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From: Gary Wright <gwtmp01@mac.com>
Subject: Re: [9fans] Easiest way to make a filesystem
Date: Mon, 14 Jan 2008 16:23:42 -0500
To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
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On Jan 14, 2008, at 4:10 PM, roger peppe wrote:

> On Jan 14, 2008 9:00 PM, Gary Wright <gwtmp01@mac.com> wrote:
>> I've been playing around with my own implementation of 9P in Ruby in
>> an effort to explore this problem space and to better understand 9P.
> [...]
>> I'd appreciate comments/feedback.
>
> how do you deal with filesystems where the name space is dynamically
> constructed? for instance, how would you go about specifying the #I
> (/net) namespace
> with your system?


The filesystem is just a data structure.  It can be manipulated
from the 9P side via create/remove (subject to all the regular
access rules) or it can be manipulated on the internal side:

# assume that 'd' is a reference to an instance of Directory

d['newfile'] = Resource.new

The default behavior of a resource is to just map file I/O to
an in memory string but you can define new resources that
intercept and interpret 9P ops at will:

class TimeOfDay < Resource
   def read(fid, offset, count)
     Time.now.to_s[0,count]
   end
   undef_method write
end

d['time'] = TimeOfDay.new

now every read attempt on 'time' will return  the time of day
and write requests will generate an error.


Gary Wright