Question about DAT file format capabilities

[derJörg]

Hello,

...I read about a big collection of DOS games on some forum. Some people tried to build a DAT file from this collection (I think with clrmamepro) and failed: after rescanning their folders with that newly created DAT they got tons of errors. One of the things that could have been a problem was that the folder structures contained empty folders.
Is something like that (empty folders being forgotten when creating a DAT from a folder structure) a flaw in clrmamepro's DIR2DAT utility or is it really a limitation in the DAT file format (because I couldn't find any official file format specification for DAT files)? I had a closer look on some multipart DAT files and it seems that this should actually not be a problem (for example, a "rom" entry with trailing slash could be treated as a folder).
I tried WinZip, WinRAR and 7zip, and these applications seems to work fine when fed with empty folders.

I do not have that DOS collection, otherwise I could have tried it myself, but these are a few thoughts I spent on it. Someone there who knows more?

Kind Regards,
derJörg

[PandMonium]

Hi again,

AFAIK it is a cmp limitation, it will remove empty folders. There is a flag introduced some time ago about nodump handling i think, it can have 3 dif values, something like required, ignore and some other but it only applies to nodumps (files with 0size 0crc for example) so cmp know if it should keep / create them or they can be ignored/removed.
If you have a zip with empty folders and use dir2dat they will not be present in the datfile, only if they have something inside (an empty file for example), yes i suppose this may be a limitation to some DOS games that have some empty folder that will be later used to store files (say savegames) and weren't coded to create the folder if missing (i said it may because i haven't checked if this really happens but the probabilities are high).

There have been a few DOS collections but currently i only remember one relevant that includes a lot of sets but i've never seen complains about it, it is available in a well known tracker/forum dedicated to emulation for example.

bye

[Diaboł]

There is a manager called DOSCenter created especially for managing a DOS games collections. The manager and DAT file is available at http://pc.nugnugnug.com/DOSCenter

[PandMonium]

didn't know that tool, thanks Diabol.
Added it to Weblinks section of this site, there isn't much there yet but if someone wants to have something relevant added there just say something

[derJörg]

Hello Diablo,

...interesting link, thank you. I had a look at the specific DAT file from there, and it implements this empty folder thing just like I suggested on top. Wouldn't it be great if that became implemented into clrmamepro? Maybe I will write to the clrmamepro author...

Regards,
derJörg

[Diaboł]

@PandMonium
The tool is related to the "well known tracker/forum" that you were talking about :-) There is a HUGE thread at that forum related to the DOS Collection, explaining all the problems with clrmamepro + a DOS DAT files. Unfortunately you have to be a registered user to read it and the registration seems to be permanently closed. @derJörg: Anyway, the DOSCenter is under active development so is the DAT file and for this moment it seems to be the only way to go. As far as I remember the idea behind clrmamepro is way to different form a potential "DOS tool" to make it works with DOS software but frankly I'm not familiar with the details any more.