feat: assemble 1-D same-file Virtual Datasets (VDS)

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]>

This commit is contained in:

osobh

2026-06-03 20:01:51 +00:00

co-authored by

Claude Opus 4.8

parent a24fcb8be4

commit 908af40282

6 changed files with 523 additions and 86 deletions

crates/clawhdf5-format/tests/fixtures/vds_same_file.h5

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