Fix https://github.com/Unidata/netcdf-c/issues/962
1. remove the --disable-diskless option since it is no
longer needed. Similarly for CMakeLists.txt.
2. Fixed nc4files.c where BAIL and return were mixed
leading to situation where cleanup code was not
being invoked. This probably occurs elsewhere,
but I did not find any specifically.
The file docs/indexing.dox tries to provide design
information for the refactoring.
The primary change is to replace all walking of linked
lists with the use of the NCindex data structure.
Ncindex is a combination of a hash table (for name-based
lookup) and a vector (for walking the elements in the index).
Additionally, global vectors are added to NC_HDF5_FILE_INFO_T
to support direct mapping of an e.g. dimid to the NC_DIM_INFO_T
object. These global vectors exist for dimensions, types, and groups
because they have globally unique id numbers.
WARNING:
1. since libsrc4 and libsrchdf4 share code, there are also
changes in libsrchdf4.
2. Any outstanding pull requests that change libsrc4 or libhdf4
are likely to cause conflicts with this code.
3. The original reason for doing this was for performance improvements,
but as noted elsewhere, this may not be significant because
the meta-data read performance apparently is being dominated
by the hdf5 library because we do bulk meta-data reading rather
than lazy reading.
In C, `char`, `signed char`, and `unsigned char` are three separate,
distinct types, so just because `char` happens to be signed does not
mean it is interchangeable with `signed char`.
(I hope) metadata mechanism. This mostly just adds new pieces of
code (e.g. nclistmap) and does some minor fixes.
It should be transparent to everything else.
The next set of changes will be the big step.
