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From sebb <>
Subject Re: [COMPRESS] performance improvement in Ant's ZipOutputStream
Date Wed, 16 Jul 2008 13:26:00 GMT
On 16/07/2008, Stefan Bodewig <> wrote:
> Hi all,
>  I couldn't find a JIRA for compress so I'm posting it here.

Compress is currently in the Sandbox.

>  We had a bug report against Ant's ZipOutputStream that showed that the
>  class had a way worse performance compared to's cousin
>  when it was used to compress big files.  See
>  Attached to this report is a small test class that could easily be
>  adapted to the compress library.
>  It turns out that java.util.Deflater doesn't like to see big arrays
>  passed into its setInput method and the original reporter says
>  OpenJDK's code would split the input into 512 byte chunks.  While I
>  didn't verify the OpenJDK code I went looking into zlib and InfoZIP
>  and at least InfoZIP's zipup.c uses smaller chunks (between 2kB and
>  16kB) as well when compressing files.
>  The change I've committed
>  sped up the test by a factor of 40 on my machine.
>  It won't have any effect on Ant since <zip> has always split up the
>  file's content before writing it to the archive, but it would affect
>  other direct users of our API - and would probably benefit the
>  compress component for just that reason as well.
>  Stefan
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