Reading DB2 files - some questions

[Brainy]

Hey

a few hours ago I've started writing a PHP library to access the db2 files of the current WoW client. 

To test my library I've implemented the structure of CharTitles.db2. This looks like that:

class CharTitles extends DB2File
{
    public function __construct(File $file)
    {
        parent::__construct(new BinaryReader($file->getBuffer()));
    }

    public function getStructure() : array
    {
        return [
            DB2File::FIELD_STR,
            DB2File::FIELD_STR,
            DB2File::FIELD_INT16,
            DB2File::FIELD_BYTE
        ];
    }

    public function hasIndexFieldInData() : bool
    {
        return true;
    }
}

I've taken the structure from the current trinitycore version.

If I load the file now, I'll just get one correct record (the first one). The others are containing bad data.

The reason for this is a single byte after each record so if change the structure to this

            DB2File::FIELD_STR,
            DB2File::FIELD_STR,
            DB2File::FIELD_INT16,
            DB2File::FIELD_INT16

all will work as it should.

Now my question.

What exactly is that byte after each record? Is it a kind of seperator or is the structure of the current trinitycore just outdated?

Thanks in advance!

[Brainy]

I did another test with ChatChannels.db2. It seems that the total amount of bytes in a record modulo 4 must be 0.

So I've implemented following logic

            $bytesToSkip = 4 - ($recordSize % 4);
            if ($bytesToSkip != 4)
                $this->reader->skip($bytesToSkip);

Is this correct or just a bad hack?

 

EDIT#1: In general it seems to work

  [records:protected] => Array
        (
            [0] => DB2\DB2Record Object
                (
                    [id:protected] => 1
                    [fields:protected] => Array
                        (
                            [0] => 1572875
                            [1] => General - %s
                            [2] => General
                            [3] => 0
                        )

                )

            [1] => DB2\DB2Record Object
                (
                    [id:protected] => 2
                    [fields:protected] => Array
                        (
                            [0] => 1048635
                            [1] => Trade - %s
                            [2] => Trade
                            [3] => 0
                        )

                ) .....
 

[Shauren]

They are not aligned to 4 bytes, they are aligned to RecordSize from db2 header

[Brainy]

Ok understand. Thanks you Shauren.

But now I have another question. 

For the AreaTable.db2 I can read this header

DB2Header Object
(
    [magic] => WDB5
    [recordCount] => 5564
    [fieldCount] => 23
    [recordSize] => 56
    [stringTableSize] => 158430
    [tableHash] => 1918102339
    [layoutHash] => 886938365
    [minId] => 1
    [maxId] => 8623
    [locale] => 1
    [copyTableSize] => 0
    [flags] => 262144
    [idIndex] => 0
)
You see the recordSize of 56 but if I count the bytes of the structure excepting the ID field, it will be 58 bytes long.

How is this possible?

[Shauren]

Whenever you see uint32 near the end of structure its not uint32, its something called varint and its size will be determined by the field table block in header (https://github.com/TrinityCore/TrinityCore/blob/master/src/server/shared/DataStores/DB2StorageLoader.cpp#L197)

[Brainy]

Ah I understand. Thank you very much for your help!