macOS wchar_t P/Invoke Sample

Program.cs

// Require unsafe configuration.

using System.Runtime.InteropServices;
using System.Text;

namespace HelloWorld;

internal partial class NativeMethods
{
    // https://github.com/mono/mono/issues/9362
    static Encoding GetSystemUnicodeEncoding()
        => Environment.OSVersion.Platform == PlatformID.Unix ? Encoding.UTF32 : Encoding.Unicode;

    public static byte[] ConvertToWideByteArray(string s)
        => GetSystemUnicodeEncoding().GetBytes(s);
    
    private const string StandardLibraryMacOs = "libSystem.dylib";

    [DllImport(StandardLibraryMacOs,
        CallingConvention = CallingConvention.Cdecl,
        CharSet = CharSet.None,
        ExactSpelling = true,
        EntryPoint = nameof(wprintf))]
    internal static extern int wprintf(
        byte[] fmt);
    
    [DllImport(StandardLibraryMacOs,
        CallingConvention = CallingConvention.Cdecl,
        CharSet = CharSet.None,
        ExactSpelling = true,
        EntryPoint = nameof(wprintf))]
    internal static extern int wprintf(
        byte[] fmt,
        int arg0);
    
    [DllImport(StandardLibraryMacOs,
        CallingConvention = CallingConvention.Cdecl,
        CharSet = CharSet.None,
        ExactSpelling = true,
        EntryPoint = nameof(wprintf))]
    internal static extern int wprintf(
        byte[] fmt,
        int arg0, int arg1);
}

static unsafe class Program
{
    static void Main(string[] args)
    {
        const int nLength = 5;
        int* pContent = stackalloc int[nLength];
        int nResult = 0;

        for (int i = 0; i < nLength; i++)
            *(pContent + i) = i;

        nResult = NativeMethods.wprintf(
            NativeMethods.ConvertToWideByteArray("Printing %d numbers.\n"),
            nLength);
        NativeMethods.wprintf(
            NativeMethods.ConvertToWideByteArray("- Result: %d\n"),
            nResult);

        for (int i = 0; i < nLength; i++)
        {
            nResult = NativeMethods.wprintf(
                NativeMethods.ConvertToWideByteArray("Index %d: Value %d\n"),
                i, pContent[i]);
            NativeMethods.wprintf(
                NativeMethods.ConvertToWideByteArray("- Result: %d\n"),
                nResult);
        }

        nResult = NativeMethods.wprintf(
            NativeMethods.ConvertToWideByteArray("Done.\n"));
        NativeMethods.wprintf(
            NativeMethods.ConvertToWideByteArray("- Result: %d\n"),
            nResult);
    }
}