OBD:Oni2AS
The Oni2 dev disc from Angel Studios contains:
- the main ELF executable SCPS_123.45
- a plain-text configuration file SYSTEM.CNF
- a SYSTEM folder containing fifteen ELF binaries (*.IRX) and a file called IOPRP255.IMG
- the three "binary data" files BANKS.DAT, RB.DAT and STREAMS.DAT
The common format of the three "binary data" files is as follows (illustrated on the example of RB.DAT).
| Offset | Type | Raw Hex | Value | Description |
|---|---|---|---|---|
| 0x00 | 4CC | 44 41 56 45 | "DAVE" | a control code |
| 0x04 | int32 | 18 41 00 00 | 16664 | number of files |
| 0x08 | int32 | 00 18 04 00 | 0x41800 | offset to start of file name block, from 0x800, in bytes |
| 0x0C | int32 | 00 30 0A 00 | 0xA3000 | offset to start of file data block, from 0x800, in bytes |
| 0x10 | char[2032] | 00 ... | 0 | padding |
| File table, first entry | ||||
| 0x800 | int32 | 00 00 00 00 | 0x00 | offset to file name, from start of file name block, in bytes
|
| 0x804 | int32 | BC D9 1F 02 | 0x21FD9BC | absolute offset to file data, from start of DAT file, in bytes |
| 0x808 | int32 | 00 08 00 00 | 2048 | uncompressed file size, in bytes |
| 0x80C | int32 | 94 00 00 00 | 148 | compressed file size, in bytes |
| File table, second entry | ||||
| 0x810 | int32 | 0B 00 00 00 | 0x0B | offset to file name, from start of file name block, in bytes
|
| 0x814 | int32 | 22 D3 1D 02 | 0x21DD322 | absolute offset to file data, from start of DAT file, in bytes
|
| 0x818 | int32 | 00 00 00 00 | 0 | uncompressed file size (zero; it's a folder) |
| 0x81C | int32 | 00 00 00 00 | 0 | compressed file size (also zero) |
| File table, third entry | ||||
| 0x820 | int32 | 12 00 00 00 | 0x12 | offset to file name, from start of file name block, in bytes
|
| 0x824 | int32 | 22 D3 1D 02 | 0x21DD322 | absolute offset to file data, from start of DAT file, in bytes
|
| 0x828 | int32 | 00 00 00 00 | 0 | uncompressed file size (zero; it's a folder) |
| 0x82C | int32 | 00 00 00 00 | 0 | compressed file size (also zero) |
| File table, fourth entry | ||||
| 0x830 | int32 | 1F 00 00 00 | 0x1F | offset to file name, from start of file name block, in bytes
|
| 0x834 | int32 | 00 00 53 06 | 0x6530000 | absolute offset to file data, from start of DAT file, in bytes |
| 0x838 | int32 | 90 09 03 00 | 199056 | uncompressed file size, in bytes |
| 0x83C | int32 | 13 85 02 00 | 165139 | compressed file size, in bytes |
| ...etc (rest of the file table) | ||||
The file table format is apparently a PS2 standard, and there are free tools like Game Extractor (basic version) that can display the folder structure and file sizes, and extract uncompressed files. However, while Game Extractor correctly identifies the compressed and uncompressed file sizes, it apparently does not know what the compression algorithm is (at least in the free version the compressed files are extracted in their compressed form and are thus unusable). Only very short files are packed without compression, for example minor shader or animation scripts.
After some forum lurking, it becomes clear that the compression algorithm is ZIP, or rather "deflate", in its most common implementation (open-source ZLIB library). However, the compressed files have no ZIP header, so the decompressor/compressor must use the right default settings for this to work. The correct setup is as follows:
z_stream infstream; // initialization of the "inflate" stream
infstream.zalloc = Z_NULL;
infstream.zfree = Z_NULL;
infstream.opaque = Z_NULL;
infstream.avail_in = (uInt)(size_comp); // size of compressed input
infstream.next_in = (Bytef *)file_comp; // input file (char array)
infstream.avail_out = (uInt)(size_orig); // size of decompressed output
infstream.next_out = (Bytef *)file_orig; // output file (char array)
// the actual DE-compression work.
inflateInit2(&infstream,-15);
inflate(&infstream, Z_NO_FLUSH);
inflateEnd(&infstream);
The important line, which defines the decompression rules, is inflateInit2(&infstream,-15). For the meaning of the -15 value, and the detail of the algorithm, read the ZLIB docs.
With proper decompression, the DAT files extract as follows: BANKS.DAT RB.DAT STREAMS.DAT