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Improve the fix for #350 included in #1119 #1521

Merged
merged 4 commits into from
Nov 15, 2019
Merged

Improve the fix for #350 included in #1119 #1521

merged 4 commits into from
Nov 15, 2019

Commits on Nov 13, 2019

  1. Improve the fix for Unidata#350 included in Unidata#1119 

    1) We have to use H5Tequal() to compare HDF5 type IDs.
2) When checking if we can re-use an NC_CHAR attribute it is enough to
   compare data types (H5Tequal() takes care of the size comparison).
3) This commit adds missing code (reuse_att was set but not used).

Now an attribute in a NetCDF-4 file can be modified as many times as
necessary, as long its type and length remain the same.

Modifications changing either type or length of an attribute require
deleting and re-creating an attribute which increments the attribute
order creation index. Once this index reaches 65535 all attribute
modifications (for a particular group or variable) will fail.

For reference:

Issue 350 title: NetCDF-4 limits the number of times an attribute can
be modified

Pull request 1119 title: Fix checking for HDF5 max dims, no longer
re-create atts if not needed, confirm behavior for HDF5 cyclical
files, allow user to set mpiexec
    @ckhroulev
    ckhroulev committed Nov 13, 2019
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  2. Modify the condition used to check if an attribute can be re-used 

    This should make the code a bit cleaner.
    @ckhroulev
    ckhroulev committed Nov 13, 2019
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  3. Whitespace changes

    @ckhroulev
    ckhroulev committed Nov 13, 2019
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  4. Add regression tests modifying attributes 2^16 times 

    This commit adds three new tests:

- a test documenting the limitation originally reported in Unidata#350 (in
  general modifying an attribute about 2^16 times makes it impossible
  to modify this file in ways requiring nc_redef() and nc_enddef() calls).
- a test ensuring that a scalar attribute can be modified 2^16 times
  as long as its type and size remain the same
- a test ensuring that a text attribute can be modified 2^16 times as
  long as its size remains the same

This version uses the nc_redef(), nc_put_att_...(), nc_enddef()
sequence. One could also use nc_open(), nc_put_att_...(), nc_close()
but that would make these tests significantly slower.
    @ckhroulev
    ckhroulev committed Nov 13, 2019
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