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Blackrock: fix OverflowError reading .nev files over 4 GiB - #1929
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bytes_in_headers and bytes_in_data_packets are NumPy uint32 scalars. Under NumPy 2 (NEP 50), subtracting one from a Python int file size above 2**32 raises OverflowError. Cast to int before doing file-size arithmetic.
h-mayorquin
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Oct 28, 2026
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The fix looks good to me. I ran your test and it fails on master with the OverflowError and passes here.
Can you drop the test. It builds the reader with __new__, sets private attributes and mocks np.memmap, so it depends on the internals of _read_nev_data and _get_nev_rec_times. We did not add tests for the earlier overflow fixes of the same kind either (#1642, #1669, #1690).
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LGTM.
Thanks for dropping the test.
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`_read_nev_data` took `header_size` straight from `self._nev_basic_header["bytes_in_headers"]`, a NumPy `uint32` scalar. Under NumPy 2 (NEP 50), `self._get_file_size(filename) - header_size` then raises `OverflowError: Python integer ... out of bounds for uint32` for any `.nev` over 4 GiB, before the memmap is even created. `_get_nev_rec_times` has the same problem with `bytes_in_data_packets`.
Both values are now cast with `int()`. I checked the other places where header fields meet file sizes or offsets: the NSx paths (2.1, 2.2/3.0 and PTP) already use Python ints, so they are unchanged.
The new test, `test_nev_over_4_gib_does_not_overflow`, needs no data: it stubs a 5 GiB file size and a header with `uint32` fields, mocks `np.memmap`, and checks the `offset` and `shape` passed to it for both methods. It fails with the `OverflowError` above on current master (I checked each of the two fixes on its own) and passes with this change. The Blackrock rawio and io tests pass (32 passed).
This came up with a 4.6 GB spec 2.2 file written by Ripple Trellis. I have not run that file, or any real file over 4 GiB, through this branch; the test is the only check at that size.