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OBD:Instance file format: Difference between revisions
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→Template descriptors: let's use data that actually comes from level0, shall we?
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Likewise, the template descriptor array starts directly after the name descriptors. Since name descriptors are 8 bytes, 8 * 7124 (taken from the header) = 56992, or 0xDEA0, and adding that to the name descriptor array's start address (0x02DA7C) gives us 0x03B91C as the start of the template descriptors. | Likewise, the template descriptor array starts directly after the name descriptors. Since name descriptors are 8 bytes, 8 * 7124 (taken from the header) = 56992, or 0xDEA0, and adding that to the name descriptor array's start address (0x02DA7C) gives us 0x03B91C as the start of the template descriptors. | ||
The template descriptor array contains information about all templates (that is, resource types, AKA tags), used in the file (56 in this case, as we learned from the file header). Any resource occurring in this instance file has to have its type listed here. | The template descriptor array contains information about all templates (that is, resource types, AKA tags), used in the file (56 in this case, as we learned from the file header). Any resource occurring in this instance file has to have its type listed here. Here is the template descriptor at 0x3B9FC: | ||
{{Table}} | {{Table}} | ||
{{OBD_Table_Header}} | {{OBD_Table_Header}} | ||
{{OBDtr| 0x00 | int64 | | | {{OBDtr| 0x00 | int64 | | 3C B9 A6 71 08 00 00 00 | 0x871A6B93C | template checksum }} | ||
{{OBDtr| 0x08 | tag | | | {{OBDtr| 0x08 | tag | | 45 47 52 54 | 'EGRT' | template tag }} | ||
{{OBDtr| 0x0C | int32 | | 01 00 00 00 | 1 | number of resources in file that use this template }} | {{OBDtr| 0x0C | int32 | | 01 00 00 00 | 1 | number of resources in file that use this template }} | ||
|} | |} | ||
The '''template checksum''' is used to prevent loading of instance files that are not compatible with the current engine version. The '''tag''' is the same kind of number-written-as-backwards-ASCII that we discussed in the "Backwards and garbage data" section. The '''number of resources''' is self-explanatory. | The '''template checksum''' is used to prevent loading of instance files that are not compatible with the current engine version. The '''tag''' is the same kind of number-written-as-backwards-ASCII that we discussed in the "Backwards and garbage data" section; in this case, 'EGRT' means [[TRGE]]. The '''number of resources''' is self-explanatory. | ||
You might wonder how Oni knows how to read each type of data, such as a SUBT or an ABNA. The simple answer is that this information is hard-coded into Oni. In fact, the information on each instance type, as stored in Oni's code, is actually the real "template". The file data only gives the tag and checksum that refer to a certain template. Which types of data fields are encountered in which order is already known by Oni. These hardcoded templates also tell Oni which parts of the file data are reserved for pointers. | You might wonder how Oni knows how to read each type of data, such as a SUBT or an ABNA. The simple answer is that this information is hard-coded into Oni. In fact, the information on each instance type, as stored in Oni's code, is actually the real "template". The file data only gives the tag and checksum that refer to a certain template. Which types of data fields are encountered in which order is already known by Oni. These hardcoded templates also tell Oni which parts of the file data are reserved for pointers. | ||