ECC-2074: Fortran: get_message, new_from_message without memcpy

[plesskem]

Proposed extension of the fortran grib api:
2 methods which are already included in the C interface and used to directly access the coded message in main memory
these methods are for example practical for sending/receiving coded grib messages with MPI

• grib_get_message
  returns a fortran pointer to the coded message (character) of a grib_handle
• grib_new_from_message_no_copy
  creates a new grib_handle with a data buffer pointing to a provided coded message (character or integer)

[FussyDuck]

All committers have signed the CLA.

[shahramn]

Compilation fails. Can you please take a look
e.g.,

eccodes/fortran/grib_fortran.cc:905:12: error: no matching function for call to 'grib_get_message'
  iret = grib_get_message(h,&message,mess_len);
src/eccodes_prototypes.h:539:5: note: candidate function not viable:
no known conversion from 'void **' to 'const void **' for 2nd argument
 int grib_get_message(const grib_handle* h, const void** msg, size_t* size);

[shahramn]

Still failing:

eccodes/fortran/grib_fortran.cc: In function ‘int grib_f_get_message_(int*, const void**, size_t*)’:
eccodes/fortran/grib_fortran.cc:905:31: error: invalid conversion from ‘void**’ to ‘const void**’ [-fpermissive]
      iret = grib_get_message(h,&message,mess_len);
                                ^~~~~~~~
In file included from src/eccodes/grib_api_internal.h:193,
                  from eccodes/fortran/grib_fortran.cc:11:
eccodes/src/eccodes/grib_api.h:571:57: note: initializing argument 2 of ‘int grib_get_message(const grib_handle*, const void**, size_t*)’

[plesskem]

Sorry for the compilation failure! I am correcting and testing it locally. If it is successful, I'll notify you.

[plesskem]

My tests locally were successful and I noticed that I had only support for size_t message length and therefore added support for int as well.
Fingers crossed that your tests run through now. :)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.85714% with 12 lines in your changes missing coverage. Please review.

Project coverage is 87.70%. Comparing base (848f4b1) to head (d8a55c5).
Report is 5 commits behind head on develop.

Files with missing lines	Patch %	Lines
examples/F90/grib_get_message.f90	84.31%	8 Missing ⚠️
fortran/grib_fortran.cc	78.94%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #279      +/-   ##
===========================================
- Coverage    87.71%   87.70%   -0.01%     
===========================================
  Files          843      844       +1     
  Lines        62339    62409      +70     
  Branches     11126    11133       +7     
===========================================
+ Hits         54680    54738      +58     
- Misses        7659     7671      +12     

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[shahramn]

Thank you. Could you please add a test too? similar to:
examples/F90/grib_copy_message.f90
so when we run ctest, the code you have added gets exercised and we know it is functioning as expected

[shahramn]

Thank you for your contribution 🥇

[shahramn]

This has now been released as part of ecCodes v2.42.0