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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11039) ByteBufferReadable API doc is inconsistent with the implementations.
Date Tue, 30 Dec 2014 15:36:13 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11039?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14261171#comment-14261171
] 

Hudson commented on HADOOP-11039:
---------------------------------

FAILURE: Integrated in Hadoop-Mapreduce-trunk #2008 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk/2008/])
HADOOP-11039. ByteBufferReadable API doc is inconsistent with the implementations. (Yi Liu
via Colin P. McCabe) (cmccabe: rev 249cc905017948d64aab3d14d7a64df3b7b35a13)
* hadoop-common-project/hadoop-common/CHANGES.txt
* hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/ByteBufferReadable.java


> ByteBufferReadable API doc is inconsistent with the implementations.
> --------------------------------------------------------------------
>
>                 Key: HADOOP-11039
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11039
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: documentation
>            Reporter: Yi Liu
>            Assignee: Yi Liu
>            Priority: Minor
>             Fix For: 2.7.0
>
>         Attachments: HADOOP-11039.001.patch
>
>
> In {{ByteBufferReadable}}, API doc of {{int read(ByteBuffer buf)}} says:
> {quote}
> 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.
> {quote}
> {quote}
> @param buf
>                 the ByteBuffer to receive the results of the read operation. Up to
>                 buf.limit() - buf.position() bytes may be read.
> {quote}
> But actually the implementations (e.g. {{DFSInputStream}}, {{RemoteBlockReader2}}) would
be: 
> *Upon return, buf.position() will be advanced by the number of bytes read.*
> code implementation of {{RemoteBlockReader2}} is as following:
> {code}
> @Override
>   public int read(ByteBuffer buf) throws IOException {
>     if (curDataSlice == null || curDataSlice.remaining() == 0 && bytesNeededToFinish
> 0) {
>       readNextPacket();
>     }
>     if (curDataSlice.remaining() == 0) {
>       // we're at EOF now
>       return -1;
>     }
>     int nRead = Math.min(curDataSlice.remaining(), buf.remaining());
>     ByteBuffer writeSlice = curDataSlice.duplicate();
>     writeSlice.limit(writeSlice.position() + nRead);
>     buf.put(writeSlice);
>     curDataSlice.position(writeSlice.position());
>     return nRead;
>   }
> {code}
> This description is very important and will guide user how to use this API, and all the
implementations should keep the same behavior. We should fix the javadoc.



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