videos/OneLoneCoder_EmbeddingLua_Part1.cpp

/*
	Embedding Lua in C++ Part #1
	"Stupid 3D printer, I didn't want a nest..." - javidx9

	License (OLC-3)
	~~~~~~~~~~~~~~~

	Copyright 2018-2019 OneLoneCoder.com

	Redistribution and use in source and binary forms, with or without
	modification, are permitted provided that the following conditions
	are met:

	1. Redistributions or derivations of source code must retain the above
	copyright notice, this list of conditions and the following disclaimer.

	2. Redistributions or derivative works in binary form must reproduce
	the above copyright notice. This list of conditions and the following
	disclaimer must be reproduced in the documentation and/or other
	materials provided with the distribution.

	3. Neither the name of the copyright holder nor the names of its
	contributors may be used to endorse or promote products derived
	from this software without specific prior written permission.

	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	Relevant Video: https://youtu.be/4l5HdmPoynw

	Links
	~~~~~
	YouTube:	https://www.youtube.com/javidx9
				https://www.youtube.com/javidx9extra
	Discord:	https://discord.gg/WhwHUMV
	Twitter:	https://www.twitter.com/javidx9
	Twitch:		https://www.twitch.tv/javidx9
	GitHub:		https://www.github.com/onelonecoder
	Patreon:	https://www.patreon.com/javidx9
	Homepage:	https://www.onelonecoder.com

	Author
	~~~~~~
	David Barr, aka javidx9, <EFBFBD>OneLoneCoder 2019
*/

#include <iostream>
#include <string>

// include Lua, assumes it is local to this file
extern "C"
{
#include "lua535/include/lua.h"
#include "lua535/include/lauxlib.h"
#include "lua535/include/lualib.h"
}

// Link to lua library
#ifdef _WIN32
#pragma comment(lib, "lua535/liblua53.a")
#endif


// Little error checking utility function
bool CheckLua(lua_State *L, int r)
{
	if (r != LUA_OK)
	{
		std::string errormsg = lua_tostring(L, -1);
		std::cout << errormsg << std::endl;
		return false;
	}
	return true;
}


int lua_HostFunction(lua_State *L)
{
	float a = (float)lua_tonumber(L, 1);
	float b = (float)lua_tonumber(L, 2);
	std::cout << "[CPP S4] HostFunction(" << a << ", " << b << ") called from Lua" << std::endl;
	float c = a * b;
	lua_pushnumber(L, c);
	return 1;
}


// NOTE !!!
// YOU WILL NEED THE "EmbeddingLua1.lua" FILE FROM GITHUB REPO


int main()
{

	struct Player
	{
		std::string title;
		std::string name;
		std::string family;
		int level;
	} player;
	
	// Create Lua State
	lua_State *L = luaL_newstate();

	// Add standard libraries to Lua Virtual Machine
	luaL_openlibs(L);

	// Register our C++ Function in the global Lua space
	lua_register(L, "HostFunction", lua_HostFunction);
	 

	// Load and parse the Lua File
	if(CheckLua(L, luaL_dofile(L, "EmbeddingLua1.lua")))
	{ 
		// Stage 1: Just read simple variables
		std::cout << "[CPP] Stage 1 - Read Simple Variables" << std::endl;
		lua_getglobal(L, "a");
		if (lua_isnumber(L, -1)) std::cout << "[CPP S1] a = " << (int)lua_tointeger(L, -1) << std::endl;
		lua_getglobal(L, "b");
		if (lua_isnumber(L, -1)) std::cout << "[CPP S1] b = " << (int)lua_tointeger(L, -1) << std::endl;
		lua_getglobal(L, "c");
		if (lua_isnumber(L, -1)) std::cout << "[CPP S1] c = " << (int)lua_tointeger(L, -1) << std::endl;
		lua_getglobal(L, "d");
		if (lua_isstring(L, -1)) std::cout << "[CPP S1] d = " << lua_tostring(L, -1) << std::endl << std::endl;

		// Stage 2: Read Table Object
		std::cout << "[CPP] Stage 2 - Read Table (Key/Value pairs)" << std::endl;
		lua_getglobal(L, "player");
		if (lua_istable(L, -1))
		{
			lua_pushstring(L, "Name");
			lua_gettable(L, -2);
			player.name = lua_tostring(L, -1);
			lua_pop(L, 1);

			lua_pushstring(L, "Family");
			lua_gettable(L, -2);
			player.family = lua_tostring(L, -1);
			lua_pop(L, 1);

			lua_pushstring(L, "Title");
			lua_gettable(L, -2);
			player.title = lua_tostring(L, -1);
			lua_pop(L, 1);

			lua_pushstring(L, "Level");
			lua_gettable(L, -2);
			player.level = (int)lua_tointeger(L, -1);
			lua_pop(L, 1);
		}
		std::cout << "[CPP S2] " << player.title << " " << player.name << " of " << player.family << " [Lvl: " << player.level << "]" << std::endl << std::endl; 

		// Stage 3: Call Lua Function
		std::cout << "[CPP] Stage 3 - Call Lua Function" << std::endl;
		lua_getglobal(L, "CalledFromCPP1");
		if (lua_isfunction(L, -1))
		{
			lua_pushnumber(L, 5.0f);
			lua_pushnumber(L, 6.0f);
			lua_pushstring(L, "Bwa ha ha!");
			std::cout << "[CPP S3] Calling 'CalledFromCPP1' in lua script" << std::endl;
			if (CheckLua(L, lua_pcall(L, 3, 1, 0)))
			{
				std::cout << "[CPP S3] 'CalledFromCPP1' returned " << (float)lua_tonumber(L, -1) << std::endl << std::endl;
			}
		}

		// Stage 4: Call Lua Function, which calls C++ Function
		std::cout << "[CPP] Stage 4 - Call Lua Function, whcih in turn calls C++ Function" << std::endl;
		lua_getglobal(L, "CalledFromCPP2");
		if (lua_isfunction(L, -1))
		{
			lua_pushnumber(L, 5.0f);
			lua_pushnumber(L, 6.0f);
			std::cout << "[CPP S4] Calling 'CalledFromCPP2' in lua script" << std::endl;
			if (CheckLua(L, lua_pcall(L, 2, 1, 0)))
			{
				std::cout << "[CPP S4] 'CalledFromCPP2' returned " << (float)lua_tonumber(L, -1) << std::endl << std::endl;
			}
		}
	}

	



	system("pause");
	lua_close(L);
	return 0;
}