How do I set integer endianness using htonl in Swift?

Question

I'm trying to set integer endianness using htonl() in Swift but the compiler isn't finding the htonl() method.

I've been using this as my reference: Append NSInteger to NSMutableData

Here's my code:

import Foundation import CFNetwork import CoreFoundation  var data = NSMutableData() var number : UInt32 = 12 var convertedNumber : UInt32 = htonl(number) data.appendBytes(&convertedNumber, length: 4) 

I've just been running this in a playground. The error is:

Use of unresolved identifier 'htonl' 

Answer 1

As of Xcode 6, Beta 3, all integer types have a bigEndian method which returns the big-endian representation of the integer and changes the byte order if necessary. Example:

var data = NSMutableData() var number : UInt32 = 0x12345678 var convertedNumber = number.bigEndian data.appendBytes(&convertedNumber, length: 4) print(data) // Output: <12345678> 

Update for Swift 3:

let data = NSMutableData() let number: UInt32 = 0x12345678 var convertedNumber = number.bigEndian data.append(&convertedNumber, length: 4) 

Or, using the new Data value type:

var data = Data() let number: UInt32 = 0x12345678 var convertedNumber = number.bigEndian withUnsafePointer(to: &convertedNumber) {     data.append(UnsafeRawPointer($0).assumingMemoryBound(to: UInt8.self), count: 4) } 

Answer 2

Update: Martin R's answer is the correct answer for current versions of Swift: https://stackoverflow.com/a/24653879/195691

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You should use the CFSwapInt32HostToBig() CoreFoundation method, as htonl is likely implemented as a C macro that will not work in swift.

However, it looks like this doesn't currently work in the Swift playground. I'm getting the error Playground execution failed: error: error: Couldn't lookup symbols: __OSSwapInt32 despite the fact that the CoreFoundation documentation now includes method signatures in Swift for its byte swapping methods.

Interestingly, it looks like at least part of <arpa/inet.h> has been ported to swift, as methods like inet_ntoa() and inet_addr() are available to Swift, but the htonl family is not.