[jira] Created: (COMPRESS-115) Imploded entry decompression for Zip archives (method 6)

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[jira] Created: (COMPRESS-115) Imploded entry decompression for Zip archives (method 6)

JIRA jira@apache.org
Imploded entry decompression for Zip archives (method 6)
--------------------------------------------------------

                 Key: COMPRESS-115
                 URL: https://issues.apache.org/jira/browse/COMPRESS-115
             Project: Commons Compress
          Issue Type: New Feature
    Affects Versions: 1.0
            Reporter: Emmanuel Bourg


This is a RFE to implement the decompression of zip file entries using the imploded compression method (aka method 6). This method is found in archives created with old versions of PKZip. Only the decompression operation is really useful since this method is less efficient than deflate.

Some links with technical information about this format:

http://www.pkware.com/documents/casestudies/APPNOTE.TXT

http://en.wikipedia.org/wiki/Shannon%E2%80%93Fano_coding

http://en.wikipedia.org/wiki/LZ77

http://src.opensolaris.org/source/xref/sfw/usr/src/cmd/unzip/explode.c

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[jira] Updated: (COMPRESS-115) Imploded entry decompression for Zip archives (method 6)

JIRA jira@apache.org

     [ https://issues.apache.org/jira/browse/COMPRESS-115?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Emmanuel Bourg updated COMPRESS-115:
------------------------------------

    Attachment: imploding-4Kdict-2trees.zip
                imploding-8Kdict-3trees.zip

Here are 2 test files covering the variants of the imploded format (4K or 8K sliding dictionary, 2 or 3 Shannon-Fano trees)

> Imploded entry decompression for Zip archives (method 6)
> --------------------------------------------------------
>
>                 Key: COMPRESS-115
>                 URL: https://issues.apache.org/jira/browse/COMPRESS-115
>             Project: Commons Compress
>          Issue Type: New Feature
>    Affects Versions: 1.0
>            Reporter: Emmanuel Bourg
>         Attachments: imploding-4Kdict-2trees.zip, imploding-8Kdict-3trees.zip
>
>
> This is a RFE to implement the decompression of zip file entries using the imploded compression method (aka method 6). This method is found in archives created with old versions of PKZip. Only the decompression operation is really useful since this method is less efficient than deflate.
> Some links with technical information about this format:
> http://www.pkware.com/documents/casestudies/APPNOTE.TXT
> http://en.wikipedia.org/wiki/Shannon%E2%80%93Fano_coding
> http://en.wikipedia.org/wiki/LZ77
> http://src.opensolaris.org/source/xref/sfw/usr/src/cmd/unzip/explode.c

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[jira] Commented: (COMPRESS-115) Imploded entry decompression for Zip archives (method 6)

JIRA jira@apache.org
In reply to this post by JIRA jira@apache.org

    [ https://issues.apache.org/jira/browse/COMPRESS-115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12877381#action_12877381 ]

Emmanuel Bourg commented on COMPRESS-115:
-----------------------------------------

Alternative explode implementation in ClamAV:

http://git.clamav.net/gitweb?p=clamav-devel.git;a=blob;f=libclamav/explode.h
http://git.clamav.net/gitweb?p=clamav-devel.git;a=blob;f=libclamav/explode.c


> Imploded entry decompression for Zip archives (method 6)
> --------------------------------------------------------
>
>                 Key: COMPRESS-115
>                 URL: https://issues.apache.org/jira/browse/COMPRESS-115
>             Project: Commons Compress
>          Issue Type: New Feature
>    Affects Versions: 1.0
>            Reporter: Emmanuel Bourg
>         Attachments: imploding-4Kdict-2trees.zip, imploding-8Kdict-3trees.zip
>
>
> This is a RFE to implement the decompression of zip file entries using the imploded compression method (aka method 6). This method is found in archives created with old versions of PKZip. Only the decompression operation is really useful since this method is less efficient than deflate.
> Some links with technical information about this format:
> http://www.pkware.com/documents/casestudies/APPNOTE.TXT
> http://en.wikipedia.org/wiki/Shannon%E2%80%93Fano_coding
> http://en.wikipedia.org/wiki/LZ77
> http://src.opensolaris.org/source/xref/sfw/usr/src/cmd/unzip/explode.c

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