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Have you ever looked at this?
https://zlib.net/

My main interest is in the compression/decompression part, which has worked well for me since the 1990s, but I think there is some attempt somewhere in this package to handle ZIP files...

I'm not sure this will solve anything, but if you are stuck ...

#14

User contributions / Re: Github-kuba miniz for Pell...

Last post by John Z - April 26, 2026, 04:11:08 PM

Well newer versions of miniz definitely work, but seems some incompatibility with some programs.

This newest version does not cleanly work with LibreOffice 25.8, or Excel 2010 (both will 'repair' the file and then are OK) but DOES work with LibreOffice 7, without repair (as Timo pointed out above, and I've verified as well). Yet a quite a bit older version of miniz works for both newer LibreOffice, older LibreOffice, and Excel several generations, no repair, no errors.

Newer miniz zipped file open ok with miniz definitely, and with Windows Zip and 7z as far as I can tell.

It is a conundrum!

The one thing I see in a Hex display/comparison is that the newer version of miniz appears to be appending to the filenames 01000000 maybe some sort of padding? When using Windows built in ZIP or using 7z, or using the older version of miniz these bytes are not there. The resulting spreadsheet from these three methods all open OK no repair needed.

So this is just a caution in using miniz created zip files in other applications, some may not be compatible. Sadly I'll just have to stick with the older miniz version for now.

John Z

#15