CHANGELOG (Unreleased) records libver_bounds and the 1.8 checks;
known-issues moves "the writer does not produce output HDF5 1.8 can
read" to Fixed (history) as an opt-in fix and keeps what is still open
(Python 'w' has no libver, no pre-1.8 format, B-tree node filling vs
libhdf5's chunk cache); README's capability table lists 1.8 output and
v1 B-tree chunk indexes as written; BENCHMARKS gains the dated A/B of the
two formats on the read harness (tank, 2026-09-28, under load), which is
why the default stays the 1.10 format.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
New `LibVer` (V18, V110, V112, V114, V200, Latest) and
`libver_bounds(low, high)` on the format crate's `FileWriter` and the
facade's `FileBuilder`, as libhdf5's H5Pset_libver_bounds / h5py's
libver=(low, high). The default stays (V110, Latest), byte for byte what
was written before.
With a low bound of 1.8: superblock version 2, layout message version 3
(contiguous, compact, chunked) and a version-1 B-tree chunk index for
every chunked dataset, resizable ones included -- what libhdf5 2.x writes
under libver=('v108', 'latest'). The new chunk B-tree writer
(btree_v1_write.rs) replays H5B_insert with the H5Dbtree.c callbacks for
row-major insertion (split ratios 0.1/0.5/0.9, right keys moved as
H5D__btree_cmp3 moves them, root kept in place): its trees equal
libhdf5's node for node for 1-D/2-D/3-D, 2- and 3-level, filtered and
unfiltered datasets (libhdf5 writing without a chunk cache).
The high bound refuses, with FormatError::LibverBound before anything is
written, what needs a newer format: virtual datasets and the paged
file-space strategy (1.10), the 1.12 reference types (datatype v4),
native complex (datatype v5, HDF5 2.0), and a low bound above the high.
Tests: tools/tests/libver_v18.rs writes every writer feature under
(V18, V18), and HDF5 1.8.23's h5dump (scripts/build-hdf5-1.8.sh; skipped
when absent) dumps it exactly as h5dump 1.14 does and returns our bytes
for every numeric dataset; h5py, clawhdf5 and h5rs check --data agree;
then FileEditor grows/appends/annotates it and h5py appends, and every
reader checks again. read_harness gains --v18 and --chunk N.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
Variables got the first unused dimension of equal size, so a variable on
an unlimited dimension with fewer records got an anonymous dim_<n>, and
dimensions of one size could be swapped. Resolve them as netCDF-C does
(libhdf5/hdf5open.c): _Netcdf4Coordinates ids, else the scales
DIMENSION_LIST references (the last one attached to an axis), searched in
the variable's group and its parents; a coordinate variable is on its own
scale. Size matching remains only for axes the file names nothing for.
variables()/variable_names() leave out dimension scales that are only
dimensions, and _nc4_non_coord_<name> is the variable <name>.
Variable::shape is the netCDF shape (an unlimited dimension's length) and
the reads pad unwritten records with the fill value (_FillValue, else
NC_FILL_*; NaN from read_f64); Variable::stored_shape is the HDF5 extent.
New NetCDF4File::variable_names.
Tests compare with netCDF4-python variable by variable: the known-issues
reproducer, equal sizes, (p, p), scalars, inherited dimensions, unwritten
records, h5py dimension scales, h5netcdf and xarray files. CI installs
h5netcdf. known-issues entry moved to Fixed (history); stale open-table
row for the unlimited-size fix removed.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
