MHServerEmu/docs/GameData/PakFile.md

Pak File

A pak file (also known as GPAK by its signature and sip by its extension) is an archive that contains game data. Early versions of the game used a SQLite database for storage, but later on it was replaced with a custom format.

SQLite-based paks store all data in a single mu_cdata.sip file located in %GameDirectory%\UnrealEngine3\Binaries\Win32\Data. Custom format paks store data in two separate files (Calligraphy.sip and mu_cdata.sip) located in %GameDirectory%\Data\Game.

SQLite Paks

These older paks can be opened with existing general-purpose tools, such as DB Browser for SQLite. They contain two tables: data_tbl and ver.

The data_tbl table has the following columns:

Name	Type	Constraints	Description
i	INTEGER		File id / hash
n	TEXT	UNIQUE COLLATE NOCASE	File name
b	BLOB		Data
l	INTEGER		Data size
s	INTEGER		Timestamp

The ver table has only a single row with the following columns:

Name	Type	Description
v	REAL	Format version number
s	TEXT	Format version note

There are two known versions of these SQLite-based paks:

Format Version	Note	Client Version
1.5	Added back index for names for non-maxload optimization	1.9-?
1.6	Added lz4 compression for stored data to speed up shipping client load time

Custom Gazillion Paks

At some currently unknown point in 2014-2015 the original SQLite-based archives were replaced with a new custom format developed by Gazillion. Data was also split into two files: Calligraphy.sip for data exported from Calligraphy and mu_cdata.sip for resource data. These custom paks can be opened with MHDataParser.

Files with this format have the following structure:

struct PakFile
{
    uint Header;    // KAPG
    uint Version;

    int NumEntries;
    PakEntry[NumEntries] Entries;

    byte[] CompressedRawData;
}

Entries have the following structure:

struct PakEntry
{
    ulong FileHash;
    int FileNameLength;
    byte[FileNameLength] FileName; // UTF-8
    int ModTime;
    int Offset;
    int CompressedSize;
    int UncompressedSize;
}

The entries are followed by raw data compressed using the LZ4 algorithm. The offsets specified in the entries are from where the raw data begins.