redef fun decode_string(ns, len) do
		assert len >= 0
		var ret = ns.to_s_unsafe(len, copy=false)
		var rit = ret.as(FlatString).items
		if rit == ns then
			var nns = new CString(len)
			rit.copy_to(nns, len, 0, 0)
			return nns.to_s_unsafe(ret.byte_length, ret.length, copy=false)
		end
		return ret
	end

	redef fun decode_string(b, len) do
		var buf = new Bytes.with_capacity(len)
		for i in [0 .. len[ do buf.add_char(b[i].to_i.code_point)
		return buf.to_s
	end