Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/filelock/_unix.py: 67%

1from __future__ import annotations 

2 

3import os 

4import sys 

5from errno import ENOSYS 

6from typing import cast 

7 

8from ._api import BaseFileLock 

9 

10#: a flag to indicate if the fcntl API is available 

11has_fcntl = False 

12if sys.platform == "win32": # pragma: win32 cover 

13 

14 class UnixFileLock(BaseFileLock): 

15 """Uses the :func:`fcntl.flock` to hard lock the lock file on unix systems.""" 

16 

17 def _acquire(self) -> None: 

18 raise NotImplementedError 

19 

20 def _release(self) -> None: 

21 raise NotImplementedError 

22 

23else: # pragma: win32 no cover 

24 try: 

25 import fcntl 

26 except ImportError: 

27 pass 

28 else: 

29 has_fcntl = True 

30 

31 class UnixFileLock(BaseFileLock): 

32 """Uses the :func:`fcntl.flock` to hard lock the lock file on unix systems.""" 

33 

34 def _acquire(self) -> None: 

35 open_flags = os.O_RDWR | os.O_CREAT | os.O_TRUNC 

36 fd = os.open(self.lock_file, open_flags, self._context.mode) 

37 try: 

38 os.fchmod(fd, self._context.mode) 

39 except PermissionError: 

40 pass # This locked is not owned by this UID 

41 try: 

42 fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB) 

43 except OSError as exception: 

44 os.close(fd) 

45 if exception.errno == ENOSYS: # NotImplemented error 

46 raise NotImplementedError("FileSystem does not appear to support flock; user SoftFileLock instead") 

47 else: 

48 self._context.lock_file_fd = fd 

49 

50 def _release(self) -> None: 

51 # Do not remove the lockfile: 

52 # https://github.com/tox-dev/py-filelock/issues/31 

53 # https://stackoverflow.com/questions/17708885/flock-removing-locked-file-without-race-condition 

54 fd = cast(int, self._context.lock_file_fd) 

55 self._context.lock_file_fd = None 

56 fcntl.flock(fd, fcntl.LOCK_UN) 

57 os.close(fd) 

58 

59 

60__all__ = [ 

61 "has_fcntl", 

62 "UnixFileLock", 

63]