Get unsafe struct from GTA Native function

LeeC_HBD.cs

using System;
using System.Runtime.InteropServices;
using GTA;
using GTA.Native;

// shvdn2

public static class SHVNative
{
	// These are borrowed from ScriptHookVDotNet's 
	[DllImport("ScriptHookV.dll", ExactSpelling = true, EntryPoint = "?nativeInit@@YAX_K@Z")]
	static extern void NativeInit(ulong hash);

	[DllImport("ScriptHookV.dll", ExactSpelling = true, EntryPoint = "?nativePush64@@YAX_K@Z")]
	static extern void NativePush64(ulong val);

	[DllImport("ScriptHookV.dll", ExactSpelling = true, EntryPoint = "?nativeCall@@YAPEA_KXZ")]
	static extern unsafe ulong* NativeCall();

	// These are from ScriptHookV's nativeCaller.h
	static unsafe void nativePush<T>(T val) where T: unmanaged
	{
		ulong val64 = 0;
		*(T*)(&val64) = val;
		NativePush64(val64);
	}

	public static unsafe R invoke<R>(ulong hash) where R : unmanaged
	{
		NativeInit(hash);
		return *(R*)(NativeCall());
	}

	// Apparently this works, but might be less efficient than C++'s variadic things
	public static unsafe R invoke<R>(ulong hash, params dynamic[] args)
		where R : unmanaged
	{
		NativeInit(hash);

		foreach(var arg in args)
			nativePush(arg);

		return *(R*)(NativeCall());
	}
}

public class HeadBlendDataTest : Script
{
	[StructLayout(LayoutKind.Explicit, Size = 80)]
	public struct HeadBlendData
	{
		[FieldOffset(0)]
		public int ShapeFirst;

		[FieldOffset(8)]
		public int ShapeSecond;

		[FieldOffset(16)]
		public int ShapeThird;

		[FieldOffset(24)]
		public int SkinFirst;

		[FieldOffset(32)]
		public int SkinSecond;

		[FieldOffset(40)]
		public int SkinThird;

		[FieldOffset(48)]
		public float ShapeMix;

		[FieldOffset(56)]
		public float SkinMix;

		[FieldOffset(64)]
		public float ThirdMix;
	}

	public HeadBlendDataTest()
	{
		Tick += OnTick;
		lastPed = Game.Player.Character;
	}

	private Ped lastPed;

	void OnTick(object sender, EventArgs e)
	{
		// just a sanity check for invoke
		ShowText(0.5f, 0.00f, SHVNative.invoke<int>((ulong)Hash.GET_GAME_TIMER).ToString());

		Ped playerPed = Game.Player.Character;

		if (playerPed != lastPed)
		{
			Function.Call(Hash.SET_PED_HEAD_BLEND_DATA, playerPed, 1, 2, 3, 4, 5, 6, 1.0f, 2.0f, 3.0f);
		}

		var hbd = GetHeadBlendData(playerPed);
		ShowText(0.5f, 0.250f, hbd.ShapeFirst.ToString());
		ShowText(0.5f, 0.275f, hbd.ShapeSecond.ToString());
		ShowText(0.5f, 0.300f, hbd.ShapeThird.ToString());
		ShowText(0.5f, 0.325f, hbd.SkinFirst.ToString());
		ShowText(0.5f, 0.350f, hbd.SkinSecond.ToString());
		ShowText(0.5f, 0.375f, hbd.SkinThird.ToString());
		ShowText(0.5f, 0.400f, hbd.ShapeMix.ToString());
		ShowText(0.5f, 0.425f, hbd.SkinMix.ToString());
		ShowText(0.5f, 0.450f, hbd.ThirdMix.ToString());
	}

	public unsafe HeadBlendData GetHeadBlendData(Ped ped)
	{
		HeadBlendData hbd = new HeadBlendData() {ShapeFirst = -1};
		HeadBlendData* pHbd = &hbd;

		bool result = SHVNative.invoke<bool>((ulong)Hash._GET_PED_HEAD_BLEND_DATA, ped.Handle, (IntPtr)pHbd);

		// result handling might be useful

		return *pHbd;
	}

	void ShowText(float x, float y, string text, float size = 0.2f)
	{
		Function.Call(Hash.SET_TEXT_FONT, 0);
		Function.Call(Hash.SET_TEXT_SCALE, size, size);
		Function.Call(Hash.SET_TEXT_COLOUR, 255, 255, 255, 255);
		Function.Call(Hash.SET_TEXT_WRAP, 0.0, 1.0);
		Function.Call(Hash.SET_TEXT_CENTRE, 0);
		Function.Call(Hash.SET_TEXT_OUTLINE, true);
		Function.Call(Hash._SET_TEXT_ENTRY, "STRING");
		Function.Call(Hash._ADD_TEXT_COMPONENT_STRING, text);
		Function.Call(Hash._DRAW_TEXT, x, y);
	}
}