Complete roguelike tutorial using C++ and libtcod - part 10.1: persistence
| Complete roguelike tutorial using C++ and libtcod -originally written by Jice Text in this tutorial was released under the Creative Commons Attribution-ShareAlike 3.0 Unported and the GNU Free Documentation License (unversioned, with no invariant sections, front-cover texts, or back-cover texts) on 2015-09-21. |
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In this part, we will implement saving and loading the game to be able to close it and resume it later. And this is not going to be pleasing. C++ has a few great feats, but it certainly sucks at type introspection and object serialization. Most modern languages have these features built in. For this reason, the article 10 of Jotaf's python tutorial will be split in two for the C++ version.
In fact, there's a way to serialize a C++ object and store it on the disk using only a couple of lines of code : using boost Serialization library. But we're not going to use it for several reasons :
- this tutorial is not about using boost but rather how to code the features yourself using basic C++.
- even if using boost would considerably reduce the size of the code to write, you still have to embed boost in your game. Using hand-made code will replace 8000 lines of boost code with less than 300 lines of specific code, resulting in a lighter executable and a simplified compilation process for your project.
- using libtcod's zip toolkit means that the save file will be compressed. Of course, this means less space used on the disk, but also harder to hack savegame files. Of course, using boost doesn't keep you from compressing the file, but it just comes at no cost when using libtcod.
Anyway if you prefer to use boost, you can follow this article to reorganize the Map and Engine code, and just skip the whole Persistent stuff and replace Engine::load and Engine::save code with boost invocation.
libtcod features used in this article :
The plan
Since this part does not include a game menu, we're going to do a minimal savegame support :
- when the player closes the game window, the game state is saved to a file
- when the player starts the game, it resumes the last saved game
- when the player dies, the savegame is deleted (you wouldn't write a roguelike without permadeath, would you?)
While this simplifies the article, it leaves an annoying case : when the player manage to kill all monsters, he will be stuck. The only way to restart a game is to erase the savegame by hand. This will be fixed in the next article.
Refactoring
The engine
The first thing, obviously, is to be able to save and load the whole game. We also need to remove the initializing code from the Engine constructor, because when the Engine is created, we don't know yet if we have to generate a new map or load a previously saved one. We put the functions in the Engine class :
Engine.hpp
bool pickATile(int *x, int *y, float maxRange = 0.0f);
void init();
void load();
void save();
};
The new constructor doesn't create the map and actors anymore :
Engine::Engine(int screenWidth, int screenHeight) : gameStatus(STARTUP),
player(NULL),map(NULL),fovRadius(10),
screenWidth(screenWidth),screenHeight(screenHeight) {
TCODConsole::initRoot(screenWidth,screenHeight,"libtcod C++ tutorial",false);
gui = new Gui();
}
All the initialization code has been moved to the init function :
void Engine::init() {
player = new Actor(40,25,'@',"player",TCODColor::white);
player->destructible=new PlayerDestructible(30,2,"your cadaver");
player->attacker=new Attacker(5);
player->ai = new PlayerAi();
player->container = new Container(26);
actors.push(player);
map = new Map(80,43);
map->init(true);
gui->message(TCODColor::red,
"Welcome stranger!\nPrepare to perish in the Tombs of the Ancient Kings.");
}
Now the load function will either load a saved game or call Engine::init to create a new one. We simply call it before the main loop. We also save the game once the player closes the game window.
main.cpp :
int main() {
engine.load();
while ( !TCODConsole::isWindowClosed() ) {
engine.update();
engine.render();
TCODConsole::flush();
}
engine.save();
return 0;
}
The map
We could save the map by putting every tile property in the file. Or we can only save the seed of the random number generator and re-generate the map. For this, we need to store the seed and the random number generator in the map class. Previously, we were using libtcod's default random number generator with an unknown seed. We also have to move the map initialization code out of the constructor so that we're able to call it when the map is loaded from the file :
Map.hpp
void init(bool withActors); protected : Tile *tiles; TCODMap *map; long seed; TCODRandom *rng; friend class BspListener; void dig(int x1, int y1, int x2, int y2); void createRoom(bool first, int x1, int y1, int x2, int y2, bool withActors);
The withActors parameter tells the map whether it should create monsters and items or if they will be loaded from a saved game. The constructor new only gets some random seed :
Map::Map(int width, int height)
: width(width),height(height) {
seed=TCODRandom::getInstance()->getInt(0,0x7FFFFFFF);
}
In case you wonder, 0x7FFFFFFF is the highest possible 32 bit signed integer value. The init function uses the code that was previously in the constructor, but the splitRecursive function now uses the map's RNG :
void Map::init(bool withActors) {
rng = new TCODRandom(seed, TCOD_RNG_CMWC);
tiles=new Tile[width*height];
map=new TCODMap(width,height);
TCODBsp bsp(0,0,width,height);
bsp.splitRecursive(rng,8,ROOM_MAX_SIZE,ROOM_MAX_SIZE,1.5f,1.5f);
BspListener listener(*this);
bsp.traverseInvertedLevelOrder(&listener,(void *)withActors);
}
The withActors boolean is passed the the BSP listener in the userData parameter. It's a void * parameter that can contain pretty much anything. You can use it to store any numeric value (an int, a float, a boolean, a char...) or the adress of some struct/class. Here, we're simply casting the boolean into void *.
The room creation code now uses the map's RNG instead of libtcod's default one. It also retrieve the withActors value to pass it to the createRoom function. In Map.cpp, BspListener::visitNode :
bool withActors=(bool)userData;
// dig a room
w=map.rng->getInt(ROOM_MIN_SIZE, node->w-2);
h=map.rng->getInt(ROOM_MIN_SIZE, node->h-2);
x=map.rng->getInt(node->x+1, node->x+node->w-w-1);
y=map.rng->getInt(node->y+1, node->y+node->h-h-1);
map.createRoom(roomNum == 0, x, y, x+w-1, y+h-1, withActors);
The createRoom function digs the room, then handle actors only if withActors is true :
void Map::createRoom(bool first, int x1, int y1, int x2, int y2, bool withActors) { dig (x1,y1,x2,y2); if (!withActors) { return; } if ( first ) {
If you want to be able to restart a game using the exact same map as before by entering the same seed, you also need to use the map's RNG in the createRoom, addMonster and addItem functions. But since there's no way to enter a seed right now, we won't do it.
A persistent engine
Now everything is ready and all we have to do is to implement the Engine::save and Engine::load functions. If you want to use boost, it's time you leave this tutorial and go on your own. For the others, brace yourselves ! It's time to reinvent the wheel ! Let's define some abstract interface for everything that must be saved :
Persistent.hpp :
class Persistent {
public :
virtual void load(TCODZip &zip) = 0;
virtual void save(TCODZip &zip) = 0;
};
This file has to be included early in main.hpp as pretty much everything must inherit from Persistent.
main.hpp :
#include "libtcod.hpp"
class Actor;
#include "Persistent.hpp"
#include "Destructible.hpp"
We're going to use the top-down way, starting with the higher level class down to the smallest ones. In the attached source code, all the save/load method have been implemented in the Persistent.cpp file. While that might not be very orthodox, it helps keeping the bloat out of all the cpp files and having all the persistent stuff in a single file. Let's start with the Engine class. We obviously have to save the map and the actors. Another thing is the message log.
First, handle the permadeath :
void Engine::save() {
if ( player->destructible->isDead() ) {
TCODSystem::deleteFile("game.sav");
else save the map :
} else {
TCODZip zip;
// save the map first
zip.putInt(map->width);
zip.putInt(map->height);
map->save(zip);
The map could save the width/height fields in its own save function, but since it won't be able to load them (because we need them to create the Map object), we keep the symmetry between the load and save functions and handle the width/height field in the Engine.
then the actors. Note that since we want to be able to know who is the player, we save him first. That's why we decrement the number of remaining actors (actors.size()-1).
// then the player
player->save(zip);
// then all the other actors
zip.putInt(actors.size()-1);
for (Actor **it=actors.begin(); it!=actors.end(); it++) {
if ( *it != player ) {
(*it)->save(zip);
}
}
Finally, the message log. Then dump the compressed data to a file :
// finally the message log
gui->save(zip);
zip.saveToFile("game.sav");
}
}
I always start with the save function because it seems more intuitive to me. Then, writing the load function is just a mirroring process :
void Engine::load() {
if ( TCODSystem::fileExists("game.sav")) {
TCODZip zip;
zip.loadFromFile("game.sav");
// load the map
int width=zip.getInt();
int height=zip.getInt();
map = new Map(width,height);
map->load(zip);
Then we load the player.
// then the player player=new Actor(0,0,0,NULL,TCODColor::white); player->load(zip); actors.push(player);
The rest of the code is almost copied and pasted from the save function :
// then all other actors
int nbActors=zip.getInt();
while ( nbActors > 0 ) {
Actor *actor = new Actor(0,0,0,NULL,TCODColor::white);
actor->load(zip);
actors.push(actor);
nbActors--;
}
// finally the message log
gui->load(zip);
}
Note that we have to call the Actor constructor with dummy parameters. We could define some default Actor::Actor() constructor for that. If there is no game.sav file, we initialize some new random map :
} else {
engine.init();
}
}
A persistent map
Let Map implement the Persistent interface :
Map.hpp
class Map : public Persistent { public : int width,height; ... void load(TCODZip &zip); void save(TCODZip &zip);
We save the seed that will allow to reconstruct the dungeon without having to save the whole tile grid, and the memory map (list of explored tiles).
void Map::save(TCODZip &zip) {
zip.putInt(seed);
for (int i=0; i < width*height; i++) {
zip.putInt(tiles[i].explored);
}
}
We store the explored booleans as int since TCODZip only support a few basic types. The conversion is implicit (false=0, true=1). Now let's implement the loading part :
void Map::load(TCODZip &zip) {
seed=zip.getInt();
init(false);
Initializing the map with withActors = false will dig the rooms, but create no actor nor try to move the player in the first room. Then we restore the memory map :
for (int i=0; i < width*height; i++) {
tiles[i].explored=zip.getInt();
}
}