[jira] [Created] (HADOOP-11039) ByteBufferReadable API doc is inconsistent with the implementations.

["Yi Liu (JIRA)" <ji...@apache.org>]

Yi Liu created HADOOP-11039:
-------------------------------

             Summary: 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


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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