[GRASS5] shift bug in r.in.ascii/r.out.ascii

[Glynn Clements]

Roger Bivand wrote:

> > just found (obviously) a bug in r.in.ascii/r.out.ascii:
> > 
> > if you export/import the same map several times, it get's
> > shifted each time!
> > 
> >      r.out.ascii in=dem out=dem0.asc
> >      r.in.ascii in=dem0.asc out=dem1
> > 
> >      r.out.ascii in=dem1 out=dem1.asc
> >      r.in.ascii in=dem1.asc out=dem2
> > 
> >      r.out.ascii in=dem2 out=dem2.asc
> >      r.in.ascii in=dem2.asc out=dem3
> >      d.rast dem
> >      d.rast dem1
> >      d.rast dem2
> >      d.rast dem3
> > 
> > As being lack of time today, any volunteers?
> 
> Looks to me as if fseek is moving one byte too far back in the buffer on
> line 142 in r.in.ascii/cmd/gethead.c, putting the last digit of the number
> of columns as the first cell value read. Since it is followed by a
> newline, it is treated as value. 
>       fseek(fd, -(len+1), SEEK_CUR);
> 
> For me,       fseek(fd, -(len), SEEK_CUR); fixes it, but I haven't tried
> it with other header fields or command line options.

Suggestion: call ftell() before G_getl() and use fseek(SEEK_SET) to
restore the position. Alternatively, you could use fgetpos() and
fsetpos(); these are more portable, but that probably isn't an issue
here.

-- 
Glynn Clements <glynn.clements at virgin.net>