NDS File System Structure

This explains the relevant parts of the NDS File System.

Header

The important parts of the header are

Offset	Value Type	Used for
0x40	Int32	Start offset of Name Table
0x48	Int32	Start offset of File Allocation Table

Name Table

The name table stores the names of the files and the structure of the file system. From the information stored, the index of the the file's entry in the File Allocation Table can be found.

It is split into two parts:

• Folder Allocation Table
• Name List

Folder Allocation Table

Each folder in the file system has a 8 byte long entry. The first one is for the root folder, and acts as an entry point to the file system. Each entry looks something like this:

DF 01 00 00 6F 01 02 F0

Within the entry is the following information

Offset	Value Type	Used for
0x00	Int32	Start offset of folder contents within Name List relative to start of NameTable
0x04	Int16	Index of first file within folder in File Allocation Table
0x06	Byte/Int16	Byte Index of parent folder in current table; for root folder this is an int16 which holds the number of entries in the table
0x07	Byte	Unknown, always 0xF0 except for root folder where it is part of above

Name List

The name list holds the names of the folders, and their contents in order, with references back to the Folder Allocation Table.

Example:

86 64 6C 5F 72 6F 6D 25 F0

Information Contained:

Offset	Value Type	Used for
0x00	Byte	The least significant 7 bits store the length of the name, and the most significant bit indicates whether it is a folder (1 = folder, 0 = file).
0x01 ...	Utf8 String	The variable length name
Finally	UInt16	Only there if it is a folder. Refers to the the index of it within the Folder allocation table, allowing its contents to be found.

You can find the offset of a particular file within the File Allocation Table by keeping count of the file's index with a folder, and adding that to the index of the first file within the folder (stored within the entry of the folder within the Folder Allocation Table).

File Allocation Table

The structure of the file allocation table is very simple, it's just a table of 8 byte entries, e.g.:

00 A4 07 00 04 A8 07 00

The entry is just two int32 values referring to global offsets:

Offset	Value Type	Used for
0x00	Int32	Start offset of file
0x04	Int32	End offset of file (after this is padding)