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import threading
import collections
# reference: https://gist.github.com/vitaliyp/6d54dd76ca2c3cdfc1149d33007dc34a
class FIFOLock(object):
def __init__(self):
self._lock = threading.Lock()
self._inner_lock = threading.Lock()
self._pending_threads = collections.deque()
def acquire(self, blocking=True):
with self._inner_lock:
lock_acquired = self._lock.acquire(False)
if lock_acquired:
return True
elif not blocking:
return False
release_event = threading.Event()
self._pending_threads.append(release_event)
release_event.wait()
return self._lock.acquire()
def release(self):
with self._inner_lock:
if self._pending_threads:
release_event = self._pending_threads.popleft()
release_event.set()
self._lock.release()
__enter__ = acquire
def __exit__(self, t, v, tb):
self.release()
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