RomFS

Overview

RomFS (or Read-Only Filesystem) is part of the NCCH format, and is used as external file storage.

RomFS can be used:

• in conjunction with the ExeFS of a NCCH

• to contain the game manual accessible from the Home Menu)

• to contain the DLP Child CIA)

• or to contain game cartridge update data

(There may be more implementations in the future)

Format

The RomFS is wrapped inside a IVFC hash-tree container, and the actual data is structured like a node-based tree, starting at the root level directory node, moving down to other directory and file nodes. Each directory node has pointers to child directory nodes and siblings, together with a pointer to the first file node for that directory. Each file node has pointers to their next file node, together with information about the actual file data.

The RomFS IVFC hash-tree header is 0x5C bytes long and is structured as follows:

START	SIZE	DESCRIPTION
0x00	0x4	Magic "IVFC"
0x04	0x4	Magic number 0x10000
0x08	0x4	Master hash size
0x0C	0x8	Level 1 logical offset
0x14	0x8	Level 1 hashdata size
0x1C	0x4	Level 1 block size, in log2
0x20	0x4	Reserved
0x24	0x8	Level 2 logical offset
0x2C	0x8	Level 2 hashdata size
0x34	0x4	Level 2 block size, in log2.
0x38	0x4	Reserved
0x3C	0x8	Level 3 logical offset
0x44	0x8	Level 3 hashdata size
0x4C	0x4	Level 3 block size, in log2.
0x50	0x4	Reserved
0x54	0x4	Reserved
0x58	0x4	Optional info size.