How do I reference an uploaded file in a server-side Classic ASP page?

Question

I am trying to upload a file via Ajax to a server-side script written in classic ASP.

This is the relevant HTML and JavaScript code:

<input type="file" id="fileInput" />

and

function saveToServer(file) {
    const fd = new FormData();
    fd.append('image', file);
    const xhr = new XMLHttpRequest();
    xhr.open('POST', 'http://localhost/post.asp', true);
    xhr.onload = () => {
        if (xhr.status === 200) {
            // Do stuff with response
        }
    };
    xhr.send(fd);
}

const fileInput = document.getElementById("fileInput");

fileInput.addEventListener("change", () => {
    const file = fileInput.files[0];
    if (/^image\//.test(file.type)) {
        saveToServer(file);
    } else {
        console.warn('You can only upload images.');
    }
});

My question is: how can I get a reference to the uploaded file in my Classic ASP page (post.asp)?

In PHP there is a global variable $_FILES available, which would contain something like:

Array
(
  [image] => Array
  (
    [name] => cat.png
    [type] => image/png
    [tmp_name] => /tmp/phpOjXMW3
    [error] => 0
    [size] => 10603
  )
)

Is there something equivalent in Classic ASP?

---

This is the post page:

Set upl = New FileUploader 
upl.Upload()
If upl.Files.Count = 1 Then
  For Each File In upl.Files.Items
    If File.FileSize < 100000 Then
      File.FileName =  upl.Form ("id") & ".jpg"
      File.SaveToDisk Server.MapPath("/Images")
  next
end if

This is an include at the top of the post page:

Class FileUploader
    Public  Files
    Private mcolFormElem

    Private Sub Class_Initialize()
        Set Files = Server.CreateObject("Scripting.Dictionary")
        Set mcolFormElem = Server.CreateObject("Scripting.Dictionary")
    End Sub

    Private Sub Class_Terminate()
        If IsObject(Files) Then
            Files.RemoveAll()
            Set Files = Nothing
        End If
        If IsObject(mcolFormElem) Then
            mcolFormElem.RemoveAll()
            Set mcolFormElem = Nothing
        End If
    End Sub

    Public Property Get Form(sIndex)
        Form = ""
        If mcolFormElem.Exists(LCase(sIndex)) Then Form = mcolFormElem.Item(LCase(sIndex))
    End Property

    Public Default Sub Upload()
        Dim biData, sInputName
        Dim nPosBegin, nPosEnd, nPos, vDataBounds, nDataBoundPos
        Dim nPosFile, nPosBound
    'response.Flush

        biData = Request.BinaryRead(Request.TotalBytes)
        nPosBegin = 1
        nPosEnd = InstrB(nPosBegin, biData, CByteString(Chr(13)))

        If (nPosEnd-nPosBegin) <= 0 Then Exit Sub

        vDataBounds = MidB(biData, nPosBegin, nPosEnd-nPosBegin)
        nDataBoundPos = InstrB(1, biData, vDataBounds)

        Do Until nDataBoundPos = InstrB(biData, vDataBounds & CByteString("--"))

            nPos = InstrB(nDataBoundPos, biData, CByteString("Content-Disposition"))
            nPos = InstrB(nPos, biData, CByteString("name="))
            nPosBegin = nPos + 6
            nPosEnd = InstrB(nPosBegin, biData, CByteString(Chr(34)))
            sInputName = CWideString(MidB(biData, nPosBegin, nPosEnd-nPosBegin))
            nPosFile = InstrB(nDataBoundPos, biData, CByteString("filename="))
            nPosBound = InstrB(nPosEnd, biData, vDataBounds)

            If nPosFile <> 0 And  nPosFile < nPosBound Then
                Dim oUploadFile, sFileName
                Set oUploadFile = New UploadedFile

                oUploadFile.FormElement = MidB(biData, nPos, 5)


                nPosBegin = nPosFile + 10
                nPosEnd =  InstrB(nPosBegin, biData, CByteString(Chr(34)))
                sFileName = CWideString(MidB(biData, nPosBegin, nPosEnd-nPosBegin))
                oUploadFile.FileName = Right(sFileName, Len(sFileName)-InStrRev(sFileName, "\"))

                nPos = InstrB(nPosEnd, biData, CByteString("Content-Type:"))
                nPosBegin = nPos + 14
                nPosEnd = InstrB(nPosBegin, biData, CByteString(Chr(13)))

                oUploadFile.ContentType = CWideString(MidB(biData, nPosBegin, nPosEnd-nPosBegin))

                nPosBegin = nPosEnd+4
                nPosEnd = InstrB(nPosBegin, biData, vDataBounds) - 2
                oUploadFile.FileData = MidB(biData, nPosBegin, nPosEnd-nPosBegin)

                If oUploadFile.FileSize > 0 Then Files.Add LCase(sInputName), oUploadFile
            Else
                nPos = InstrB(nPos, biData, CByteString(Chr(13)))
                nPosBegin = nPos + 4
                nPosEnd = InstrB(nPosBegin, biData, vDataBounds) - 2
                If Not mcolFormElem.Exists(LCase(sInputName)) Then mcolFormElem.Add LCase(sInputName), CWideString(MidB(biData, nPosBegin, nPosEnd-nPosBegin))
            End If

            nDataBoundPos = InstrB(nDataBoundPos + LenB(vDataBounds), biData, vDataBounds)
        Loop
    End Sub

    'String to byte string conversion
    Private Function CByteString(sString)
        Dim nIndex
        For nIndex = 1 to Len(sString)
           CByteString = CByteString & ChrB(AscB(Mid(sString,nIndex,1)))
        Next
    End Function

    'Byte string to string conversion
    Private Function CWideString(bsString)
        Dim nIndex
        CWideString =""
        For nIndex = 1 to LenB(bsString)
           CWideString = CWideString & Chr(AscB(MidB(bsString,nIndex,1))) 
        Next
    End Function
End Class

Class UploadedFile
    Public ContentType
    Public FileName
    Public FileData
    Public FormElement

    Public Property Get FileSize()
        FileSize = LenB(FileData)
    End Property

    Public Sub SaveToDisk(sPath)
        Dim oFS, oFile
        Dim nIndex

        If sPath = "" Or FileName = "" Then Exit Sub
        If Mid(sPath, Len(sPath)) <> "\" Then sPath = sPath & "\"

        Set oFS = Server.CreateObject("Scripting.FileSystemObject")
        If Not oFS.FolderExists(sPath) Then Exit Sub

        Set oFile = oFS.CreateTextFile(sPath & FileName, True)

        For nIndex = 1 to LenB(FileData)
            oFile.Write Chr(AscB(MidB(FileData,nIndex,1)))
        Next

        oFile.Close
    End Sub

    Public Sub SaveToDatabase(ByRef oField)
        If LenB(FileData) = 0 Then Exit Sub

        If IsObject(oField) Then
            oField.AppendChunk FileData
        End If
    End Sub

End Class

Answer 1

Once a file has been uploaded you could use FileSystemObject to check the file exists and retrieve its properties via the GetFile method. Use a function to save space and return a dictionary of properties, making them easier to reference:

function getFileInfo(ByVal fileLocation)

    ' Use MapPath to convert to an absolute path

    fileLocation = Server.MapPath(fileLocation)

    ' Set the file system and dictionary objects using reserved words

    set fileSystem = Server.CreateObject("Scripting.FileSystemObject")
    Set dictionary = Server.CreateObject("Scripting.Dictionary")

    ' Check that the file exists

    if fileSystem.FileExists(fileLocation) then

        ' Use GetFile to retrieve the files properties

        set file = fileSystem.GetFile(fileLocation)

        ' Add each property to the dictionary object

        dictionary.add "FileFound",true
        dictionary.add "Attributes",file.Attributes
        dictionary.add "DateCreated",file.DateCreated
        dictionary.add "DateLastAccessed",file.DateLastAccessed
        dictionary.add "DateLastModified",file.DateLastModified
        dictionary.add "Drive",file.Drive
        dictionary.add "Name",file.Name
        dictionary.add "ParentFolder",file.ParentFolder
        dictionary.add "Path",file.Path
        dictionary.add "ShortName",file.ShortName
        dictionary.add "ShortPath",file.ShortPath
        dictionary.add "Size",file.Size
        dictionary.add "Type",file.Type

        ' Attributes translations:
        ' 0 = Normal file
        ' 1 = Read-only file
        ' 2 = Hidden file
        ' 4 = System file
        ' 16 = Folder or directory
        ' 32 = File has changed since last backup
        ' 1024 = Link or shortcut
        ' 2048 = Compressed file

    else

        ' File not found

        dictionary.add "FileFound",false

    end if

    ' Return the dictionary object

    set getFileInfo = dictionary

    ' Set all objects to nothing

    set fileSystem = nothing
    set dictionary = nothing
    set file = nothing

end function

To check a file has been uploaded and retrieve its properties:

Dim fileInfo : Set fileInfo = getFileInfo("../../uploads/cat.jpg")  

    ' getFileInfo("/Images/" & upl.Form ("id") & ".jpg") 

    if fileInfo.item("FileFound") then

        ' Output all the file properties

        for each item in fileInfo
            response.write "<b>" & item & "</b>: " & fileInfo.item(item) & "<br>"
        next

        ' Output a specific file property

        response.write "<b>The file size is</b>: " & fileInfo.item("Size") & " bytes<br>"
        response.write "<b>The file type is</b>: " & fileInfo.item("Type") & "<br>"

    else

        response.write "File not found"

    end if

Set fileInfo = nothing

Example output:

FileFound : True
Attributes : 32
DateCreated : 20/03/2019 12:40:09
DateLastAccessed : 20/03/2019 12:40:09
DateLastModified : 20/03/2019 12:40:09
Drive : C:
Name : cat.jpg
ParentFolder : C:\\inetpub\\wwwroot\\uploads
Path : C:\\inetpub\\wwwroot\\uploads\\cat.jpg
ShortName : cat.jpg
ShortPath : C:\\inetpub\\wwwroot\\uploads\\cat.jpg
Size : 992514
Type : JPEG image
The file size is : 992514 bytes
The file type is : JPEG image

EDIT: Following on from Lankymart's comment, you can use the upl.Files object to perform some preliminary checks before saving the file to disk:

function randomFileName()

    ' Randomize() generates quite a small seed number, so you will generate duplicate
    ' filenames if you upload enough images. To prevent this, prefix a random number
    ' with a unix timestamp.

    Dim uts : uts = DateDiff("s","1970-01-01 00:00:00",Now())

    Randomize()

    ' filename format: [unix timestamp][random 7 digit number]

    randomFileName = cStr(uts & Int((9999999-1000000+1)*Rnd+1000000))

end function

function validExtension(ByVal allowed, ByVal fileName)

    Dim extRegexp : Set extRegexp = New RegExp

    extRegexp.Pattern = "^.*\.(" & lCase(allowed) & ")$"
    validExtension = extRegexp.Test(lCase(fileName))

end function

if Request.TotalBytes > 0 then

    Const max_upload_size = 100000 ' bytes
    Const allowed_extensions = "jpg|jpeg|png"
    Const upload_folder = "/Images/"

    Dim upload_successful : upload_successful = false
    Dim upload_message : upload_message = ""
    Dim rndFileName, fileExt, fileSplit

    Dim upl : Set upl = New FileUploader 
    upl.Upload()

    If upl.Files.Count = 1 Then

        For Each File In upl.Files.Items

            file.ContentType = lCase(file.ContentType)
            File.FileName = trim(File.FileName)

            if NOT (file.ContentType = "image/jpeg" _
            OR file.ContentType = "image/jpg" _
            OR file.ContentType = "image/png") then

                upload_message = "Invalid file type"

            elseif NOT validExtension(allowed_extensions,File.FileName) then

                upload_message = "Invalid file type"

            elseif File.FileSize > max_upload_size then

                upload_message = "File too big"

            else

                ' Extract the file extension

                fileSplit = split(File.FileName,".")
                fileExt = lCase(fileSplit(uBound(fileSplit)))

                ' Generate a random file name

                rndFileName = randomFileName() & "." & fileExt

                ' Everything checks out, save to disk

                File.FileName = rndFileName
                File.SaveToDisk Server.MapPath(upload_folder)

                upload_message = "Upload successful"

                upload_successful = true

            end if

        next

    else

        upload_message = "Maximum upload count exceeded"

    end if

    Set upl = nothing

    ' Return a JSON string      

    Response.ContentType = "application/json"

    response.write _
    "{""uploaded"":" & lCase(upload_successful) & "," &_
    """message"":""" & upload_message & """," &_
    """file"":""" & upload_folder & rndFileName & """}"

end if

Answer 2

This question doesn't make much sense...

My question is:

How can I get a reference to the uploaded file in my Classic ASP page (post.asp)?

From the code you have posted it's clear you are using a custom class to support the upload FileUploader which parses the binary for you and builds a collection of objects that represent the uploaded files (the UploadedFile class).

In the code you posted you are accessing the UploadedFile object in a For Each loop;

Set upl = New FileUploader 
upl.Upload()
If upl.Files.Count = 1 Then
  For Each File In upl.Files.Items
    If File.FileSize < 100000 Then
      File.FileName =  upl.Form ("id") & ".jpg"
      File.SaveToDisk Server.MapPath("/Images")
    End If
  Next
End If

^{Corrected typo where End If was missing before the For Each ends.}

In that example, your File object is the UploadedFile class object containing the file properties populated during the parse of the binary by the FileUploader .