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PakFile.md

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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.

Initially all data was stored in a single mu_cdata.sip file located in %GameDirectory%\UnrealEngine3\Binaries\Win32\Data. Eventually data was separated into two files (Calligraphy.sip and mu_cdata.sip), and then moved to %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 name 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 1.9-1.21
1.6 Added lz4 compression for stored data to speed up shipping client load time 1.22-1.28

Custom Gazillion Paks

In version 1.29.0.25 released on November 11, 2014 the original SQLite-based archives were replaced with a new custom format developed by Gazillion. Later on in version 1.0.4458.0 released on January 24, 2015 data was also split into two files: Calligraphy.sip for data exported from Calligraphy and mu_cdata.sip for resource data.

Note: it's possible to force newer client versions to load all data from the mu_cdata.sip archive by using the -nocalligraphypak launch parameter.

Files with this newer 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;
}

FileHash is FileName hashed using the same algorithm as Calligraphy / resource data references, but without any additional formatting. Files are sorted by their hash value.

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.

These custom paks can be unpacked and packed with the MHPakTool included in this repository. Data can be parsed with MHDataParser,