Swift 3: How to convert byte array into Data?

Question

I know how to convert int value into data

let value: NSInteger = 1
let valueData:Data = Data(buffer: UnsafeBufferPointer(start: &intVal, count: 1))

Now I want to do the same with RGB color denoted in the following way 0xRRGGBB

How can I achieve it? Should I write it as String, e.q. "543621", then convert it into byte array then convert it to Data?

In Swift 3 you can even initialize the data let valueData = Data([1]) — vadian
– vadian, Commented Oct 20, 2016 at 13:01
@vadian Could you provide the code snippet how would initialize Data of hex string to get color as data? — theDC
– theDC, Commented Oct 20, 2016 at 13:04
@MartinR which one would be more convenient to initliaze it? It does not matter, can be string, can be int, the point is I have to update value on bluetooth peripheral by this hex color so I need to convert it into Data — theDC
– theDC, Commented Oct 20, 2016 at 13:06

dfrib · Accepted Answer · 2016-10-20 15:38:22Z

2

It seems it would be appropriate to store the color as an UInt32 instance, in which case you've already posted a method for initializing a Data instance from it

var pink: UInt32 = 0xCC6699

let pinkData = Data(buffer: UnsafeBufferPointer(start: &pink, count: 1))
print(pinkData.map {$0}) // [153, 102, 204, 0]

print(0x99, 0x66, 0xCC) // 153 102 204

As MartinR points out in a comment below, to ensure the hex number representation 0xCC6699 is stored in its little endian representation (even for systems which employ big endian host byte order), the pink variable should be initialized as:

var pink = UInt32(0xCC6699).littleEndian

// or ...
var pink = UInt32(littleEndian: 0xCC6699)

edited Oct 20, 2016 at 15:38

answered Oct 20, 2016 at 13:07

dfrib

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1 Comment

Martin R Over a year ago

Strictly speaking it should be var pink = UInt32(0xCC6699).littleEndian to make the data independent of the host byte order. How knows to which platform Swift will be ported in the future?

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