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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1385) MD5Hash has a bad hash function
Date Fri, 18 May 2007 22:20:16 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12497060
] 

Raghu Angadi commented on HADOOP-1385:
--------------------------------------

Do we need a for loop and an extra function call for hashCode()? Why not just return 
{{((digest[0] & 0xff)  << 24)  | ((digest[1] & 0xff) << 16) | ((digest[2]
& 0xff) << 8) | (digest[3] & 0xff)}}

> 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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