iOS Base64URL编码 等同于java中的Base64.URL_SAFE | Base64.NO_WRAP | Base64.NO_PADDING

一. iOS Base64URL编码：
java中，在进行base64编码时会看到相似如下代码：

    String result = Base64.encodeToString(bytedata, Base64.URL_SAFE | Base64.NO_WRAP |  Base64.NO_PADDING)；

其中参数的含义是：

    URL_SAFE：安全的URL编码，base64转码过程中会生成“+”，“/”，“=”这些会被URL进行转码的特殊字符，导致前后端数据不同，所以需要将这些字符替代为URL不会进行转码的字符，保证数据同步；        "-" -> "+"        "_" -> "/"    NO_WRAP：不换行    NO_PADDING："="号补齐去除，base64会对字符进行串长度余4的"="的补位，需去除"="。

这些功可以都是android.utils.Base64中自带的
在iOS中没有，所以我们只可以自己动手了～

Swift代码：

//MARK: Data转Base64URL加密internal class func convertByte(bytedata:Data?) -> String {    guard let bytedata = bytedata else {        return ""    }    // data数据进行base64加密    guard let result = bytedata.base64EncodedString() else {        return ""    }    // %替换为_    let result4 = result.replacingOccurrences(of: "%", with: "_")    // =替换为空    let result1 = result4.replacingOccurrences(of: "=", with: "")    // +替换为—    let result2 = result1.replacingOccurrences(of: "+", with: "-")    // /替换为_    let result3 = result2.replacingOccurrences(of: "/", with: "_")    return result3}//MARK: 后端反回的base64字符串转为datainternal class func convertBase64URL(base64:String?) -> Data? {    guard let base64 = base64 else {        return nil    }    // -替换为+    let base64Str = base64.replacingOccurrences(of: "-", with: "+")    // _替换为/    let base64Str2 = base64Str.replacingOccurrences(of: "_", with: "/")    var base64Str3 = ""    // =号补全    let mod4 = base64Str.count % 4    if mod4 > 0 {        let appStr = ("====" as NSString).substring(to: (4 - mod4))        base64Str3 = base64Str2 + appStr    }    // base64Str转data并进行Base64Decoding    return Data(base64Encoded: base64Str3, options: Data.Base64DecodingOptions.init(rawValue: 0))}

OC:

//MARK: 将saveBase64编码中的"-"，"_"字符串转换成"+"，"/"，字符串长度余4倍的位补"="+(NSData*)safeUrlBase64Decode:(NSString*)safeUrlbase64Str{            // '-' -> '+'            // '_' -> '/'            // 不足4倍长度，补'='            NSMutableString * base64Str = [[NSMutableString alloc]initWithString:safeUrlbase64Str];            base64Str = (NSMutableString * )[base64Str stringByReplacingOccurrencesOfString:@"-" withString:@"+"];            base64Str = (NSMutableString * )[base64Str stringByReplacingOccurrencesOfString:@"_" withString:@"/"];            NSInteger mod4 = base64Str.length % 4;            if(mod4 > 0)                    [base64Str appendString:[@"====" substringToIndex:(4-mod4)]];            NSLog(@"Base64原文：%@", base64Str);            return [GTMBase64 decodeData:[base64Str dataUsingEncoding:NSUTF8StringEncoding]];            }//MARK: 由于Base64编码中包含有+,/,=这些不安全的URL字符串，所以要进行换字符+(NSString*)safeUrlBase64Encode:(NSData*)data{            // '+' -> '-'            // '/' -> '_'            // '=' -> ''            NSString * base64Str = [GTMBase64 stringByEncodingData:data];            NSMutableString * safeBase64Str = [[NSMutableString alloc]initWithString:base64Str];            safeBase64Str = (NSMutableString * )[safeBase64Str stringByReplacingOccurrencesOfString:@"+" withString:@"-"];            safeBase64Str = (NSMutableString * )[safeBase64Str stringByReplacingOccurrencesOfString:@"/" withString:@"_"];            safeBase64Str = (NSMutableString * )[safeBase64Str stringByReplacingOccurrencesOfString:@"=" withString:@""];            NSLog(@"safeBase64编码：%@", safeBase64Str);            return safeBase64Str;}