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From "Tim Broberg (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-8148) Zero-copy ByteBuffer-based compressor / decompressor API
Date Wed, 07 Mar 2012 19:30:58 GMT
Zero-copy ByteBuffer-based compressor / decompressor API
--------------------------------------------------------

                 Key: HADOOP-8148
                 URL: https://issues.apache.org/jira/browse/HADOOP-8148
             Project: Hadoop Common
          Issue Type: New Feature
          Components: io
            Reporter: Tim Broberg


Per Todd Lipcon's comment in HDFS-2834, "
  Whenever a native decompression codec is being used, ... we generally have the following
copies:

  1) Socket -> DirectByteBuffer (in SocketChannel implementation)
  2) DirectByteBuffer -> byte[] (in SocketInputStream)
  3) byte[] -> Native buffer (set up for decompression)
  4*) decompression to a different native buffer (not really a copy - decompression necessarily
rewrites)
  5) native buffer -> byte[]

  with the proposed improvement we can hopefully eliminate #2,#3 for all applications, and
#2,#3,and #5 for libhdfs.
"

The interfaces in the attached patch attempt to address:
 A - Compression and decompression based on ByteBuffers (HDFS-2834)
 B - Zero-copy compression and decompression (HDFS-3051)
 C - Provide the caller a way to know how the max space required to hold compressed output.


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