Array2(2) Then
                ' Found it
            End If
        Next

And loop through finding it by brute force but array 2 will be a different size on each system so doing the above, although I could make it work, isn't practical. I could even do multiple if's like if I find the first byte then find the second, then find the third, and make it a little more bearable but still. Is there a simple way to find a array inside another array?

-Allan

[DataMiser]

I would think that you could copy the array into a string variable and use instr() to locate the position you seek. Not sure how fast it would be but it should work. Of course there may very well be a better approach.

[CrystalAnnoysMe]

yeah, I actually have done that I just hate converting from one type to another then back. It's really not that much slower, doing a simple:

MyPosition = InStr(myFirstArrayAsString, MySecondArrayAsString)

But then I need to figure out the position difference when I do this compared to doing the byte array directly. If I have to though this is what I'll end up doing, I just through that finding a array inside a array was possible somehow.

[CrystalAnnoysMe]

I'm going to have to use the extended if then for this. I converted my byte arrays into strings then because the array is actually in hex (yet the read registry function pulls in decimal) I had to covert each value to hex before adding to the string (so every two positions is one byte so I can use the position later). I can get the full byte array as a hex string however:

myRegistryKeyAsByte = ReadCURKByte("Software\Microsoft\Windows\CurrentVersion\Explorer\TrayNotify", "IconStreams", Nothing)
                For x = 0 To UBound(myRegistryKeyAsByte)
                    myHolderString = double_to_hex(myRegistryKeyAsByte(x))
                    Select Case myHolderString.Length
                        Case 0
                            myRegistryKeyAsString += "00"
                        Case 1
                            myRegistryKeyAsString += "0" + myHolderString
                        Case 2
                            myRegistryKeyAsString += myHolderString
                    End Select
                Next

But for some reason a InStr function will NOT work on the two strings. If I take the values and past my registry string (from above) into Notepad and then search using the string I'm looking for it does find it. But the VB InStr does not. Maybe it can't deal with searching a 36,000 character string for a 500 character string. Not sure, gonna keep playing.

[DataMiser]

Could it be a case sensitivity issue.

There should only be a position difference of 1 in the value returned by instr vs the actual array location. e.g. first array element is 0 instr() will return 1 for the first position so it should just be a matter of subtracting one from the result of the instr() if you choose to go that route.

[Oblio]

This isn't complete, but it should give you some ideas. You will need to check bounds

        Dim rDataGen As New Random
        Dim bBuf(9999) As Byte
        Dim fndA() As Byte = New Byte() {1, 2}
        Dim loc As Integer
        Dim found As Boolean
        rDataGen.NextBytes(bBuf) 'generate some test data
        loc = 0
        Do
            loc = Array.IndexOf(bBuf, fndA(0), loc) 'find the first byte
            If loc <> -1 Then 'then check the rest
                found = True
                For x As Integer = 1 To fndA.Length - 1
                    loc += 1
                    If bBuf(loc) <> fndA(x) Then
                        found = False
                        Exit For
                    End If
                Next
                If found Then Exit Do
            End If
        Loop

[CrystalAnnoysMe]

Thanks for the example. I got my goofy "switch byte array to hex string" example above working and I did find the string within the string and figured out how to then go back and change the byte I needed (it was always 10 bytes in front of the first character of my string, or 20 spaces in string format).

I think I am giving up on it though....I've been working on this to solve this solution: http://www.codeguru.com/forum/showthread.php?t=306661 which with this done I think I have solved. Problem is solving the problem programmaticly is almost not worth doing to get through the hoops to do it.

[dglienna]

If you use a List, you can use FIND for the first value, then skip to the end or something