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[netCDFJava #MQO-415619]: Efficiently serializing NetCDF in memory objects



This question has come up before.
This is currently not possible for netcdf-4 files.
Using the NC_DISKLESS mode flag allows for keeping
the file in memory. The nc_open_mem function allows for the
read only access to treat a chunk of memory as if it was
a netcdf file. Unfortunately, for netcdf-4, we ultimately
depend on the HDF5 operation H5P_set_core
(https://support.hdfgroup.org/HDF5/doc/RM/RM_H5P.html#Property-SetFaplCore).
Upon close(), this can optionally store the memory buffer in a file.
Unfortunately, it does not (currently) provide an option to copy out the memory.
The only solution I can see for now is to build an alternative to the core 
driver
that provides access (somehow) to the memory.
BTW, this is all going on at the netcdf-c library level. Our pure jave HDF5
reader is read-only, hence cannot create or modify files.

I have created an issue for this
(https://github.com/Unidata/netcdf-c/issues/708)
but it is not likely to get implemented anytime soon.

You will have to be content with writing the contents to a file.



> 
> I am using NetCDF Java library 4.6.10.
> 
> My goal is to efficiently send NetcdfFile
> <https://www.unidata.ucar.edu/software/thredds/current/netcdf-java/javadoc/ucar/nc2/NetcdfFile.html>
> objects over the network using a communication library (such as ZeroMQ).
> Because the NetcdfFile
> <https://www.unidata.ucar.edu/software/thredds/current/netcdf-java/javadoc/ucar/nc2/NetcdfFile.html>
> class
> does not implement Serializable, I need to implement that step myself.
> 
> Since NetCDF is a machine independent data format, I would like to access
> the raw binary data.
> 
> This is trivial if the data kas been written to a file on the disk. But,
> what about in memory datasets ? If possible, I would like to access to
> binary data without writing it to disk...
> 
> Can I access the buffer of an in-memory NetcdfFile
> <https://www.unidata.ucar.edu/software/thredds/current/netcdf-java/javadoc/ucar/nc2/NetcdfFile.html>
> object
> from the Java API ? Any pointers will be appreciated.
> 
> Kind regards,
> 
> MichaÃl
> 
> 

=Dennis Heimbigner
  Unidata


Ticket Details
===================
Ticket ID: MQO-415619
Department: Support netCDF Java
Priority: Normal
Status: Open
===================
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