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