Save.h File Reference

Saving: a record in flash that survives power cycles and re-uploads. More...

#include <stdint.h>

Go to the source code of this file.

Namespaces
namespace	save
	Saved records: load, store, and the raw read/write underneath.

Functions
constexpr uint32_t	save::magic (const char(&s)[5])
	Four characters as a magic number ("CHCR" -> 0x52434843).
bool	save::available ()
	Whether saving works in this image.
const void *	save::read (uint32_t magic, uint8_t version, uint16_t size, uint8_t *flag=nullptr)
	Find the newest valid record.
void *	save::buffer ()
	The page buffer to fill before write(): writing in place.
bool	save::write (uint32_t magic, uint8_t version, uint16_t size, uint8_t flag=0)
	Write what is in buffer() as a new record, to the older page.
template<class T >
bool	save::load (uint32_t magic, uint8_t version, T &data, uint8_t *flag=nullptr)
	Load a struct from the newest valid record.
template<class T >
bool	save::store (uint32_t magic, uint8_t version, const T &data, uint8_t flag=0)
	Save a struct as a new record.

Variables
static const uint16_t	save::MAX_DATA = 256 - 12
	The most data a record holds: a 256-byte page less the header and CRC.

Detailed Description

Saving: a record in flash that survives power cycles and re-uploads.

CHGame has no EEPROM. The bootloader erases only the flash pages a new sketch occupies, so the last two pages of the application region (0xF500, 0xF600) survive. A record is a header, the game's own data and a CRC; saves take turns between the pages, so a power cut in the middle of one loses only that save. Every game shares the two pages and tells its records apart by a magic number of its own (each game needs a different one). If the sketch grows into the pages, saving switches itself off rather than overwrite code: an image up to 50,432 B keeps both pages, up to 50,688 B one.