codekingpro/portable-devtools

1from __future__ import annotations2 3import os4import sys5from contextlib import suppress6from errno import ENOSYS7from pathlib import Path8from typing import cast9 10from ._api import BaseFileLock11from ._util import ensure_directory_exists12 13#: a flag to indicate if the fcntl API is available14has_fcntl = False15if sys.platform == "win32":  # pragma: win32 cover16 17    class UnixFileLock(BaseFileLock):18        """Uses the :func:`fcntl.flock` to hard lock the lock file on unix systems."""19 20        def _acquire(self) -> None:21            raise NotImplementedError22 23        def _release(self) -> None:24            raise NotImplementedError25 26else:  # pragma: win32 no cover27    try:28        import fcntl29    except ImportError:30        pass31    else:32        has_fcntl = True33 34    class UnixFileLock(BaseFileLock):35        """Uses the :func:`fcntl.flock` to hard lock the lock file on unix systems."""36 37        def _acquire(self) -> None:38            ensure_directory_exists(self.lock_file)39            open_flags = os.O_RDWR | os.O_TRUNC40            if not Path(self.lock_file).exists():41                open_flags |= os.O_CREAT42            fd = os.open(self.lock_file, open_flags, self._context.mode)43            with suppress(PermissionError):  # This locked is not owned by this UID44                os.fchmod(fd, self._context.mode)45            try:46                fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)47            except OSError as exception:48                os.close(fd)49                if exception.errno == ENOSYS:  # NotImplemented error50                    msg = "FileSystem does not appear to support flock; use SoftFileLock instead"51                    raise NotImplementedError(msg) from exception52            else:53                self._context.lock_file_fd = fd54 55        def _release(self) -> None:56            # Do not remove the lockfile:57            #   https://github.com/tox-dev/py-filelock/issues/3158            #   https://stackoverflow.com/questions/17708885/flock-removing-locked-file-without-race-condition59            fd = cast(int, self._context.lock_file_fd)60            self._context.lock_file_fd = None61            fcntl.flock(fd, fcntl.LOCK_UN)62            os.close(fd)63 64 65__all__ = [66    "UnixFileLock",67    "has_fcntl",68]69