how can i modify and reverse every bit in NSData using swift language ?

Question

how can i modify and reverse every bit in NSData using swift language ? i want to make something like code confustion.

//.....
let tempstring : String = "hello world!" 
let tempnsstring : NSString = tempstring as NSString 
var tempnsdata : NSData! 
tempnsdata = tempnsstring.dataUsingEncoding(encoding) 
//.... 

then .. please tell me how to modify the data in NSData ? give me some hint on coding . thanks

Answer 1

NSData is an immutable type, so you cannot modify its content.

Two alternatives.

(1) Create a new NSData with modified content.

let tempstring = "hello world!"
let encoding = NSUTF8StringEncoding
let tempnsdata = tempstring.dataUsingEncoding(encoding)!

var tempbytes: [UInt8] = Array(count: tempnsdata.length, repeatedValue: 0)

tempnsdata.getBytes(&tempbytes, length: tempbytes.count)

for i in tempbytes.indices {
    tempbytes[i] = ~tempbytes[i]
}

let modifiednsdata = NSData(bytes: tempbytes, length: tempbytes.count)
//Use `modifiednsdata`...

(2) Create a mutable copy and modify the content in it.

let tempstring = "hello world!"
let encoding = NSUTF8StringEncoding
let tempnsdata = tempstring.dataUsingEncoding(encoding)!

let tempnsmutabledata = tempnsdata.mutableCopy() as! NSMutableData

let mutabledataptr = UnsafeMutablePointer<UInt8>(tempnsmutabledata.mutableBytes)

for i in 0..<tempnsmutabledata.length {
    mutabledataptr[i] = ~mutabledataptr[i]
}

//Use `tempnsmutabledata` as `NSData`