48 lines
1.7 KiB
Python
48 lines
1.7 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, EEXIST
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from pathlib import Path
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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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class SoftFileLock(BaseFileLock):
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"""Simply watches the existence of the lock file."""
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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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# first check for exists and read-only mode as the open will mask this case as EEXIST
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flags = (
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os.O_WRONLY # open for writing only
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| os.O_CREAT
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| os.O_EXCL # together with above raise EEXIST if the file specified by filename exists
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| os.O_TRUNC # truncate the file to zero byte
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)
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try:
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file_handler = os.open(self.lock_file, flags, self._context.mode)
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except OSError as exception: # re-raise unless expected exception
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if not (
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exception.errno == EEXIST # lock already exist
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or (exception.errno == EACCES and sys.platform == "win32") # has no access to this lock
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): # pragma: win32 no cover
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raise
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else:
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self._context.lock_file_fd = file_handler
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def _release(self) -> None:
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assert self._context.lock_file_fd is not None # noqa: S101
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os.close(self._context.lock_file_fd) # the lock file is definitely not None
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self._context.lock_file_fd = None
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with suppress(OSError): # the file is already deleted and that's what we want
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Path(self.lock_file).unlink()
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__all__ = [
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"SoftFileLock",
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]
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