How to Rerun the TextStream.AtEndOfStream - vbscript

Question

I'm successfully running the code below to display a text file to the browser, line by line:
<%
Filename = "/pages/test.txt"
Set FSO = server.createObject("Scripting.FileSystemObject")
Filepath = Server.MapPath(Filename)
Set file = FSO.GetFile(Filepath)
Set TextStream = file.OpenAsTextStream(1, -2)
Do While Not TextStream.AtEndOfStream
Line = TextStream.readline
Response.Write Line & "<br>"
Loop
Set TextStream = nothing
Set FSO = nothing
%>
I'd like to run the Do While Not TextStream.AtEndOfStream loop one more time, right before the Set TextStream = nothing statement.
Turns out I cannot "just" copy the Do While loop and place it below the first instance. There are no results from the TextStream anymore.
Is there a way to reset the TextStream object back to the beginning of the stream?
I could store the lines in an array and utilize that, but I wanted to see if there was an easier route.

Answer 1

Unfortunately, there's no way to manually position the pointer in a TextStream object. You can Close the TextStream and reopen it. Or, you can just read the file once into an array, as you implied. Considering you're outputting the entirety of the file to a web page, I'll assume it's not incredibly large and, therefore, storing it in an array would not be too memory intensive.
' Create an array containing each line from the text file...
a = Split(file.OpenAsTextStream(1, -2).ReadAll(), vbCrLf)
For i = 0 To UBound(a)
Response.Write a(i) & "<br>"
Next
' Repeat the process...
For i = 0 To UBound(a)
Response.Write a(i) & "<br>"
Next
You could even replace the line endings with <br> and write it in one operation:
strText = Replace(file.OpenAsTextStream(1, -2).ReadAll(), vbCrLf, "<br>")
Response.Write strText
Response.Write strText ' Write it again

Answer 2

Limitations of the TextStream Object
The TextStream object in the Visual Basic Script Runtime is very limited in what it can do.
Reading is Forward Only which means you cannot go back to an earlier point in the stream.
Writing is all or nothing, when a file is open in ForWriting mode the contents of the file is truncated before being overwritten (as pointed out to avoid this use ForAppending).
Is There Another Way?
Introducing the ADODB.Stream Object!
Fortunately ADODB provides a far more flexible streaming object called ADODB.Stream which among other things allows you to open a file (text or binary) and control the Position property allowing you to read from an earlier point in the stream.
Something like;
<%
Dim TextStream, Filename, Filepath
Filename = "/pages/test.txt"
Filepath = Server.MapPath(Filename)
Set TextStream = Server.CreateObject("ADODB.Stream")
Call TextStream.Open()
TextStream.Type = adTypeText
Call TextStream.LoadFromFile(Filepath)
Do While Not TextStream.EOS
Line = TextStream.ReadText(adReadLine)
Call Response.Write(Line & "<br>")
Loop
'Reset stream back to start of the stream
TextStream.Position = 0
Do While Not TextStream.EOS
Line = TextStream.ReadText(adReadLine)
Call Response.Write(Line & "<br>")
Loop
Call TextStream.Close()
Set TextStream = Nothing
%>
Obviously this is just a quick example (untested) of how to work with the ADODB.Stream. It's worth noting that you can improve this by moving the TextStream.Position = 0 and Do While loop into a separate function that can be re-used and cuts down on the duplication. For the purposes of this answer however have kept it simple.
More Information
MSDN Library - Stream Object (ADO)
Using METADATA to Import DLL Constants (For avoiding issues with Named Constants used in this example)