UnsafePointer使用swift 2.0 swift 3.0

Question

这里是我的代码与swift 3.0 md5，但有一个关于UnsafePointer与3个地方的错误，我该如何解决它？

let shift : [UInt32] = [7, 12, 17, 22, 5, 9, 14, 20, 4, 11, 16, 23, 6, 10, 15, 21] 
let table: [UInt32] = (0 ..< 64).map { UInt32(0x100000000 * abs(sin(Double($0 + 1)))) } 
    func md5(message: [UInt8]) -> [UInt8] { 
      var message = message 
      var messageLenBits = UInt64(message.count) * 8 
      message.append(0x80) 
      while message.count % 64 != 56 { 
       message.append(0) 
      } 

      var lengthBytes = [UInt8](repeating: 0, count: 8) 
      UnsafeMutablePointer<UInt64>(lengthBytes).memory = messageLenBits.littleEndian 

      message += lengthBytes 

    var a : UInt32 = 0x67452301 
    var b : UInt32 = 0xEFCDAB89 
    var c : UInt32 = 0x98BADCFE 
    var d : UInt32 = 0x10325476 
    for chunkOffset in stride(from: 0, to: message.count, by: 64) { 
     let chunk = UnsafePointer<UInt32>(UnsafePointer<UInt8>(message) + chunkOffset) 
     let originalA = a 
     let originalB = b 
     let originalC = c 
     let originalD = d 
     for j in 0 ..< 64 { 
      var f : UInt32 = 0 
      var bufferIndex = j 
      let round = j >> 4 
      switch round { 
      case 0: 
       f = (b & c) | (~b & d) 
      case 1: 
       f = (b & d) | (c & ~d) 
       bufferIndex = (bufferIndex*5 + 1) & 0x0F 
      case 2: 
       f = b^c^d 
       bufferIndex = (bufferIndex*3 + 5) & 0x0F 
      case 3: 
       f = c^(b | ~d) 
       bufferIndex = (bufferIndex * 7) & 0x0F 
      default: 
       assert(false) 
      } 
      let sa = shift[(round<<2)|(j&3)] 
      let tmp = a &+ f &+ UInt32(littleEndian: chunk[bufferIndex]) &+ table[j] 
      a = d 
      d = c 
      c = b 
      b = b &+ (tmp << sa | tmp >> (32-sa)) 
     } 
     a = a &+ originalA 
     b = b &+ originalB 
     c = c &+ originalC 
     d = d &+ originalD 
    } 



     var result = [UInt8](repeating: 0, count: 16) 


      for (i, n) in [a, b, c, d].enumerated() { 

       let pointer = UnsafeMutablePointer<UInt32>.allocate(capacity: 1) 
       result[i] = UInt8(n.littleEndian) 

      } 
      return result 

    } 

Answer 1

要的整数变量的（小端）值复制到 一个字节数组可以使用的 UnsafeMutableRawBufferPointer的storeBytes()方法：

var lengthBytes = [UInt8](repeating: 0, count: 8) 
lengthBytes.withUnsafeMutableBytes { 
    $0.storeBytes(of: messageLenBits.littleEndian, as: UInt64.self) 
} 

相同的方法工作复制的最终值为a,b,c, d进入result阵列。

重读一个UInt8指针作为UInt32指针完成 与withMemoryRebound()：

(UnsafePointer(message) + chunkOffset).withMemoryRebound(to: UInt32.self, capacity: 16) { 
     chunk in 

     // ... 
     let tmp = a &+ f &+ UInt32(littleEndian: chunk[bufferIndex]) &+ table[j] 
     // ... 
    } 

全部放在一起，你的方法变得

func md5(message: [UInt8]) -> [UInt8] { 
    var message = message 
    let messageLenBits = UInt64(message.count) * 8 
    message.append(0x80) 
    while message.count % 64 != 56 { 
     message.append(0) 
    } 

    var lengthBytes = [UInt8](repeating: 0, count: 8) 
    lengthBytes.withUnsafeMutableBytes { 
     $0.storeBytes(of: messageLenBits.littleEndian, as: UInt64.self) 
    } 
    message += lengthBytes 

    var a : UInt32 = 0x67452301 
    var b : UInt32 = 0xEFCDAB89 
    var c : UInt32 = 0x98BADCFE 
    var d : UInt32 = 0x10325476 
    for chunkOffset in stride(from: 0, to: message.count, by: 64) { 
     (UnsafePointer(message) + chunkOffset).withMemoryRebound(to: UInt32.self, capacity: 16) { 
      chunk in 

      let originalA = a 
      let originalB = b 
      let originalC = c 
      let originalD = d 
      for j in 0 ..< 64 { 
       var f : UInt32 = 0 
       var bufferIndex = j 
       let round = j >> 4 
       switch round { 
       case 0: 
        f = (b & c) | (~b & d) 
       case 1: 
        f = (b & d) | (c & ~d) 
        bufferIndex = (bufferIndex*5 + 1) & 0x0F 
       case 2: 
        f = b^c^d 
        bufferIndex = (bufferIndex*3 + 5) & 0x0F 
       case 3: 
        f = c^(b | ~d) 
        bufferIndex = (bufferIndex * 7) & 0x0F 
       default: 
        assert(false) 
       } 
       let sa = shift[(round<<2)|(j&3)] 
       let tmp = a &+ f &+ UInt32(littleEndian: chunk[bufferIndex]) &+ table[j] 
       a = d 
       d = c 
       c = b 
       b = b &+ (tmp << sa | tmp >> (32-sa)) 
      } 
      a = a &+ originalA 
      b = b &+ originalB 
      c = c &+ originalC 
      d = d &+ originalD 
     } 
    } 
    var result = [UInt8](repeating: 0, count: 16) 
    result.withUnsafeMutableBytes { ptr in 
     ptr.storeBytes(of: a.littleEndian, toByteOffset: 0, as: UInt32.self) 
     ptr.storeBytes(of: b.littleEndian, toByteOffset: 4, as: UInt32.self) 
     ptr.storeBytes(of: c.littleEndian, toByteOffset: 8, as: UInt32.self) 
     ptr.storeBytes(of: d.littleEndian, toByteOffset: 12, as: UInt32.self) 
    } 
    return result 
}