Revision 1302602

HBASE-5521 [jira] Move compression/decompression to an encoder specific encoding
context

Author: Yongqiang He

Summary:
https://issues.apache.org/jira/browse/HBASE-5521

As part of working on HBASE-5313, we want to add a new columnar encoder/decoder.
It makes sense to move compression to be part of encoder/decoder:
1) a scanner for a columnar encoded block can do lazy decompression to a
specific part of a key value object
2) avoid an extra bytes copy from encoder to hblock-writer.

If there is no encoder specified for a writer, the HBlock.Writer will use a
default compression-context to do something very similar to today's code.

Test Plan: existing unit tests verified by mbautin and tedyu. And no new test
added here since this code is just a preparation for columnar encoder. Will add
testcase later in that diff.

Reviewers: dhruba, tedyu, sc, mbautin

Reviewed By: mbautin

Differential Revision: https://reviews.facebook.net/D2097