ios – 如何在Swift中的NSData和NSString表示之间转换推送令牌？

func dataToHex(data: NSData) -> String
{
    var str: String = String()
    let p = UnsafePointer<UInt8>(data.bytes)
    let len = data.length

    for var i=0; i<len; ++i {
        str += String(format: "%02.2X",p[i])
    }
    return str
}@H_675_10@ 
 
但是,给定一个NSString对象,转换回NSData对象有点困难.如果您在模拟器中进行测试,从真实设备获得字符串标记,并且需要它来注册服务,则可能需要执行此操作.
 
 
我采用的第一种方法试图复制我之前使用的代码,通过创建一个包含字符对的字符串,并调用strtol：
 
 
 
 
func hexToData0(str: NSString) -> NSData {
    let len = str.length/2
    var data = NSMutableData(capacity:len)!
    var num: [Int8] = [ 0,0 ]
    let ptr = str.cStringUsingEncoding(NSUTF8StringEncoding)

    for var i=0; i<len; ++i {
        num[0] = ptr[i*2+0]
        num[1] = ptr[i*2+1]
        var n = UInt8 ( strtol(&num,nil,16) )

        data.appendBytes(&n,length:1)
    }
    return data;
}@H_675_10@ 
 
我只觉得strtol有点像黑客,所以我使用NSScAnner做了同样的代码大小相同,但效率最低：
 
 
 
 
func hexToData1(str: NSString) -> NSData {
    var data = NSMutableData(capacity: str.length/2)!
    for var i = 0; i<str.length; i+=2 {
        let r = NSRange(LOCATIOn: i,length: 2)
        let s = str.subStringWithRange(r)
        let sc = NSScAnner(String: s)

        var val: UInt32 = 0
        let ret = sc.scanHexInt(&val)
        if ret {
            var b = UInt8(val)
            data.appendBytes(&b,length: 1)
        } else {
            assert(false,"Yikes!")
        }
    }
    return data
}@H_675_10@ 
 
然后,我想到我可以在Swift中完成所有工作,不需要达尔文或基金会,而代价是更多的代码：
 
 
 
 
// Swift 4
func hexToData(str: String) -> Data {
    let len = str.count/2
    var data = Data(capacity:len)
    let ptr = str.cString(using: String.Encoding.utf8)!

    for i in 0..<len {
        var num: UInt8 = 0
        var multi: UInt8 = 16;
        for j in 0..<2 {
            let c: UInt8 = UInt8(ptr[i*2+j])
            var offset: UInt8 = 0

            switch c {
            case 48...57:   // '0'-'9'
                offset = 48
            case 65...70:   // 'A'-'F'
                offset = 65 - 10         // 10 since 'A' is 10,not 0
            case 97...102:  // 'a'-'f'
                offset = 97 - 10         // 10 since 'a' is 10,not 0
            default:
                assert(false)
            }

            num += (c - offset)*multi
            multi = 1
        }
        data.append(num)
    }
    return data;
}@H_675_10@ 
 
我在我的代码中使用了最终的hexToData.