我用jsPDF生成了一个PDF，它的结果为dataURL：
data:application/pdf;filename=generated.pdf;base64,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
但是我无法在Swift 4中解码base64字符串。
几个在线工具完全可以解码字符串，Safari可以打开URL，但是Swift不能这样解码：
let base64Encoded = "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"
let decodeData = Data(base64Encoded: base64Encoded, options: Data.Base64DecodingOptions.ignoreUnknownCharacters)!
我阅读了有关填充字符串的解决方案，但是即使添加=字符以使字符计数为4的倍数，我也无法解码该字符串。base64字符串或我的代码怎么了？