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",
]
