osobhandClaude Opus 5
367faad7f7
A dataset with exactly one unlimited dimension — the ordinary append-only case — is indexed by an Extensible Array. Only its first few chunk entries (4 by default) sit inline in the index block, and everything past them was read with the wrong layout. In the default shape the 37th chunk onward came back from the wrong place: a 400-chunk dataset returned 364 wrong values while reporting success, and beyond about a thousand chunks the read failed outright. Silently wrong data is the worse half of that. It survived because the only Extensible Array fixture in the suite had three chunks — inside the inline limit — so no test ever reached a data block. Four layout errors, each confirmed against files written by HDF5 2.0 and against the library source rather than inferred: - super block `u` owns 2^(u/2) data blocks, not 2^u; - each holds 2^((u+1)/2) * data_blk_min_elmts elements — the two quantities double every *other* level, a half step apart; - a super block carries a block-offset field before its data block addresses, which was not skipped; - the page-init bitmap belongs to the super block, one bit per page packed across all of its data blocks and read MSB-first, rather than living inside the data block; a paged data block also ends its prefix with a checksum before the first page. Where the spec left room for doubt the file settled it: decoding a paged block's elements and reading the chunk values they address identifies the mapping exactly, and the bitmap's 68 set bits matched the 34 data blocks x 2 pages that 200 000 elements need, which only holds MSB-first. New interop tests cross every boundary — 4, 37, 400, 5 000 and 200 000 chunks, the last with paged data blocks — plus sparse (uninitialised pages taking fill values), gzip-filtered elements and a 2-D dataset. All three fail against the old traversal. Writing is untouched; this was a read-path bug. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
clawhdf5-format
Pure-Rust HDF5 binary format parsing and writing — no C dependencies.
Features
- Zero-copy superblock, object header, and B-tree parsing
- Chunked dataset read/write with filter pipelines
no_stdsupport (disablestdfeature)- Optional parallel reads via Rayon
- SHA-256 provenance tracking
Usage
use clawhdf5_format::Superblock;
let data = std::fs::read("data.h5").unwrap();
let sb = Superblock::from_bytes(&data).unwrap();
println!("HDF5 version {}.{}", sb.version_major(), sb.version_minor());
License
MIT