Swift 将十六进制字符串或字符转换为整数

Question

I have a data source that is passing me a hex string (such as 11C01) that I need to convert each character in it into an integer or byte value so that I can use it as a bit field (ie doing things like value | 0x01 == 0 like you would in old C-style bit fields). The language for this will be Swift.

For the life of me I cannot find a way to convert a character containing a hex value into an integer without doing some weird round-about putting into NSData then converting it from there or doing it using C in an Objective-C class. Just looking for something in Swift to do this instead of resorting to that.

A sample string would be this: 11C01 I need it to create an array of bytes or integers like this: 0x1, 0x1, 0xC, 0x0, 0x1.

The output should be an int or byte that I can do the bitwise operation on.

How would I go about doing this?

Thanks in advance!

Answer 1

edit/update:

Swift 5 or later you can use Character property hexDigitValue:

let hexaString = "11C01"

let integers = hexaString.compactMap(\.hexDigitValue)
let bytes = integers.map(UInt8.init)
let hexaArray = hexaString.map { "0x" + String($0) }

print(integers)  // "[1, 1, 12, 0, 1]"
print(bytes)  // "[1, 1, 12, 0, 1]"
print(hexaArray)  // "["0x1", "0x1", "0xC", "0x0", "0x1"]\n"

To convert every 2 characters into a byte (hexa to byte):

extension Collection {
    func unfoldSubSequences(limitedTo maxLength: Int) -> UnfoldSequence<SubSequence,Index> {
        sequence(state: startIndex) { start in
            guard start < self.endIndex else { return nil }
            let end = self.index(start, offsetBy: maxLength, limitedBy: self.endIndex) ?? self.endIndex
            defer { start = end }
            return self[start..<end]
        }
    }
}

---

extension StringProtocol {
    var byte: UInt8? { UInt8(self, radix: 16) }
    var hexaToBytes: [UInt8] { unfoldSubSequences(limitedTo: 2).compactMap(\.byte) }
    var hexaToData: Data { .init(hexaToBytes) }
}

---

"11C011".hexaToBytes  // [17, 192, 17]
"11C011".hexaToData  // 3 bytes
[0x11, 0xC0, 0x11]   // [17, 192, 17]

Answer 2

let int_value = UInt64("11c01", radix: 16)

Then can shift the bits out

NOTE: Make sure data type can hold value

Answer 3

For the purposes of fun rather than clarity:

let hex_string = "11C01"

let result = map(hex_string.utf8) {
   $0 & 0xf + $0 >> 6 | ($0 & 0x40) >> 3
}
// result: UInt8 array: [1, 1, 12, 0, 1]