Datatype::serialize returned an empty message for these four classes, so
any dataset or attribute of them (including a Raw attribute copied from
another file) was unreadable by libhdf5 ("ran off end of input buffer
while decoding"). They now encode exactly as libhdf5 does: legacy object
and region references as datatype version 1, H5T_STD_REF kinds as version
4 with their encoding version, opaque tags NUL-padded to 8 bytes.
Parsing an opaque tag now stops at its first NUL, so libhdf5's padding
no longer becomes part of the tag. Datatype::check_encodable rejects
what has no encoding (an opaque tag over 248 bytes); FileWriter::finish
calls it for every dataset and attribute type.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
A v2 object header message has a 2-byte size field. The writer truncated
larger sizes to 16 bits, so an attribute over ~64 KiB (or a compact
dataset of 65532-65535 bytes, whose layout message adds 4 bytes) produced
a file libhdf5 rejects ("message of unshareable class flagged as
shareable", "bad flag combination").
ObjectHeaderWriter::serialize now returns a Result and fails on any message
over MAX_MESSAGE_SIZE; FileWriter::finish propagates it. Compact storage
falls back to contiguous above 65531 bytes, the real limit. Dense storage
for large attributes remains future work.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
