Saves

engine/save.hpp, engine/engine.hpp

Saves are numbered slots, each holding one block of bytes, usually a struct. See the saving tutorial.

Functions

bool read_save(char *data, uint32_t length, int slot = 0);
void write_save(const char *data, uint32_t length, int slot = 0);
bool remove_save(int slot = 0);

template<class T> bool read_save(T &data, int slot = 0);
template<class T> void write_save(const T &data, int slot = 0);

read_save(data, slot)

Reads slot slot into data. Returns true if the save exists and holds at least sizeof(data) bytes; otherwise returns false, and data may be partly overwritten, so reset it to defaults.

write_save(data, slot)

Writes data to the slot, replacing what was there.

remove_save(slot)

Deletes the slot. Returns true if it was deleted.

slot

Any number. Each slot is a separate file and can hold a different type.

The template versions take any type and use sizeof(T). The type must be trivially copyable: numbers, bool, enums, fixed-size arrays and structs of those. No pointers, std::string or containers.

struct Progress {
  uint32_t version = 1;
  uint8_t level = 1;
  bool unlocked[10] = {};
  char name[12] = "PLAYER";
};

Progress progress;

if(!read_save(progress, 1) || progress.version != 1)
  progress = Progress();

Saving when the player quits

extern void (*on_quit)();

Set on_quit to a function that saves, and the SDK calls it when the player quits: from the system menu or by holding HOME on the VGC Zero, or by closing the window on the desktop. API 0.5+. See on_quit for the details, and save at checkpoints too: switching the console off isn't caught.

Where saves are stored

Platform	Slot n of a game titled Title
VGC Zero	.blit/Title/save<n> on the CHILICHIP USB drive
Linux, macOS, Windows	save<n> in SDL's per-user data folder for the game's author and title, e.g. ~/.local/share/<author>/<title>/
Web	the browser's IndexedDB storage for the page

On the VGC Zero saves are kept when a game is updated, and the player is asked whether to delete them when the game is deleted. Writing a save writes to flash and takes a few milliseconds.