vb.net efficiently finding byte sequence in byte array - vb.net

Question

so I am creating a piece of software that in short, has a list of original byte sequences and new sequences that those bytes need to be changed into, kinda like this in text form "original location(currently irrelevant as sequence can be in different places) $ 56,69,71,73,75,77 : 56,69,71,80,50,54"
I already have code that works fine, however there can be up to 600+ of these sequences to find and change and in some cases it is taking a really really long time 15 mins +, i think it is down to how long it is taking to find the sequences to them change so i am trying to find a better way to do this as currently it is unusable due to how long it takes.
I have copied the whole code for this function below in hopes one of you kind souls can have a look and help =)
Dim originalbytes() As Byte
Dim fd As OpenFileDialog = New OpenFileDialog()
fd.Title = "Select the file"
fd.Filter = "All files (*.*)|*.*|All files (*.*)|*.*"
fd.FilterIndex = 2
If fd.ShowDialog() = DialogResult.OK Then
TextBox2.Text = fd.FileName
originalbytes = File.ReadAllBytes(fd.FileName)
End If
Dim x As Integer = 0
Dim y As Integer = 0
Dim textbox1array() = TextBox1.Lines
Dim changedbytes() = originalbytes
Dim startvalue As Integer = 0
Dim databoxarray() As String
Dim databoxarray2() As String
While x < textbox1array.Length - 1
'for each change to make
databoxarray = textbox1array(x).Replace(" $ ", vbCr).Replace(" : ", vbCr).Split
databoxarray2 = databoxarray(1).Replace(",", vbCr).Split
Dim databox2bytes() As String = databoxarray2
'copy original bytes line to databox2 lines
y = 0
While y < (originalbytes.Length - databox2bytes.Length)
'repeat for all bytes in ori file - size of data to find
If originalbytes(y) = databox2bytes(0) Then
startvalue = y
Dim z As String = 1
Dim samebytecounter As Integer = 1
While z < databox2bytes.Length
'repeat for all ori bytes
If originalbytes(y + z) = databox2bytes(z) Then
samebytecounter = samebytecounter + 1
End If
z = z + 1
End While
If samebytecounter = databox2bytes.Length Then
'same original data found, make changes
Dim bytestoinsert() As String = databoxarray(2).Replace(",", vbCr).Split
Dim t As Integer = 0
While t < bytestoinsert.Length
changedbytes(startvalue + t) = bytestoinsert(t)
t = t + 1
End While
End If
End If
y = y + 1
End While
x = x + 1
End While
File.WriteAllBytes(TextBox2.Text & " modified", changedbytes)

Answer 1

Let 's take a look at that inner while loop in your code, there are some things that can be optimized:
There is no need to check the total length all the time
Dim length as Integer = originalbytes.Length - databox2bytes.Length
While y < length
'repeat for all bytes in ori file - size of data to find
If originalbytes(y) = databox2bytes(0) Then
startvalue = y
z is not necessary, samebytecounter does exactly the same
Dim samebytecounter As Integer = 1
This while loop is a real bottleneck, since you always check the full length of your databox2bytes, you should rather quit the while loop when they don't match
While samebytecounter < databox2bytes.Length AndAlso originalbytes(y + samebytecounter ) = databox2bytes(samebytecounter )
samebytecounter = samebytecounter + 1
End While
This seems fine, but you already splitted the data at the top of your while loop, so, no need to create another array that does the same operation again
If samebytecounter = databox2bytes.Length Then
'same original data found, make changes
Dim t As Integer = 0
While t < databoxarray2.Length
changedbytes(startvalue + t) = databoxarray2(t)
t = t + 1
End While
End If
End If
y = y + 1
End While
For the rest I would agree that the algorithm you created is hugely inefficient, theoretically your code could have been rewritten like eg: (didn't really test this code)
Dim text = System.Text.Encoding.UTF8.GetString(originalbytes, 0, originalbytes.Length)
dim findText = System.Text.Encoding.UTF8.GetString(stringToFind, 0, stringToFind.Length)
dim replaceWith = System.Text.Encoding.UTF8.GetString(stringToSet, 0, stringToSet.Length)
text = text.Replace( findText, replaceWith )
dim outbytes = System.Text.Encoding.UTF8.GetBytes(text)
which would probably be a huge time saver.
For the rest your code seems to be created in such a way that nobody will really understand it if it's laying around for a month or so, I would say, including yourself