revlog: move the "index header" struct inside revlog.utils.constants
The struct was previous called "version", but this is actually "version" +
"flags". So header seems like a better name.
The move to the `constants` module has the same motivation as the INDEX_ENTRY_V#
ones.
Differential Revision: https://phab.mercurial-scm.org/D10306
from ..i18n import _
from .. import error
def get_checker(ui, revlog_name=b'changelog'):
"""Get a function that checks file handle position is as expected.
This is used to ensure that files haven't been modified outside of our
knowledge (such as on a networked filesystem, if `hg debuglocks` was used,
or writes to .hg that ignored locks happened).
Due to revlogs supporting a concept of buffered, delayed, or diverted
writes, we're allowing the files to be shorter than expected (the data may
not have been written yet), but they can't be longer.
Please note that this check is not perfect; it can't detect all cases (there
may be false-negatives/false-OKs), but it should never claim there's an
issue when there isn't (false-positives/false-failures).
"""
vpos = ui.config(b'debug', b'revlog.verifyposition.' + revlog_name)
# Avoid any `fh.tell` cost if this isn't enabled.
if not vpos or vpos not in [b'log', b'warn', b'fail']:
return None
def _checker(fh, fn, expected):
if fh.tell() <= expected:
return
msg = _(b'%s: file cursor at position %d, expected %d')
# Always log if we're going to warn or fail.
ui.log(b'debug', msg + b'\n', fn, fh.tell(), expected)
if vpos == b'warn':
ui.warn((msg + b'\n') % (fn, fh.tell(), expected))
elif vpos == b'fail':
raise error.RevlogError(msg % (fn, fh.tell(), expected))
return _checker