from __future__ import annotations import os import sys from errno import EACCES, EEXIST, ENOENT from ._api import BaseFileLock from ._util import raise_on_exist_ro_file class SoftFileLock(BaseFileLock): """Simply watches the existence of the lock file.""" def _acquire(self) -> None: raise_on_exist_ro_file(self._lock_file) # first check for exists and read-only mode as the open will mask this case as EEXIST mode = ( 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: fd = os.open(self._lock_file, mode) except OSError as exception: if exception.errno == EEXIST: # expected if cannot lock pass elif exception.errno == ENOENT: # No such file or directory - parent directory is missing raise elif exception.errno == EACCES and sys.platform != "win32": # pragma: win32 no cover # Permission denied - parent dir is R/O raise # note windows does not allow you to make a folder r/o only files else: self._lock_file_fd = fd def _release(self) -> None: os.close(self._lock_file_fd) # type: ignore # the lock file is definitely not None self._lock_file_fd = None try: os.remove(self._lock_file) except OSError: # the file is already deleted and that's what we want pass __all__ = [ "SoftFileLock", ]