diff options
| -rw-r--r-- | src/storage.cc | 41 |
1 files changed, 33 insertions, 8 deletions
diff --git a/src/storage.cc b/src/storage.cc index fef0ee2..bd35780 100644 --- a/src/storage.cc +++ b/src/storage.cc @@ -270,16 +270,41 @@ void Storage::load(uint8_t idx, uint8_t *data) void Storage::save(uint8_t *data) { - num_anims++; - i2c_write(0, num_anims, 1, &first_free_page); - append(data); + /* + * Technically, we can store up to 255 patterns. However, Allowing + * 255 patterns (-> num_anims = 0xff) means we can't easily + * distinguish between an EEPROM with 255 patterns and a factory-new + * EEPROM (which just reads 0xff everywhere). So only 254 patterns + * are allowed. + */ + if (num_anims < 254) { + /* + * Bytes 0 .. 255 (pages 0 .. 7) are reserved for storage metadata, + * first_free_page counts pages starting at byte 256 (page 8). + * So, first_free_page == 247 addresses EEPROM bytes 8160 .. 8191. + * first_free_page == 248 would address bytes 8192 and up, which don't + * exist -> don't save anything afterwards. + * + * Note that at the moment (stored patterns are aligned to page + * boundaries) this means we can actually only store up to 248 + * patterns. + */ + if (first_free_page < 248) { + num_anims++; + i2c_write(0, num_anims, 1, &first_free_page); + append(data); + } + } } void Storage::append(uint8_t *data) { - // the header indicates the length of the data, but we really don't care - // - it's easier to just write the whole page and skip the trailing - // garbage when reading. - i2c_write(1 + (first_free_page / 8), (first_free_page % 8) * 32, 32, data); - first_free_page++; + // see comment in Storage::save() + if (first_free_page < 248) { + // the header indicates the length of the data, but we really don't care + // - it's easier to just write the whole page and skip the trailing + // garbage when reading. + i2c_write(1 + (first_free_page / 8), (first_free_page % 8) * 32, 32, data); + first_free_page++; + } } |