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",
]
|