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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10047) Add a directbuffer Decompressor API to hadoop
Date Thu, 31 Oct 2013 17:35:17 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-10047?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13810463#comment-13810463
] 

Colin Patrick McCabe commented on HADOOP-10047:
-----------------------------------------------

Looks good.  I assume the patch apply failure is something trivial you'll fix soon.

Thanks for writing some unit tests, too.  I see that we're already catching some bugs in the
exception handling of the current code :)

In {{DirectDecompressor#decompress}}, it's interesting that there is both a src and dst buffer.
 In the equivalent non-direct-buffer {{Decompressor#decompress}} function, there is only an
output array.  Is it possible to use different 'src' buffers for each call you make to {{DirectDecompressor#decompress}}?
 If so, it might be worth documenting this.  If not, I wonder if the src buffer could be supplied
to the {{DirectDecompressionCodec#createDirectDecompressor}} function so that only a dst buffer
needed to be supplied to {{decompress}}?

> Add a directbuffer Decompressor API to hadoop
> ---------------------------------------------
>
>                 Key: HADOOP-10047
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10047
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: io
>    Affects Versions: 2.3.0
>            Reporter: Gopal V
>            Assignee: Gopal V
>              Labels: compression
>             Fix For: 2.3.0
>
>         Attachments: DirectCompressor.html, DirectDecompressor.html, HADOOP-10047-WIP.patch,
HADOOP-10047-final.patch, HADOOP-10047-redo-WIP.patch, HADOOP-10047-with-tests.patch
>
>
> With the Zero-Copy reads in HDFS (HDFS-5260), it becomes important to perform all I/O
operations without copying data into byte[] buffers or other buffers which wrap over them.
> This is a proposal for adding a DirectDecompressor interface to the io.compress, to indicate
codecs which want to surface the direct buffer layer upwards.
> The implementation should work with direct heap/mmap buffers and cannot assume .array()
availability.



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