[gradsusr] big/little endian bug in OpenGrads v2.0.a9.oga.1 for 2-byte integers files

[David Lorenz]

I've run into the same problem in the GrADS binary for Mac. I sent a message to these forums a while back and didn't get a response.

There's also a problem when you mix two-byte and four-byte variables together in the same file. GrADS get confused and acts like all variables are the same size as the variable you are trying to display. 


-Dave

On 05/19/11, Henrique Barbosa   wrote:
> Dear all,
> 
> I was trying to read a single variable written as 2-byte signed integer in a big endian file. Plain binary file, i.e. stream, with no header. Should be really simple, but it was not. For handling this, I had my CTL as:
> 
> 
> 
> (...)
> options big_endian
> (...)
> myvar 0 -1,40,2,-1 ** my variable
> (...)
> 
> However, it did not work. The values were completely wrong. After a day trying to understand what as going on, I decided to force 'little_endian' on the CTL despite the file being big-endian... and it worked!! and I could read the data. 
> 
> 
> 
> However, USGS claims gtopo30 to be big_endian. To make sure,  I wrote a  F90 program to read it. I could only get the correct data inside the program if I opened the file as big_endian. Therefore, as USGS and my program agree, I believe the data is big_endian.
> 
> 
> 
> Therefore the problem should be in grads. I made a series of tests, writing 1-byte, 2-byte and 4-byte integer binary files, and 4-byte float files, for both little and big endian types. The only problem I found was with 2-byte integers. I think that it is a bug in grads, actually, OpenGrads v2.0.a9.oga.1. The necessary data to reproduce the problem can be found here:
> 
> 
> 
> 
> 
> <http://www.fap.if.usp.br/~hbarbosa/file_format.tgz>
> 
> 
> 
> Can some expert have a look in the source code? Arlindo? Jennifer? By the way, I am on x86-64 machine, runing ubuntu 64bits and using grads-2.0.a9.oga.1-bundle-x86_64-rhel5.5-linux-gnu.tar.gz.
> 
> Sincerely,
> Henrique
> 
> 
> 
> 
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