def _readFromUrl(cls, url, writable):
        """
        Writes the contents of a file to a source (writes url to writable)
        using a ~10Mb buffer.

        :param str url: A path as a string of the file to be read from.
        :param object writable: An open file object to write to.
        """
        # we use a ~10Mb buffer to improve speed
        with open(cls._extractPathFromUrl(url), 'rb') as readable:
            shutil.copyfileobj(readable, writable, length=cls.BUFFER_SIZE)