Changes

Each metadata "superblock" starts with the 4 magic bytes "SFFS", followed by a 4-byte "generation number" and another 4-byte number (always 0x10?). When accessing the FS, IOS will choose the superblock with the highest generation number and use it; whenever it modifies the filesystem in any way, it will increment the generation number by 1 and write out an entirely new superblock in the next slot (in round-robin order).

Each metadata "superblock" starts with the 4 magic bytes "SFFS", followed by a 4-byte "generation number" and another 4-byte number (always 0x10?). When accessing the FS, IOS will choose the superblock with the highest generation number and use it; whenever it modifies the filesystem in any way, it will increment the generation number by 1 and write out an entirely new superblock in the next slot (in round-robin order).

The next 0x10000 bytes (bytes 0xc:0x1000c within the superblock) are 0x8000 2-byte cluster numbers, and comprise the FAT. The FAT is followed by the FST -- the tree structure containing the directory hierarchy and (plaintext!) filenames.

The next 0x10000 bytes (bytes 0xc:0x1000c within the superblock) are 0x8000 2-byte cluster numbers, and comprise the FAT. The FAT is followed by the FST — the tree structure containing the directory hierarchy and (plaintext!) filenames.

=== FAT ===

=== FAT ===

The FAT contains cluster chain / allocation information for the entire NAND chip, including parts of it which are not technically part of the filesystem!

The FAT contains cluster chain / allocation information for the entire NAND chip, including parts of it which are not technically part of the filesystem!

The first 64 entries will always be 0xFFFC, which indicates that this cluster is "reserved". These correspond to the first 64 clusters or 8 blocks -- which is where boot1 and boot2 are stored.

The first 64 entries will always be 0xFFFC, which indicates that this cluster is "reserved". These correspond to the first 64 clusters or 8 blocks — which is where boot1 and boot2 are stored.

Special values include:

Special values include:

* 0xFFFB - last cluster within a chain

* 0xFFFB - last cluster within a chain

* 0xFFFC - reserved cluster

* 0xFFFC - reserved cluster

* 0xFFFD - bad block (marked at factory) -- you should always see these in groups of 8 (8 clusters per NAND block)

* 0xFFFD - bad block (marked at factory) — you should always see these in groups of 8 (8 clusters per NAND block)

* 0xFFFE - empty (unused / available) space

* 0xFFFE - empty (unused / available) space