Read and write arrays to from file - arrays

Question

I have a class which create session file on disk with written inside colon-separated fields.
<%
Class MySession
Private session_key, stream
Private Sub Class_Initialize
set stream = createobject("adodb.stream")
session_key = request.cookies("sessionkey")
if len(session_key) = 0 then
CreateSession()
end if
End Sub
' read from session file
Public Property Get val()
on error resume next
val = ""
stream.open
stream.loadfromfile "d:\" & session_key
val = stream.readtext
stream.close
End Property
' write session to file
Public Property Let val(userval)
on error resume next
stream.open
stream.writetext mycstr(userval)
for err11 = 0 to 50
stream.savetofile "d:\" & session_key, 2
if Err.Number = 0 then exit for
Err.Clear
next
stream.close
End Property
End Class
%>
Now to fill session file I do
Set SessionID = new MySession
FillArr = FillArr & Request.cookies("sessionkey") & ":" & now()+1
For Row = 0 to Ubound(arrRst,1)
FillArr = FillArr & ":" & arrRst(Row, 0)
Next
SessionID.val() = FillArr
To read all data in session file I use
AllData = sessionID.val()
Now I need to add additional field to this file.
Problem is:
How to check if this field already exist in the file?
How to update only this field in the file?
So I think there is good to use arrays which I can call by it names.
In session file I need data to be written like:
{"sessionkey":"3yut267d273";"session_exp":"51453463";"username":"Alex"}
I think it must be something like this to get needed filed from file:
AllData = sessionID.val("username")
So help me write a right syntax to do that:
How to write array to file?
How to call only needed array element from file?
How to change only needed (or multiple specified field) array element in file and if it not exist then create it?

Answer 1

The canonical way is to import the file (if it exists) into an in-memory data structure when the custom object is created, and write the data structure back to a file when the object is destroyed. You can do it every time a value is requested or changed, but you'll need to read or write the entire file every time.
To do what you're asking you'd need an abstraction layer mapping the data structure elements to bytes on disk. NoSQL databases are implementations of such an abstraction layer. I have never worked with one, though, so I can't tell you how to establish a connection from VBScript. From what I gleaned from the web you may have to use a REST API (via XMLHttpRequest).