Can a NativeArray be construed from stackalloc memory?

Unity Engine
,
1

I am trying to stackalloc some memory; and use it as a NativeArray like this:

[StructLayout(LayoutKind.Sequential)]
public struct Vertex : IComparable<Vertex>
{
    public readonly static int Size = UnsafeUtility.SizeOf<Vertex>();
    public float2 Point;
    public float2 Comparend;
    public int CompareTo(Vertex other)
    {
        var diff = Comparend.x - other.Comparend.x;
        return diff == 0 ? 0 : diff > 0 ? 1 : -1;
    }
}
public void SomeFunction()
{
    var n = H.Length;
    byte* stackB = stackalloc byte[n * Vertex.Size];
    var a= NativeArrayUnsafeUtility.ConvertExistingDataToNativeArray<Vertex>(stackB ,n, Allocator.None);
    //pop some data
    a.Sort();
}

Is it safe to use it this way? Is the NativeArray okay without safety handle?

2

stackB will be automatically deleted from stack when the function is exited. As long as you don’t return the array there shouldn’t be a problem.

1 Like
3

Greate that exactly what I am expecting. I just want to use Sort function from NativeArray. I am using stackB directly in other parts.

4

NativeArray just grants the access to a memory block, just like Span. I have tried both stackalloc and Sort() in jobs, pay attention that Sort will perform poorly when more elements are added (i.e 250+ elements). Also instead of allocating memory all the time you could just have a preallocated memory block via Malloc and just pass its pointer to a job and do the same thingy with ConvertExistingDataToNativeArray. Don’t forget AtomicSafetyHandle though or you will get null ref.