How to use UnsafeMutableRawPointer to fill an array?

Question

I have a Metal texture, I want to access its data from Swift by making it a float4 array (so that I can access each pixel 4 color components).

I discovered this method

Answer 1

First, let's assume you have a UnsafeRawPointer and a length:

let ptr: UnsafeRawPointer = ...
let length: Int = ...

Now you want to convert that to an [float4]. First, you can convert your UnsafeRawPointer to a typed pointer by binding it to a type:

let float4Ptr = ptr.bindMemory(to: float4.self, capacity: length)

Now you can convert that to a typed buffer pointer:

let float4Buffer = UnsafeBufferPointer(start: float4Ptr, count: length)

And since a buffer is a collection, you can initialize an array with it:

let output = Array(float4Buffer)

For much more on working with UnsafeRawPointer, see SE-0138, SE-0107, and the UnsafeRawPointer Migration Guide.