CODEWITHSUNDEEP
stringutf-8swift3
Travis Griggs
Travis Griggs

Reputation: 22252

Swift 3 method to create utf8 encoded Data from String

I know there's a bunch of pre Swift3 questions regarding NSData stuff. I'm curious how to go between a Swift3 String to a utf8 encoded (with or without null termination) to Swift3 Data object.

The best I've come up with so far is:

let input = "Hello World"
let terminatedData = Data(bytes: Array(input.nulTerminatedUTF8))
let unterminatedData = Data(bytes: Array(input.utf8))

Having to do the intermediate Array() construction seems wrong.

Upvotes: 26

Views: 40206

Answers (2)

Wojciech Nagrodzki
Wojciech Nagrodzki

Reputation: 2868

NSString methods from NSFoundation framework should be dropped in favor for Swift Standard Library equivalents. Data can be initialized with any Sequence which elements are UInt8. String.UTF8View satisfies this requirement.

let input = "Hello World"
let data = Data(input.utf8)
// [72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100]

String null termination is an implementation detail of C language and it should not leak outside. If you are planning to work with C APIs, please take a look at the utf8CString property of String type:

public var utf8CString: ContiguousArray<CChar> { get }

Data can be obtained after CChar is converted to UInt8:

let input = "Hello World"
let data = Data(input.utf8CString.map { UInt8($0) })
// [72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 0]

Upvotes: 4

Code Different
Code Different

Reputation: 93141

It's simple:

let input = "Hello World"
let data = input.data(using: .utf8)!

If you want to terminate data with null, simply append a 0 to it. Or you may call cString(using:)

let cString = input.cString(using: .utf8)! // null-terminated

Upvotes: 61

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