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", ]