Efficient Data to hex string

DataHex.swift

extension Data {
    private static let hexDigits = Array("0123456789abcdef".utf8)
    var hex: String {
        var chars = [Unicode.UTF8.CodeUnit]()
        chars.reserveCapacity(2 * count)
        for byte in self {
            chars.append(Self.hexDigits[Int(byte >> 4)]) // byte / 16
            chars.append(Self.hexDigits[Int(byte & 15)]) // byte % 16
        }
        return String(decoding: chars, as: UTF8.self)
    }
}