这是不可能的.您可以做的***的事情是验证一个字符串是否是有效的 Base 64，尽管许多仅包含 ASCII 文本的字符串可以被解码为 Base 64.

This isn't possible. The best you could do would be to verify that a string might be valid Base 64, although many strings consisting of only ASCII text can be decoded as if they were Base 64.