ARC (Gotcha Force)

This article is about Gotcha Force ARC file format and ongoing researches on it.

This file format needs more research.
Researches on headers / bodies structures are partially achieved.

ARC seems to be the diminutive of archive.

Format

In the main executable boot.dol we found the debug string "Archive_Parse: Byte-Order mismatch" related to HSD (HAL SysDolphin) archives. The "Super Smash Bros. Melee" GameCube community has reversed this HSD lib function (Gotcha Force use not the same HSD lib version):

hsd archive.h

hsd archive.c

All ARC files named with _mdl in their title are HSD models.

Header

The HSD header seems to match others ARC headers:

typedef struct _HSD_ArchiveHeader {
    u32 file_size; // 0x00
    u32 data_size; // 0x04
    u32 nb_reloc;  // 0x08
    u32 nb_public; // 0x0C
    u32 nb_extern; // 0x10
    u8 version[4]; // 0x14
    u32 pad[2];    // 0x18 In debugging there is 4 bytes pad / not 2
} HSD_ArchiveHeader;

Observations

Unused textures

In the afs_data.afs (USA/NTSC version) we find 3 unused textures which have possibly been used in the game demo:

nwld00_mdl.arc
nwld01_mdl.arc
nwld02_mdl.arc

All headers of the "afs_data.afs" have been verified without decompress using automated scripts. PZZ files haven't been verified except for HSD models. ARC files seems to use this information. "Archive_Parse: Byte-Order mismatch" is referenced twice in the code (USA/NTSC dol version) boot.dol at addresses 8004d548 and 80006c88.

8004d548 is called when starting the game. We get HSD_archiveParse(*bufferDest=r3=0x81489c40, *bufferSrc=r4=0x80f2b1c0, len?=r5=0x4d7b). We found back arg (*bufferSrc) as a pointer to an ARC file like.