Given a Hexadecimal String in Swift, Convert to Hex Value

Given a hexadecimal string in Swift, convert to hex value

A possible solution:

let string = "D7C17A4F"

let chars = Array(string)
let numbers = map (stride(from: 0, to: chars.count, by: 2)) {
    strtoul(String(chars[$0 ..< $0+2]), nil, 16)
}

Using the approach from https://stackoverflow.com/a/29306523/1187415,
the string is split into substrings of two characters.
Each substring is interpreted as a sequence of digits
in base 16, and converted to a number with strtoul().

Verify the result:

println(numbers)
// [215, 193, 122, 79]

println(map(numbers, { String(format: "%02X", $0) } ))
// [D7, C1, 7A, 4F]

Update for Swift 2 (Xcode 7):

let string = "D7C17A4F"
let chars = Array(string.characters)

let numbers = 0.stride(to: chars.count, by: 2).map {
    UInt8(String(chars[$0 ..< $0+2]), radix: 16) ?? 0
}

print(numbers) 

or

let string = "D7C17A4F"

var numbers = [UInt8]()
var from = string.startIndex
while from != string.endIndex {
    let to = from.advancedBy(2, limit: string.endIndex)
    numbers.append(UInt8(string[from ..< to], radix: 16) ?? 0)
    from = to
}

print(numbers) 

The second solution looks a bit more complicated but has the small
advantage that no additional chars array is needed.

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)
        }
    }
}

Swift3 convert string value to hexadecimal string

This produces the same output as the ObjC version

let str = "Say Hello to My Little Friend"
let data = Data(str.utf8)
let hexString = data.map{ String(format:"%02x", $0) }.joined()

Cant convert string hex into hexint and then into UIColor

You have to remove the 0x prefix and then specify the radix 16:

let s = "0xe7c79d"
print(Int(s)) // nil

let value = s.hasPrefix("0x")
    ? String(s.dropFirst(2))
    : s
print(Int(value, radix: 16)) // 15189917

How to convert a text string to hex string?

Couldn't able to write in swift, but in Objective-C below code is may be what you are looking for:

    NSString * str = @"Say Hello to My Little Friend";

    NSString * hexString = [NSString stringWithFormat:@"%@",
                         [NSData dataWithBytes:[str cStringUsingEncoding:NSUTF8StringEncoding]
                                        length:strlen([str cStringUsingEncoding:NSUTF8StringEncoding])]];

    for(NSString * toRemove in [NSArray arrayWithObjects:@"<", @">", @" ", nil])
        hexString = [hexString stringByReplacingOccurrencesOfString:toRemove withString:@""];

    NSLog(@"hexStr:%@", hexString);

Above code gives exact string as you given:

5361792048656c6c6f20746f204d79204c6974746c6520467269656e64

Hope it will help:)

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)
}

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

How to convert an Int to Hex String in Swift

You can now do:

let n = 14
var st = String(format:"%02X", n)
st += " is the hexadecimal representation of \(n)"
print(st)

0E is the hexadecimal representation of 14

Note: The 2 in this example is the field width and represents the minimum length desired. The 0 tells it to pad the result with leading 0's if necessary. (Without the 0, the result would be padded with leading spaces). Of course, if the result is larger than two characters, the field length will not be clipped to a width of 2; it will expand to whatever length is necessary to display the full result.

This only works if you have Foundation imported (this includes the import of Cocoa or UIKit). This isn't a problem if you're doing iOS or macOS programming.

Use uppercase X if you want A...F and lowercase x if you want a...f:

String(format: "%x %X", 64206, 64206)  // "face FACE"

If you want to print integer values larger than UInt32.max, add ll (el-el, not eleven) to the format string:

let n = UInt64.max
print(String(format: "%llX is hexadecimal for \(n)", n))

FFFFFFFFFFFFFFFF is hexadecimal for 18446744073709551615

---

Original Answer

You can still use NSString to do this. The format is:

var st = NSString(format:"%2X", n)

This makes st an NSString, so then things like += do not work. If you want to be able to append to the string with += make st into a String like this:

var st = NSString(format:"%2X", n) as String

or

var st = String(NSString(format:"%2X", n))

or

var st: String = NSString(format:"%2X", n)

Then you can do:

let n = 123
var st = NSString(format:"%2X", n) as String
st += " is the hexadecimal representation of \(n)"
// "7B is the hexadecimal representation of 123"

Swift native functions to have numbers as hex strings

As of Swift 2, all integer types have a constructor

init?(_ text: String, radix: Int = default)

so that both integer
to hex string and hex string to integer conversions can be done
with built-in methods. Example:

let num = 1000
let str = String(num, radix: 16)
print(str) // "3e8"

if let num2 = Int(str, radix: 16) {
    print(num2) // 1000
}

---

(Old answer for Swift 1:) The conversion from an integer to a hex string can be done with

let hex = String(num, radix: 16)

(see for example How to convert a decimal number to binary in Swift?). This does not require the import of any Framework
and works with any base between 2 and 36.

The conversion from a hex string to an integer can be done with the BSD
library function strtoul() (compare How to convert a binary to decimal in Swift?) if you are willing to import Darwin.

Otherwise there is (as far as I know) no built-in Swift method. Here is an extension
that converts a string to a number according to a given base:

extension UInt {
    init?(_ string: String, radix: UInt) {
        let digits = "0123456789abcdefghijklmnopqrstuvwxyz"
        var result = UInt(0)
        for digit in string.lowercaseString {
            if let range = digits.rangeOfString(String(digit)) {
                let val = UInt(distance(digits.startIndex, range.startIndex))
                if val >= radix {
                    return nil
                }
                result = result * radix + val
            } else {
                return nil
            }
        }
        self = result
    }
}

Example:

let hexString = "A0"
if let num = UInt(hexString, radix: 16) {
    println(num)
} else {
    println("invalid input")
}

---

Related Topics