def iter_decode(input, fallback_encoding, errors='replace'):
    """
    "Pull"-based decoder.

    :param input:
        An iterable of byte strings.

        The input is first consumed just enough to determine the encoding
        based on the precense of a BOM,
        then consumed on demand when the return value is.
    :param fallback_encoding:
        An :class:`Encoding` object or a label string.
        The encoding to use if :obj:`input` does note have a BOM.
    :param errors: Type of error handling. See :func:`codecs.register`.
    :raises: :exc:`~exceptions.LookupError` for an unknown encoding label.
    :returns:
        An ``(output, encoding)`` tuple.
        :obj:`output` is an iterable of Unicode strings,
        :obj:`encoding` is the :obj:`Encoding` that is being used.

    """

    decoder = IncrementalDecoder(fallback_encoding, errors)
    generator = _iter_decode_generator(input, decoder)
    encoding = next(generator)
    return generator, encoding
"Pull"-based decoder.

    :param input:
        An iterable of byte strings.

        The input is first consumed just enough to determine the encoding
        based on the precense of a BOM,
        then consumed on demand when the return value is.
    :param fallback_encoding:
        An :class:`Encoding` object or a label string.
        The encoding to use if :obj:`input` does note have a BOM.
    :param errors: Type of error handling. See :func:`codecs.register`.
    :raises: :exc:`~exceptions.LookupError` for an unknown encoding label.
    :returns:
        An ``(output, encoding)`` tuple.
        :obj:`output` is an iterable of Unicode strings,
        :obj:`encoding` is the :obj:`Encoding` that is being used.