PAK (File Format)/RetroStudios

PAK is an archive file format used in games such as Donkey Kong Country Returns created by RetroStudios.

File Format

Header

The file starts with the following header:

Offset	Type	Description
0x00	UInt32	Unknown. Always 2, possibly a version number.
0x04	UInt32	Header size. Always 0x40.
0x08	Byte[0x10]	MD5 hash of the file data following the header.
0x18	Byte[0x18]	Padding.

Table Of Content

After the header, a table of content structure specify what sections are stored in the file. It has the following structure:

Offset	Type	Description
0x00	UInt32	Section count (N). In practice this will always be 3 with order STRG, RSHD, DATA.

N entries of the following structure follows.

Offset	Type	Description
0x00	Char[4]	Section magic.
0x04	UInt32	Section size in bytes.

At 0x80 the section data for each section starts. They are laid out in the same order as they are specified above.

STRG

The STRG section specifies files which are named, in other words identified by a string. It starts with the following structure:

Offset	Type	Description
0x00	UInt32	Number of named resources (N).

Immediately afterwards N named resources follows.

Named Resource

Each resource has the following structure:

Offset	Type	Description
0x00	Char[N + 1]	Resource name stored as a null-terminated string of length N.
N + 1	Char[4]	Resource magic. File magic of the resource specifying file type.
N + 5	UInt64	Resource ID. There is always an entry in the RSHD section with the same Resource ID.

RSHD

The RSHD section specifies all files, where the files are identified by a 64-bit integer. All files in STRG are also stores in the RSHD section. It starts with the following structure:

Offset	Type	Description
0x00	UInt32	Number of resources (N).

Immediately afterwards N resources follows.

Resource

Each resource has the following structure:

Offset	Type	Description
0x00	UInt32	Compression flag. Either 0 (uncompressed) or 1 (compressed). See here for more details.
0x04	Char[4]	Resource magic. File magic of the resource specifying file type.
0x08	UInt64	Resource ID.
0x10	UInt32	File data size in bytes. Files are always padded with 0x40, which is reflected in the file data size.
0x14	UInt32	File data offset, relative to the start of the DATA section.

DATA

All file data is stored in the DATA section and references by each resource. File data is always padded to nearest 0x40 with 0xFF.

Compressed Data

File data may be compressed. In Donkey Kong Country Returns, files may be compressed using ZLib. Compressed data starts with the following header:

Offset	Type	Description
0x00	Char[4]	Data magic. Always CMPD in ASCII.
0x04	UInt32	Block count (N). Specifies the number of compressed blocks the data has been divided into.

Following the header N block entries follows:

Offset	Type	Description
0x00	Byte	Flag.
0x01	UInt24	Compressed size in bytes.
0x04	UInt32	Decompressed size in bytes. If the compressed size is identical to the decompressed size, it means the block data is not compressed and the data should be copied directly rather than decompressing.

Afterwards the compressed file data is stored. Like with decompressed data, the compressed data is padded with 0xFF to nearest 0x40.

Tools

The following tools can handle PAK files:

• crPakTool by jellees