Re: [nft PATCH RFC] libnftables: Implement JSON output support

[Phil Sutter <phil@nwl.cc>]

On Wed, Jan 17, 2018 at 07:59:34PM +0100, Pablo Neira Ayuso wrote:
> On Wed, Jan 17, 2018 at 07:56:30PM +0100, Phil Sutter wrote:
> > On Wed, Jan 17, 2018 at 07:45:04PM +0100, Pablo Neira Ayuso wrote:
> > [...]
> > > > On Wed, Jan 17, 2018 at 01:50:26PM +0100, Pablo Neira Ayuso wrote:
> > > > > On Wed, Jan 17, 2018 at 01:44:06PM +0100, Pablo Neira Ayuso wrote:
> > > > > > On Wed, Jan 17, 2018 at 12:51:40PM +0100, Phil Sutter wrote:
> > > > > [...]
> > > > > > 
> > > > > > > * There is quite some code-duplication involved given that this
> > > > > > >   introduces an alternative function for almost any function in the
> > > > > > >   affected code path.
> > > > > > 
> > > > > > You mean, a new callback for each expr/datatype? We should not expose
> > > > > > bitwise/byteorder and such, it's too low level.
> > > > > 
> > > > > I'd rather see you map the abstract syntax tree that is represented
> > > > > through parser_bison.y to your json representation. I think this patch
> > > > > is mapping the tree that we obtain after the evaluation phase, which
> > > > > comes with low level expressions such as bitwise/byteorder.
> > > > 
> > > > I don't get your point here, either: Not sure what this has to do with
> > > > parser_bison.y - my patch handles output only for now, I didn't bother
> > > > with input yet. Or am I on the completely wrong track now?
> > > 
> > > Sorry, I was refering about the input support.
> > 
> > Ah, I see. For input, I did consider using bison BTW, but doubt it will
> > lead to less code than implementing everything with libjansson. And yes,
> > this will then be on the same level as parser_bison.y, so what is parsed
> > will then be fed to cmd_evaluate().
> 
> Not asking to build a json parser in bison. I mean, json layout should
> result in an abstract syntax tree, that is exactly what nft bison
> would generate.
> 
> Does this clarify?

Well, it was clear all the time. :)

We were talking about maybe using bison as code generator to keep the
layer that translates from JSON to the abstract syntax tree you are
talking about slim in matters of lines of code. Hence why I mentioned
it.

Cheers, Phil