tuesday, 6 february 2007

posted at 09:26

I'm making good progress, and am quietly confident about success. I can see the next few steps I need to take, which always motivates me, and usually means I'm on the right track.

Yesterday I started porting FATFileSystem to AROS. Of course it won't work, given that packets aren't available, but I'm looking to have something around for me to write the emulation around. The port has not gone without issue - it seems to depend on a deviceio.library, but Google knows nothing about it. I have managed to track down the author, one Marcin 'Morgoth' Kurek, so I emailed him last night asking for more information. My goal in all this is to make porting filesystems as simple as possible, so I want to make sure AROS has everything a packet filesystem might need. Marek Szyprowski's filesystems use this library, and my understanding is that they will be the first filesystems that are ported, so making it available can only be a good thing. For now, however, I've just commented out the code, and a bunch of other stuff too, mostly related to missing DOS fields and structures in AROS. My goal is compiling, not working.

As far as I'm able to tell, traditional packet handlers are basically normal programs except that they use a function called startup() instead of main(). I can only assume this means there's a specific loader somewhere in dos.library to load and run them. I had planned to write a loader of my own in packet.handler to do this, but it proved to be more difficult to get the thing to compile than I'd anticipated. As I was investigating, I came up with a better idea - make the handler a library, with the startup function as a single vector entry point. This is easy to realise - all thats necessary is to add AROS build files (mmakefile.src, lib.conf, a header to define the LIBBASE structure) and then change the entry point, from this:

void startup(void)

to this:

AROS_LH0(void, startup, LIBBASETYPEPTR, LIBBASE, 5, FSHandler)

Its a small requirement, but one that is easily described in a porting doc, so I'm happy with it.

Then, in packet.handler, the "loader" becomes something as simple as:

    handler = OpenLibrary("DEVS:fs.phandler", 0);
    AROS_LVO_CALL0(void, struct Library *, handler, 5, );

It'll be a little more complex, as it will have to setup a process and such, but thats the basic idea. Work will start on the loader on the way home this afternoon, now that FATFileSystem is compiling :)