U8 (File Format)
An U8 file is an archive containing a hierarchical file system. In Mario Kart Wii all U8 files are compressed using the YAZ0 format and stored as SZS files. For publishing track files it is better to use the WU8 format to avoid/reduce license conflicts. See »File format: U8 archives« for details.
U8 header
The header of a U8 file is 32 bytes long. All numeric values are stored as big endian values.
| Offset | Type | Description |
|---|---|---|
| 0x00 | u32 | File magic. Always 0x55AA382D = U.8-. |
| 0x04 | u32 | Offset to the first node. |
| 0x08 | u32 | Size of all nodes including the string table. |
| 0x0c | u32 | File offset of data. |
| 0x10 | u32[4] | Reserved. |
File System
The file system consists on a list of nodes (12 byte each) followed by a string pool for the file names. This file system part is identical to the file system of every Wii disc. The first node ('root' node, index #0) is referenced by the U8 header (see above). Each node has the following data structure:
Each Wii disc uses the same directory and file structure.
| Offset | Type | Description |
|---|---|---|
| 0x00 | byte | 0x00=data file, 0x01=directory entry (other values never seen) |
| 0x01 | u24 | Three bytes: Offset into the string pool for the file name |
| 0x04 | u32 | File: Offset of begin of data Directory: Index of the parent directory. |
| 0x08 | u32 | File: Size of data Directory: Index of the first node that is not part of this directory (skip to node). |
- The size value of the root node (zero base index #0) is equal to the total number of nodes. The string pool start with the first byte behind the last node.
- The string pool is coded ASCII. Each string is terminated by NULL.
- The string pool offsets are relative to the start of the string pool.
- The string pool contains only the last part of the filename. The full path with slashes ('/') in the example listing are only printed for a better overview.
- The file name of the root node is always empty.
- In Mario Kart the node at index #1 is nearly always a directory with name ".". If this file exists all other files are part of this directory. It is not really needed and never seen for file systems of Wii disc partitions.
- The natural sort order (that one used by Nintendo) is:
- ('/' is less than) '.' is less than digits is less than letters is less than others.
- The case of letters is ignored.
- For same group of characters use ASCII order.
- For each directory: Real files are inserted before sub directories.
- Example listing (made with "wszst list -lll" or "wszst llll")
* Files of YAZ.U8:Scene/UI/Title_G.szs idx off/hex siz/hex size/dec magic file or directory/ ------------------------------------------------------------------------------- 0: 0< 1b> - - 1: 0< 1b> - - ./ 2: 1< 3> - - ./bg/ 3: 1< 4> - - ./button/ 4: 1< 5> - - ./control/ 5: 1< 6> - - ./debug/ 6: 1< 7> - - ./dpd_pointer/ 7: 1< a> - - ./message/ 8: 300 2580 9600 MESG ./message/Common.bmg 9: 2880 18300 99072 MESG ./message/Menu.bmg a: 1< b> - - ./message_window/ b: 1< c> - - ./pad_recognize/ c: 1< d> - - ./press_start/ d: 1< 1b> - - ./title/ e: d< 12> - - ./title/anim/ f: 1ab80 88 136 RLAN ./title/anim/title_off.brlan 10: 1ac20 9c 156 RLAN ./title/anim/title_off_to_on.brlan 11: 1acc0 88 136 RLAN ./title/anim/title_on.brlan 12: d< 15> - - ./title/blyt/ 13: 1ad60 370 880 RLYT ./title/blyt/title.brlyt 14: 1b0e0 448 1096 RLYT ./title/blyt/title_boke.brlyt 15: d< 1b> - - ./title/timg/ 16: 1b540 840 2112 . .0 ./title/timg/tt_pattern_chek_bokashi_32x32.tpl 17: 1bd80 80640 525888 . .0 ./title/timg/tt_title_screen_mario0.tpl 18: 9c3c0 80640 525888 . .0 ./title/timg/tt_title_screen_mario0_bokeboke.tpl 19: 11ca00 38e40 233024 . .0 ./title/timg/tt_title_screen_title_rogo_bokeboke.tpl 1a: 155840 38e40 233024 . .0 ./title/timg/tt_title_screen_title_rogo_tm_only.tpl
- GNU C example
typedef struct u8_node_t
{
union
{
u8 is_dir; // directory flag
be32_t name_off; // mask with 0x00ffffff
};
be32_t offset;
be32_t size;
}
__attribute__ ((packed)) u8_node_t;
File Data
The file data is dependent of the related file type. See the other file formats descriptions for more details.
Tools
The following tools can handle U8 files (often stored as .arc or .szs):
- CTools Pack, by MrBean35000vr and Chadderz
- Every File Explorer, by Gericom
- SZS Modifier, by MrBean35000vr and Chadderz
- Wexos's Toolbox, by Wexos
- Wiimms SZS Tools, by Wiimm