On Feb 14, 2014, at 9:42 AM, Manuel Klimek <[email protected]> wrote:
> On Fri, Feb 14, 2014 at 6:40 PM, Argyrios Kyrtzidis <[email protected]>
> wrote:
>
> On Feb 14, 2014, at 9:26 AM, Rafael Espíndola <[email protected]>
> wrote:
>
> >> So you’re suggesting something like this:
> >>
> >> class AbstactFileSystem {
> >> …
> >> class FileDescriptor {
> >> public:
> >> virtual ErrorOr<Status> status() = 0;
> >> virtual error_code getBuffer(…) = 0;
> >> virtual error_code close() = 0;
> >> };
> >> ...
> >> };
> >
> > That looks odd. If we can keep it to one virtual interface (like in
> > the patch) that would probably be better. On llvm a file descriptor in
> > always an int. There is some desire to use a file handles on windows,
> > but that is also just a abstract pointer.
> >
> > Can't we make the file handle an arbitrary uintptr_t sized object? The
> > FileSystem is then able to interpret it in any way it wants.
>
> I find it natural, the file descriptor encapsulates the file operations that
> you perform on a “file entity” (which can be a virtual file or whatever) and
> this is what we are modeling.
>
> I would find it unnatural that you have a series of multiplexed
> AbstractFileSystem objects and you constantly have to thread through them
> uintptr_t's that every AFS object has to say whether it understands that
> particular uintptr_t or not.
> it could be complicated to have them cooperating on the interpretation of the
> uintptr_t.
>
> Why wouldn't a multi-plexing AbstractFileSystem implementation exactly know
> which FDs go to which one of its file system operations? A non-multi-plexing
> implementation could then just assert the FD is one of its own.
> It feels rather natural to me that if you have multiple layers of
> implementations that make up a "tree" of file systems, a request would go
> through all the layers until landing at the lowest one...
The “get a file descriptor object” will land on the appropriate AFS which will
return a proper implementation to do file operations on.
There is no significant difference on the client side (instead of calling a
method on the AFS, it calls a method on the FileDescriptor), it may simplify a
bit some functions to just accept a FileDescriptor if they only need such a
thing (instead of always passing an AFS + FD), and the multiplex implementation
becomes simpler._______________________________________________
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