Lua interacts with C

mylua.c

#include "lua.h"
#include "lauxlib.h"

int l_bar(lua_State *L)
{
	const char *str = lua_tostring(L, -1);
	int length;
	while (1) {
		char c = str[length];
		if (c == '\0')
			break;
		length++;
	}
	lua_pushstring(L, str);
	lua_pushnumber(L, length);
	return 2;
}

int l_WriteOut(lua_State *L)
{
	const char *str = lua_tostring(L, -1);
	printf("%s", str);
	return 0;
}

int main()
{
	lua_State *L = luaL_newstate();
	luaL_openlibs(L);
	luaL_dofile(L, "test.lua");
	lua_pushcfunction(L, l_bar);
	lua_setglobal(L, "bar");
	lua_pushcfunction(L, l_WriteOut);
	lua_setglobal(L, "WriteOut");

	lua_getglobal(L, "foo");
	if (lua_isnil(L, -1)) {
		printf("The number is nil!\n");
	} else {
		lua_pushstring(L, "cheeseburger");
		lua_pcall(L, 1, 1, 0);
		int result = lua_tonumber(L, -1);
		printf("The result is %d\n", result);
		lua_pop(L, 1);
	}

	int total = 0x480000, current, code = 0;
	for (current = 0; current <= total; current += 0x1) {
		lua_getglobal(L, "ProgressBar");
		lua_pushnumber(L, total);
		lua_pushnumber(L, current);
		lua_pushnumber(L, code);
		if (lua_pcall(L, 3, 0, 0) != 0)
			lua_error(L);
	}

	lua_getglobal(L, "x");
	int x = lua_tonumber(L, -1);
	printf("x = %d\n", x);

	return 1;
}

test.lua

local clock = os.clock
function sleep(n)  -- seconds
	local t0 = clock()
	while clock() - t0 <= n do end
end

foo = function(str)
	local s, len = bar(str)
	print(s)
	return len
end

ProgressBar = function(Total, Current, Code)
	local percentage = Current * 100 / Total
	if Current < Total then
		WriteOut(string.format("Progress... 0x%08X (%.0f%%)\r", Current, percentage))
	else
		WriteOut(string.format("Progress... Success (%.0f%%)    \n", percentage))
	end
--	sleep(1)
end

x = 5