I need to URL decode a string in a VBScript. The string may contain Unicode characters which are encoded as multiple bytes as per UTF-8. So for example "Paris%20%E2%86%92%20Z%C3%BCrich" would decode to "Paris → Zürich".
To do the job, I'm using a piece of code that looks like this:
Function URLDecode(str)
    set list = CreateObject("System.Collections.ArrayList")
    strLen = Len(str)
    for i = 1 to strLen
        sT = mid(str, i, 1)
        if sT = "%" then
            if i + 2 <= strLen then
                list.Add cbyte("&H" & mid(str, i + 1, 2))
                i = i + 2
            end if
        else
            list.Add asc(sT)
        end if
    next
    depth = 0
    for each by in list.ToArray()
        if by and &h80 then
            if (by and &h40) = 0 then
                if depth = 0 then Err.Raise 5
                val = val * 2 ^ 6 + (by and &h3f)
                depth = depth - 1
                if depth = 0 then
                    sR = sR & chrw(val)
                    val = 0
                end if
            elseif (by and &h20) = 0 then
                if depth > 0 then Err.Raise 5
                val = by and &h1f
                depth = 1
            elseif (by and &h10) = 0 then
                if depth > 0 then Err.Raise 5
                val = by and &h0f
                depth = 2
            else
                Err.Raise 5
            end if
        else
            if depth > 0 then Err.Raise 5
            sR = sR & chrw(by)
        end if
    next
    if depth > 0 then Err.Raise 5
    URLDecode = sR
End Function
This seems to be working well, but it looks exaggeratedly complex to me. In times of HTML5 and web standards, there must be a simpler way to get this done without a bunch of hand-made loops and conditions. Any suggestions?