Re: Lua in-kernel (lbuf library)

[Justin Cormack <justin%specialbusservice.com@localhost>]

On 16 Oct 2013 15:41, "Lourival Vieira Neto" <lourival.neto%gmail.com@localhost>
wrote:
>
> Hi Justin,
>
> On Tue, Oct 15, 2013 at 7:38 PM, Justin Cormack
> <justin%specialbusservice.com@localhost> wrote:
> > On Thu, Oct 10, 2013 at 7:15 PM, Lourival Vieira Neto
> > <lourival.neto%gmail.com@localhost> wrote:
> >> Hi folks,
> >>
> >> It has been a long time since my GSoC project and though I have tried
> >> to come back, I've experienced some personal issues. However, now I'm
> >> coding again.
> >>
> >> I'm developing a library to handle buffers in Lua, named lbuf. It is
> >> been developed as part of my efforts to perform experimentation in
> >> kernel network stack using Lua. Initially, I intended to bind mbuf to
> >> allow, for example, to write protocols dissectors in Lua. For example,
> >> calling a Lua function to inspect network packets:
> >>
> >> function filter(packet)
> >>   if packet.field == value then return DROP end
> >>   return PASS
> >> end
> >>
> >> Thus, I started to design a Lua binding to mbuf inspired by '#pragma
> >> pack' and bitfields of C lang. Then, I realized that this Lua library
> >> could be useful to other kernel (and user-space) areas, such as device
> >> drivers and user-level protocols. So, I started to develop this
> >> binding generically as a independent library to give random access to
> >> bits in a buffer. It is just in the early beginning, but I want to
> >> share some thoughts.
> >
> > I have been using the luajit ffi and luaffi, which let you directly
> > use C structs (with bitfields) in Lua to do this. It makes it easier
> > to reuse stuff that is already defined in C. (luaffi is not in its
> > current state portable but my plan is to strip out the non portable
> > bits, which are the function call support).
> >
> > Justin
>
> I never used luaffi. It sounds very interesting and I think it could
> be very useful to bind already defined C structs, but my purpose is to
> dynamically define data layouts using Lua syntax (without parsing C
> code).
>

Yes absolutely it makes more sense if already defined in C. For parsing
binary stuff I would look at Erlang for inspiration too, it is one of the
nicer designs.

Justin