convert NSData -> [UInt8]

bytes.swift

import Foundation

let n = 256
let a = Array(0..<n).map { UInt8($0) }
let data = NSData(bytes: a, length: a.count)
print(data)  // "<0001...feff>"

let stream = NSInputStream(data: data)
stream.open()

//------------------------------------

// now, allocate the memory we need
var buffer = Array<UInt8>(count: n, repeatedValue: 0)

// and read the bytes into the buffer
let r = stream.read(&buffer, maxLength: n)

// result indicates the number of bytes read
print(r)  // 256
print(stream.hasBytesAvailable)  // false

//------------------------------------

let R = Array(0..<n)
let arr: [UInt8] = R.map { buffer[$0] }
print(arr)  // [0, 1, 2 ... 253, 254, 255]

//------------------------------------

// forgot I had this more direct approach!!
var b: [UInt8] = [0x60,0x61,0x62]
b
let d = NSData(bytes: b, length: 3)
d.length  // 3

let count = d.length/sizeof(UInt8)
var a4 = [UInt8](count: count, repeatedValue: 0)
d.getBytes(&a4, length:count * sizeof(UInt8))
a4 // [96, 97, 98]