b7d59ec748
Partial-Bug: #1374202 Documents what the function parameters are, what is the type of the parameters passed what return values are, how it is used and what they should provide for it when using a method/class or deriving from an existing class. Change-Id: Ie81b3a446c9fee2dad9411efa28dad8d455b06ba
67 lines
2.1 KiB
Python
67 lines
2.1 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2014 Yahoo! Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import threading
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from taskflow.types import timing as tt
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class Latch(object):
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"""A class that ensures N-arrivals occur before unblocking.
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TODO(harlowja): replace with http://bugs.python.org/issue8777 when we no
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longer have to support python 2.6 or 2.7 and we can only support 3.2 or
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later.
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"""
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def __init__(self, count):
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count = int(count)
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if count <= 0:
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raise ValueError("Count must be greater than zero")
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self._count = count
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self._cond = threading.Condition()
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@property
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def needed(self):
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"""Returns how many decrements are needed before latch is released."""
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return max(0, self._count)
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def countdown(self):
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"""Decrements the internal counter due to an arrival."""
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with self._cond:
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self._count -= 1
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if self._count <= 0:
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self._cond.notify_all()
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def wait(self, timeout=None):
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"""Waits until the latch is released.
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:param timeout: wait until the timeout expires
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:type timeout: number
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:returns: true if the latch has been released before the
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timeout expires otherwise false
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:rtype: boolean
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"""
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watch = tt.StopWatch(duration=timeout)
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watch.start()
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with self._cond:
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while self._count > 0:
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if watch.expired():
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return False
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else:
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self._cond.wait(watch.leftover(return_none=True))
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return True
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