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From "Stefan Bodewig (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COMPRESS-384) Tar File EOF not being detected
Date Sun, 23 Apr 2017 09:19:04 GMT

    [ https://issues.apache.org/jira/browse/COMPRESS-384?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15980334#comment-15980334
] 

Stefan Bodewig commented on COMPRESS-384:
-----------------------------------------

Oh my, tar dialects. Here is the full story.

Tar archive consist of records (512 bytes each) grouped in blocks (usually 20 records, i.e.
10kB). The end of the tar archive is signalled by two consecutive records of zeros, your archive
has such a trailer and {{TarArchiveInputStream}} detects it. But your archive ends after those
two records while {{TarArchiveInputStream}} tries to finish reading the current block (there
are still > 3500 bytes missing for the first block). So 7z uses one of the dialects that
don't pad out the last block but {{TarArchiveInputStream}} has to try to consume it and thus
still tries to read when your archive is done.

I'm afraid there isn't anything we can do about it. See my suggestion from about half an hour
ago for a workaround.

> Tar File EOF not being detected
> -------------------------------
>
>                 Key: COMPRESS-384
>                 URL: https://issues.apache.org/jira/browse/COMPRESS-384
>             Project: Commons Compress
>          Issue Type: Bug
>          Components: Build
>    Affects Versions: 1.13
>         Environment: Windows 10, JDK 1.8
>            Reporter: Jason Shattu
>         Attachments: file.tar
>
>
> I've created both a zip and tar file, with the same contents using the latest version
of 7zip. When I read both archives using code of the form:
> ArchiveStreamFactory().createArchiveInputStream(format, inputStream);
> I notice that both formats correctly list their contents, however the Tar Input doesn't
return a "null" entry when it hits the EOF from archiveStream.getNextEntry() 
> this makes it hard to distinguish between a genuine EOF or a file which is still being
written to. 



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