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https://issues.apache.org/jira/browse/HADOOP-6297?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kevin J. Price updated HADOOP-6297:
-----------------------------------
Affects Version/s: (was: 0.21.0)
site
Status: Patch Available (was: Open)
Exposes the ability to pass a flush level through to the zlib deflate function
call. This is achieved by:
* Creating a FlushLevel enumeration that mirrors the zlib values.
* Adding a 'flushLevel' parameter to the compress function that takes a value
in this enumeration, and sets a local private variable to the integer
corresponding to this enumeration. (If the finish boolean is true, then FINISH
is used in place of the flushLevel parameter, which matches current behavior.
* Create a new compress function that matches the old signature that just calls
the new compress with NO_FLUSH for the flush level, which should maintain
existing behavior.
* Make the native code wrapper check for the private flushLevel variable and
pass that along to the underlying deflate call.
Also added a TestZlib unit test that tests the three possible flush levels.
> Hadoop's support for zlib library lacks support to perform flushes
> (Z_SYNC_FLUSH and Z_FULL_FLUSH)
> --------------------------------------------------------------------------------------------------
>
> Key: HADOOP-6297
> URL: https://issues.apache.org/jira/browse/HADOOP-6297
> Project: Hadoop Common
> Issue Type: Improvement
> Components: io
> Affects Versions: site
> Reporter: Kevin J. Price
> Priority: Minor
>
> The zlib library supports the ability to perform two types of flushes when
> deflating data. It can perform both a Z_SYNC_FLUSH, which forces all input to
> be written as output and byte-aligned and resets the Huffman coding, and it
> also supports a Z_FULL_FLUSH, which does the same thing but additionally
> resets the compression dictionary. The Hadoop wrapper for the zlib library
> does not support either of these two methods.
> Adding support should be fairly trivial. An additional deflate method that
> takes a fourth "flush" parameter, and a modification to the native c code to
> accept this fourth parameter and pass it along to the zlib library. I can
> submit a patch for this if desired.
> It should be noted that the native SUN Java API is likewise missing this
> functionality, as has been noted for over a decade here:
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4206909
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