from __future__ import annotations import os import sys from contextlib import suppress from errno import EACCES from pathlib import Path from typing import cast from ._api import BaseFileLock from ._util import ensure_directory_exists, raise_on_not_writable_file if sys.platform == "win32": # pragma: win32 cover import msvcrt class WindowsFileLock(BaseFileLock): """Uses the :func:`msvcrt.locking` function to hard lock the lock file on Windows systems.""" def _acquire(self) -> None: raise_on_not_writable_file(self.lock_file) ensure_directory_exists(self.lock_file) flags = ( os.O_RDWR # open for read and write | os.O_CREAT # create file if not exists | os.O_TRUNC # truncate file if not empty ) try: fd = os.open(self.lock_file, flags, self._context.mode) except OSError as exception: if exception.errno != EACCES: # has no access to this lock raise else: try: msvcrt.locking(fd, msvcrt.LK_NBLCK, 1) except OSError as exception: os.close(fd) # close file first if exception.errno != EACCES: # file is already locked raise else: self._context.lock_file_fd = fd def _release(self) -> None: fd = cast("int", self._context.lock_file_fd) self._context.lock_file_fd = None msvcrt.locking(fd, msvcrt.LK_UNLCK, 1) os.close(fd) with suppress(OSError): # Probably another instance of the application hat acquired the file lock. Path(self.lock_file).unlink() else: # pragma: win32 no cover class WindowsFileLock(BaseFileLock): """Uses the :func:`msvcrt.locking` function to hard lock the lock file on Windows systems.""" def _acquire(self) -> None: raise NotImplementedError def _release(self) -> None: raise NotImplementedError __all__ = [ "WindowsFileLock", ]