Added a mechanism to swap save files at runtime and a corresponding mod API export (#101)

librecomp/include/librecomp/game.hpp

@@ -109,6 +109,7 @@ namespace recomp {
 
     void start_game(const std::u8string& game_id);
     std::u8string current_game_id();
+    std::string current_mod_game_id();
 }
 
 #endif

librecomp/src/mod_config_api.cpp

@@ -63,6 +63,16 @@ void recomp_get_mod_version(uint8_t* rdram, recomp_context* ctx, size_t mod_inde
     *patch_out = version.patch;
 }
 
+void recomp_change_save_file(uint8_t* rdram, recomp_context* ctx, size_t mod_index) {
+    std::string name = _arg_string<0>(rdram, ctx);
+    std::u8string name_u8 = std::u8string{reinterpret_cast<const char8_t*>(name.data()), name.size()};
+
+    std::string mod_id = recomp::mods::get_mod_id(mod_index);
+    std::u8string mod_id_u8 = std::u8string{reinterpret_cast<const char8_t*>(mod_id.data()), mod_id.size()};
+
+    ultramodern::change_save_file(mod_id_u8, name_u8);
+}
+
 void recomp_free_config_string(uint8_t* rdram, recomp_context* ctx) {
     gpr str_rdram = (gpr)_arg<0, PTR(char)>(rdram, ctx);
     gpr offset = str_rdram - 0xFFFFFFFF80000000ULL;
@@ -75,5 +85,6 @@ void recomp::mods::register_config_exports() {
     recomp::overlays::register_ext_base_export("recomp_get_config_double", recomp_get_config_double);
     recomp::overlays::register_ext_base_export("recomp_get_config_string", recomp_get_config_string);
     recomp::overlays::register_ext_base_export("recomp_get_mod_version", recomp_get_mod_version);
+    recomp::overlays::register_ext_base_export("recomp_change_save_file", recomp_change_save_file);
     recomp::overlays::register_base_export("recomp_free_config_string", recomp_free_config_string);
 }

librecomp/src/pi.cpp

@@ -88,7 +88,12 @@ void recomp::do_rom_pio(uint8_t* rdram, gpr ram_address, uint32_t physical_addr)
 struct {
     std::vector<char> save_buffer;
     std::thread saving_thread;
+    std::filesystem::path save_file_path;
     moodycamel::LightweightSemaphore write_sempahore;
+    // Used to tell the saving thread that a file swap is pending.
+    moodycamel::LightweightSemaphore swap_file_pending_sempahore;
+    // Used to tell the consumer thread that the saving thread is ready for a file swap.
+    moodycamel::LightweightSemaphore swap_file_ready_sempahore;
     std::mutex save_buffer_mutex;
 } save_context;
 
@@ -97,7 +102,15 @@ const std::u8string save_folder = u8"saves";
 extern std::filesystem::path config_path;
 
 std::filesystem::path get_save_file_path() {
-    return config_path / save_folder / (std::u8string{recomp::current_game_id()} + u8".bin");
+    return save_context.save_file_path;
+}
+
+void set_save_file_path(const std::u8string& subfolder, const std::u8string& name) {
+    std::filesystem::path save_folder_path = config_path / save_folder;
+    if (!subfolder.empty()) {
+        save_folder_path = save_folder_path / subfolder;
+    }
+    save_context.save_file_path = save_folder_path / (name + u8".bin");
 }
 
 void update_save_file() {
@@ -143,6 +156,10 @@ void saving_thread_func(RDRAM_ARG1) {
         if (save_buffer_updated) {
             update_save_file();
         }
+
+        if (save_context.swap_file_pending_sempahore.tryWait()) {
+            save_context.swap_file_ready_sempahore.signal();
+        }
     }
 }
 
@@ -207,14 +224,12 @@ size_t get_save_size(recomp::SaveType save_type) {
     return 0;
 }
 
-void ultramodern::init_saving(RDRAM_ARG1) {
+void read_save_file() {
     std::filesystem::path save_file_path = get_save_file_path();
 
     // Ensure the save file directory exists.
     std::filesystem::create_directories(save_file_path.parent_path());
 
-    save_context.save_buffer.resize(get_save_size(recomp::get_save_type()));
-
     // Read the save file if it exists.
     std::ifstream save_file = recomp::open_input_file_with_backup(save_file_path, std::ios_base::binary);
     if (save_file.good()) {
@@ -224,10 +239,28 @@ void ultramodern::init_saving(RDRAM_ARG1) {
         // Otherwise clear the save file to all zeroes.
         std::fill(save_context.save_buffer.begin(), save_context.save_buffer.end(), 0);
     }
+}
+
+void ultramodern::init_saving(RDRAM_ARG1) {
+    set_save_file_path(u8"", recomp::current_game_id());
+
+    save_context.save_buffer.resize(get_save_size(recomp::get_save_type()));
+
+    read_save_file();
 
     save_context.saving_thread = std::thread{saving_thread_func, PASS_RDRAM};
 }
 
+void ultramodern::change_save_file(const std::u8string& subfolder, const std::u8string& name) {
+    // Tell the saving thread that a file swap is pending.
+    save_context.swap_file_pending_sempahore.signal();
+    // Wait until the saving thread indicates it's ready to swap files.
+    save_context.swap_file_ready_sempahore.wait();
+    // Perform the save file swap.
+    set_save_file_path(subfolder, name);
+    read_save_file();
+}
+
 void ultramodern::join_saving_thread() {
     if (save_context.saving_thread.joinable()) {
         save_context.saving_thread.join();

librecomp/src/recomp.cpp

@@ -490,6 +490,13 @@ std::u8string recomp::current_game_id() {
     return current_game.value();
 };
 
+std::string recomp::current_mod_game_id() {
+    auto find_it = game_roms.find(current_game_id());
+    const recomp::GameEntry& game_entry = find_it->second;
+
+    return game_entry.mod_game_id;
+}
+
 void recomp::start_game(const std::u8string& game_id) {
     std::lock_guard<std::mutex> lock(current_game_mutex);
     current_game = game_id;

ultramodern/include/ultramodern/ultramodern.hpp

@@ -37,6 +37,9 @@ void init_events(RDRAM_ARG renderer::WindowHandle window_handle);
 void init_timers(RDRAM_ARG1);
 void init_thread_cleanup();
 
+// Saving
+void change_save_file(const std::u8string& subfolder, const std::u8string& name);
+
 // Thread queues.
 constexpr PTR(PTR(OSThread)) running_queue = (PTR(PTR(OSThread)))-1;