mirror of
https://github.com/morpheus65535/bazarr
synced 2024-12-27 01:57:33 +00:00
132 lines
4.4 KiB
Python
132 lines
4.4 KiB
Python
from .compat import threading
|
|
|
|
import logging
|
|
log = logging.getLogger(__name__)
|
|
|
|
|
|
class LockError(Exception):
|
|
pass
|
|
|
|
|
|
class ReadWriteMutex(object):
|
|
"""A mutex which allows multiple readers, single writer.
|
|
|
|
:class:`.ReadWriteMutex` uses a Python ``threading.Condition``
|
|
to provide this functionality across threads within a process.
|
|
|
|
The Beaker package also contained a file-lock based version
|
|
of this concept, so that readers/writers could be synchronized
|
|
across processes with a common filesystem. A future Dogpile
|
|
release may include this additional class at some point.
|
|
|
|
"""
|
|
|
|
def __init__(self):
|
|
# counts how many asynchronous methods are executing
|
|
self.async_ = 0
|
|
|
|
# pointer to thread that is the current sync operation
|
|
self.current_sync_operation = None
|
|
|
|
# condition object to lock on
|
|
self.condition = threading.Condition(threading.Lock())
|
|
|
|
def acquire_read_lock(self, wait=True):
|
|
"""Acquire the 'read' lock."""
|
|
self.condition.acquire()
|
|
try:
|
|
# see if a synchronous operation is waiting to start
|
|
# or is already running, in which case we wait (or just
|
|
# give up and return)
|
|
if wait:
|
|
while self.current_sync_operation is not None:
|
|
self.condition.wait()
|
|
else:
|
|
if self.current_sync_operation is not None:
|
|
return False
|
|
|
|
self.async_ += 1
|
|
log.debug("%s acquired read lock", self)
|
|
finally:
|
|
self.condition.release()
|
|
|
|
if not wait:
|
|
return True
|
|
|
|
def release_read_lock(self):
|
|
"""Release the 'read' lock."""
|
|
self.condition.acquire()
|
|
try:
|
|
self.async_ -= 1
|
|
|
|
# check if we are the last asynchronous reader thread
|
|
# out the door.
|
|
if self.async_ == 0:
|
|
# yes. so if a sync operation is waiting, notifyAll to wake
|
|
# it up
|
|
if self.current_sync_operation is not None:
|
|
self.condition.notifyAll()
|
|
elif self.async_ < 0:
|
|
raise LockError("Synchronizer error - too many "
|
|
"release_read_locks called")
|
|
log.debug("%s released read lock", self)
|
|
finally:
|
|
self.condition.release()
|
|
|
|
def acquire_write_lock(self, wait=True):
|
|
"""Acquire the 'write' lock."""
|
|
self.condition.acquire()
|
|
try:
|
|
# here, we are not a synchronous reader, and after returning,
|
|
# assuming waiting or immediate availability, we will be.
|
|
|
|
if wait:
|
|
# if another sync is working, wait
|
|
while self.current_sync_operation is not None:
|
|
self.condition.wait()
|
|
else:
|
|
# if another sync is working,
|
|
# we dont want to wait, so forget it
|
|
if self.current_sync_operation is not None:
|
|
return False
|
|
|
|
# establish ourselves as the current sync
|
|
# this indicates to other read/write operations
|
|
# that they should wait until this is None again
|
|
self.current_sync_operation = threading.currentThread()
|
|
|
|
# now wait again for asyncs to finish
|
|
if self.async_ > 0:
|
|
if wait:
|
|
# wait
|
|
self.condition.wait()
|
|
else:
|
|
# we dont want to wait, so forget it
|
|
self.current_sync_operation = None
|
|
return False
|
|
log.debug("%s acquired write lock", self)
|
|
finally:
|
|
self.condition.release()
|
|
|
|
if not wait:
|
|
return True
|
|
|
|
def release_write_lock(self):
|
|
"""Release the 'write' lock."""
|
|
self.condition.acquire()
|
|
try:
|
|
if self.current_sync_operation is not threading.currentThread():
|
|
raise LockError("Synchronizer error - current thread doesn't "
|
|
"have the write lock")
|
|
|
|
# reset the current sync operation so
|
|
# another can get it
|
|
self.current_sync_operation = None
|
|
|
|
# tell everyone to get ready
|
|
self.condition.notifyAll()
|
|
|
|
log.debug("%s released write lock", self)
|
|
finally:
|
|
# everyone go !!
|
|
self.condition.release()
|