How To Compress Folder-Contents in 1 Statement on Windows? - vba

Question

I'm attempting to zip a folder containing subfolders and items, using Windows shell CopyHere command:
https://msdn.microsoft.com/en-us/library/windows/desktop/bb787866(v=vs.85).aspx
https://msdn.microsoft.com/en-us/library/windows/desktop/ms723207(v=vs.85).aspx
Update: Note, prefer a native solution-- this is for a distributed Excel VBA tool, so bundling 3rd-party files is not ideal. And, need synchronous compression.
I can easily add a folder and its contents to the zip:
oShell.Namespace(sZipPath).CopyHere "C:\My Folder"
So we know CopyHere can process multiple objects inside a folder in 1 statement.
The problem is, the above command puts the containing-folder at the root of the zip, and it's contents inside of it. But, i don't want the containing folder-- just its contents.
The doc mentions a wildcard (option 128), but when i use a wildcard, i get an error:
oShell.Namespace(sZipPath).CopyHere "C:\My Folder\*"
The file name you specified is not valid or too long.
Perhaps there's a way to use my 1st command above, and then move the items in the zip to the root of the zip?
It would be acceptable to loop through each item in the source folder, adding one at a time to the zip. But, because CopyHere is asynchronous, each subsequent CopyHere fails if the previous CopyHere is not finished. None of the fixes work for this issue:
Comparing number of items in source-folder and destination-zip fail, because if the zip contains a folder, that counts as only 1 item (the items it contains are not counted. https://stackoverflow.com/a/16603850/209942
Waiting a while between each item works, but a timer is unacceptable: it's arbitrary. I cannot guess in advance the size or compress-time of each object.
Checking to see if the zip is locked for access failed for me. If I block my loop until the file is not locked, I still get a file-access error. https://stackoverflow.com/a/6666663/209942
Function FileIsOpen(sPathname As String) As Boolean ' true if file is open
Dim lFileNum As Long
lFileNum = FreeFile
Dim lErr As Long
On Error Resume Next
Open sPathname For Binary Access Read Write Lock Read Write As #lFileNum
lErr = Err
Close #lFileNum
On Error GoTo 0
FileIsOpen = (lErr <> 0)
End Function
Update: VBA can call shell commands synchronously (instead of creating a shell32.shell object in VBA), so if CopyHere works on command-line or PowerShell, that could be the solution. Investigating...

Answer 1

Automating Shell objects really isn't a viable approach as you have already discovered. The Explorer Shell doesn't really expose this capability in any other manner though, at least not before Windows Vista and then not in any fashion easily used from VB6 programs or VBA macros.
Your best bet is a 3rd party ActiveX library, but be careful about 64-bit VBA hosts where you'll need a 64-bit version of such a library.
Another option is to acquire a later copy of the zlibwapi.dll and use some VB6 wrapper code with it. This is also a 32-bit solution.
That's what Zipper & ZipWriter, Zipping from VB programs does. Considering your requirements (which for some reason includes a fear of the Timer control) you could use the synchronous ZipperSync Class. See post #4 there. That code includes a simple AddFolderToZipperSync bundling up the logic to add a folder instead of just a single file.
The downside of the synchronous class is that a large archival operation freezes your program UI until it completes. If you don't want that use the Zipper UserControl instead.
You could also take the ideas from that to write your own wrapper class.

Answer 2

Solution:
Windows contains another native compression utility: CreateFromDirectory at a PowerShell prompt.
https://msdn.microsoft.com/en-us/library/system.io.compression.zipfile.createfromdirectory(v=vs.110).aspx
https://blogs.technet.microsoft.com/heyscriptingguy/2015/03/09/use-powershell-to-create-zip-archive-of-folder/
This requires .Net 4.0 or later:
> Add-Type -AssemblyName System.IO.Compression
> $src = "C:\Users\v1453957\documents\Experiment\rezip\aFolder"
> $zip="C:\Users\v1453957\Documents\Experiment\rezip\my.zip"
> [io.compression.zipfile]::CreateFromDirectory($src, $zip)
Note, you may have to provide the complete pathnames-- active directory was not implicit on my machine.
The above compression is synchronous at the PowerShell prompt, as the OP requests.
Next step is executing synchronously from VBA. The solution there is the .Run method in Windows Script Host Object Model. In VBA, set a reference to that, and do the following, setting the 3rd parameter of .Run command, bWaitOnReturn to True:
Function SynchronousShell(sCmd As String)As Long
Dim oWSH As New IWshRuntimeLibrary.WshShell
ShellSynch = oWSH.Run(sCmd, 3, True)
Set oWSH = Nothing
End Function
Now call SynchronousShell, and pass it the entire compression script.
I believe the only way for this process to work is if CreateFromDirectory is executed in the same session as Add-Type.
So, we must pass the whole thing as 1 string. That is, load all 4 commands into a single sCmd variable, so that Add-Type remains associated with the subsequent CreateFromDirectory. In PowerShell syntax, you can separate them with ;
https://thomas.vanhoutte.be/miniblog/execute-multiple-powershell-commands-on-one-line/
Also, you'll want to use single-quotes instead of double-quotes, else double quotes around the strings are removed when the daisy-chained commands are passed to powershell.exe
https://stackoverflow.com/a/39801732/209942
sCmd = "ps4 Add-Type -AssemblyName System.IO.Compression; $src = 'C:\Users\v1453957\documents\Experiment\rezip\aFolder'; $zip='C:\Users\v1453957\Documents\Experiment\rezip\my.zip'; [io.compression.zipfile]::CreateFromDirectory($src, $zip)"
Solved. The above constitutes the complete solution.
Extra info: Additional comments below are for special circumstances:
Multi-version .Net environments
If a .NET < 4.0 is the active environment on your OS, then System.IO.Compression does not exist-- the Add-Type command will fail. But if your machine has the .NET 4 assemblies available, you can still do this:
Create a batch file which runs PowerShell with .Net 4. See https://stackoverflow.com/a/31279372
In your Add-Type command above, use the exact path to the .Net 4 Compression assembly. On my Win Server 2008:
Add-Type -Path "C:\Windows\Microsoft.NET\assembly\GAC_MSIL\System.IO.Compression.FileSystem\v4.0_4.0.0.0__b77a5c561934e089\System.IO.Compression.FileSystem.dll"
Portability
Turns out, on my machine, I can copy the compression dll to any folder, and make calls to the copy and it works:
Add-Type -Path "C:\MyFunnyFolder\System.IO.Compression.FileSystem.dll"
I don't know what's required to ensure this works-- it might require the full .Net 4.0 or 2.0 files to be located in their expected directories. I assume the dll makes calls to other .Net assemblies. Maybe we just got lucky with this one :)
Character Limit
Depending on the depth of our paths and filenames, character-count may be a concern. PowerShell may have a 260-character limit (not sure).
https://support.microsoft.com/en-us/kb/830473
https://social.technet.microsoft.com/Forums/windowsserver/en-US/f895d766-5ffb-483f-97bc-19ac446da9f8/powershell-command-size-limit?forum=winserverpowershell
Since .Run goes through the Windows shell, you also have to worry about that character limit, but at 8k+, it's a bit roomier:
https://blogs.msdn.microsoft.com/oldnewthing/20031210-00/?p=41553
https://stackoverflow.com/a/3205048/209942
Site below offers a 24k+ character method, but i've not studied it yet:
http://itproctology.blogspot.com/2013/06/handling-freakishly-long-strings-from.html
At minimum, since we can put the dll wherever we like, we can put it in a folder near C: root-- keeping our character-count down.
Update: This post shows how we can put the whole thing in a script-file, and call it with ps4.cmd. This may become my preferred answer:
.\ps4.cmd GC .\zipper.ps1 | IEX
-- depending on answer here.
CopyHere:
Re the question: can CopyHere command execute on command-line?
CopyHere can be executed directly at PowerShell prompt (code below). However, even in powershell it's asynchronous-- control returns to PowerShell prompt before the process is finished. Therefore, no solution for the OP. Here's how it's done:
> $shellapp=new-object -com shell.application
> $zippath="test.zip"
> $zipobj=$shellapp.namespace((Get-Location).Path + "\$zippath")
> $srcpath="src"
> $srcobj=$shellapp.namespace((Get-Location).Path + "\$srcpath")
> $zipobj.Copyhere($srcobj.items())