public static Hash getInstance() {
    return _instance;
  }
Produces 32-bit hash for hash table lookup.

<pre>
lookup3.c, by Bob Jenkins, May 2006, Public Domain.

You can use this free for any purpose.  It's in the public domain.
It has no warranty.
</pre>

@see <a href="http://burtleburtle.net/bob/c/lookup3.c">lookup3.c</a>
@see <a href="http://www.ddj.com/184410284">Hash Functions (and how this function compares to
     others such as CRC, MD?, etc</a>
@see <a href="http://burtleburtle.net/bob/hash/doobs.html">Has update on the Dr. Dobbs
     Article</a>
hbase-common/src/main/java/org/apache/hadoop/hbase/util/JenkinsHash.java