class SocketReader(object):
  def __init__(self, fp):
    self._fp = fp
    self.handlers = []

  def add_handler(self, handler):
    self.handlers.append(handler)

  def read(self, n=-1):
    buf = self._fp.read(n)
    if not buf:
      return ''
    for handler in self.handlers:
      handler(buf)
    return buf

  def tell(self):
    raise IOError('Stream is not seekable.')


def wrap_with_hash(in_fp, hash_obj):
  wrapper = SocketReader(in_fp)
  wrapper.add_handler(hash_obj.update)
  return wrapper