69 lines
2.2 KiB
Python
69 lines
2.2 KiB
Python
from __future__ import annotations
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import os
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import sys
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from contextlib import suppress
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from errno import ENOSYS
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from pathlib import Path
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from typing import cast
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from ._api import BaseFileLock
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from ._util import ensure_directory_exists
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#: a flag to indicate if the fcntl API is available
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has_fcntl = False
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if sys.platform == "win32": # pragma: win32 cover
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class UnixFileLock(BaseFileLock):
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"""Uses the :func:`fcntl.flock` to hard lock the lock file on unix systems."""
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def _acquire(self) -> None:
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raise NotImplementedError
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def _release(self) -> None:
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raise NotImplementedError
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else: # pragma: win32 no cover
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try:
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import fcntl
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except ImportError:
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pass
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else:
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has_fcntl = True
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class UnixFileLock(BaseFileLock):
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"""Uses the :func:`fcntl.flock` to hard lock the lock file on unix systems."""
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def _acquire(self) -> None:
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ensure_directory_exists(self.lock_file)
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open_flags = os.O_RDWR | os.O_TRUNC
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if not Path(self.lock_file).exists():
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open_flags |= os.O_CREAT
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fd = os.open(self.lock_file, open_flags, self._context.mode)
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with suppress(PermissionError): # This locked is not owned by this UID
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os.fchmod(fd, self._context.mode)
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try:
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fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
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except OSError as exception:
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os.close(fd)
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if exception.errno == ENOSYS: # NotImplemented error
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msg = "FileSystem does not appear to support flock; use SoftFileLock instead"
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raise NotImplementedError(msg) from exception
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else:
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self._context.lock_file_fd = fd
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def _release(self) -> None:
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# Do not remove the lockfile:
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# https://github.com/tox-dev/py-filelock/issues/31
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# https://stackoverflow.com/questions/17708885/flock-removing-locked-file-without-race-condition
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fd = cast(int, self._context.lock_file_fd)
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self._context.lock_file_fd = None
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fcntl.flock(fd, fcntl.LOCK_UN)
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os.close(fd)
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__all__ = [
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"UnixFileLock",
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"has_fcntl",
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]
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