return an iterator that returns a chunk of a string every time it is
    called.  notice that even though bufsize_type might be line buffered, we're
    not doing any line buffering here.  that's because our StreamBufferer
    handles all buffering.  we just need to return a reasonable-sized chunk.

def get_iter_string_reader(stdin):
    """ return an iterator that returns a chunk of a string every time it is
    called.  notice that even though bufsize_type might be line buffered, we're
    not doing any line buffering here.  that's because our StreamBufferer
    handles all buffering.  we just need to return a reasonable-sized chunk. """
    bufsize = 1024
    iter_str = (stdin[i:i + bufsize] for i in range(0, len(stdin), bufsize))
    return get_iter_chunk_reader(iter_str)