Re: [Opensg-users] FileIO for remote files

[<c.f...@gm...>]

Hi Dirk,

Dirk Reiners wrote:
> Marcus Lindblom wrote:
>   
>> I see. I would assume it uses the PathHandler, so that should be 
>> extended into an istreamhandler etc?
>>   
>>     
> That's where I got stuck, too, the last time I looked into this.
>
>   
Yes, I think, this is a natural generalization. The istreamhandler could 
also create a local temporary if required
and do some bookkeeping, which files have been accessed for a scene.
> I wouldn't mind rethinking the File IO structure for 2 and having a more 
> flexible system that allows things like  relative data loaded from 
> archives like zips or from other sources like FTP servers or the web.  
> There are some systems that do similar things, like PhysFS or Parrot 
> (http://www.cse.nd.edu/~ccl/software/parrot/), and we might want to look 
> into them for inspiration. On Linux there is Fuse (fuse.sf.net), but 
> that would be hard to port to other systems.
>
>   
Oh, along the lines of virtual file systems there is also
http://witme.sourceforge.net/libferris.web/features.html  (linux only)
which is called semantic virtual file system, as it also holds metadata 
gathered from the file source
and the file header/contents itself.
But I guess, all those are quite system dependent.
> The big problem with those is the ability to use other, existing code, 
> as most existing loaders either use FILEs (if they're C) or iostreams 
> (if they're C++). iostreams can be wrapped, but I don't know if any 
> existing fs abstractions do that.
>
>   
I do not know if it is worth it to redirect or to emulate plain Cs FILE* 
behaviour (like downloading
the required file to a local temporary and then open as a FILE* ..).
Without a virtual file system approach those loaders would always 
require modification.
With istreams it seems easier. The library boost.asio pointed out by 
Allen seems to fit in nicely here
with boost.iostreams.
I need to get some practice with it.
Currently, there are some loaders which open additional streams during 
loading besides the one passed in.
> Input welcome
>
>      Dirk
>   
Regards,
Christoph