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https://issues.apache.org/jira/browse/HDFS-7825?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sergey Shelukhin updated HDFS-7825:
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Summary: HdfsDataInputStream::read(ByteBuffer) method doesn't conform to
its API (was: read(ByteBuffer) method doesn't conform to its API)
> HdfsDataInputStream::read(ByteBuffer) method doesn't conform to its API
> -----------------------------------------------------------------------
>
> Key: HDFS-7825
> URL: https://issues.apache.org/jira/browse/HDFS-7825
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Sergey Shelukhin
>
> ByteBufferReadable::read(ByteBuffer) javadoc says:
> {noformat}
> After a successful call, buf.position() and buf.limit() should be unchanged,
> and therefore any data can be immediately read from buf. buf.mark() may be
> cleared or updated.
> {noformat}
> I have the following code:
> {noformat}
> ByteBuffer directBuf = ByteBuffer.allocateDirect(len);
> int pos = directBuf.position();
> int count = file.read(directBuf);
> if (count < 0) throw new EOFException();
> if (directBuf.position() != pos) {
> RecordReaderImpl.LOG.info("Warning - position mismatch from " +
> file.getClass()
> + ": after reading " + count + ", expected " + pos + " but
> got " + directBuf.position());
> }
> {noformat}
> and I get:
> {noformat}
> 15/02/23 15:30:56 [pool-4-thread-1] INFO orc.RecordReaderImpl : Warning -
> position mismatch from class
> org.apache.hadoop.hdfs.client.HdfsDataInputStream: after reading 6, expected
> 0 but got 6
> {noformat}
> So the position is changed, unlike the API doc indicates.
> Also, while I haven't verified yet, it may be that the 0-length read is not
> handled properly.
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