Re: partition tables and ocaml

[Sven Luther <sven.luther@wanadoo.fr>]

On Tue, May 24, 2005 at 11:06:12PM -0700, Taras wrote:
> Sven Luther wrote:
> 
> >On Mon, Apr 11, 2005 at 08:57:05AM -0400, Eric Cooper wrote:
> > 
> >
> >>On Mon, Apr 11, 2005 at 09:46:19AM +0200, Sven Luther wrote:
> >>   
> >>
> >>>I had plans to do a rewrite of GNU parted, a project which i am
> >>>involved with, in ocaml, and am being blocked by a few issues.
> >>>[...]
> >>> 1) most disk partition tables and filesystem have a mapping from a
> >>> given disk 512 byte sector to a descriptive structure.
> >>> [...]
> >>> or to have access functions which transform parts of
> >>> a byte array into values. The first one is ugly, as i was aiming
> >>> for a purely ocaml solution (so i can build and arch/plateform
> >>> independent bytecode tool), and the second would probably be a
> >>> disaster speed wise, and also somewhat ugly unless properly
> >>> encapsulated in an abstract module.
> >>>     
> >>>
> >>I would use the second approach.  I would define a logically
> >>equivalent OCaml record or class, and conversion functions between
> >>that object and a string + offset (or Bigarray of bytes, plus
> >>offset).  Passing around an offset into a larger byte array can save a
> >>lot of copying.
> >>
> >>You can probably structure your code so that you only convert to/from
> >>bytes in a few places, not likely to be performance-critical.
> >>   
> >>
> >
> >Mmm, one could imagine a generic set of access function inside a byte array
> >(would have to handle endianess and such though), and then a structure 
> >defined
> >as a set of lazy values corresponding to the access functions in question, 
> >so
> >only values actually accessed get computed.
> >
> >That said, 
> > 
> >
> Hello,
> Is a port of Parted to OCaml still in the works? In case you are still 

Yes, altough i am a bit short on time right now.

> wondering, I would like to show out that OCaml can indeed deal with 
> partitions in a painless manner.
> See http://glek.net/subversion/os/kernel/modules/PartitionTable.ml

Cool, will look at this. Also maybe you would be interested in cooperating on
the project ? 

> The read_tables function is capable of doing primary and extended 
> partition table parsing in next to no code. Obviously Parted would need 
> a bit more code than that, but things wouldn't get much hairier since 
> partition entries are only 16 bytes and that code parses 6 of them :)

Yes, but fdisk/mbr like partition tables are trivial, parted supports many
kind of partition table, among them the mac/amiga ones which i am most
familiar with, and which handle linked lists of partitions.

Friendly,

Sven Luther