[9fans] using Tree* and File* vs imlementing own 9p-handling routines?

[9fans] using Tree* and File* vs imlementing own 9p-handling routines?

[mirtchov]

I'd like to have a comment from the 9p(2) man page clarified:

          In general, the File interface is appropriate for maintain-
          ing arbitrary file trees (as in ramfs). The File interface
          is best avoided when the tree structure is easily generated
          as necessary; this is true when the tree is highly struc-
          tured (as in cdfs and nntpfs) or is maintained elsewhere.

Is there a penalty associated with using the File interface?  It seems
to simplify greatly the implementation of 9p servers, so why should it
be avoided?

Say I have a server with static files that never change, should I use
File or roll my own Qid-handling routines a-la mntgen and friends?

thanks: andrey

Re: [9fans] using Tree* and File* vs imlementing own 9p-handling routines?

[Russ Cox]

> I'd like to have a comment from the 9p(2) man page clarified:
>
>           In general, the File interface is appropriate for maintain-
>           ing arbitrary file trees (as in ramfs). The File interface
>           is best avoided when the tree structure is easily generated
>           as necessary; this is true when the tree is highly struc-
>           tured (as in cdfs and nntpfs) or is maintained elsewhere.
>
> Is there a penalty associated with using the File interface?  It seems
> to simplify greatly the implementation of 9p servers, so why should it
> be avoided?

the penalty is that the interface is slightly clunky
and for things with easily generated structure
i've found that using just the qid is easier than
hanging an allocated structure off the aux in the File.
the main overhead is code complexity.

if your tree is fixed then Files are good.
if your tree is a dynamic but regular structure
then it's easier to avoid it.