A virtual layout previously returned UnsupportedVersion. Implement reading
for the common 1-D, same-file case, reverse-engineered and validated against
HDF5 2.0.
- Rewrite parse_vds_mappings to the real global-heap block format
(version(1) · nused(length_size) · entries · checksum(4)), where each
entry is source-file(null) · source-dataset(null) · source-selection ·
virtual-selection. Block version 1 encodes a same-file source as a single
0x04 marker in place of the file name; version 0 stores an explicit file
name. The selections are H5S-serialized and self-describing in length, so
they are decoded to find entry boundaries. The previous parser used a
guessed layout that did not match real files.
- Extend Selection with decode_serialized() (H5S_select_serialize: ALL,
NONE, and version-3 regular hyperslabs) and iter_linear_1d().
- Add read_virtual_data: resolve the mapping block from the global heap,
read each same-file source dataset, and scatter its selected elements into
the virtual buffer; unmapped regions stay at the zero fill value.
External-file sources and N-D selections return a clean unsupported error.
Tests: real-file integration test (vds_same_file.h5: partial source slice +
fill gap), selection decoder unit tests built from the fixture bytes, and
same-file/external mapping-parser unit tests.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
