48 lines
1.6 KiB
Python
48 lines
1.6 KiB
Python
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from __future__ import annotations
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import os
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import sys
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from errno import EACCES, EEXIST, ENOENT
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from ._api import BaseFileLock
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from ._util import raise_on_exist_ro_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_exist_ro_file(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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mode = (
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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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fd = os.open(self._lock_file, mode)
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except OSError as exception:
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if exception.errno == EEXIST: # expected if cannot lock
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pass
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elif exception.errno == ENOENT: # No such file or directory - parent directory is missing
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raise
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elif exception.errno == EACCES and sys.platform != "win32": # pragma: win32 no cover
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# Permission denied - parent dir is R/O
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raise # note windows does not allow you to make a folder r/o only files
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else:
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self._lock_file_fd = fd
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def _release(self) -> None:
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os.close(self._lock_file_fd) # type: ignore # the lock file is definitely not None
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self._lock_file_fd = None
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try:
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os.remove(self._lock_file)
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except OSError: # the file is already deleted and that's what we want
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pass
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__all__ = [
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"SoftFileLock",
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]
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