In ByteBufferReadable, API doc of int read(ByteBuffer buf) says:
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.
the ByteBuffer to receive the results of the read operation. Up to
buf.limit() - buf.position() bytes may be read.
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:
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.