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filelock.py
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136 lines (106 loc) · 3.75 KB
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# The MIT License
#
# Copyright (c) 2015-2021 Sebastian Ramacher
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
from typing import IO, Literal
from types import TracebackType
class BaseLock:
"""Base class for file locking"""
def __init__(self) -> None:
self.locked = False
def acquire(self) -> None:
pass
def release(self) -> None:
pass
def __enter__(self) -> "BaseLock":
self.acquire()
return self
def __exit__(
self,
exc_type: type[BaseException] | None,
exc: BaseException | None,
exc_tb: TracebackType | None,
) -> Literal[False]:
if self.locked:
self.release()
return False
def __del__(self) -> None:
if self.locked:
self.release()
try:
import fcntl
import errno
class UnixFileLock(BaseLock):
"""Simple file locking for Unix using fcntl"""
def __init__(self, fileobj, mode: int = 0) -> None:
super().__init__()
self.fileobj = fileobj
self.mode = mode | fcntl.LOCK_EX
def acquire(self) -> None:
try:
fcntl.flock(self.fileobj, self.mode)
self.locked = True
except OSError as e:
if e.errno != errno.ENOLCK:
raise e
def release(self) -> None:
self.locked = False
fcntl.flock(self.fileobj, fcntl.LOCK_UN)
has_fcntl = True
except ImportError:
has_fcntl = False
try:
import msvcrt
import os
class WindowsFileLock(BaseLock):
"""Simple file locking for Windows using msvcrt"""
def __init__(self, filename: str) -> None:
super().__init__()
self.filename = f"{filename}.lock"
self.fileobj = -1
def acquire(self) -> None:
# create a lock file and lock it
self.fileobj = os.open(
self.filename, os.O_RDWR | os.O_CREAT | os.O_TRUNC
)
msvcrt.locking(self.fileobj, msvcrt.LK_NBLCK, 1)
self.locked = True
def release(self) -> None:
self.locked = False
# unlock lock file and remove it
msvcrt.locking(self.fileobj, msvcrt.LK_UNLCK, 1)
os.close(self.fileobj)
self.fileobj = -1
try:
os.remove(self.filename)
except OSError:
pass
has_msvcrt = True
except ImportError:
has_msvcrt = False
def FileLock(
fileobj: IO, mode: int = 0, filename: str | None = None
) -> BaseLock:
if has_fcntl:
return UnixFileLock(fileobj, mode)
elif has_msvcrt and filename is not None:
return WindowsFileLock(filename)
return BaseLock()
# vim: sw=4 ts=4 sts=4 ai et