[Feature] Support for Doom WAD Files about fq

[gcr]

Here's a very rudimentary decoder you can use in fq. Run fq -d raw -i . MAPS2.wad and paste the following into the REPL:

def num_le: tobytes|explode|reverse|map(. band 0xff)|tobytes|tonumber;
tobytes as $file | {} 
| .type = $file[:4]
| .n_lumps = ($file[4:8]|num_le)
| .offset = ($file[8:12]|num_le)
| ($file[.offset:]) as $lumpdir 
| .lumps = [
    range(.n_lumps)
    | ($lumpdir[16* . :16*( . +1)]) as $rec | {}
    | .offset = ($rec[:4]|num_le)
    |.size = ($rec[4:8]|num_le)
    |.name = ($rec[8:16]|gsub("\u0000";""))
    |.data = $file[.offset:.offset+.size]
]

fq doesn't support creating Decode Values, so you don't get those nice-looking hexdumps like this, but it's a start.

[wader]

Hey! sure i'm willing to add any format that is used publicly. Want to work on adding support? as it seems to be a quite basic archive format i'm guessing it shouldn't be that much work.

[sleibrock]

Definitely! I can't say I'm familiar with the internals of fq just yet but I would love to get started and see what I can pull off. Doom WADs have a very simple structure of header, LUMP table, then a blob of all object tables. It should be fun to add in.

[wader]

Nice! hopefully you should not need to know much about most internals, the decode API used by a format decoders don't know much a the rest of fq on puropse. Maybe a good start is to look at some existing format decode that is similar, maybe ar, tar or zip? also i'm happy to help out, you can for example open a PR with a early draft and then we work from that.

[wader]

Nice! tip is to put the code into a file wad.jq as a function from_wad and then do fq -d bytes -I . 'include "wad"; from_wad' file.wad

btw is this for an older version of fq? the band infix-operator is now a function band/2 and -d raw has been split into bytes and bits for different slicing units.