前言
我在简书或者别的地方找的MD5计算几乎全部都是使用了Objective-C的库。前几日在看喵神Kingfisher的源码的时候发现有纯Swift实现的MD5，然后我把这部分剥离出来，并做提升了大概25%的速度（没卵用的提升，因为原本的就已经很快）。
环境
- Xcode 8.2
- Swift 3.0
- macOS 10.12.3
实现
主要的实现都在MD5.swift中
struct MD5 {
let message: [UInt8]
init (_ message: [UInt8]) {
self.message = message
}
/** specifies the per-round shift amounts */
private let shifts: [UInt32] = [7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21]
/** binary integer part of the sines of integers (Radians) */
private let sines: [UInt32] = [0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x4881d05,
0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391]
private let hashes: [UInt32] = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476]
func calculate() -> [UInt8] {
var tmpMessage = prepare(64)
tmpMessage.reserveCapacity(tmpMessage.count + 4)
// hash values
var hh = hashes
// Step 2. Append Length a 64-bit representation of lengthInBits
let lengthInBits = (message.count * 8)
let lengthBytes = lengthInBits.bytes(64 / 8)
tmpMessage += lengthBytes.reversed()
// Process the message in successive 512-bit chunks:
let chunkSizeBytes = 512 / 8 // 64
for chunk in BytesSequence(chunkSize: chunkSizeBytes, data: tmpMessage) {
// break chunk into sixteen 32-bit words M[j], 0 ≤ j ≤ 15
var M = toUInt32Array(chunk)
assert(M.count == 16, "Invalid array")
// Initialize hash value for this chunk:
var A = hh[0]
var B = hh[1]
var C = hh[2]
var D = hh[3]
var dTemp: UInt32 = 0
// Main loop
for j in 0 ..< sines.count {
var g = 0
var F: UInt32 = 0
switch j {
case 0...15:
F = (B & C) | ((~B) & D)
g = j
case 16...31:
F = (D & B) | (~D & C)
g = (5 * j + 1) % 16
case 32...47:
F = B ^ C ^ D
g = (3 * j + 5) % 16
case 48...63:
F = C ^ (B | (~D))
g = (7 * j) % 16
default:
break
}
dTemp = D
D = C
C = B
B = B &+ rotateLeft((A &+ F &+ sines[j] &+ M[g]), bits: shifts[j])
A = dTemp
}
hh[0] = hh[0] &+ A
hh[1] = hh[1] &+ B
hh[2] = hh[2] &+ C
hh[3] = hh[3] &+ D
}
var result = [UInt8]()
result.reserveCapacity(hh.count / 4)
hh.forEach {
let itemLE = $0.littleEndian
let r1 = UInt8(itemLE & 0xff)
let r2 = UInt8((itemLE >> 8) & 0xff)
let r3 = UInt8((itemLE >> 16) & 0xff)
let r4 = UInt8((itemLE >> 24) & 0xff)
result += [r1, r2, r3, r4]
}
return result
}
private func toUInt32Array(_ slice: ArraySlice<UInt8>) -> Array<UInt32> {
var result = Array<UInt32>()
result.reserveCapacity(16)
for idx in stride(from: slice.startIndex, to: slice.endIndex, by: MemoryLayout<UInt32>.size) {
let d0 = UInt32(slice[idx.advanced(by: 3)]) << 24
let d1 = UInt32(slice[idx.advanced(by: 2)]) << 16
let d2 = UInt32(slice[idx.advanced(by: 1)]) << 8
let d3 = UInt32(slice[idx])
let val: UInt32 = d0 | d1 | d2 | d3
result.append(val)
}
return result
}
private func rotateLeft(_ value: UInt32, bits: UInt32) -> UInt32 {
return ((value << bits) & 0xFFFFFFFF) | (value >> (32 - bits))
}
private func prepare(_ len: Int) -> Array<UInt8> {
var tmpMessage = message
// Step 1. Append Padding Bits
tmpMessage.append(0x80) // append one bit (UInt8 with one bit) to message
// append "0" bit until message length in bits ≡ 448 (mod 512)
var msgLength = tmpMessage.count
var counter = 0
while msgLength % len != (len - 8) {
counter += 1
msgLength += 1
}
tmpMessage += Array<UInt8>(repeating: 0, count: counter)
return tmpMessage
}
}
extension MD5 {
fileprivate struct BytesIterator: IteratorProtocol {
let chunkSize: Int
let data: [UInt8]
init(chunkSize: Int, data: [UInt8]) {
self.chunkSize = chunkSize
self.data = data
}
var offset = 0
mutating func next() -> ArraySlice<UInt8>? {
let end = min(chunkSize, data.count - offset)
let result = data[offset..<offset + end]
offset += result.count
return result.count > 0 ? result : nil
}
}
fileprivate struct BytesSequence: Sequence {
let chunkSize: Int
let data: [UInt8]
func makeIterator() -> BytesIterator {
return BytesIterator(chunkSize: chunkSize, data: data)
}
}
}
其中使用到了Int的一个拓展
extension Int {
/** Array of bytes with optional padding (little-endian) */
func bytes(_ totalBytes: Int = MemoryLayout<Int>.size) -> [UInt8] {
let valuePointer = UnsafeMutablePointer<Int>.allocate(capacity: 1)
valuePointer.pointee = self
let bytes = valuePointer.withMemoryRebound(to: UInt8.self, capacity: totalBytes) { (bytesPointer) -> [UInt8] in
var bytes = [UInt8](repeating: 0, count: totalBytes)
let minNum = MemoryLayout<Int>.size < totalBytes ? MemoryLayout<Int>.size : totalBytes
for j in 0..<minNum {
bytes[totalBytes - 1 - j] = (bytesPointer + j).pointee
}
return bytes
}
valuePointer.deinitialize()
valuePointer.deallocate(capacity: 1)
return bytes
}
}
最后在拓展String
extension String {
var md5: String {
if let data = self.data(using: .utf8, allowLossyConversion: true) {
let message = data.withUnsafeBytes { bytes -> [UInt8] in
return Array(UnsafeBufferPointer(start: bytes, count: data.count))
}
let MD5Calculator = MD5(message)
let MD5Data = MD5Calculator.calculate()
var md5String = String()
for c in MD5Data {
md5String += String(format: "%02x", c)
}
return md5String
} else {
return self
}
}
}
使用：
let md5 = "HelloWorld".md5
