Re: [Opengrads-devel] [Junk released by Allow List] Re: [Junk released by Allow List] Building GrADS v2 with new supplibs: first crack

[Arlindo da S. <da...@al...>]

On Feb 3, 2008 9:57 AM, Brian Doty <do...@co...> wrote:

> lengths in a GRIB msg are defined by the GRIB specification and are
> independent of systems definitions like g2int.  It is appropriate to
> hardcode the length.  Or to use a typedef that is dependent on the
> GRIB definitions (ie, hardcoded).  It probably doesn't matter how
> long hdr is (as long as it is at least 4 bytes ) but you want to read
> exactly 4 bytes no more no less.. Brian
>


You and Jennifer are right. Do you think grib2c is robust enough to work on
machines where sizeof(int)!=4? If not, it may pay to add something to
configure.ac to detect such cases and stop with an error.

Pat: do you know how to do this?

         Arlindo


>
> On Feb 3, 2008, at 12:09 AM, Arlindo da Silva wrote:
>
>  > On Feb 2, 2008 7:21 PM, Jennifer Adams <jm...@co...> wrote:
> >
> >
> > Arlindo --
> > There is a bug in seekgb.c of the g2clib that causes it to fail to
> > detect the end of a grib2 record if sizeof(g2int) != 4 (i.e. on 64-
> > bit systems). I guess we should put the patch in the subblib src
> > files we are redistributing (on your site and COLA's). This bug
> > causes gribmap to fail to find any records -- pretty bad.
> >
> >  # diff ./seekgb.c ~/Desktop/seekgb.c
> > 39a40
> > >       int hdr;
> > 68,69c69,70
> > <             k4=fread(&end,sizeof(g2int),1,lugb);
> > <             if (k4 == 1 && end == 926365495) {      //GRIB
> > message found
> > ---
> > >             k4=fread(&hdr,4,1,lugb);
> > >             if (k4 == 1 && hdr == 926365495) {      //GRIB
> > message found
> >
> >
> > If it is OK with you I'll replace int with g2int for consistency
> > with rest of grib2c. They do assume that g2int = int are 32 bits,
> > but keeping everything in terms of g2int will make it easier to
> > update the code if we ran into ints that are > 32 bits.
> >
> >             g2int hdr;
> > ...
> >             k4=fread(&hdr,sizeof(hdr),1,lugb);
> >             if (k4 == 1 && hdr == 926365495) {      //GRIB message
> > found
> >
> >
> >
> > --
> > Arlindo da Silva
> > da...@al...
>
>


-- 
Arlindo da Silva
da...@al...