Zip archive corrupted or not?

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tbeu
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Zip archive corrupted or not?

Post by *tbeu » 2012-07-19, 09:06 UTC

I got a zip file (about 1.5GB in size) that 7zip 9.20 x64 reports as broken due to failed CRC. There are 3 files in the zip archive with one file obviously larger than 4GB. If I verify this archive in TC8.01RC4 (both 32 and 64 bit) I do not get a CRC error.

The displayed file size of that large file within the archive is about 2.5Gb (same as showed by 7zip) whereas unpacked file size is about 7GB.

Two ideas (if possible at all):
- ZIP64 can lead to incompatibilities with other tools and should be reported somehow at CRC test of archives.
- If file sizes do not match there should be some information, too after CRC test
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Post by *MaxX » 2012-07-19, 09:24 UTC

2tbeu
That's normal for zip - it does not support files >4Gb, you must use zip64 for them. Zip64 is not supported by most of zip-packers, but TC works with it good.
Try testing your archive with TC and (if you get no errors) then repack it to something more common, like rar or 7z...

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Post by *MVV » 2012-07-19, 10:47 UTC

But as I see TC shows wrong file size, so it may be fixed.

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Post by *tbeu » 2012-07-19, 11:11 UTC

MVV wrote:But as I see TC shows wrong file size, so it may be fixed.
Yes, if after successful CRC test file sizes are different there should be some information that point to ZIP64.
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Post by *tbeu » 2012-07-19, 12:33 UTC

I repacked the 3 files with internal zip of TC8 and now the file sizes match. Thus for archives with not-matching files sizes some tools (like 7zip, Winzip) report failures others (like Winrar, TC) do not. It would be nice if TC could print a warning here after archive CRC test, like it does when creating such archives:

Code: Select all

Warning: The total size of all selected files (unpacked) is > 2 GB. If the resulting archive is larger than 2 GB, it will be unreadable by some ZIP unpackers.
Continue anyway?
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Post by *MaxX » 2012-07-19, 12:54 UTC

archive is larger than 2 GB, it will be unreadable by some ZIP unpackers
archive is larger than 2 GB, it will be unreadable by some ZIP unpackers
That's what I was talking about.
Only few packers work with big files properly.

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Post by *tbeu » 2012-07-19, 13:07 UTC

But orginal archive (with invalid file size) was not created by TC. TC claims CRC is fine but rather could give some information that other tools might fail. This would have saved me a lot of time.
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Post by *ghisler(Author) » 2012-07-19, 13:51 UTC

Sorry but these files follow the ZIP standard from PKWare, so TC doesn't show any error because the file is correct. It's not TC's fault that some unpackers cannot handle these files although they follow the standard.
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Post by *tbeu » 2012-07-19, 14:15 UTC

Yes, for that reason I lost belief in 7zip.
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