十六进制字符串的NSData？ [英] NSData from hex String?

问题描述

我知道这个问题已被要求为 ObjectiveC ，但我的 Swift 还不够强大 char * bytes 的东西。

I know this question has been asked for ObjectiveC, but my Swift isn't strong enough yet to transliterate the char *bytes stuff.

给出

let string = "600DBEEF"

如何创建一个 NSData 表示这4个字节： 60 0D BE EF ？

How do I create an NSData which represents those 4 bytes: 60 0D BE EF?

推荐答案

随着Swift3和新的基础数据类型的到来，我终于回到了这里：

With the arrival of Swift3 and the new Foundation Data type, I finally circled back to this:

extension UnicodeScalar {
    var hexNibble:UInt8 {
        let value = self.value
        if 48 <= value && value <= 57 {
            return UInt8(value - 48)
        }
        else if 65 <= value && value <= 70 {
            return UInt8(value - 55)
        }
        else if 97 <= value && value <= 102 {
            return UInt8(value - 87)
        }
        fatalError("\(self) not a legal hex nibble")
    }
}

extension Data {
    init(hex:String) {
        let scalars = hex.unicodeScalars
        var bytes = Array<UInt8>(repeating: 0, count: (scalars.count + 1) >> 1)
        for (index, scalar) in scalars.enumerated() {
            var nibble = scalar.hexNibble
            if index & 1 == 0 {
                nibble <<= 4
            }
            bytes[index >> 1] |= nibble
        }
        self = Data(bytes: bytes)
    }
}

现在我可以用类似于它们的打印形式构造Data对象：

Now I can construct Data objects in a fashion similar to their printed form:

Data(hex: "600dBeef")

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