'Process the blocks that hold a GNU longname
or longlink member.'

def _proc_gnulong(self, tarfile):

    buf = tarfile.fileobj.read(self._block(self.size))
    try:
        next = self.fromtarfile(tarfile)
    except HeaderError:
        raise SubsequentHeaderError('missing    or    bad    subsequent    header')
    next.offset = self.offset
    if (self.type == GNUTYPE_LONGNAME):
        next.name = nts(buf, tarfile.encoding, tarfile.errors)
    elif (self.type == GNUTYPE_LONGLINK):
        next.linkname = nts(buf, tarfile.encoding, tarfile.errors)
    return next
