MarshallingUtils.cs

// The 'unmanaged' keyword was added in C# 7.3, to allow type restriction for unmanaged types (it checks if type has references recursively)
// https://docs.microsoft.com/fr-fr/dotnet/csharp/whats-new/csharp-7-3
#define CSHARP_7_3_OR_ABOVE
// Marshal.SizeOf(Type) was changed for Marshal.SizeOf<T>() in .NET 4.5.1, and the first constructor became obsolete in NET Standard.
// https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.marshal.sizeof?view=netframework-4.5
#define NET_4_5_1_OR_ABOVE

using System;
using System.Runtime.InteropServices;
using System.Security;

public static class MarshallingUtils {

    [DllImport("msvcrt.dll", EntryPoint = "memcpy", CallingConvention = CallingConvention.Cdecl, SetLastError = false), SuppressUnmanagedCodeSecurity]
    private static unsafe extern void* msvrt_memcpy(void* dest, void* src, ulong count);

#if CSHARP_7_3_OR_ABOVE
    public static unsafe T[] Memcpy<T>(void* nativePtr, int length) where T : unmanaged {
        T[] managedArray = new T[length];
        GCHandle handle = GCHandle.Alloc(managedArray, GCHandleType.Pinned);
        IntPtr ptr = handle.AddrOfPinnedObject();
        msvrt_memcpy(ptr.ToPointer(), nativePtr, (ulong)(length * sizeof(T)));
        handle.Free();
        return managedArray;
    }

    private static unsafe T[] Memcpy<T>(IntPtr nativeIntPtr, int length) where T : unmanaged {
        return Memcpy<T>(nativeIntPtr.ToPointer(), length);
    }
#else
    public static unsafe T[] Memcpy<T>(void* nativePtr, int length) {
        T[] managedArray = new T[length];
        GCHandle handle = GCHandle.Alloc(managedArray, GCHandleType.Pinned);
        IntPtr ptr = handle.AddrOfPinnedObject();
#if NET_4_5_1_OR_ABOVE
        msvrt_memcpy(ptr.ToPointer(), nativePtr, (ulong)(length * Marshal.SizeOf<T>()));
#else
        msvrt_memcpy(ptr.ToPointer(), nativePtr, (ulong)(length * Marshal.SizeOf(typeof(T))));
#endif
        handle.Free();
        return managedArray;
    }

    private static unsafe T[] Memcpy<T>(IntPtr nativeIntPtr, int length) {
        return Memcpy<T>(nativeIntPtr.ToPointer(), length);
    }
#endif
}