SOLVED: How do I get a [UInt32] into a Data?

@sbeitzel HWS+

Jun '21

This feels like something there ought to be a straightforward API call for, but I'm not seeing it. So before I go writing the code to turn a UInt32 into two UInt8, I thought I'd ask if anyone knows the right way to do it?

Because, fundamentally, what I'm doing is building an array of 32 bit pixels and then turning it into a CIImage, whose constructor wants a Data. All of which feels way more complicated that I expected; I guess nobody builds bitmaps any more?

@roosterboy HWS+

Jun '21

Try something lilke this:

import Foundation

//method 1
extension UInt32 {
    var data: Data {
        var int = self
        return Data(bytes: &int, count: MemoryLayout<UInt32>.size)
    }
}

let testInt1 = UInt32.random(in: UInt32.min...UInt32.max)
let data1 = testInt1.data
print(data1)

//method 2
let testInt2 = UInt32.random(in: UInt32.min...UInt32.max)
let data2 = withUnsafeBytes(of: testInt2) { Data($0) }
print(data2)

@sbeitzel HWS+

Jun '21

Nice, that's the sort of thing I was looking for. What I've ultimately gone with is a variation on your method 1:

extension UInt32 {
    var bytes: [UInt8] {
        var bend = bigEndian
        let count = MemoryLayout<UInt32>.size
        let bytePtr = withUnsafePointer(to: &bend) {
            $0.withMemoryRebound(to: UInt8.self, capacity: count) {
                UnsafeBufferPointer(start: $0, count: count)
            }
        }
        return Array(bytePtr)
    }
}

This means that over where I'm transforming my pixel array, it looks like:

  var pixels: [UInt32]

  // ...

  var pixelData = Data()

        for pixel in pixels {
            pixelData.append(contentsOf: pixel.bytes)
        }

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