#
# REQUIRE: `length % 4 == 0`
private fun decode_base64(length: Int, padding: nullable Byte): Bytes do
if padding == null then padding = '='.ascii
var inv = once inverted_base64_chars
if length == 0 then return new Bytes.empty
#
# REQUIRE: `length % 4 == 0`
private fun decode_base64(length: Int, padding: nullable Byte): Bytes do
if padding == null then padding = '='.ascii
var inv = once inverted_base64_chars
if length == 0 then return new Bytes.empty