OBD:Instance file format: Difference between revisions

{{OBDtr| 0x20 | uint32  | | A0 BC 03 00 | 0x03BCA0  | data table offset }}

{{OBDtr| 0x24 | uint32  | | A0 35 25 00 | 2438560  | data table size }}

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

{{OBDtr| 0x2C | uint32  | | 04 4F 02 00 | 151300    | name table size }}

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

After the name table'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)-->.

|align=left | data offset (relative to data table)

|align=left | name offset (relative to name table)

|align=left | data offset (relative to data table)

|align=left | name offset (relative to name table)

The retail version of this instance descriptor tells us that a resource of '''type''' SUBT (a subtitle file for Oni; there are only two of these, one containing all speech subtitles, and one for help messages) has '''data''' that can be found 0x2230C8 bytes into the data table, which we learned from the file header starts at 0x03BCA0. Its '''name''' can be found 0xCB01 bytes into the name table that starts, according to the file header, at 0x28F240.

Before we talk about the name table in depth, we can peek ahead at the name of this resource using the offset we've just been given. Let's add the offset 0xCB01 to 0x28F240, the file header's address for the name table. This gives us the address 0x29BD41. There we find the string "SUBTsubtitles".

The actual subtitle data should be found by adding the offset 0x2230C8 to 0x03BCA0, the file header's address for the data table, to get 0x25ED68. We're going to leave the full details of the data table for later, but below is the data you should actually see for the English Oni SUBT file at this address. You have to consult the [[SUBT]] page to know how to read this data.

The name descriptor array stores the numbers of all named instances in the alphabetical order by said names, which are found in the name table but also pointed to by these entries. This array is used by the engine to look up instances by name; it's also used to find instances by template (scanning just the tag at the start of each name). The purpose of this array being alphabetized was to allow the engine to do a binary search to find instances by name more quickly, but the retail engine no longer attempts a binary search and merely iterates over the array from start to end.

The index number here is referring to the instance's position in the instance descriptor array. This number is also used by the data table to identify each instance, thus it is found in two places in the data explicitly and one place implicitly.

==Data table==

The data table 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.

The reason we'd need to align to 32 bytes is that the start of each instance's record (the instance ID) is always 32 byte-aligned. Thus, even though the template descriptors ended at 0x03BC9C, there are four empty bytes here so that the data table can begin at 0x03BCA0, which divides evenly by 32. This alignment rule also means that the instance-specific data will always start at an offset like 0x0008, 0x0028, 0x0148, etc.  

By the way, if you pick a random place in the data table to look at with a hex editor, how do you know which resource you're looking at? You would look for the highest data offset in the instance descriptor array that is less than your position in the file. Let's say that the string at 0x3BD40 caught our eye: "powerup_ammo". Subtracting the start of the data table, 0x3BCA0, gives us 0xA0 as the position of this string. Now looking back at the instance descriptor array, the instances' data offsets occur every 20 bytes and come directly after the tags. We can see that the first data offset is 0x8 and the next one is 0xF68, thus our offset into the data table of 0xA0 means we are looking at the instance which starts at 0x8. It's the very first instance listed at the start of the instance descriptor array:

{{OBDtr| 0x04 | int32  | | 08 00 00 00 | 0x08    | data offset (relative to data table) }}

{{OBDtr| 0x08 | int32  | | 00 00 00 00 | 0x00    | name offset (relative to name table) }}

So this tells us that the first data in the data table belongs to the solitary [[ONGS]] resource, and that it extends for 3,936 bytes. Since its name offset is 0x0, it's the first string in the name table, which we can see below is SUBTsubtitles.

==Name table==

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 table, the name table'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 table.