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from __future__ import annotations
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from ..i18n import _
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from .. import error
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def get_checker(ui, revlog_name=b'changelog'):
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"""Get a function that checks file handle position is as expected.
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This is used to ensure that files haven't been modified outside of our
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knowledge (such as on a networked filesystem, if `hg debuglocks` was used,
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or writes to .hg that ignored locks happened).
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Due to revlogs supporting a concept of buffered, delayed, or diverted
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writes, we're allowing the files to be shorter than expected (the data may
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not have been written yet), but they can't be longer.
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Please note that this check is not perfect; it can't detect all cases (there
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may be false-negatives/false-OKs), but it should never claim there's an
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issue when there isn't (false-positives/false-failures).
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"""
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vpos = ui.config(b'debug', b'revlog.verifyposition.' + revlog_name)
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# Avoid any `fh.tell` cost if this isn't enabled.
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if not vpos or vpos not in [b'log', b'warn', b'fail']:
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return None
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def _checker(fh, fn, expected):
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if fh.tell() <= expected:
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return
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msg = _(b'%s: file cursor at position %d, expected %d')
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# Always log if we're going to warn or fail.
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ui.log(b'debug', msg + b'\n', fn, fh.tell(), expected)
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if vpos == b'warn':
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ui.warn((msg + b'\n') % (fn, fh.tell(), expected))
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elif vpos == b'fail':
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raise error.RevlogError(msg % (fn, fh.tell(), expected))
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return _checker
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