Example of embedding Lua in C

lua_map.c

#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>
#include <stdlib.h>

int map_create(lua_State *lua);
int map_slice(lua_State *lua);

int main(int argc, char **argv){
	lua_State *lua = lua_open();
	luaL_openlibs(lua);

	static const struct luaL_reg map_lib[] = {
		{"create", map_create},
		{"slice", map_slice},
		{NULL, NULL}};

	luaL_openlib(lua, "Map", map_lib, 0);

	luaL_dostring(lua, "map = Map.create(256, 256)");
	luaL_dostring(lua, "s = Map.slice(map, 256, 0, 0, 5, 5)");
	luaL_dostring(lua, "for i=0,4 do print(table.concat(s,' ',5*i, 5*i+4)) end");

	return 0;
}

int map_create(lua_State *lua){
	int w = luaL_checkinteger(lua, 1);
	int h = luaL_checkinteger(lua, 2);

	unsigned char *map = malloc(w * h);

	int n;
	for(n = 0; n != w * h; n++){
		map[n] = n % 10;
	}

	lua_pushlightuserdata(lua, map);
	return 1;
}

int map_slice(lua_State *lua){
	unsigned char *map = lua_touserdata(lua, 1);
	int map_width = luaL_checkinteger(lua, 2);
	int x = luaL_checkinteger(lua, 3); int y = luaL_checkinteger(lua, 4);
	int w = luaL_checkinteger(lua, 5); int h = luaL_checkinteger(lua, 6);

	lua_newtable(lua);

	int cx, cy;
	for(cy = 0; cy != h; cy++)
		for(cx = 0; cx != w; cx++){
			lua_pushnumber(lua, cx + w * cy);
			lua_pushnumber(lua, map[x + cx + (y + cy) * map_width]);
			lua_settable(lua, -3);
		}

	return 1;
}