docs: the SWMR follow loop stops for a writer that died, not only one that closed

The README example looped while swmr_writer_active(), which never ends when the writer crashed or was killed: libhdf5 clears the SWMR-write flag only on close (the mid-write fixture keeps it set for good). The loop now also stops after a minute without growth, and the README, the swmr_writer_active docs (with the same loop as a compiled no_run doctest) and the design say why. Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
2026-09-27 07:33:46 -05:00
parent 4467d9dd32
commit 8ef7e80473
3 changed files with 48 additions and 7 deletions
@@ -121,6 +121,9 @@ writer keeps appending. What the format and the library guarantee:
   the index entry, only appends), as for libhdf5's reader.
 5. **Writer state.** `File::swmr_writer_active()` reads the superblock
   flags again, so a reader can tell when the writer has closed the file.
+   A writer that crashed or was killed never clears the flag, so a reader
+   that follows a file needs a second stop condition (the README example
+   stops after a minute without growth).

 What stays out: SWMR writing, VFD SWMR (HDF5 1.13's page-buffer protocol,
 not in 1.14 or 2.0), remote SWMR, refresh of groups/attributes (a SWMR