FST

FST, "Filesystem Table", is the format that Wii U title contents are stored in. Used for digital and disc contents.

Some information from the WiiUBrew FST page, some from cdecrypt with assistance from MarcusD. Numbers are big-endian.

Python parser and extractor can be found at wiiu_extract.py. Decryptor can be found at wiiu_decrypt.py.

Table of Contents FST contents Header Secondary header File entries header File entries Name entry table Hash tree

FST contents

Header

Offset	Size	Description
0x0	0x4	'FST\0' magic
0x4	0x4	Unknown, usually 0x20 (size of entries in secondary header). Seen as 0x1 for things like OSv10.
0x8	0x4	Amount of entries in secondary header
0xC	0x14	Unused

Secondary header

Lists contents. Index corresponds with an entry in the TMD content chunk records.

Offset	Size	Description
0x0	0x4	Offset in 0x8000(32768) sectors (e.g. 0x2 = 0x10000). Probably only useful for disc contents. Some titles like OSv10 don't seem to use this.
0x4	0x4	Related to size - TODO: put more details here
0x8	0x8	Title ID; only seems to be used for contents containing files in /content.
0x10	0x4	Group ID; not always used. Values can be 0x400, part of the Title ID(tid >> 8 & 0xFFFF), or something else.
0x14	0x2	Flags 0x000: first content with FST header (most of the time) 0x100: content without hash tree 0x200: content with hash tree
0x16	0xA	Unused(all zero)

Group ID was seen to be 0x10000 in Nintendo Land disc FST, despite tid being 0005000010102000. System titles seem to be limited to nothing/0x400.

File entries header

Offset	Size	Description
0x0	0x8	Unknown, probably unused
0x8	0x4	Total file entries
0xC	0x4	Unknown, probably unused

File entries

Offset	Size	Description
0x0	0x1	Type with bitmasks: 0x00: file 0x01: directory 0x02: special file used for Wii VC (/content/*.nfs) contents 0x80: deleted item, used for title updates that remove files
0x1	0x3	Name offset, relative to start of name entry table offset
0x4	0x4	File offset, in sectors of 0x20 (e.g. 0x2 = 0x40), or bytes if (flags & 4). Non-inclusive of content hash tree.
0x8	0x4	File size, in bytes
0xC	0x2	File flags with bitmasks: 0x000: content doesn't have hash tree, used for items in /code 0x004: file offset is in bytes 0x040: content has hash tree, used for items in /meta 0x400: content has hash tree, used for items in /content
0xE	0x2	Content index; corresponds with an entry in the TMD content chunk records

Name entry table

Null-terminated item names. Offsets are found in file entries in the above header.

Hash tree

WIP. it sucks.