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https://issues.apache.org/jira/browse/HADOOP-1385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12496871
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Tom White commented on HADOOP-1385:
-----------------------------------
This looks good except I was confused by the collision test as there doesn't
seem to be a collision. Shouldn't closeHash1 and closeHash2 share the same
first four bytes but differ in (some of) the others? Then they would not be
equal (according to the equals method) but the hash codes would be equal.
Also, this looks like a 0.14.0 fix since the existing code isn't broken, just
inefficient in some cases.
> MD5Hash has a bad hash function
> -------------------------------
>
> Key: HADOOP-1385
> URL: https://issues.apache.org/jira/browse/HADOOP-1385
> Project: Hadoop
> Issue Type: Bug
> Components: io
> Affects Versions: 0.12.3
> Reporter: Owen O'Malley
> Assigned To: Owen O'Malley
> Fix For: 0.13.0
>
> Attachments: 1385.patch
>
>
> The MD5Hash class has a really bad hash function, that will cause most most
> md5s to hash to 0xFFFFFFxx leaving only the low order byte as meaningful. The
> problem comes from the automatic sign extension when promoting from byte to
> int.
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