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Re: [netcdfgroup] Sort of Inverse of netcdf diskless mode

Hi Roy: I had a similar problem earlier this year. I wanted to open a netCDF 3 file and read from it using the netCDF library when the file was presented to me in memory instead of as a disk file.
I spent some time examining the netCDF library source and talking to UNIDATA folks about this and determined that the library was too hard to change. The interface depended upon passing in a file name and it would be too hard to modify it to add an 'ncopen' that took a pointer to memory instead.
What I ended up doing was writing a reader from scratch in perl (since this application was in perl using the PDL::NetCDF interface) that reads the raw netCDF3 binary format.
This has proved to be a good lightweight solution for us, but it does restrict us to netCDF 3. 

I'd be happy to share my perl netCDF 3 reader library if you are interested.
Incidentally, as a result of this experience, I came away with an appreciation for the elegance and good design of the netCDF 3 binary format and a suspicion of the netCDF 4 format as being too complex and having too much library overhead. 

Regards,

  Doug

On 11/19/14 18:41, Roy Mendelssohn - NOAA Federal wrote:

Hi All:

Netcdf now has the option of  creating or reading a file entirely in memory, a 
nice option to have. I am wondering if there is any way to do sort of the 
inverse.  Some web libraries allow for a pure binary download of a file into 
memory, so what I have sitting there is essentially a binary image of the 
netcdf file.  Is there any way to open that image without writing to disk?

As an example, the R httr library allows this.  I can for example download to memory a netcdf 
file from ERDDAP, and if I then do a binary save in httr and then read it back in using the 
ncdf4 package, it all works great.   But it would be even better if I could skip the extra 
steps, and “open” the image in ncdf4 directly  (ncdf4 btw can do whatever the 
netcdf libraries can do, so it is a question of the base libraries).

Thanks,

-Roy


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"The contents of this message do not reflect any position of the U.S. Government or 
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Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
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