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DBT - Database Table

Applies to: GT4, GT5, GTPSP · Extension: .dbt · Endian: Platform Dependent

DBT Stands for Database Table.

DBT files is a non-standard database table format that supports compression. This format is directly linked to IDI, Label Information. No column information is present in this file, they had to be figured out from raw row data.

Note

All the database tables are loaded at boot fully in memory. When a row is extracted, a row is decompressed, but not in-place. The DBT format supports compressed and uncompressed tables, although uncompressed is generally not compatible with GT4 and will easily run out of memory. GTSpecDB will save compressed by default.

GT6 and above have moved away from this format, using SQLite instead.


Size: 0x10

Field Offset Type Description
GTDB 0x00 Int Magic, (Enforced, cannot be different)
Version/Flags 0x04 Int If 0x01 is toggled, the database is not compressed
Row Count 0x08 Int Number of rows in the table
Row Data Length 0x0C Int The size of one row in bytes, when extracted
Row Infos 0x10 RowInfos[] Row Infos start here
Huffman Dictionary N/A Huffman Dictionary Huffman dictionary (only when compressed)
Row Data N/A N/A Row Data

Row Infos

Size: 0x08

Field Offset Type Description
Row ID 0x00 Int Row ID of this row
Data Offset 0x04 char* If uncompressed, this will point to the row's data. If compressed it will point to the huffman codes used by this row to extract the row's data.

Tip

This table must be ordered by Row ID for binary search.

Huffman Dictionary

This is only present if the database is compressed.

Field Offset Type Description
Dictionary Size 0x00 Int Size of dictionary (relative from here)
Dict Entry Count 0x04 Int Number of entries in the dictionary
Prefix Lookup Table 0x08 Prefix Lookup Entry[256] Lookup tables mapping every byte (for codes under 8 bits)
Code Definitions N/A Code Definition[] Defines each code in the huffman dictionary

Prefix Lookup Entry

Field Offset Type Description
Byte Data 0x00 byte Byte data or this indexed entry
Code Bit Size 0x01 byte Size of this indexed code in bits

Code Definition

Field Offset Type Description
Code Bit Size 0x00 byte Size of the code in bits
Data 0x01 byte Data linked to this code
Padding 0x02 short N/A
Code 0x04 Int Huffman Code

Tip

This table must be ordered for binary search first by code, then by code bit size.

Row Data

If the table is compressed, bytes will be extracted from here to form the row

Otherwise uncompressed data for all rows is located here.

Field Offset Type Description
Uncompressed Size 0x00 Int Size of the uncompressed data in the table (only if compressed) relative to here
Uncomp. Row Count 0x04 Int Count of uncompressed rows in this table (only if compressed)

Uncompressed data then starts from here based on the count, and the size of one row defined in the header.

Huffman Codes

This is only present if the database is compressed.

Each row info will point to an unique place in the huffman codes table. The first code to be extracted is the number of codes needed to extract the row. Following that, the next code to be used will be a header packed in one byte:

  • 6 bits: Row Index
  • 2 bits: Extraction Type

It determines how a row is compressed:

  • Type 0: Row is uncompressed. Use row index to index the uncompressed rows.
  • Type 1: Row is compressed, each following code equals one byte in the row data.
  • Type 2: Row is compressed, we use an uncompressed row (using row index) and patch bytes into it to have our final row. Using the next codes, there will be 1 bit for each row byte, for each toggled bit it tells whether a byte in the uncompressed base row to use needs to be patched. After that, aligned to next byte, codes for each byte data to patch appears after.

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