How to Convert Hexstring to Bytearray in Swift 3

How do i convert HexString To ByteArray in Swift 3

This code can generate the same output as your swift 2 code.

func stringToBytes(_ string: String) -> [UInt8]? {
    let length = string.characters.count
    if length & 1 != 0 {
        return nil
    }
    var bytes = [UInt8]()
    bytes.reserveCapacity(length/2)
    var index = string.startIndex
    for _ in 0..<length/2 {
        let nextIndex = string.index(index, offsetBy: 2)
        if let b = UInt8(string[index..<nextIndex], radix: 16) {
            bytes.append(b)
        } else {
            return nil
        }
        index = nextIndex
    }
    return bytes
}

let bytes = stringToBytes("7661706f72")
print(String(bytes: bytes!, encoding: .utf8)) //->Optional("vapor")

How to convert hexadecimal string to an array of UInt8 bytes in Swift?

You can convert your hexa String back to array of [UInt8] iterating every two hexa characters and initialize an UInt8 using its string radix initializer. The following implementation assumes the hexa string is well formed:

---

Edit/update: Xcode 11 • Swift 5.1

extension StringProtocol {
    var hexaData: Data { .init(hexa) }
    var hexaBytes: [UInt8] { .init(hexa) }
    private var hexa: UnfoldSequence<UInt8, Index> {
        sequence(state: startIndex) { startIndex in
            guard startIndex < self.endIndex else { return nil }
            let endIndex = self.index(startIndex, offsetBy: 2, limitedBy: self.endIndex) ?? self.endIndex
            defer { startIndex = endIndex }
            return UInt8(self[startIndex..<endIndex], radix: 16)
        }
    }
}

---

let string = "e0696349774606f1b5602ffa6c2d953f"
let data = string.hexaData    // 16 bytes
let bytes = string.hexaBytes  // [224, 105, 99, 73, 119, 70, 6, 241, 181, 96, 47, 250, 108, 45, 149, 63]

---

If you would like to handle malformed hexa strings as well you can make it a throwing method:

extension String {
    enum DecodingError: Error {
        case invalidHexaCharacter(Character), oddNumberOfCharacters
    }
}

---

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

---

extension StringProtocol {
    func hexa<D>() throws -> D where D: DataProtocol & RangeReplaceableCollection {
        try .init(self)
    }
}

---

extension DataProtocol where Self: RangeReplaceableCollection {
    init<S: StringProtocol>(_ hexa: S) throws {
        guard hexa.count.isMultiple(of: 2) else {
            throw String.DecodingError.oddNumberOfCharacters
        }
        self = .init()
        reserveCapacity(hexa.utf8.count/2)
        for pair in hexa.unfoldSubSequences(limitedTo: 2) {
            guard let byte = UInt8(pair, radix: 16) else {
                for character in pair where !character.isHexDigit {
                    throw String.DecodingError.invalidHexaCharacter(character)
                }
                continue
            }
            append(byte)
        }
    }
}

---

Usage:

let hexaString = "e0696349774606f1b5602ffa6c2d953f"
do {
    let bytes: [UInt8] = try hexaString.hexa()
    print(bytes)
    let data: Data = try hexaString.hexa()
    print(data)
} catch {
    print(error)
}

This will print

[224, 105, 99, 73, 119, 70, 6, 241, 181, 96, 47, 250, 108, 45, 149, 63]

16 bytes

Swift Hex to byte (iOS)

You can convert your hexa string back to array of UInt8 using this extension :

extension StringProtocol {
    var hexa2Bytes: [UInt8] {
        let hexa = Array(self)
        return stride(from: 0, to: count, by: 2).compactMap { UInt8(String(hexa[$0..<$0.advanced(by: 2)]), radix: 16) }
    }}

How to convert Data to hex string in swift

A simple implementation (taken from How to hash NSString with SHA1 in Swift?, with an additional option for uppercase output) would be

extension Data {
    struct HexEncodingOptions: OptionSet {
        let rawValue: Int
        static let upperCase = HexEncodingOptions(rawValue: 1 << 0)
    }

    func hexEncodedString(options: HexEncodingOptions = []) -> String {
        let format = options.contains(.upperCase) ? "%02hhX" : "%02hhx"
        return self.map { String(format: format, $0) }.joined()
    }
}

I chose a hexEncodedString(options:) method in the style of the existing method base64EncodedString(options:).

Data conforms to the Collection protocol, therefore one can use
map() to map each byte to the corresponding hex string.
The %02x format prints the argument in base 16, filled up to two digits
with a leading zero if necessary. The hh modifier causes the argument
(which is passed as an integer on the stack) to be treated as a one byte
quantity. One could omit the modifier here because $0 is an unsigned
number (UInt8) and no sign-extension will occur, but it does no harm leaving
it in.

The result is then joined to a single string.

Example:

let data = Data([0, 1, 127, 128, 255])
// For Swift < 4.2 use:
// let data = Data(bytes: [0, 1, 127, 128, 255])
print(data.hexEncodedString()) // 00017f80ff
print(data.hexEncodedString(options: .upperCase)) // 00017F80FF

---

The following implementation is faster by a factor about 50
(tested with 1000 random bytes). It is inspired to
RenniePet's solution
and Nick Moore's solution, but takes advantage of
String(unsafeUninitializedCapacity:initializingUTF8With:)
which was introduced with Swift 5.3/Xcode 12 and is available on macOS 11 and iOS 14 or newer.

This method allows to create a Swift string from UTF-8 units efficiently, without unnecessary copying or reallocations.

An alternative implementation for older macOS/iOS versions is also provided.

extension Data {
    struct HexEncodingOptions: OptionSet {
        let rawValue: Int
        static let upperCase = HexEncodingOptions(rawValue: 1 << 0)
    }

    func hexEncodedString(options: HexEncodingOptions = []) -> String {
        let hexDigits = options.contains(.upperCase) ? "0123456789ABCDEF" : "0123456789abcdef"
        if #available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
            let utf8Digits = Array(hexDigits.utf8)
            return String(unsafeUninitializedCapacity: 2 * self.count) { (ptr) -> Int in
                var p = ptr.baseAddress!
                for byte in self {
                    p[0] = utf8Digits[Int(byte / 16)]
                    p[1] = utf8Digits[Int(byte % 16)]
                    p += 2
                }
                return 2 * self.count
            }
        } else {
            let utf16Digits = Array(hexDigits.utf16)
            var chars: [unichar] = []
            chars.reserveCapacity(2 * self.count)
            for byte in self {
                chars.append(utf16Digits[Int(byte / 16)])
                chars.append(utf16Digits[Int(byte % 16)])
            }
            return String(utf16CodeUnits: chars, count: chars.count)
        }
    }
}

how Hexadecimal string to Bytes

To answer your immediate question: UInt32(intValue) creates a new (constant) value whose address cannot be taken with &. So

var intValue: UInt
scanner.scanHexInt32(&UInt32(intValue))

should be

var intValue: UInt32 = 0
scanner.scanHexInt32(&intValue)

And

dataBytes.append(&intValue, count: 1)

does not compile because &intValue is a pointer to an integer, not to an UInt8. Here you can do

dataBytes.append(UInt8(intValue))

because the value is known to fit in a single byte.

Having said that, all the conversions from String to NSString are not needed. A more “Swifty” translation of that Objective-C code to Swift would be

func convertHex(toDataBytes hexStr: String) -> Data {
    var dataBytes = Data()
    var startPos = hexStr.startIndex
    while let endPos = hexStr.index(startPos, offsetBy: 2, limitedBy: hexStr.endIndex) {
        let singleHexStr = hexStr[startPos..<endPos]
        let scanner = Scanner(string: String(singleHexStr))
        var intValue: UInt32 = 0
        scanner.scanHexInt32(&intValue)
        dataBytes.append(UInt8(intValue))
        startPos = endPos
    }
    return dataBytes
}

For an alternative approach (which includes error checking) see for example
hex/binary string conversion in Swift

Hex string to text conversion - swift 3

You probably can use something like this:

func hexToStr(text: String) -> String {

    let regex = try! NSRegularExpression(pattern: "(0x)?([0-9A-Fa-f]{2})", options: .caseInsensitive)
    let textNS = text as NSString
    let matchesArray = regex.matches(in: textNS as String, options: [], range: NSMakeRange(0, textNS.length))
    let characters = matchesArray.map {
        Character(UnicodeScalar(UInt32(textNS.substring(with: $0.rangeAt(2)), radix: 16)!)!)
    }

    return String(characters)
}

Converting Hex String to NSData in Swift

This is my hex string to Data routine:

extension String {
    
    /// Create `Data` from hexadecimal string representation
    ///
    /// This creates a `Data` object from hex string. Note, if the string has any spaces or non-hex characters (e.g. starts with '<' and with a '>'), those are ignored and only hex characters are processed.
    ///
    /// - returns: Data represented by this hexadecimal string.
    
    var hexadecimal: Data? {
        var data = Data(capacity: count / 2)
        
        let regex = try! NSRegularExpression(pattern: "[0-9a-f]{1,2}", options: .caseInsensitive)
        regex.enumerateMatches(in: self, range: NSRange(startIndex..., in: self)) { match, _, _ in
            let byteString = (self as NSString).substring(with: match!.range)
            let num = UInt8(byteString, radix: 16)!
            data.append(num)
        }
        
        guard data.count > 0 else { return nil }
        
        return data
    }
    
}

And for the sake of completeness, this is my Data to hex string routine:

extension Data {
    
    /// Hexadecimal string representation of `Data` object.
    
    var hexadecimal: String {
        return map { String(format: "%02x", $0) }
            .joined()
    }
}

---

Note, as shown in the above, I generally only convert between hexadecimal representations and NSData instances (because if the information could have been represented as a string you probably wouldn't have created a hexadecimal representation in the first place). But your original question wanted to convert between hexadecimal representations and String objects, and that might look like so:

extension String {
    
    /// Create `String` representation of `Data` created from hexadecimal string representation
    ///
    /// This takes a hexadecimal representation and creates a String object from that. Note, if the string has any spaces, those are removed. Also if the string started with a `<` or ended with a `>`, those are removed, too.
    ///
    /// For example,
    ///
    ///     String(hexadecimal: "<666f6f>")
    ///
    /// is
    ///
    ///     Optional("foo")
    ///
    /// - returns: `String` represented by this hexadecimal string.
    
    init?(hexadecimal string: String, encoding: String.Encoding = .utf8) {
        guard let data = string.hexadecimal() else {
            return nil
        }
        
        self.init(data: data, encoding: encoding)
    }
            
    /// Create hexadecimal string representation of `String` object.
    ///
    /// For example,
    ///
    ///     "foo".hexadecimalString()
    ///
    /// is
    ///
    ///     Optional("666f6f")
    ///
    /// - parameter encoding: The `String.Encoding` that indicates how the string should be converted to `Data` before performing the hexadecimal conversion.
    ///
    /// - returns: `String` representation of this String object.
    
    func hexadecimalString(encoding: String.Encoding = .utf8) -> String? {
        return data(using: encoding)?
            .hexadecimal
    }
    
}

You could then use the above like so:

let hexString = "68656c6c 6f2c2077 6f726c64"
print(String(hexadecimal: hexString))

Or,

let originalString = "hello, world"
print(originalString.hexadecimalString())

For permutations of the above for earlier Swift versions, see the revision history of this question.

Swift convert HexString to Integer

Hope this will help you

let hexaString = "72AE"
var byteArray = [UInt8]()
byteArray += hexaString.utf8  // Convert into byte array

// Retain the orginal string from byte array
let stringFromByteArray = NSString(bytes: byteArray, length: byteArray.count, encoding: NSUTF8StringEncoding)

---

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