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| from __future__ import annotations | |
| import os | |
| import sys | |
| from contextlib import suppress | |
| from errno import EACCES, EEXIST | |
| from pathlib import Path | |
| from ._api import BaseFileLock | |
| from ._util import ensure_directory_exists, raise_on_not_writable_file | |
| class SoftFileLock(BaseFileLock): | |
| """Simply watches the existence of the lock file.""" | |
| def _acquire(self) -> None: | |
| raise_on_not_writable_file(self.lock_file) | |
| ensure_directory_exists(self.lock_file) | |
| # first check for exists and read-only mode as the open will mask this case as EEXIST | |
| flags = ( | |
| os.O_WRONLY # open for writing only | |
| | os.O_CREAT | |
| | os.O_EXCL # together with above raise EEXIST if the file specified by filename exists | |
| | os.O_TRUNC # truncate the file to zero byte | |
| ) | |
| try: | |
| file_handler = os.open(self.lock_file, flags, self._context.mode) | |
| except OSError as exception: # re-raise unless expected exception | |
| if not ( | |
| exception.errno == EEXIST # lock already exist | |
| or (exception.errno == EACCES and sys.platform == "win32") # has no access to this lock | |
| ): # pragma: win32 no cover | |
| raise | |
| else: | |
| self._context.lock_file_fd = file_handler | |
| def _release(self) -> None: | |
| assert self._context.lock_file_fd is not None # noqa: S101 | |
| os.close(self._context.lock_file_fd) # the lock file is definitely not None | |
| self._context.lock_file_fd = None | |
| with suppress(OSError): # the file is already deleted and that's what we want | |
| Path(self.lock_file).unlink() | |
| __all__ = [ | |
| "SoftFileLock", | |
| ] | |