66 lines
2.1 KiB
Python
66 lines
2.1 KiB
Python
from __future__ import annotations
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import os
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import sys
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from contextlib import suppress
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from errno import EACCES
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from pathlib import Path
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from typing import cast
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from ._api import BaseFileLock
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from ._util import ensure_directory_exists, raise_on_not_writable_file
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if sys.platform == "win32": # pragma: win32 cover
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import msvcrt
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class WindowsFileLock(BaseFileLock):
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"""Uses the :func:`msvcrt.locking` function to hard lock the lock file on Windows systems."""
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def _acquire(self) -> None:
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raise_on_not_writable_file(self.lock_file)
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ensure_directory_exists(self.lock_file)
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flags = (
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os.O_RDWR # open for read and write
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| os.O_CREAT # create file if not exists
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| os.O_TRUNC # truncate file if not empty
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)
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try:
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fd = os.open(self.lock_file, flags, self._context.mode)
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except OSError as exception:
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if exception.errno != EACCES: # has no access to this lock
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raise
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else:
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try:
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msvcrt.locking(fd, msvcrt.LK_NBLCK, 1)
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except OSError as exception:
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os.close(fd) # close file first
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if exception.errno != EACCES: # file is already locked
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raise
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else:
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self._context.lock_file_fd = fd
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def _release(self) -> None:
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fd = cast(int, self._context.lock_file_fd)
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self._context.lock_file_fd = None
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msvcrt.locking(fd, msvcrt.LK_UNLCK, 1)
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os.close(fd)
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with suppress(OSError): # Probably another instance of the application hat acquired the file lock.
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Path(self.lock_file).unlink()
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else: # pragma: win32 no cover
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class WindowsFileLock(BaseFileLock):
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"""Uses the :func:`msvcrt.locking` function to hard lock the lock file on Windows systems."""
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def _acquire(self) -> None:
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raise NotImplementedError
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def _release(self) -> None:
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raise NotImplementedError
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__all__ = [
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"WindowsFileLock",
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]
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