vbscript - Write to file using CopyHere without using WScript.Sleep

Question

I've written a small VBScript to creates a .zip file and then copies the contents of a specified folder into that .zip file.

I copy the files over one by one for a reason (I know I can do the whole lot at once). However my problem is when I try to copy them one by one without a WScript.Sleep between each loop iteration I get a "File not found or no read permission." error; if I place a WScript.Sleep 200 after each write it works but not 100% of the time.

Pretty much I'd like to get rid of the Sleep function and not rely on that because depending on the file size it may take longer to write therefore 200 milliseconds may not be enough etc.

As you can see with the small piece of code below, I loop through the files, then if they match the extension I place them into the .zip (zipFile)

For Each file In folderToZip.Items
    For Each extension In fileExtensions
        if (InStr(file, extension)) Then
            zipFile.CopyHere(file)
            WScript.Sleep 200
            Exit For
        End If
    Next
Next

Any suggestions on how I can stop relying on the Sleep function?

Thanks

Answer 1

This is how we do it in VB6. After calling CopyHere on the zip we wait for async compression to complete like this

    Call Sleep(100)
    Do
        Do While Not pvCanOpenExclusive(sZipFile)
            Call Sleep(100)
        Loop
        Call Sleep(100)
    Loop While Not pvCanOpenExclusive(sZipFile)

where the helper function looks like this

Private Function pvCanOpenExclusive(sFile As String) As Boolean
    Dim nFile       As Integer

    nFile = FreeFile
    On Error GoTo QH
    Open sFile For Binary Access Read Lock Write As nFile
    Close nFile
    pvCanOpenExclusive = True
QH:
End Function

Nice side-effect is that even if zipping fails this will not end up in infinite loop.

The trouble comes when accessing the zip-file when it's closed by zipfldr.dll, that is when pvCanOpenExclusive returns true.