OBD:Instance file format: Difference between revisions

:You should read the [[Game data terminology]] page before this one.<br>

:The [[Raw|Raw and separate file formats]] page should be read after this one.}}

The level 0 files do not contain resources for a specific level but rather resources (instances) shared across all levels. Level 0 is loaded when the game starts and is never unloaded. All other level files, 1-19, are only loaded when their corresponding level starts and then unloaded when it ends. Oni can only hold two level files in memory concurrently. Thus, resources have to be duplicated on disk whenever a character class, sound effect, etc. occurs in more than one level. For instance, although there are only 2,380 unique sounds in the game, there are 7,386 sounds stored across all level data files.

==Backwards and garbage data==

As mentioned, the game's developers used the in-game editor to create AIs, particles, etc. in a level. When one of these developers saved his work, the contents of the level, stored in his PC's RAM, were flushed directly to disk. Thus the structure of the .dat/.raw/.sep files reflects the way in which Bungie West chose to store levels in memory. So when we read the data in the files with a hex editor, we can see eccentricities such as blank space (coming from unused fields and byte-alignment padding) and garbage data (such as now-meaningless pointer values). [[OBD:Raw and separate file formats#Gaps|Further gaps]], mostly representing orphaned obsolete resources, add up to about 25 MB for the whole game.

Additionally, because the levels were built on Intel-based machines, which use a little-endian architecture, sequences of bytes which represent numbers were written from least-significant to most-significant byte. [[wp:FourCC|FourCCs]] in the data are stored "backwards", such as "13RV" which is meant to be read "VR31", because Bungie defined those four bytes as a 32-bit integer, not a string, causing them to be written to disk in little-endian order.

*Max number of instance files in GameDataFolder: 512 (Windows), 16 (Windows demo, Mac)

*0x0003BCDF33DC271F (PC v1.0) - templates compatible with Windows retail engine

*0x0003BCDF23C13061 (PC v1.1) - templates compatible with Windows demo and Mac engines

*0x0003BA70A8DBAE11 (PS2) - templates compatible with PlayStation 2 engine

<!--*0x0000000000000000 (blank) - for use with [[OniX]] engine, which instead handle data versioning using the 0x3C field below-->

OniSplit's .oni files use PC 1.0 checksum by default and 1.1 checksums when holding data that is stored differently in the 1.1 format (SNDD, TXMP, AGQG, M3GM, IGSt, TSFT/TSGA, TRAM/TREX) }}

{{OBDtr| 0x18 | uint32  | | D4 1B 00 00 | 7124      | name descriptor count }}

{{OBDtr| 0x1C | uint32  | | 38 00 00 00 | 56        | template descriptor count }}

{{OBDtr| 0x28 | uint32  | | 40 F2 28 00 | 0x28F240  | name block offset }}

{{OBDtr| 0x30 | uint32  | | 99 CF 40 00 | (garbage) | used by OniSplit for raw table offset }}

{{OBDtr| 0x34 | uint32  | | 90 4F 63 00 | (garbage) | used by OniSplit for raw table size }}

Next we are told the addresses and sizes of the '''data and name tables''' in the instance file. The name block simply follows the data block, as you'll see if you add the data block offset plus the data block size, so the name block offset is technically redundant. The name block offset plus the name block size equals the total size of the file since it's the last segment of the file.

After the name block's size comes four "int"s of '''garbage'''; this is padding in order to align the start of the next segment of the file on a 32-byte boundary. The first two 32-bit fields in this space are, however, used in .oni files generated by OniSplit<!--, and the last 32-bit field is partly used by OniX for a new form of template versioning. Future usage of these fields by OniSplit and/or OniX may change (hopefully not too much)-->.

The data block occupies the majority of the file and stores all the instance data (though this data sometimes points to the location of more data in a raw/separate file). We peeked at this table before when we looked at the instance descriptor for SUBTsubtitles. The table's starting point is found at the offset given in the header, in this case 0x03BCA0, saving us the trouble of adding up the size of the four preceding segments of the file and then aligning to the next 32-byte boundary.

{{OBDtr| 0x08 | ...    | | ...        | ...  | [[OBD:File types|type-specific data]]... }}

This final segment of the file stores all the instance names as C-style ASCII strings (terminated by a zero byte). We peeked at this before when we looked at the instance descriptor for SUBTsubtitles. The start of this table is 32-byte aligned but after that the strings are simply packed end to end, separated only by their null terminator. As with the data block, the name block's starting point is given in the header, in this case 0x28F240.

These names can be up to 63 characters long, counting the tag. The instance file concludes with the end of the name block.