Lua Stack Inspector with Relative Indices

inspect.cpp

extern "C"
{
#include <lua.h>
#include <lauxlib.h>
}
#include <cstdio>
#include <sstream>

static std::string luax_checkstring(lua_State *L, int i)
{
	size_t size;
	const char *str = luaL_checklstring(L, i, &size);
	return std::string(str, size);
}

void inspect(lua_State *L)
{
	std::stringstream ss;
	int top = lua_gettop(L);

	for (int i = 1; i <= top; i++)
	{
		int type = lua_type(L, i);
		ss << (i - top - 1) << ". ";

		switch (type)
		{
		case LUA_TNONE:
		case LUA_TNIL:
			ss << "LUA_TNIL";
			break;
		case LUA_TBOOLEAN:
			ss << "LUA_TBOOLEAN " << bool(lua_toboolean(L, i));
			break;
		case LUA_TLIGHTUSERDATA:
			ss << "LUA_TLIGHTUSERDATA " << lua_topointer(L, i);
			break;
		case LUA_TNUMBER:
			ss << "LUA_TNUMBER " << lua_tonumber(L, i);
			break;
		case LUA_TSTRING:
			ss << "LUA_TSTRING " << luax_checkstring(L, i);
			break;
		case LUA_TTABLE:
			ss << "LUA_TTABLE " << lua_topointer(L, i);
			break;
		case LUA_TFUNCTION:
			ss << "LUA_TFUNCTION " << lua_topointer(L, i);
			break;
		case LUA_TUSERDATA:
			ss << "LUA_TUSERDATA " << lua_topointer(L, i);
			break;
		case LUA_TTHREAD:
			ss << "LUA_TTHREAD " << lua_topointer(L, i);
			break;
		default:
			ss << "LUA_TUNKNOWN(" << type << ")";
			break;
		}

		ss << "\n";
	}

	std::string result = ss.str();
	fwrite(result.data(), 1, result.length(), stdout);
}