MACAddress value type in Swift, for storing a MAC address. Its rawValue is of type Data, and it provides serialization and deserialization.

MACAddress.swift

//
//  MACAddress.swift
//
//
//  Created by Mathijs on 23/01/2024.
//

import Foundation

/// Model for a standard MAC (Media Access Control) address, which consists of 6 bytes
/// and can be represented as 6 hexadecimals separated by a colon. For example: `00:0C:6E:D2:11:E6`.
struct MACAddress: RawRepresentable, CustomStringConvertible, Hashable, Sendable {
    let rawValue: Data

    init?(rawValue: Data) {
        guard rawValue.count == 6 else { return nil }
        self.rawValue = rawValue
    }

    init?(string: String) {
        let components = string.split(separator: ":").map { String($0) }
        guard components.count == 6 else { return nil }

        var bytes = Data()
        for component in components {
            guard let byte = UInt8(component, radix: 16) else { return nil }
            bytes.append(byte)
        }

        self.init(rawValue: bytes)
    }

    var description: String {
        return rawValue.map { String(format: "%02X", $0) }.joined(separator: ":")
    }
}

MACAddressTests.swift

//
//  MACAddressTests.swift
//
//
//  Created by Mathijs on 23/01/2024.
//

import Foundation
import Testing
@testable import MACAddress

@Test func testValidMACAddress() {
    #expect(MACAddress(string: "00:0C:6E:D2:11:E6") != nil)
    #expect(MACAddress(string: "FF:FF:FF:FF:FF:FF") != nil)
}

@Test func testInvalidMACAddress() {
    #expect(MACAddress(string: "") == nil)
    #expect(MACAddress(string: "00:0C:6E:D2:11:E6:FF") == nil, "Too many bytes")
    #expect(MACAddress(string: "00:0C:6E:D2:11") == nil, "Too few bytes")
    #expect(MACAddress(rawValue: Data([0x00, 0x1A, 0x2B, 0x3C, 0x4D, 0x5E, 0xFF])) == nil, "Too many bytes")
    #expect(MACAddress(rawValue: Data([0x00, 0x1A, 0x2B, 0x3C, 0x4D])) == nil, "Too few bytes")
}

@Test func testByteOrdering() throws {
    let macAddress = try #require(MACAddress(rawValue: Data([0x00, 0x1A, 0x2B, 0x3C, 0x4D, 0x5E])))
    let macAddressFromString = try #require(MACAddress(string: "00:1A:2B:3C:4D:5E"))
    #expect(macAddress == macAddressFromString)
    #expect(macAddress.description == "00:1A:2B:3C:4D:5E")
}