class Net::BufferedIO

def rbuf_fill
  tmp = @rbuf.empty? ? @rbuf : nil
  case rv = @io.read_nonblock(BUFSIZE, tmp, exception: false)
  when String
    return if rv.equal?(tmp)
    @rbuf << rv
    rv.clear
    return
  when :wait_readable
    (io = @io.to_io).wait_readable(@read_timeout) or raise Net::ReadTimeout.new(io)
    # continue looping
  when :wait_writable
    # OpenSSL::Buffering#read_nonblock may fail with IO::WaitWritable.
    # http://www.openssl.org/support/faq.html#PROG10
    (io = @io.to_io).wait_writable(@read_timeout) or raise Net::ReadTimeout.new(io)
    # continue looping
  when nil
    raise EOFError, 'end of file reached'
  end while true
end