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Rotor class

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Eryn Wells 2015-07-18 10:23:54 -07:00
parent b3a98177bb
commit f4b3982986
2 changed files with 54 additions and 0 deletions
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4
Enigma.xcodeproj/project.pbxproj
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Enigma/Rotor.swift Normal file
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//
// Rotor.swift
// Enigma
//
// Created by Eryn Wells on 2015-07-18.
// Copyright © 2015 Eryn Wells. All rights reserved.
//
import Foundation
class Rotor {
enum Error: ErrorType {
/** Thrown when the initializer is given an invalid series. */
case InvalidSeries
case InvalidCharacter
}
static let alphabet: [Character] = Array("ABCDEFGHIJKLMNOPQRSTUVWXYZ".characters)
/** The position of first letter in `series` in the `alphabet`. */
var position: Int
/** The series of characters that this rotor cycles through. */
let series: [Character]!
convenience init(series: String) throws {
try self.init(series: Array(series.characters))
}
init(series: [Character]) throws {
self.position = 0
guard series.count == Rotor.alphabet.count else {
self.series = nil
throw Error.InvalidSeries
}
self.series = series
}
func advance() {
position = position.successor() % Rotor.alphabet.count
}
func encode(c: Character) throws -> Character {
let offset: Int! = Rotor.alphabet.indexOf(c)
guard offset != nil else {
throw Error.InvalidCharacter
}
return series[(offset + position) % series.count]
}
}