module RLP::Decode

def descend(rlp, *path)
  rlp = str_to_bytes(rlp)
  path.each do |pa|
    pos = 0
    type, len, pos = consume_length_prefix rlp, pos
    raise DecodingError.new("Trying to descend through a non-list!", rlp) if type != :list
    pa.times do |i|
      t, l, s = consume_length_prefix(rlp, pos)
      pos = l + s
    end
    t, l, s = consume_length_prefix rlp, pos
    rlp = rlp[pos...(l+s)]
  end
  rlp
end