Re: [PATCH 1/1] platform: extract common fields of IPv4/IPv6 addresses and routes to base struct

[Dan Williams <dcbw redhat com>]

On Fri, 2014-04-04 at 23:02 +0200, Thomas Haller wrote:
> On Fri, 2014-04-04 at 15:13 -0500, Dan Williams wrote:
> > On Thu, 2014-04-03 at 14:23 +0200, Thomas Haller wrote:
> > > Especially the calculation of timestamps is identicall for addresses.
> > > By creating a "base struct", we can use the same code for that, because
> > > NMPlatformIP4Address and NMPlatformIP6Address can now both be treated as
> > > NMPlatformIPAddress (and the same for routes).
> >
> > Is the only reason for the #define of the common fields so that you
> > don't have to do another level of indirection?  It looks somewhat ugly
> > and my personal preference would be to just declare the base struct in
> > the functions you want to use it in and up-cast if you need the v4 or v6
> > version...  kinda like we do with objects.  So I certainly agree with
> > the principle, but lets see what other people say about the
> > implementation...
>
>
> Hi Dan,
>
> could you elaborate an what would be your preference? I don't
> understand.

Sorry :)  I mean that I'm not wild about the #define of the common
fields,  but I'm OK with it if others think its fine.  Typically it be
something more like this:

typedef struct {
   NMPlatformIPAddress p;
   <ipv4 stuff>
} NMPlatformIP4Address;

typedef struct {
   NMPlatformIPAddress p;
   <ipv6 stuff>
} NMPlatformIP6Address;

void option1 (NMPlatformIP4Address *addr)
{
    NMPlatformIPAddress *parent = (NMPlatformIP4Address *) addr;
    addr->address = xxx;
}

void option2 (NMPlatformIP4Address *addr)
{
    addr->p.address = xxx;
}

which is more in line with kernel/glibc style I think.  It does mean a
bit more typing though.

Dan