How to cancel a long running native function — from c# — with a CancellationToken!

InteropCancellationToken.cs

using System.Runtime.InteropServices;
using System.Threading;

[StructLayout(LayoutKind.Sequential)]
internal struct InteropCancellationToken
{
    public InteropCancellationToken(CancellationToken ct)
    {
        IsCancellationRequested = () => ct.IsCancellationRequested;
    }

    // ReSharper disable once PrivateFieldCanBeConvertedToLocalVariable
    private IsCancellationRequestedCallback IsCancellationRequested;

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate bool IsCancellationRequestedCallback();
}

NativeFunctions.cs

public class NativeFunctions
{
    public static int ParseHugeFile(CancellationToken ct = default)
    {
        return parse_huge_file(new InteropCancellationToken(ct));
    }

    [DllImport("someNativeCode", EntryPoint = "parse_huge_file")]
    private static extern int parse_huge_file(InteropCancellationToken ct);
}

parse_huge_file.cpp

extern "C" {
    typedef struct CancellationToken {
        bool (*IsCancellationRequested)();
    } CancellationToken;

    int parse_huge_file(CancellationToken ct);
}

int parse_huge_file(CancellationToken ct) {
    while (!ct.IsCancellationRequested()) {
        // ...
    }
    return 0;
}