├── MarvelAPI.playground
    ├── contents.xcplayground
    ├── Sources
    │   ├── Models
    │   │   ├── ComicCharacter.swift
    │   │   ├── MarvelError.swift
    │   │   ├── Comic.swift
    │   │   ├── DataContainer.swift
    │   │   ├── APIRequest.swift
    │   │   ├── MarvelResponse.swift
    │   │   └── Image.swift
    │   ├── Requests
    │   │   ├── GetComic.swift
    │   │   ├── GetCharacters.swift
    │   │   └── GetComics.swift
    │   ├── Utils
    │   │   ├── URLQueryItemEncoder.swift
    │   │   ├── HTTPParameter.swift
    │   │   └── md5.swift
    │   └── MarvelAPIClient.swift
    └── Contents.swift
├── README.md
├── .gitignore
└── LICENSE


/MarvelAPI.playground/contents.xcplayground:
--------------------------------------------------------------------------------
1 | <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
2 | <playground version='5.0' target-platform='macos'>
3 |     <timeline fileName='timeline.xctimeline'/>
4 | </playground>


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Models/ComicCharacter.swift:
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1 | import Foundation
2 | 
3 | public struct ComicCharacter: Decodable {
4 | 	public let id: Int
5 | 	public let name: String?
6 | 	public let description: String?
7 | 	public let thumbnail: Image?
8 | }
9 | 


--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
1 | # MarvelAPI
2 | 
3 | Proof of concept API Client written in Swift 5 to easily read the Marvel API.
4 | 
5 | You need Xcode 10.2 to run this playground.
6 | 
7 | ### [Related Blog Post](https://medium.com/makingtuenti/writing-a-scalable-api-client-in-swift-4-b3c6f7f3f3fb)
8 | 


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/MarvelAPI.playground/Sources/Models/MarvelError.swift:
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 1 | import Foundation
 2 | 
 3 | /// Dumb error to model simple errors
 4 | /// In a real implementation this should be more exhaustive
 5 | public enum MarvelError: Error {
 6 | 	case encoding
 7 | 	case decoding
 8 | 	case server(message: String)
 9 | }
10 | 


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/MarvelAPI.playground/Sources/Models/Comic.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | public struct Comic: Decodable {
 4 | 	public let id: Int
 5 | 	public let title: String?
 6 | 	public let issueNumber: Double?
 7 | 	public let description: String?
 8 | 	public let pageCount: Int?
 9 | 	public let thumbnail: Image?
10 | }
11 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Models/DataContainer.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | /// All successful responses return this, and contains all
 4 | /// the metainformation about the returned chunk.
 5 | public struct DataContainer<Results: Decodable>: Decodable {
 6 | 	public let offset: Int
 7 | 	public let limit: Int
 8 | 	public let total: Int
 9 | 	public let count: Int
10 | 	public let results: Results
11 | }
12 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Requests/GetComic.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | public struct GetComic: APIRequest {
 4 | 	public typealias Response = [Comic]
 5 | 
 6 | 	// Notice how we create a composed resourceName
 7 | 	public var resourceName: String {
 8 | 		return "comics/\(comicId)"
 9 | 	}
10 | 
11 | 	// Parameters
12 | 	private let comicId: Int
13 | 
14 | 	public init(comicId: Int) {
15 | 		self.comicId = comicId
16 | 	}
17 | }
18 | 


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/MarvelAPI.playground/Sources/Utils/URLQueryItemEncoder.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | /// Encodes any encodable to a URLQueryItem list
 4 | enum URLQueryItemEncoder {
 5 | 	static func encode<T: Encodable>(_ encodable: T) throws -> [URLQueryItem] {
 6 | 		let parametersData = try JSONEncoder().encode(encodable)
 7 | 		let parameters = try JSONDecoder().decode([String: HTTPParameter].self, from: parametersData)
 8 | 		return parameters.map { URLQueryItem(name: $0, value: $1.description) }
 9 | 	}
10 | }
11 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Models/APIRequest.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | /// All requests must conform to this protocol
 4 | /// - Discussion: You must conform to Encodable too, so that all stored public parameters
 5 | ///   of types conforming this protocol will be encoded as parameters.
 6 | public protocol APIRequest: Encodable {
 7 | 	/// Response (will be wrapped with a DataContainer)
 8 | 	associatedtype Response: Decodable
 9 | 
10 | 	/// Endpoint for this request (the last part of the URL)
11 | 	var resourceName: String { get }
12 | }
13 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Models/MarvelResponse.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | /// Top level response for every request to the Marvel API
 4 | /// Everything in the API seems to be optional, so we cannot rely on having values here
 5 | public struct MarvelResponse<Response: Decodable>: Decodable {
 6 | 	/// Whether it was ok or not
 7 | 	public let status: String?
 8 | 	/// Message that usually gives more information about some error
 9 | 	public let message: String?
10 | 	/// Requested data
11 | 	public let data: DataContainer<Response>?
12 | }
13 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Requests/GetCharacters.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | public struct GetCharacters: APIRequest {
 4 | 	public typealias Response = [ComicCharacter]
 5 | 
 6 | 	public var resourceName: String {
 7 | 		return "characters"
 8 | 	}
 9 | 
10 | 	// Parameters
11 | 	public let name: String?
12 | 	public let nameStartsWith: String?
13 | 	public let limit: Int?
14 | 	public let offset: Int?
15 | 
16 | 	// Note that nil parameters will not be used
17 | 	public init(name: String? = nil,
18 | 	            nameStartsWith: String? = nil,
19 | 	            limit: Int? = nil,
20 | 	            offset: Int? = nil) {
21 | 		self.name = name
22 | 		self.nameStartsWith = nameStartsWith
23 | 		self.limit = limit
24 | 		self.offset = offset
25 | 	}
26 | }
27 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Models/Image.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | /// Common object for images coming from the Marvel API
 4 | /// Shows how to fully conform to Decodable
 5 | public struct Image: Decodable {
 6 | 	/// Server sends the remote URL splits in two: the path and the extension
 7 | 	enum ImageKeys: String, CodingKey {
 8 | 		case path = "path"
 9 | 		case fileExtension = "extension"
10 | 	}
11 | 
12 | 	/// The remote URL for this image
13 | 	public let url: URL
14 | 
15 | 	public init(from decoder: Decoder) throws {
16 | 		let container = try decoder.container(keyedBy: ImageKeys.self)
17 | 
18 | 		let path = try container.decode(String.self, forKey: .path)
19 | 		let fileExtension = try container.decode(String.self, forKey: .fileExtension)
20 | 
21 | 		guard let url = URL(string: "\(path).\(fileExtension)") else { throw MarvelError.decoding }
22 | 
23 | 		self.url = url
24 | 	}
25 | }
26 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Requests/GetComics.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | public struct GetComics: APIRequest {
 4 | 	// When encountered with this kind of enums, it will spit out the raw value
 5 | 	public enum ComicFormat: String, Encodable {
 6 | 		case comic = "comic"
 7 | 		case digital = "digital comic"
 8 | 		case hardcover = "hardcover"
 9 | 	}
10 | 
11 | 	public typealias Response = [Comic]
12 | 
13 | 	public var resourceName: String {
14 | 		return "comics"
15 | 	}
16 | 
17 | 	// Parameters
18 | 	public let title: String?
19 | 	public let titleStartsWith: String?
20 | 	public let format: ComicFormat?
21 | 	public let limit: Int?
22 | 	public let offset: Int?
23 | 
24 | 	// Note that nil parameters will not be used
25 | 	public init(title: String? = nil,
26 | 	            titleStartsWith: String? = nil,
27 | 	            format: ComicFormat? = nil,
28 | 	            limit: Int? = nil,
29 | 	            offset: Int? = nil) {
30 | 		self.title = title
31 | 		self.titleStartsWith = titleStartsWith
32 | 		self.format = format
33 | 		self.limit = limit
34 | 		self.offset = offset
35 | 	}
36 | }
37 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Utils/HTTPParameter.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | // Utility type so that we can decode any type of HTTP parameter
 4 | // Useful when we have mixed types in a HTTP request
 5 | enum HTTPParameter: CustomStringConvertible, Decodable {
 6 | 	case string(String)
 7 | 	case bool(Bool)
 8 | 	case int(Int)
 9 | 	case double(Double)
10 | 
11 | 	init(from decoder: Decoder) throws {
12 | 		let container = try decoder.singleValueContainer()
13 | 
14 | 		if let string = try? container.decode(String.self) {
15 | 			self = .string(string)
16 | 		} else if let bool = try? container.decode(Bool.self) {
17 | 			self = .bool(bool)
18 | 		} else if let int = try? container.decode(Int.self) {
19 | 			self = .int(int)
20 | 		} else if let double = try? container.decode(Double.self) {
21 | 			self = .double(double)
22 | 		} else {
23 | 			throw MarvelError.decoding
24 | 		}
25 | 	}
26 | 
27 | 	var description: String {
28 | 		switch self {
29 | 		case .string(let string):
30 | 			return string
31 | 		case .bool(let bool):
32 | 			return String(describing: bool)
33 | 		case .int(let int):
34 | 			return String(describing: int)
35 | 		case .double(let double):
36 | 			return String(describing: double)
37 | 		}
38 | 	}
39 | }
40 | 


--------------------------------------------------------------------------------
/.gitignore:
--------------------------------------------------------------------------------
 1 | # Xcode
 2 | #
 3 | # gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore
 4 | 
 5 | ## Build generated
 6 | build/
 7 | DerivedData/
 8 | 
 9 | ## Various settings
10 | *.pbxuser
11 | !default.pbxuser
12 | *.mode1v3
13 | !default.mode1v3
14 | *.mode2v3
15 | !default.mode2v3
16 | *.perspectivev3
17 | !default.perspectivev3
18 | xcuserdata/
19 | 
20 | ## Other
21 | *.moved-aside
22 | *.xccheckout
23 | *.xcscmblueprint
24 | .DS_Store
25 | 
26 | ## Obj-C/Swift specific
27 | *.hmap
28 | *.ipa
29 | *.dSYM.zip
30 | *.dSYM
31 | 
32 | ## Playgrounds
33 | timeline.xctimeline
34 | playground.xcworkspace
35 | 
36 | # Swift Package Manager
37 | #
38 | # Add this line if you want to avoid checking in source code from Swift Package Manager dependencies.
39 | # Packages/
40 | # Package.pins
41 | .build/
42 | 
43 | # CocoaPods
44 | #
45 | # We recommend against adding the Pods directory to your .gitignore. However
46 | # you should judge for yourself, the pros and cons are mentioned at:
47 | # https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
48 | #
49 | # Pods/
50 | 
51 | # Carthage
52 | #
53 | # Add this line if you want to avoid checking in source code from Carthage dependencies.
54 | # Carthage/Checkouts
55 | 
56 | Carthage/Build
57 | 
58 | # fastlane
59 | #
60 | # It is recommended to not store the screenshots in the git repo. Instead, use fastlane to re-generate the
61 | # screenshots whenever they are needed.
62 | # For more information about the recommended setup visit:
63 | # https://docs.fastlane.tools/best-practices/source-control/#source-control
64 | 
65 | fastlane/report.xml
66 | fastlane/Preview.html
67 | fastlane/screenshots
68 | fastlane/test_output
69 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Contents.swift:
--------------------------------------------------------------------------------
 1 | import Cocoa
 2 | import PlaygroundSupport
 3 | 
 4 | // Put your own keys!
 5 | // You can freely get a key here: https://developer.marvel.com/docs
 6 | let apiClient = MarvelAPIClient(publicKey: "650e801e1408159969078d2a1361c71c",
 7 |                                 privateKey: "20112b45612fd05f0d21d80d70bc8c971695c7f1")
 8 | 
 9 | // A simple request with no parameters
10 | apiClient.send(GetCharacters()) { response in
11 | 	print("\nGetCharacters finished:")
12 | 
13 | 	response.map { dataContainer in
14 | 		for character in dataContainer.results {
15 | 			print("  Title: \(character.name ?? "Unnamed character")")
16 | 			print("  Thumbnail: \(character.thumbnail?.url.absoluteString ?? "None")")
17 | 		}
18 | 	}
19 | }
20 | 
21 | // Another request filling interesting optional parameters, a string and an enum
22 | apiClient.send(GetComics(titleStartsWith: "Avengers", format: .digital)) { response in
23 | 	print("\nGetComics finished:")
24 | 
25 | 	do {
26 | 		let dataContainer = try response.get()
27 | 
28 | 		for comic in dataContainer.results {
29 | 			print("  Title: \(comic.title ?? "Unnamed comic")")
30 | 			print("  Thumbnail: \(comic.thumbnail?.url.absoluteString ?? "None")")
31 | 		}
32 | 	} catch {
33 | 		print(error)
34 | 	}
35 | }
36 | 
37 | // Yet another request with a mandatory parameter
38 | apiClient.send(GetComic(comicId: 61537)) { response in
39 | 	print("\nGetComic finished:")
40 | 
41 | 	switch response {
42 | 	case .success(let dataContainer):
43 | 		let comic = dataContainer.results.first
44 | 
45 | 		print("  Title: \(comic?.title ?? "Unnamed comic")")
46 | 		print("  Thumbnail: \(comic?.thumbnail?.url.absoluteString ?? "None")")
47 | 	case .failure(let error):
48 | 		print(error)
49 | 	}
50 | }
51 | 
52 | PlaygroundPage.current.needsIndefiniteExecution = true
53 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/MarvelAPIClient.swift:
--------------------------------------------------------------------------------
 1 | import Foundation
 2 | 
 3 | public typealias ResultCallback<Value> = (Result<Value, Error>) -> Void
 4 | 
 5 | /// Implementation of a generic-based Marvel API client
 6 | public class MarvelAPIClient {
 7 | 	private let baseEndpointUrl = URL(string: "https://gateway.marvel.com:443/v1/public/")!
 8 | 	private let session = URLSession(configuration: .default)
 9 | 
10 | 	private let publicKey: String
11 | 	private let privateKey: String
12 | 
13 | 	public init(publicKey: String, privateKey: String) {
14 | 		self.publicKey = publicKey
15 | 		self.privateKey = privateKey
16 | 	}
17 | 
18 | 	/// Sends a request to Marvel servers, calling the completion method when finished
19 | 	public func send<T: APIRequest>(_ request: T, completion: @escaping ResultCallback<DataContainer<T.Response>>) {
20 | 		let endpoint = self.endpoint(for: request)
21 | 
22 | 		let task = session.dataTask(with: URLRequest(url: endpoint)) { data, response, error in
23 | 			if let data = data {
24 | 				do {
25 | 					// Decode the top level response, and look up the decoded response to see
26 | 					// if it's a success or a failure
27 | 					let marvelResponse = try JSONDecoder().decode(MarvelResponse<T.Response>.self, from: data)
28 | 
29 | 					if let dataContainer = marvelResponse.data {
30 | 						completion(.success(dataContainer))
31 | 					} else if let message = marvelResponse.message {
32 | 						completion(.failure(MarvelError.server(message: message)))
33 | 					} else {
34 | 						completion(.failure(MarvelError.decoding))
35 | 					}
36 | 				} catch {
37 | 					completion(.failure(error))
38 | 				}
39 | 			} else if let error = error {
40 | 				completion(.failure(error))
41 | 			}
42 | 		}
43 | 		task.resume()
44 | 	}
45 | 
46 | 	/// Encodes a URL based on the given request
47 | 	/// Everything needed for a public request to Marvel servers is encoded directly in this URL
48 | 	private func endpoint<T: APIRequest>(for request: T) -> URL {
49 | 		guard let baseUrl = URL(string: request.resourceName, relativeTo: baseEndpointUrl) else {
50 | 			fatalError("Bad resourceName: \(request.resourceName)")
51 | 		}
52 | 
53 | 		var components = URLComponents(url: baseUrl, resolvingAgainstBaseURL: true)!
54 | 
55 | 		// Common query items needed for all Marvel requests
56 | 		let timestamp = "\(Date().timeIntervalSince1970)"
57 | 		let hash = "\(timestamp)\(privateKey)\(publicKey)".md5
58 | 		let commonQueryItems = [
59 | 			URLQueryItem(name: "ts", value: timestamp),
60 | 			URLQueryItem(name: "hash", value: hash),
61 | 			URLQueryItem(name: "apikey", value: publicKey)
62 | 		]
63 | 
64 | 		// Custom query items needed for this specific request
65 | 		let customQueryItems: [URLQueryItem]
66 | 
67 | 		do {
68 | 			customQueryItems = try URLQueryItemEncoder.encode(request)
69 | 		} catch {
70 | 			fatalError("Wrong parameters: \(error)")
71 | 		}
72 | 
73 | 		components.queryItems = commonQueryItems + customQueryItems
74 | 
75 | 		// Construct the final URL with all the previous data
76 | 		return components.url!
77 | 	}
78 | }
79 | 


--------------------------------------------------------------------------------
/MarvelAPI.playground/Sources/Utils/md5.swift:
--------------------------------------------------------------------------------
  1 | // MARK: - Utilities
  2 | 
  3 | public typealias Byte = UInt8
  4 | typealias Word = UInt32
  5 | 
  6 | public struct Digest {
  7 | 	public let digest: [Byte]
  8 | 
  9 | 	init(_ digest: [Byte]) {
 10 | 		assert(digest.count == 16)
 11 | 		self.digest = digest
 12 | 	}
 13 | 
 14 | 	public var checksum: String {
 15 | 		return encodeMD5(digest: digest)
 16 | 	}
 17 | }
 18 | 
 19 | private func F(_ b: Word, _ c: Word, _ d: Word) -> Word {
 20 | 	return (b & c) | ((~b) & d)
 21 | }
 22 | 
 23 | private func G(_ b: Word, _ c: Word, _ d: Word) -> Word {
 24 | 	return (b & d) | (c & (~d))
 25 | }
 26 | 
 27 | private func H(_ b: Word, _ c: Word, _ d: Word) -> Word {
 28 | 	return b ^ c ^ d
 29 | }
 30 | 
 31 | private func I(_ b: Word, _ c: Word, _ d: Word) -> Word {
 32 | 	return c ^ (b | (~d))
 33 | }
 34 | 
 35 | private func rotateLeft(_ x: Word, by: Word) -> Word {
 36 | 	return ((x << by) & 0xFFFFFFFF) | (x >> (32 - by))
 37 | }
 38 | 
 39 | // MARK: - Calculating a MD5 digest of bytes from bytes
 40 | public func calculateMD5(_ bytes: [Byte]) -> Digest {
 41 | 	// Initialization
 42 | 	let s: [Word] = [
 43 | 		7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
 44 | 		5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20,
 45 | 		4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
 46 | 		6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21
 47 | 	]
 48 | 	let K: [Word] = [
 49 | 		0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
 50 | 		0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
 51 | 		0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
 52 | 		0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
 53 | 		0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
 54 | 		0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
 55 | 		0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
 56 | 		0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
 57 | 		0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
 58 | 		0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
 59 | 		0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
 60 | 		0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
 61 | 		0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
 62 | 		0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
 63 | 		0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
 64 | 		0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
 65 | 	]
 66 | 
 67 | 	var a0: Word = 0x67452301 // A
 68 | 	var b0: Word = 0xefcdab89 // B
 69 | 	var c0: Word = 0x98badcfe // C
 70 | 	var d0: Word = 0x10325476 // D
 71 | 
 72 | 	// Pad message with a single bit "1"
 73 | 	var message = bytes
 74 | 
 75 | 	let originalLength = bytes.count
 76 | 	let bitLength = UInt64(originalLength * 8)
 77 | 
 78 | 	message.append(0x80)
 79 | 
 80 | 	// Pad message with bit "0" until message length is 64 bits fewer than 512
 81 | 	repeat {
 82 | 		message.append(0x0)
 83 | 	} while (message.count * 8) % 512 != 448
 84 | 
 85 | 	message.append(Byte((bitLength >> 0) & 0xFF))
 86 | 	message.append(Byte((bitLength >> 8) & 0xFF))
 87 | 	message.append(Byte((bitLength >> 16) & 0xFF))
 88 | 	message.append(Byte((bitLength >> 24) & 0xFF))
 89 | 	message.append(Byte((bitLength >> 32) & 0xFF))
 90 | 	message.append(Byte((bitLength >> 40) & 0xFF))
 91 | 	message.append(Byte((bitLength >> 48) & 0xFF))
 92 | 	message.append(Byte((bitLength >> 56) & 0xFF))
 93 | 
 94 | 	let newBitLength = message.count * 8
 95 | 
 96 | 	assert(newBitLength % 512 == 0)
 97 | 
 98 | 	// Transform
 99 | 
100 | 	let chunkLength = 512 // 512-bit
101 | 	let chunkLengthInBytes = chunkLength / 8 // 64-bytes
102 | 	let totalChunks = newBitLength / chunkLength
103 | 
104 | 	assert(totalChunks >= 1)
105 | 
106 | 	for chunk in 0..<totalChunks {
107 | 		let index = chunk*chunkLengthInBytes
108 | 		var chunk: [Byte] = Array(message[index..<index+chunkLengthInBytes]) // 512-bit/64-byte chunk
109 | 
110 | 		// break chunk into sixteen 32-bit words
111 | 		var M: [Word] = []
112 | 		for j in 0..<16 {
113 | 			let m0 = Word(chunk[4*j+0]) << 0
114 | 			let m1 = Word(chunk[4*j+1]) << 8
115 | 			let m2 = Word(chunk[4*j+2]) << 16
116 | 			let m3 = Word(chunk[4*j+3]) << 24
117 | 			let m = Word(m0 | m1 | m2 | m3)
118 | 
119 | 			M.append(m)
120 | 		}
121 | 
122 | 		assert(M.count == 16)
123 | 
124 | 		var A: Word = a0
125 | 		var B: Word = b0
126 | 		var C: Word = c0
127 | 		var D: Word = d0
128 | 
129 | 		for i in 0..<64 {
130 | 			var f: Word = 0
131 | 			var g: Int = 0
132 | 
133 | 			if i < 16 {
134 | 				f = F(B, C, D)
135 | 				g = i
136 | 			} else if i >= 16 && i <= 31 {
137 | 				f = G(B, C, D)
138 | 				g = ((5*i + 1) % 16)
139 | 			} else if i >= 32 && i <= 47 {
140 | 				f = H(B, C, D)
141 | 				g = ((3*i + 5) % 16)
142 | 			} else if i >= 48 && i <= 63 {
143 | 				f = I(B, C, D)
144 | 				g = ((7*i) % 16)
145 | 			}
146 | 
147 | 			let dTemp = D
148 | 			D = C
149 | 			C = B
150 | 
151 | 			let x = A &+ f &+ K[i] &+ M[g]
152 | 			let by = s[i]
153 | 
154 | 			B = B &+ rotateLeft(x, by: by)
155 | 			A = dTemp
156 | 		}
157 | 
158 | 		a0 = a0 &+ A
159 | 		b0 = b0 &+ B
160 | 		c0 = c0 &+ C
161 | 		d0 = d0 &+ D
162 | 	}
163 | 
164 | 	assert(a0 >= 0)
165 | 	assert(b0 >= 0)
166 | 	assert(c0 >= 0)
167 | 	assert(d0 >= 0)
168 | 
169 | 	let digest0: Byte =   Byte((a0 >> 0) & 0xFF)
170 | 	let digest1: Byte =   Byte((a0 >> 8) & 0xFF)
171 | 	let digest2: Byte =   Byte((a0 >> 16) & 0xFF)
172 | 	let digest3: Byte =   Byte((a0 >> 24) & 0xFF)
173 | 
174 | 	let digest4: Byte =   Byte((b0 >> 0) & 0xFF)
175 | 	let digest5: Byte =   Byte((b0 >> 8) & 0xFF)
176 | 	let digest6: Byte =   Byte((b0 >> 16) & 0xFF)
177 | 	let digest7: Byte =   Byte((b0 >> 24) & 0xFF)
178 | 
179 | 	let digest8: Byte =   Byte((c0 >> 0) & 0xFF)
180 | 	let digest9: Byte =   Byte((c0 >> 8) & 0xFF)
181 | 	let digest10: Byte =  Byte((c0 >> 16) & 0xFF)
182 | 	let digest11: Byte =  Byte((c0 >> 24) & 0xFF)
183 | 
184 | 	let digest12: Byte =  Byte((d0 >> 0) & 0xFF)
185 | 	let digest13: Byte =  Byte((d0 >> 8) & 0xFF)
186 | 	let digest14: Byte =  Byte((d0 >> 16) & 0xFF)
187 | 	let digest15: Byte =  Byte((d0 >> 24) & 0xFF)
188 | 
189 | 	let digest = [
190 | 		digest0, digest1, digest2, digest3, digest4, digest5, digest6, digest7,
191 | 		digest8, digest9, digest10, digest11, digest12, digest13, digest14, digest15,
192 | 		]
193 | 
194 | 	assert(digest.count == 16)
195 | 
196 | 	return Digest(digest)
197 | }
198 | 
199 | // MARK: - Encoding a MD5 digest of bytes to a string
200 | public func encodeMD5(digest: [Byte]) -> String {
201 | 	assert(digest.count == 16)
202 | 
203 | 	let str = digest.reduce("") { str, byte in
204 | 		let radix = 16
205 | 		let s = String(byte, radix: radix)
206 | 		// Ensure byte values less than 16 are padding with a leading 0
207 | 		let sum = str + (byte < Byte(radix) ? "0" : "") + s
208 | 		return sum
209 | 	}
210 | 
211 | 	return str
212 | }
213 | 
214 | // MARK: - String extension
215 | extension String {
216 | 	public var md5: String {
217 | 		return encodeMD5(digest: md5Digest)
218 | 	}
219 | 
220 | 	public var md5Digest: [Byte] {
221 | 		let bytes = [Byte](self.utf8)
222 | 		let digest = calculateMD5(bytes)
223 | 		return digest.digest
224 | 	}
225 | }
226 | 


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