FAQ
Hadoop's support for zlib library lacks support to perform flushes (Z_SYNC_FLUSH and Z_FULL_FLUSH)
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Key: HADOOP-6297
URL: https://issues.apache.org/jira/browse/HADOOP-6297
Project: Hadoop Common
Issue Type: Improvement
Components: io
Affects Versions: 0.21.0
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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postedOct 6, '09 at 3:01p
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