Swift 3 how to store a struct in a "Data" object - struct

Question

What is the "right" way to stuff an arbitrary, odd sized struct into a swift 3 Data object ?
I think that I have got there, but it seems horribly convoluted for what from prior experience was no than
dataObject.append(&structInstance, sizeof(structInstance))
My case is as follows:
The structure of interest:
public struct CutEntry {
var itemA : UInt64
var itemB : UInt32
}
I have an array of these things that I want to stuff into a data object, in a specific manner as the data object becomes a file which is eventually read by a different application on a different architecture.
The function to put them into a Data object
open func encodeCutsData() -> Data
{
var data = Data()
for entry in cutsArray
{
// bigendian stuff, as a var, just so the you can get the address
var entryCopy = CutEntry(itemA: entry.itemA.bigEndian, itemB: entry.itemB.bigEndian)
// step 1 get the address of the item as a UnsafePointer
let d2 = withUnsafePointer(to: &entryCopy) { return $0}
// step 2 cast it to a raw pointer
let d3 = UnsafeRawPointer(d2)
// step 3 create a temp data object
let d4 = Data(bytes:d3, count: MemoryLayout<CutEntry>.size )
// step 4 add the temp to main data object
data.append(d4)
}
return data
}
Earlier when we only had NSMutableData it was
let item = NSMutableData()
for entry in cutsArray
{
var entryCopy = CutEntry(cutPts: entry.cutPts.bigEndian, cutType: entry.cutType.bigEndian)
item.append(&entryCopy, length: MemoryLayout<CutEntry>.size)
}
I've spent a few hours searching for examples of manipulating struct and Data objects. I though that I was close when I found references to unsafebufferpointer. That blew up in my face when I discovered that "buffer" bit uses core memory alignment (which can be useful) and it was stuffing 16 bytes into the data object instead of the expected 12.
I am quite prepared to say that I have missed the blindingly obvious bit of RTFM somewhere. Can anyone offer a cleaner solution ? or has Swift really gone backwards here ?
If I could find a way of getting a pointer to the item as a UInt8 pointer that would remove a couple of lines, but that looks just a difficult.

Answer 1

With checking the reference of Data, I can find two things which may be useful for you:
init(bytes: UnsafeRawPointer, count: Int)
func append(Data)
You can write something like this:
var data = Data()
for entry in cutsArray {
var entryCopy = CutEntry(cutPts: entry.cutPts.bigEndian, cutType: entry.cutType.bigEndian)
data.append(Data(bytes: &entryCopy, count: MemoryLayout<CutEntry>.size))
}