Re: [Xen-devel] [PATCH RFC V2 08/10] libxl IDL: generate code to parse libxl__json_object to libxl_FOO struct

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-04-22 at 16:54 +0100, Wei Liu wrote:
> > > 
> > > +                (nparent,fexpr) = ty.member(v, f.type.keyvar, parent is 
> > > None)
> > > +                s += libxl_C_type_parse_json(f.type.keyvar.type, "x", 
> > > fexpr, "    ", nparent)
> > > +                s += "}\n"
> > > +            s += "x = libxl__json_map_get(\"%s\", %s, %s);\n" % (f.name, 
> > > w, f.type.json_parse_type)
> > > +            s += "if (x) {\n"
> > > +            (nparent,fexpr) = ty.member(v, f, parent is None)
> > > +            s += libxl_C_type_parse_json(f.type, "x", fexpr, "    ", 
> > > nparent)
> > > +            s += "    x = x->parent;\n"
> > 
> > What is this x->parent for?
> > 
> 
> To make sure when we finishes processing this member, X points back to
> its parent again, so that next call to libxl__json_map_get(x) is using
> the right "x".

Can we create temporary fixed scope "x"s for each field? It's ok if that
shadows the existing "x" (for the parent) I think, or am I missing
something?

> > > +            s += "}\n"
> > 
> > > @@ -444,4 +533,17 @@ if __name__ == '__main__':
> > >          f.write("}\n")
> > >          f.write("\n")
> > >  
> > > +    for ty in [t for t in types if t.json_parse_fn is not None]:
> > > +        f.write("int %s_parse_json(libxl_ctx *ctx, const 
> > > libxl__json_object *%s, %s)\n" % (ty.typename,"o",ty.make_arg("p", 
> > > passby=idl.PASS_BY_REFERENCE)))
> > > +        f.write("{\n")
> > 
> > Are we assuming/requiring the caller to have called the init function
> > for the type? Did you consider having this function do it?
> > 
> 
> Yes, I'm assuming so.
> 
> But I can also make this function do it if you wish.

I think that would be best, this function can be thought of as "init
from this json", so it should probably do the whole job, which includes
setting all the appropriate defaults if the json omits fields etc.

Ian.


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