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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 22:29:00 GMT


Dawid Weiss commented on COMPRESS-380:

I just realized that a *lot* of data in that archive is probably zipped as stored blocks.
The currect code uses costly bit-by-bit routine while those stored blocks are (by the spec)
byte-aligned so UncompressedState could just read byte-by-byte from the underlying reader
(remembering that some data could be still stored in the bit buffer and flushing it first).
This alone would probably give a significant speed boost.

> 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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