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CRC32 property

Posted: 02/18/2016 18:13:42
by Steve Jensen (Priority Standard support level)
Joined: 02/16/2016
Posts: 16

I am evaluating your zip library to replace Dynazip in our desktop application. I am able to create and update archives just fine. However, when I open an archive created with the library in WinZip, the CRC value in the Winzip UI is always blank. When I inspect the CRC32 property of each TElZipArchiveDirectoryEntry in the archive the value is 0. I've searched the forum and help file but can't determine what I am doing wrong. How is this property calculated/populated?

Thank you

P.S. When I add an entry from stream, CRC is populated, just when adding from file is when it's blank.
Posted: 02/18/2016 19:39:11
by Eugene Mayevski (Team)

Thank you for contacting us.

In our code CRC32 is set during compression only if "old-style" or PKWare-strong encryption is used. For WinZIP encryption it's not set. I can't say what the reason for this is, but probably there was one.

Does the lack of CRC cause some problem during decryption or it's just something you are curious about? Why I am asking - it can take quite some time to figure out the exact rules of calculating the CRC and there's no strict requirement for it to be present, we'd like to let it be the current way for the time being.

Sincerely yours
Eugene Mayevski
Posted: 02/22/2016 16:34:17
by Steve Jensen (Priority Standard support level)
Joined: 02/16/2016
Posts: 16

Thank you for the fast reply. I'm more curious than anything. I need to show this library will be a suitable replacement to our current library which has become obsolete. I may have a question or two later, but for now I'm moving forward with it just fine. Thanks.



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