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",
]
