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Thread: VB6 - Zipper & ZipWriter, Zipping from VB programs

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    Feb 2006

    Lightbulb VB6 - Zipper & ZipWriter, Zipping from VB programs


    A lot of us find the need to create ZIP archives programmatically from time to time. There are a number of techniques we can use, from spawning external utility programs to 3rd party components to Shell automation.

    Here is yet another way to accomplish this: using the free, open source zlibwapi.dll


    In addition to providing a STDCALL version of ZLib that we can call easily from VB6 programs zlibwapi.dll includes the Minizip project code as well.

    Like a lot of open source hacked out by C coders this can be rough in many places, but it is widely used and well proven. It should have few if any bugs in the most recent version.

    I'm using version 1.25 here. You can get this from:

    Minizip: Zip and UnZip additionnal library

    See the typo there? This is just one symptom of some of the issues, but fortunately the code at least seems to work fine even if its source is wonky with lots of flaws in comments and general documentation issues.

    This DLL is not included in the attachment. You must download it yourself.

    In zlib125dll.zip there is the Win32 Windows DLL of my Windows DLL named Zlibwapi.dll that contains both zLib and Minilib.
    The file you want from this ZIP archive is:



    ZipWriter is a VB6 Class that wraps zlibwapi.dll to provide you with a way to create a ZIP archive and actually write data into it as archived files with no intermediate disk I/O steps.

    You can use this as-is in many cases without the other code offered here.


    Zipper is a VB6 UserControl that wraps ZipWriter and a small helper ZipFile Class to give you the ability to create a ZIP archive (or add to an existing one) and add a list of disk files to it.

    Zipper.Zip is an async operation and reports back progress, errors, and completion through several events. There is a Zipper.Cancel method if you need that.


    ZipDemo is a VB6 project that demonstrates use of the items described above.

    You must download zlibwapi.dll and copy it into this project folder to run the program.

    Much of the bulk of this attachment consists of the sample files in the "samples2" folder included.

    There is a "ZipWriter" button that does a simple test of ZipWriter, creating a new ZIP archive "test.zip" with two files written to it. When that step completes the "Zipper" button is enabled.

    The "Zipper" button tests Zipper, adding the files it finds in the "samples2" folder to the "test.zip" created in the first stage of the demo. While running a progressbar is updated and a "Cancel" button is enabled.

    The "samples2" folder as supplied has just a few small files. Be sure to copy some larger files into it and rerun the program to see how things go with large files. The performance is fairly good.


    While you need to deploy zlibwapi.dll with your programs this is a standard DLL that you can feel free to place next to your EXE. No registration is required.

    The results are better than those achieved using most other common techniques. Progress/Cancel/Complete can be really nice to have. There is no need for the shaky, convoluted, hackish window spelunking people often resort to when automating Shell objects.

    There is a lot more you can do with zlibwapi.dll too. You can read from ZIP archives, unzip them, compress separate files outside of ZIP archives, compress/expand data in memory, etc. Even the huge-file Zip64 format is supported.

    All you need is to write additional wrappers or just make the calls directly.
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