Allows to turn NSData into String with the desired encoding, and also provides a convenient way to get an UnsafeBufferPointer from NSData

DataFormatter.swift

extension NSData
{
    /// Creates a length-delimited, byte buffer
    var buffer : UnsafeBufferPointer<UInt8> { get { return UnsafeBufferPointer(start: UnsafePointer<UInt8>(self.bytes), count: self.length) }}
}

extension String
{
    /// Initializes a string from the given data
    init?(data : NSData, encoding : NSStringEncoding)
    {
        self.init(bytes: data.buffer, encoding: encoding)
    }
    
    /// Initializes a string formatted as an hexadecimal byte array
    init(hexData data : NSData, separator: String = ":")
    {
        self.init(separator.join(map(data.buffer) { return String(format: "%hhX", $0) }))
    }
}

Example.playground

import Foundation

let original = "Hello world asdasd asds ddsa as "
let encoding = NSASCIIStringEncoding

if let data = original.dataUsingEncoding(encoding, allowLossyConversion: false)
{
    // Turn back into string
    String(data: data, encoding: encoding)
    
    // Format as hex values
    String(hexData: data, separator: ":")
}