115 lines
3.4 KiB
Python
115 lines
3.4 KiB
Python
# This file is part of Radicale - CalDAV and CardDAV server
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# Copyright © 2021 Unrud <unrud@outlook.com>
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#
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# This library is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with Radicale. If not, see <http://www.gnu.org/licenses/>.
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"""
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The multifilesystem backend without file-based locking.
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"""
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import threading
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from collections import deque
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from typing import ClassVar, Deque, Dict, Hashable, Iterator, Type
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from radicale import config, pathutils, types
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from radicale.storage import multifilesystem
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class RwLock(pathutils.RwLock):
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_cond: threading.Condition
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def __init__(self) -> None:
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super().__init__("")
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self._cond = threading.Condition(self._lock)
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@types.contextmanager
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def acquire(self, mode: str, user: str = "") -> Iterator[None]:
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if mode not in "rw":
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raise ValueError("Invalid mode: %r" % mode)
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with self._cond:
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self._cond.wait_for(lambda: not self._writer and (
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mode == "r" or self._readers == 0))
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if mode == "r":
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self._readers += 1
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else:
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self._writer = True
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try:
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yield
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finally:
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with self._cond:
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if mode == "r":
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self._readers -= 1
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self._writer = False
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if self._readers == 0:
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self._cond.notify_all()
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class LockDict:
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_lock: threading.Lock
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_dict: Dict[Hashable, Deque[threading.Lock]]
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def __init__(self) -> None:
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self._lock = threading.Lock()
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self._dict = {}
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@types.contextmanager
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def acquire(self, key: Hashable) -> Iterator[None]:
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with self._lock:
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waiters = self._dict.get(key)
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if waiters is None:
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self._dict[key] = waiters = deque()
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wait = bool(waiters)
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waiter = threading.Lock()
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waiter.acquire()
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waiters.append(waiter)
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if wait:
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waiter.acquire()
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try:
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yield
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finally:
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with self._lock:
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assert waiters[0] is waiter and self._dict[key] is waiters
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del waiters[0]
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if waiters:
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waiters[0].release()
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else:
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del self._dict[key]
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class Collection(multifilesystem.Collection):
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_storage: "Storage"
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@types.contextmanager
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def _acquire_cache_lock(self, ns: str = "") -> Iterator[None]:
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if self._storage._lock.locked == "w":
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yield
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return
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with self._storage._cache_lock.acquire((self.path, ns)):
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yield
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class Storage(multifilesystem.Storage):
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_collection_class: ClassVar[Type[Collection]] = Collection
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_cache_lock: LockDict
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def __init__(self, configuration: config.Configuration) -> None:
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super().__init__(configuration)
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self._lock = RwLock()
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self._cache_lock = LockDict()
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