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https://issues.apache.org/jira/browse/HADOOP-7444?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13064713#comment-13064713
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Jason Rutherglen commented on HADOOP-7444:
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It would be great if DFSClient (or some other class) offered an API to verify a
file manually. Right now DFSClient offers the getFileChecksum method, though
there's no way to verify the CRC against the file (eg, I think it's all under
the hood right now).
> Add Checksum API to verify and calculate checksums "in bulk"
> ------------------------------------------------------------
>
> Key: HADOOP-7444
> URL: https://issues.apache.org/jira/browse/HADOOP-7444
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: 0.23.0
>
> Attachments: hadoop-7444.txt, hadoop-7444.txt, hadoop-7444.txt
>
>
> Currently, the various checksum types only provide the capability to
> calculate the checksum of a range of a byte array. For HDFS-2080, it's
> advantageous to provide an API that, given a buffer with some number of
> "checksum chunks", can either calculate or verify the checksums of all of the
> chunks. For example, given a 4KB buffer and a 512-byte chunk size, it would
> calculate or verify 8 CRC32s in one call.
> This allows efficient JNI-based checksum implementations since the cost of
> crossing the JNI boundary is amortized across many computations.
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