A file may start with a user block (h5py userblock_size, h5jam), putting
the superblock at 512, 1024, ...; every address in the file is then
relative to the superblock. The signature search found it, but every
reader passed the whole file to the parsers, so addresses landed
userblock bytes early and the root group failed with
InvalidObjectHeaderVersion (twithub.h5, twithub513.h5,
h5clear_fsm_persist_user_*.h5).
Readers now view the file from the superblock on, taking the signature's
position as the base address as libhdf5 does: File (mmap, buffered,
from_bytes), MmapFile, LazyFile, AsyncHDF5File, the VOL and MPI VOL
readers, the HNSW loader and external VDS source files. File, MmapFile
and LazyFile gain user_block_size(). The new signature::split_user_block
returns the two parts, and Superblock::parse refuses a non-zero offset
(UserBlockNotStripped) so a format-level caller cannot silently apply
superblock-relative addresses to the whole file.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
FileWriter::with_page_size wrote a "version 4" superblock with an extra
page-size field. HDF5 has no superblock version 4, so libhdf5 refused
every such file ("bad superblock version number").
A paged file is now what libhdf5 itself writes for fs_strategy="page":
a v3 superblock whose extension object header holds a File Space Info
message (strategy PAGE, the page size, free space not persisted; same
bytes and flags as HDF5 2.0), with the file padded to a whole page.
h5py opens it, reports the strategy and page size, and can modify it in
r+ mode. Page sizes outside libhdf5's 512 B..1 GiB are an error.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
- Remove clawhdf5-types (empty 1-line stub crate; type defs already live in
clawhdf5-format). Update workspace Cargo.toml and CLAUDE.md accordingly.
- Implement HDF5 superblock v4 (page-buffer mode) read and write support in
clawhdf5-format: Superblock::parse_v4, page_size field, v4 serialize
branch, and FileWriter::with_page_size. This was the one task left
unimplemented from docs/superpowers/plans/2026-06-29-format-write-extensions.md.
- Reconcile the three docs/superpowers/plans/*.md docs (filter codecs,
format write extensions, MPI-IO VOL) against actual shipped code: they
were pre-work plans for d6c4d4f (2026-06-30) committed to git late on
2026-08-03 with all checkboxes still unchecked. Mark completed tasks done
and add a status note so they read as historical records, not open work.
- Refresh ROADMAP.md's "What's Next" section against current repo state.
Co-Authored-By: Claude Sonnet 5 <[email protected]>
