问题描述

我还没有找到正确的方法来快速将 base64URL 解码为 base64 格式.

I haven't found properly way how to decode base64URL to base64 format in swift.

根据base64url转base64 hJQWHABDBjoPHorYF5xghQ(base64URL)应该是 hJQWHABDBjoPHorYF5xghQ==(base64).这里可能会有更多差异.

According to base64url to base64 hJQWHABDBjoPHorYF5xghQ(base64URL) should be hJQWHABDBjoPHorYF5xghQ==(base64). Here could be more differences.

stackoverflow 上没有解决方案.

There are no solutions on stackoverflow.

推荐答案

base64url"与标准Base64编码有两个不同:

"base64url" differs from the standard Base64 encoding in two aspects:

• 索引 62 和 63 使用不同的字符(- 和 _+ 和 /)
• 没有强制填充 = 字符来使字符串长度四的倍数.

• different characters are used for index 62 and 63 (- and _ instead of + and /)
• no mandatory padding with = characters to make the string length a multiple of four.

(比较 https://en.wikipedia.org/wiki/Base64#Variants_summary_table).

这是一个可能的转换函数:

Here is a possible conversion function:

func base64urlToBase64(base64url: String) -> String {
    var base64 = base64url
        .replacingOccurrences(of: "-", with: "+")
        .replacingOccurrences(of: "_", with: "/")
    if base64.characters.count % 4 != 0 {
        base64.append(String(repeating: "=", count: 4 - base64.characters.count % 4))
    }
    return base64
}

例子:

let base64url = "hJQWHABDBjoPHorYF5xghQ"
let base64 = base64urlToBase64(base64url: base64url)
print(base64) // hJQWHABDBjoPHorYF5xghQ==

if let data = Data(base64Encoded: base64) {
    print(data as NSData) // <8494161c 0043063a 0f1e8ad8 179c6085>
}

为了完整起见，这将是相反的转换:

For the sake of completeness, this would be the opposite conversion:

func base64ToBase64url(base64: String) -> String {
    let base64url = base64
        .replacingOccurrences(of: "+", with: "-")
        .replacingOccurrences(of: "/", with: "_")
        .replacingOccurrences(of: "=", with: "")
    return base64url
}

<小时>

Swift 4 更新:

func base64urlToBase64(base64url: String) -> String {
    var base64 = base64url
        .replacingOccurrences(of: "-", with: "+")
        .replacingOccurrences(of: "_", with: "/")
    if base64.count % 4 != 0 {
        base64.append(String(repeating: "=", count: 4 - base64.count % 4))
    }
    return base64
}

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