alpha-wallet-ios/AlphaWallet/Extensions/Data.swift

// Copyright SIX DAY LLC. All rights reserved.

import UIKit
import CoreImage

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

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

    var hexEncoded: String {
        return "0x" + self.hex()
    }

    init(_hex value: String, chunkSize: Int) {
        if value.count > chunkSize {
            self = value.chunked(into: chunkSize).reduce(NSMutableData()) { result, chunk -> NSMutableData in
                let part = Data(_hex: String(chunk))
                result.append(part)

                return result
            } as Data
        } else {
            self = Data(_hex: value)
        }
    }
    //NOTE: renamed to `_hex` because CryptoSwift has its own implementation of `.init(hex:)` that instantiates Data() object with additionaly byte at the end. That brokes `signing` in app. Not sure that this is good name.
    init(_hex hex: String) {
        let len = hex.count / 2
        var data = Data(capacity: len)
        for i in 0..<len {
            let from = hex.index(hex.startIndex, offsetBy: i*2)
            let to = hex.index(hex.startIndex, offsetBy: i*2 + 2)
            let bytes = hex[from ..< to]
            if var num = UInt8(bytes, radix: 16) {
                data.append(&num, count: 1)
            }
        }
        self = data
    }

    //TODO remove if unused. Also confusing
    init?(fromHexEncodedString string: String) {
        // Convert 0 ... 9, a ... f, A ...F to their decimal value,
        // return nil for all other input characters
        func decodeNibble(u: UInt16) -> UInt8? {
            switch u {
            case 0x30 ... 0x39:
                return UInt8(u - 0x30)
            case 0x41 ... 0x46:
                return UInt8(u - 0x41 + 10)
            case 0x61 ... 0x66:
                return UInt8(u - 0x61 + 10)
            default:
                return nil
            }
        }

        self.init(capacity: string.utf16.count/2)
        var even = true
        var byte: UInt8 = 0
        for c in string.utf16 {
            guard let val = decodeNibble(u: c) else { return nil }
            if even {
                byte = val << 4
            } else {
                byte += val
                append(byte)
            }
            even = !even
        }
        guard even else { return nil }
    }

    func toString() -> String? {
        return String(data: self, encoding: .utf8)
    }

    func toQRCode() -> UIImage? {
        if let filter = CIFilter(name: "CIQRCodeGenerator") {
            filter.setValue(self, forKey: "inputMessage")
            let transform = CGAffineTransform(scaleX: 7, y: 7)
            if let output = filter.outputImage?.transformed(by: transform) {
                return UIImage(ciImage: output)
            }
        }
        return nil
    }
}