Explanation with SByte*/Byte* and SByte**/Byte** Conversion

Introduction

I saw problems with ClangSharpPInvokeGenerator and class UnmanagedCallerOnlyAttribute, they can't pass with struct string to static function with UnmanagedCallerOnly or your application tries to communicate with loading shared libraries.

Background

Since I had an idea, I wrote AppWithPlugin into NativeAot and I expect sbyte* for string and sbyte** for string[] pass in C/C++ as const char* and char**.
You can check out my repository at https://github.com/DeafMan1983/AppWithPluginForNativeAot.

Using the Code

Example for SDL2 Wrapper (DeafMan1983.Interop.SDL2):

For string to sbyte* (sbyte* from string):

// Example for title in SDL_CreateWindow()
sbyte* title = SBytePointerFromString("HelloSDL");
...
SDL_Window* window = SDL_CreateWindow(title, ... );

Or sbyte* to string (string from sbyte*).

// Example for printf()

[DllImport("c")]
private static extern int printf(sbyte* fmt);
public static int Printf(sbyte* fmt, params object[] args)
{
    string result = StringFromSBytePointer(fmt);
    if (result == null)
        return 1;
    return printf(SBytePointerFromString(string.Format(result, args));
}

Two nice ways for sbyte* and string, you can use like this.

And nice example with Gtk3/Gtk4:

string[] to sbyte** (sbyte** from string[])

static int Main(string[] args)
{
    GtkApplication* app = gtk_application_new(SBytePointerFromString("org.gtk.example"), 
                          GApplicationFlags.G_APPLICATION_FLAGS_NONE);
    g_signal_connect(app, ACTIVATE, G_CALLBACK
                    ((delegate* <gtkapplication*, void*, void>)&Activate), null);

    int argc = args.Length;
    sbyte** argv = SByteDoublePointersFromStringArray(args);
    int status = g_application_run(G_APPLICATION(app), argc, argv);

    g_object_unref(app);
    return status;
}

That is tricky and you can develop with C/C++ like main function with int and char* or char*[], etc. into C#.

sbyte** to string[] (string[] from sbyte**)

No code available. You know it just works like arguments/parameters from shared library example: Half-Life Sharp (still work in process).

Points of Interest

I find it very funny because ClangSharpPInvokeGenerator made const char* or char** into sbyte* or sbyte** because C/C++ <-> C# are not the same but for WinAPI is very sensitive because WinAPI doesn't support for sbyte* / sbyte** just uses char* / char** like in C/C++.

I will look for char*/char** in future. Because WinApi shows impossible language as Chinese like this:

Since it is sensitive, I need to fix for UTF8 or ANSI format in char*/char**.

History

I started with SDL2-CS by Ethan Lee. But his SDL2-CS cannot use NativeAot. That is why I reworked into DeafMan1983.Interop.SDL2 with full pointers like in C/C++ because it works fine for NativeAot support.

Nuget Gallery

dotnet add package DeafMan1983.Conversion

It uses sbyte*<->string and sbyte**<->string[].

If you want to check my Nuget packages, you can visit my packages.

Have fun and happy coding!