Open the 2dseq memory map read-only

[gdevenyi]

A dataset on a read-only file or mount cannot be loaded at all:

PermissionError: [Errno 13] Permission denied: ".../2/pdata/1/2dseq"

Cause

read_array in brukerapi/paths.py maps a filesystem path without giving a mode:

return np.array(np.memmap(path, dtype=dtype, shape=shape, order=order)[:])

np.memmap defaults to mode="r+", so every dataset load asks the operating system for write access to the raw data file. Nothing writes it — the array is copied out of the map on the same line.

This matters because a shared scanner archive is normally exposed read-only. The parameter files are unaffected, since those are opened in text mode, so the failure looks oddly selective: acqp, method, visu_pars and reco all read, and only the binary fails, once per scan.

Reproduction

Copy any PV6 study, chmod -R a-w, and load it. On the same file:

mode="r+"  (the default)  -> PermissionError: Permission denied
mode="r"                  -> OK, read 1048576 values

The change

mode="r" on that one call. The archive branch just below already reads through path.open("rb") and was never affected.

test_dataset_reads_from_a_read_only_source covers it. It lives in test_paths.py because that module's study is synthetic and needs no corpus; it fails with PermissionError without the change.

Test suite

Run against a local PV5.1/PV6.0.1/PV7.0.0 corpus:

• baseline (master): 4 failed, 245 passed, 51 skipped
• with this change: 4 failed, 246 passed, 51 skipped

The same four failures occur either way — they are corpus-dependent and unrelated to this change. ruff check clean at the pinned 0.16.0.

Found while diagnosing a user report against a downstream converter, where the raw data lives on a read-only archive mount.