多次元配列の AsSpan

AnyRankAsSpan.cs

using System;
using System.Runtime.InteropServices;

public class Program
{
    static void Main()
    {
        var x = new uint[] { 0xDEADBEEF, 1, 2, 3, 4, 5, 6, 7 };
        var y = new uint[,] { { 0xDEADBEEF, 1, 2, 3 }, { 4, 5, 6, 7 } };
        var z = new uint[,,] { { { 0xDEADBEEF, 1 }, { 2, 3 } }, { { 4, 5 }, { 6, 7 } } };

        Write(x.AsSpan());
        Write(AsSpan(y));
        Write(AsSpan(z));
    }

    // MemoryMarshal.CreateSpan が .NET Core 2.1 以降限定…
    static Span<T> AsSpan<T>(T[,] a) => MemoryMarshal.CreateSpan(ref a[0, 0], a.Length);
    static Span<T> AsSpan<T>(T[,,] a) => MemoryMarshal.CreateSpan(ref a[0, 0, 0], a.Length);

    static Span<T> AsSpan<T>(Array a)
    {
        // 任意ランクの Array に対して先頭要素の ref を取る手段がなさそうなので switch…
        switch (a)
        {
            case T[] x: return x.AsSpan();
            case T[,] x: return AsSpan(x);
            case T[,,] x: return AsSpan(x);
            default: throw new InvalidOperationException();
        }
    }

    static void Write<T>(Span<T> span)
    {
        foreach (var x in span)
        {
            Console.Write(x);
            Console.Write(' ');
        }
        Console.WriteLine();
    }
}

UnmanagedSend.cs

    public unsafe void Send<T>(string name, Array array)
        where T : unmanaged
    {
        long[] dims = new long[array.Rank];

        for (int i = 0; i < dims.Length; i++)
        {
            dims[i] = array.GetLength(i);
        }

        //一次元の長さの配列を用意
        var span = AsSpan<T>(array);

        fixed (void* address = span)
        {
            IntPtr npArray = NumPy.PyArrayNewFromDescr(NumPy.PyArrayType, Dtype.Int32, array.Rank, dims, null, address, NpConsts.NPY_ARRAY_CARRAY, IntPtr.Zero);
            PyObject.SetAttr(name, npArray);
        }
    }