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From "Dawid Weiss (JIRA)" <>
Subject [jira] [Commented] (COMPRESS-380) Support for ENHANCED_DEFLATED (Deflate64) in ZIP files
Date Mon, 08 Jan 2018 22:07:00 GMT


Dawid Weiss commented on COMPRESS-380:

I've decompressed the entire ~6GB archive without any errors with the code from the current
head of COMPRESS-380 branch (I just decompressed it, didn't diff against the original!). This
is great, although the performance penalty is huge at the moment (read: it takes forever...
an order of magnitude slower than the C version; the archive took ~3 hours to just decompress
while total commander manages the same in a few minutes). I looked at zlib implementation
of inflate (they create smart lookup tables for larger bit windows) and found a Java implementation
of this concept in [1]. The speed this implementation achieves is quite nice (see [2]); could
be something to think about in the future as an improvement. For the time being, even a slow
implementation is better than none (although this seems almost suspiciously slow).


> Support for ENHANCED_DEFLATED (Deflate64) in ZIP files
> ------------------------------------------------------
>                 Key: COMPRESS-380
>                 URL:
>             Project: Commons Compress
>          Issue Type: New Feature
>            Reporter: Dawid Weiss
>             Fix For: 1.16
>         Attachments:,,,,
compress-380.diff,, input2
> Some of the (large) ZIP files we try to process currently will throw this:
> {code}
> UnsupportedZipFeatureException: unsupported feature method 'ENHANCED_DEFLATED' 
> {code}
> which is a bummer since JDK's implementation also doesn't support Deflate64. This seems
to be PKWare's extensions, although code to decrypt it exists in zlib (and is appropriately
licensed, I believe).

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