将base64URL解码为base64 - Swift
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我还没有找到如何在swift中将base64URL解码为base64格式的正确方法。
根据base64url to base64 hJQWHABDBjoPHorYF5xghQ
(base64URL)应该是hJQWHABDBjoPHorYF5xghQ==
(base64)。这可能是更多的差异。
stackoverflow上没有解决方案。
答案
“base64url”在两个方面与标准Base64编码不同:
- 不同的字符用于索引62和63(
-
和_
而不是+
和/
) - 没有强制填充
=
字符使字符串长度为四的倍数。
(比较https://en.wikipedia.org/wiki/Base64#Variants_summary_table)。
这是一个可能的转换函数:
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:
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:
func base64ToBase64url(base64: String) -> String {
let base64url = base64
.replacingOccurrences(of: "+", with: "-")
.replacingOccurrences(of: "/", with: "_")
.replacingOccurrences(of: "=", with: "")
return base64url
}
Swift 4的更新:
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
}
另一答案
这是Martin在Swift 4扩展中发布的清理版本:
import Foundation
/// Extension for making base64 representations of `Data` safe for
/// transmitting via URL query parameters
extension Data {
/// Instantiates data by decoding a base64url string into base64
///
/// - Parameter string: A base64url encoded string
init?(base64URLEncoded string: String) {
self.init(base64Encoded: string.toggleBase64URLSafe(on: false))
}
/// Encodes the string into a base64url safe representation
///
/// - Returns: A string that is base64 encoded but made safe for passing
/// in as a query parameter into a URL string
func base64URLEncodedString() -> String {
return self.base64EncodedString().toggleBase64URLSafe(on: true)
}
}
extension String {
/// Encodes or decodes into a base64url safe representation
///
/// - Parameter on: Whether or not the string should be made safe for URL strings
/// - Returns: if `on`, then a base64url string; if `off` then a base64 string
func toggleBase64URLSafe(on: Bool) -> String {
if on {
// Make base64 string safe for passing into URL query params
let base64url = self.replacingOccurrences(of: "/", with: "_")
.replacingOccurrences(of: "+", with: "-")
.replacingOccurrences(of: "=", with: "")
return base64url
} else {
// Return to base64 encoding
var base64 = self.replacingOccurrences(of: "_", with: "/")
.replacingOccurrences(of: "-", with: "+")
// Add any necessary padding with `=`
if base64.count % 4 != 0 {
base64.append(String(repeating: "=", count: 4 - base64.count % 4))
}
return base64
}
}
}
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