Paired ARC+DIR file

ARC files (likely short for Archive) and DIR files (technically short for Bundle, though Directory makes more sense and avoids conflict with BUN files) are two peas in a pod, together representing one of the many Binary Large Object (BLOB) archive formats used in Pikmin. Together, they will henceforth be referred to as the paired ARC+DIR file archive.

With minimal metadata, the paired ARC+DIR file archive was likely used to reduce load time by packing several files into one^[unsure]. The purpose it serves is different from the bundle archive, however, as standalone files within the archive can be unpacked independently of the files before it^[unsure]. This makes the paired ARC+DIR file useful for archiving large directories with varied purposes.

File structure

As mentioned before, the paired ARC+DIR file archive consists of two files: the mock-directory (DIR) and the BLOB archive (ARC). Think of the mock-directory as a map to navigate through the BLOB archive.

DIR

DIR files consist of a header followed by a repeating struct for each mock-filepath.

Here is /dataDir/archives/pelletsbin.dir annotated for reference.

Header

Offset	Size	Purpose
0x00	4	Size of DIR file
0x04	4	Number of structs

Mock-directory struct

Offset	Size	Purpose
0x00	4	Offset of file in ARC
0x04	4	Size of file in ARC
0x08	4	Mock-directory string length
0x0C	0x08 value	Mock-directory path

Mock-directory

The DIR file emulates filepaths. When a file is unpacked in-game, it is assumed that whatever code is responsible treats the entry in the DIR file as a legitimate filepath on the disc, starting from the root.

ARC

Here is /dataDir/archives/pelletsbin.arc annotated to demonstrate searching the BLOB archive. Without the DIR file as a guide, the only way you could possibly differentiate between files would be with the 0xCC padding between files.

0xCC padding

Files in the ARC are always padded out to have an amount of bytes that is a multiple of 32. These bytes are not included in the file size recorded in the DIR for each file. It's like this because its an optimisation for loading data into the Gamecubes data registers.

Extra information

Every paired ARC+DIR file archive has an uncompressed copy elsewhere on the disc.

• In /dataDir/tekis and /dataDir/bosses, a file named arc_all.ini can be found. These INI files holds nothing, but give us a hint at how the developer's archiving tool functioned.
• It is unknown if every file in the archives is identical to its uncompressed sister file.

In the OpenGL / Dolphin System, many files are not read from the paired ARC+DIR file archives like they are in the final game, and are instead read from the un-archived versions.

Paired ARC+DIR file archives that have "bin" in their filename curiously only contain the BIN files from their respective directory.

The log.txt files left in the root of Pikmin versions USA Demo, USA v1.00, and JPN v1.02 detail the plugin "plugTexConv" creating a paired ARC+DIR file archive.

Credits: Minty_Meeo