# 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](https://sqlitebrowser.org/). 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](./Calligraphy.md) and `mu_cdata.sip` for resource data. These custom paks can be opened with [MHDataParser](https://github.com/Crypto137/MHDataParser).

Files with this format start with an eight-byte header:

```csharp
uint Header;    // KAPG
uint Version;
```

It is followed by an array of metadata entries:

```csharp
int EntriesLength;
PakEntry[EntriesLength] Entries;
```

Each entry has the following structure:

```csharp
ulong FileHash;
int FileNameLength;
char[FileNameLength] FileName;
int ModTime;
int Offset;
int CompressedSize;
int UncompressedSize;
```

The entries are followed by raw data compressed using the [LZ4](https://github.com/lz4/lz4) algorithm. The offsets specified in the entries are from where the raw data begins.