Datatype descriptors

(I don't have the sdk at hand where I'm at now)

Is there a guide somewhere on how to write the file descriptor files that the datatype system uses?

I'm going to add file type identification to a program and do not want to reinvent the wheel so using the same type of descriptor files as the datatype system would be neat.

Is it possible to use any existing datatype api (library or otherwise) to check if a file matches a descriptor file or does the datatype system hide all that functionality inside it?

Basically what I would like to do is feed a function with a path to a random file and a path to a datatype descriptor file (at a custom location not related to the installed datatypes) and find out if its a match or not.

BOOL IsFileOfType(STRPTR filepath, STRPTR descriptorpath);

@orgin

I use the following:
http://aminet.net/package/dev/misc/MakeDT-1.3

The ARexx script converts a text file (.dt) that you write into a binary descriptor file that you can put in DEVS:DataTypes. The format of the .dt file is explained in MakeDT.doc and also there are several examples in the archive.

For an example on how to use a function to check for the right filetype you can check the source code from svg_dt.

The function is in the file "descriptor.c". This is compiled into an executable using -nostartfiles and then the name of the executable is specified in the .dt file.

@salass00

Hmm okey, seems like I wont be able to do what I want with it then.

@orgin

I can't find my example code, but to check the type of a file, you need to use ObtainDataType(). This will return the internal name from the descriptor that handles the file, amongst other things.

@Chris

Yeah but that requires that the descriptor is registered in the datatype system? I need to keep my descriptors outside the existing datatype system.

@orgin

The question is why ? Why would you want to have separate descriptors ? Having a system wide datatype database can benefit every other applications, not just yours.
Oh and in just all you want is to identify the file type, why not use DefIcons ? DefIcons provides an ARexx port and a command "Identify" taking a filename as argument. you can send an Arexx message from your application and wait for the answer...

@abalaban

Can you provide an example for such an arexx call?

Btw, is it easy to add new identifiers to deficons? For example, adding an identifier for protracker modules.

@orgin

If you have ADCD 2.1 look into ":Reference/DevCon/Orlando_1993/Devcon93.1/AREXX/SimpleRexx/SimpleRexx.c" the function SendRexxMsg() you might also want to look at arexx_cl and its AM_EXECUTE method...
Basically what you would have to do is searching for DefIcons's arexx port ('DEFICONS') then send this msgport an ARexxMsg with the command 'IDENTIFY "<yourfile>" ' in it and then use the string result ARexx will get back to you.

Adding a new file recognition to DefIcons is done by launching the DefIcons preferences and then setup the recognition parameters.

@abalaban

Quote:
Really. I've been looking for that kind of info. Why is nobody ever telling anything to others in this community. (I mean without needing to ask everytime.)

Quote:
Maybe that's too slow or complicated in some cases.

@orgin
I "reinvented the wheel" and wrote my own routine. I checked from Deficons prefs how certain files are detected. I can give you that code if you think it's useful.

Quote:
I think it is.

@TSK

complicated ?
1) see rexxsyslib/CreateRexxMsg() to create the message,
2) wait on the reply port you specified to CreateRexxMsg(), add
3) call GetMsg() to retreive a struct RexxMsg (rexx/strorage.h)
4) rm_Result against RC_OK, if that's the case rm_Result2 points to a struct RexxArg in which ra_Buff should contain the type name.
5) free your RexxMsg using rexxsyslib/DeleteRexxMsg ()

That should be all

@orgin

From C you can also use ICONGETA_IdentifyBuffer (that doesn't seem to be documented in the AutoDoc for GetIconTags() so I'm not sure where I found it) to find the file type from DefIcons (or other global file ID hook).

If you really want to use your own set of Datatype descriptors - again I'd ask "why?" - then it will be a case of reading them yourself with iffparse.library. I don't see the point when datatypes.library will do all this for you, and the additional descriptors will benefit other apps too.

@Chris

Quote:

That works like a charm actually, thanks!

Tiny code example:

@Chris

Btw, it doesn't seem to work in 4.0 though even if it says v52 in the include. (4.0 has 52.2). My 4.1 has 52.6.

Weird that it's not a version change when adding a new function.

@orgin
Quote:
ICONGETA_IdentifyBuffer was added in icon.library 52.6. Sorry it isn't documented properly.

Quote:
Doh ! I think I saw this in a header file or in autodocs but I got idea that it returns only type of an icon image (like png) or something like that. I thought to test it what kind of info it returns but then I didn't bother for some reason. Thanks to everybody involved to add this functionality into the OS.

@TSK

There's another tag that does that - ICONGETA_Format or something like that.