Re: netcdf file returns corrupt byte data if using fill

Hi Bryce:

Thanks for taking the time on this. So far, I havent been able to reproduce this problem, or else im not looking in the right place. One think thats a little funny is that this line 
      dimData[0] = netCDFFile.addDimension("TIME", -1); //dynamic dimension

needs to be changed to: 
      dimData[0] = netCDFFile.addDimension("TIME", -1, true, true, false); //explicit declaration of unlimited dimension

so im not sure how you got the program to run.

I have attached my resulting netcdf file, which seems ok to me. does it look 
bad to you ?

BTW, the default value of fill i think has always been false; in the newer 
version, you should use

 public NetcdfFileWriteable(String location, boolean fill);

So maybe theres still some confusion of versions, or some other nefarious 
environmental difference between our two tests ??



Lee,Bryce [Ontario] wrote:
> Hi John,
>
> Sorry for the delay. We've been finishing up a new release here.
>
> I've now downloaded netcdf-2.2.10.jar and adapted the example source to
> it.
>
> The problem still occurs. I've attached the update source.
>
> Regards,
>
> Bryce
>   
>
> -----Original Message-----
> From: John Caron [mailto:address@hidden] 
> Sent: Wednesday, November 30, 2005 8:36 PM
> To: Lee,Bryce [Ontario]
> Subject: Re: netcdf file returns corrupt byte data if using fill
>
>
> Hi Lee, I see now that you are using an older version of the library
> (2.1). Are you able/willing to retry this with the latest version (2.2).
> I know there are a number of changes you have to make, so perhaps thats
> not feasible for you. However, the new version has lots of bugs fixed.
>
> If so, the new version is at
>
> http://www.unidata.ucar.edu/software/netcdf-java/
>
> Lee,Bryce [Ontario] wrote:
>
> > Hi John,
> >
> > Here's the sample java program.
> >
> > Regards,
> >
> > Bryce Lee
> >
> > -----Original Message-----
> > From: John Caron [mailto:address@hidden]
> > Sent: Wednesday, November 30, 2005 12:10 PM
> > To: Lee,Bryce [Ontario]
> > Subject: Re: netcdf file returns corrupt byte data if using fill
> >
> >
> > Hi Bryce:
> >
> > Thanks for reporting this bug. A sample program would be great.
> >
> > Lee,Bryce [Ontario] wrote:
> >
> >
> > > Hopefully I'm not repeating a known issue but I searched the mail 
> > > archives and didn't come across it. I've been using java netcdf to
> >
> > store
> >
> >
> > > radar scans, using a dynamic dimension of time to write data as it
> > > arrives throughout the day. Data was being written in float format and
> >
> >
> > > everything was working fine. Recently switched to store data in byte
> > > format instead, to reduce the size of information being stored. Do not
> >
> >
> > > require fill mode, as the entire each radar scan arrives in a complete
> >
> >
> > > chunk. Discovered afterwards that if the server was restarted new data
> >
> >
> > > written to the file became corrupted. I downloaded the netcdf source
> >
> > and
> >
> >
> > > traced thru it to find that when an existing netcdf file is opened in
> > > write mode, fill mode defaults to true. (This is interesting because
> >
> > the
> >
> >
> > > default when you first create a file, is off. I see in more recent
> > > documentation this is clarified a bit better.) Anyway, it turns out,
> >
> > the
> >
> >
> > > fill logic, ends up corrupting the file and adds an extra 4K chunk of
> > > 'fill' data. A hex dump of the file easily shows the problem.  Luckily
> >
> >
> > > for me the work around was simple, use the setFill() method to disable
> >
> >
> > > fill as I didn't need fill capability.
> > >
> > > The exact version I was testing  2.1.10 Build Date = 2004-07-08
> > > 08:59:07.
> > >
> > > Not sure if this stream is still being maintained etc. but if 
> > > interested, I will send a small sample program that demonstrates this
> >
> > bug.
> >
> >
> > >

Attachment: netcdftest4.nc
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