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

// Copyright SIX DAY LLC. All rights reserved.

import Foundation

extension Data {
    var hex: String {
        return map { String(format: "%02hhx", $0) }.joined()
    }

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

    init(hex: String) {
        let len = hex.count / 2
        var data = Data(capacity: len)
        for i in 0..<len {
            let j = i*2
            let bytes = hex[j..<j+2]
            if var num = UInt8(bytes, radix: 16) {
                data.append(&num, count: 1)
            }
        }
        self = data
    }

    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
                self.append(byte)
            }
            even = !even
        }
        guard even else { return nil }
    }
}