'bytes' is unavailable: use withUnsafeBytes instead

Question

Code that was previously working in Swift 2.2 is now throwing the following error in Swift 3:

Here is my code:

let tempData: NSMutableData = NSMutableData(length: 26)!
tempData.replaceBytes(in: NSMakeRange(0, data.count), withBytes:data.bytes)

What should I replace "data.bytes" with to fix the error? I've tried implementing 'withUnsafeBytes' and had a look at Apple's documentation, but can't get my head around it!

You haven't provided the source of `data`, but if you can convert that also to `Data`, this will all be much simpler and you won't need to bridge between `NSMutableData` and `Data`. You'll just use `replaceSubrange`. — Rob Napier, Aug 16 '16 at 18:10

Martin R · Accepted Answer · 2016-08-16T16:42:41.497

13

Assuming that data has type Data, the following should work:

let tempData: NSMutableData = NSMutableData(length: 26)!
data.withUnsafeBytes { 
    tempData.replaceBytes(in: NSMakeRange(0, data.count), withBytes: $0)
}

using the

/// Access the bytes in the data.
///
/// - warning: The byte pointer argument should not be stored and used outside of the lifetime of the call to the closure.
public func withUnsafeBytes<ResultType, ContentType>(_ body: @noescape (UnsafePointer<ContentType>) throws -> ResultType) rethrows -> ResultType

method of Data. Inside the closure $0 is a UnsafePointer<Void> to the bytes (UnsafeRawPointer in Xcode 8 beta 6).

edited Aug 16 '16 at 16:42

answered Aug 16 '16 at 16:39

Martin R

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@TejasArdeshna: That *is* Swift 3. – Martin R Nov 14 '16 at 12:13
why length is hardcoded as 26? will it create any problem for large data? I am new to ios, just confirming. – Rajdeep Paliwal Oct 11 '17 at 06:24
1

@Ritchierich: The number 26 comes from the code in the question. There is no problem as long as your device has enough memory. – Martin R Oct 11 '17 at 06:43

score 0 · Answer 2 · answered Mar 19 '22 at 07:12

Use this :

        let data:Data = Data()
        let myDataBytes = data.withUnsafeBytes {_ in
            UnsafePointer<UInt8>(data.withUnsafeBytes({
                $0
            }))
        }
        let writtenBytes = writeStream.write(.init(myDataBytes), maxLength: data.count)

'bytes' is unavailable: use withUnsafeBytes instead

2 Answers2

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