The length rules of canonical base64, without looking at the characters: a length that can
encode whole bytes, and padding only on a full final quantum ("xx==" or "xxx="), never on a bare
remainder. Part of IsValidBase64; exposed so a codec's fused validate-and-decode
(Base64Codec.TryDecode) applies the same rules.
The length rules of canonical base64, without looking at the characters: a length that can encode whole bytes, and padding only on a full final quantum ("xx==" or "xxx="), never on a bare remainder. Part of IsValidBase64; exposed so a codec's fused validate-and-decode (Base64Codec.TryDecode) applies the same rules.