Difference between revisions of "FST"

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|Name Offset || 4 || 0 || Offset in bytes of the name of the file from the start of the nametable
 
|Name Offset || 4 || 0 || Offset in bytes of the name of the file from the start of the nametable
 
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Revision as of 07:57, 21 June 2015

The Filesystem Table, or FST, is a file present in Wii U disk images and downloaded content that describes the folders and files contained in the image or file.

It seems to be based on the Wii's FST format, but an extra header/cluster section was added.

All numbers are big-endian.

The file is composed of four sections:

  • the main header
  • a number of secondary headers describing storage clusters
  • a number of file and directory entries, beginning with the root directory
  • a table of null-terminated names

Main Header

Size: 0x20 bytes

Field Size Offset Description
Magic 4 0 always "FST" and a null byte
Secondary header size 4 4 (not sure)
Secondary header count 4 8 Number of secondary headers in the FST

Secondary header

Each of these entries describe the position of data on disk. For downloaded content, each corresponds to one entry from the TMD.

Size: 0x20 each

File/Directory entry

Each of these represents a file or a directory.

Size: 0x10 each

Field Size Offset Description
Name Offset 4 0 Offset in bytes of the name of the file from the start of the nametable
Offset 4 4 Offset in sectors of the file in its storage cluster (multiply by 32 for byte offset)
Size 4 8 Size of the file in bytes
Storage cluster index 4 12 this field & 0xff is an index to the list of secondary headers

If the top bits of the name offset is set (&0xff000000), then this entry is a directory

In this case, the size corresponds to the number of entries this directory contains.

Nametable

Table of null-terminated filenames.

External Links

https://github.com/CarlKenner/dolphin/blob/WiiU/Source/Core/DiscIO/FileSystemWiiU.cpp - A fork of Dolphin by CarlKenner that can read WiiU disk images.

http://blog.delroth.net/2011/06/reading-wii-discs-with-python/ - some information on the Wii's FST format