Implementing an Auto-Save Feature

Implementing an auto-save feature is a great way to ensure that user progress is regularly saved without disrupting gameplay. This can be done using a background thread or a non-blocking I/O operation that periodically writes the game state to a file.

Auto-Save Using a Background Thread

One common approach is to use a separate thread that handles the auto-save process:

1#include <SDL.h>
2
3#include <atomic>
4#include <chrono>
5#include <iostream>
6#include <thread>
7
8std::atomic<bool> KeepRunning{true}; 
9
10namespace Game{
11  void AutoSave(const std::string& Path) {
12    while (KeepRunning) {
13      std::this_thread::sleep_for(
14        std::chrono::seconds(60)); 
15      SDL_RWops* Handle = SDL_RWFromFile(
16        Path.c_str(), "wb");
17      if (!Handle) {
18        std::cout << "Error opening file: " <<
19          SDL_GetError() << std::endl;
20        continue;
21      }
22
23      // Serialize and write the game state here
24      const char* GameState =
25        "Current Game State Data"; 
26      SDL_RWwrite(Handle, GameState,
27                  sizeof(char),
28                  strlen(GameState));
29      SDL_RWclose(Handle);
30
31      std::cout << "Game auto-saved" <<
32        std::endl;
33    }
34  }
35
36  void StartAutoSave(const std::string& Path) {
37    std::thread AutoSaveThread(AutoSave, Path);
38    
39    AutoSaveThread.detach();
40  }
41
42  void StopAutoSave() {
43    KeepRunning = false; 
44  }
45}

Key Features of This Approach

• Non-Blocking: The auto-save occurs in a separate thread, so it doesn't interrupt the main gameplay loop.
• Periodic Saves: The game state is saved at regular intervals, e.g., every 60 seconds.
• Graceful Shutdown: When the game exits, you can stop the auto-save thread cleanly.

Auto-Save During Gameplay Events

Another approach is to trigger auto-saves during specific gameplay events, such as after completing a level or achieving a milestone. This can be done synchronously, but you should optimize it to avoid long pauses:

1void SaveOnEvent(const std::string& Path) {
2  SDL_RWops* Handle = SDL_RWFromFile(
3    Path.c_str(), "wb");
4  if (!Handle) {
5    std::cout << "Error opening file: "
6      << SDL_GetError() << '\n';
7    return;
8  }
9
10  // Serialize and write the game state here
11  const char* GameState =
12    "Game State After Event"; 
13  SDL_RWwrite(Handle, GameState, sizeof(char),
14              strlen(GameState));
15  SDL_RWclose(Handle);
16
17  std::cout << "Game auto-saved after event\n";
18}

Considerations

• Performance: Ensure the auto-save process is optimized and doesn't cause noticeable lag during gameplay.
• Data Integrity: If using background threads, ensure thread safety when accessing shared game state data to avoid corruption.
• Frequency: Adjust the auto-save frequency based on your game's needs—too frequent saves can cause performance issues, while too infrequent saves risk losing progress.

This approach helps maintain a smooth gameplay experience while ensuring that progress is regularly saved, reducing the risk of data loss due to crashes or unexpected exits.