Disney NDS Game Archive Formats (*.ARC, *.FUN, and *.RDT)

[wertercatt]

For a reason I'm not entirely sure of, Disney's DS games (particularly ones that support DGamer) appear to use 3 or 4 different compression formats.

The first format uses the extension rdt with this file signature:

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52 44 54 01 01    RDT..

Sample: WifiLogos.rdt.bin

The second and third formats use the extension arc with no consistent file signature.
I believe the chunks.arc files might be a different format than the other arc samples, but I'm not sure.
Samples (sorted by rom): https://www.dropbox.com/sh/7e3z43aftnnp ... cDbha?dl=0

The last format uses the extension fun with two similar file signatures (appears to be multiple versions)
Sample 1 (DGamerArchive.fun (v2).bin):

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00 02 00 00 8A 71 00 00 00 74 00 00 48 28 00 00    ....Šq...t..H(..

Sample 2 (DGamerArchive.fun (v4).bin):

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00 02 00 00 09 76 00 00 00 7A 00 00 B0 29 00 00    .....v...z..°)..

[aluigi]

The problem of ARC is that there is nothing that specifies if a file is compressed or not, so if you try to decompress all of them then you get an error.
There is no solution and it's a known problem, unfortunately I don't remember what was the other topic and script that contained some work-arounds:

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comtype lz77wii
get FILES long
for i = 0 < FILES
    get NAME_CRC long
    get OFFSET long
    get SIZE long
    clog "" OFFSET SIZE SIZE
next i

FUN is completely different and quite strange at a first look.