A SWMR writer does not keep the superblock's end-of-file address up to
date: a copy h5py made of its own file mid-write records 715 in a
6 030-byte file. Superblock::data_end only ignored the recorded end when
it lay past the end of the file, so every open path bounded reads at
715: the file listed, but every chunked read failed ("unexpected EOF:
need 787 bytes, have 715") and h5rs check reported the chunk indexes
past the end of the file. libhdf5's SWMR reader skips the
end-of-allocation check for every read (H5FD_read); for a v3 superblock
with the SWMR-write flag the data now ends at the end of the file.
Test: tests/swmr_interop.rs over the mid-write copy (fixture), through
File::open, open_buffered and from_bytes, and against h5py's SWMR reader.
Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
