add block handler to handle block files on different under file systems[Tachyon-33][SubTask 1]

resubmitted.
I can make a block handler based off bytebuffers.  Check permissions would
then not make sense.  We have contemplated prototyping this.

So keep the checks in local for now.
On Aug 27, 2014 9:32 PM, "shimingfei" <notifications@github.com> wrote:

> In core/src/main/java/tachyon/client/BlockHandler.java:
>
> > +   *
> > +   * @param blockOffset
> > +   *          starting position of the block file
> > +   * @param srcBuf
> > +   *          ByteBuffer that data is stored in
> > +   * @return size of data that is written
> > +   * @throws IOException
> > +   */
> > +  protected abstract int append_(long blockOffset, ByteBuffer srcBuf) throws IOException;
> > +
> > +  /**
> > +   * Check to get permission to modify or delete the block file.
> > +   *
> > +   * @throws IOException
> > +   */
> > +  protected abstract void checkPermission() throws IOException;
>
> @dcapwell <https://github.com/dcapwell>
> I think checkPermission is needed on all under file systems when writing
> or deleting some file.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/amplab/tachyon/pull/395/files#r16820263>.
>