apache-ignite

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# Licensed to the Apache Software Foundation (ASF) under one or more
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# contributor license agreements.  See the NOTICE file distributed with
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# this work for additional information regarding copyright ownership.
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# The ASF licenses this file to You under the Apache License, Version 2.0
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# (the "License"); you may not use this file except in compliance with
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# the License.  You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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This module contains concurrent utils.
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"""
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import threading
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class CountDownLatch:
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    """
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    A count-down latch.
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    """
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    def __init__(self, count=1):
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        self.count = count
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        self.cond_var = threading.Condition()
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    def count_down(self):
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        """
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        Decreases the latch counter.
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        """
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        with self.cond_var:
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            if self.count > 0:
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                self.count -= 1
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            if self.count == 0:
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                self.cond_var.notifyAll()
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    def wait(self):
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        """
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        Blocks current thread if the latch is not free.
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        """
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        with self.cond_var:
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            while self.count > 0:
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                self.cond_var.wait()
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class AtomicValue:
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    """
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    An atomic reference holder.
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    """
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    def __init__(self, value=None):
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        self.value = value
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        self.lock = threading.Lock()
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    def set(self, value):
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        """
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        Sets new value to hold.
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        :param value: New value to hold.
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        """
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        with self.lock:
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            self.value = value
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    def get(self):
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        """
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        Gives current value.
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        """
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        with self.lock:
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            return self.value
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    def compare_and_set(self, expected, value):
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        """
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        Sets new value to hold if current one equals expected.
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        :param expected: The value to compare with.
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        :param value: New value to hold.
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        """
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        return self.check_and_set(lambda: self.value == expected, value)
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    def check_and_set(self, condition, value):
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        """
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        Sets new value to hold by condition.
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        :param condition: The condition to check.
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        :param value: New value to hold.
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        """
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        with self.lock:
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            if condition():
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                self.value = value
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            return self.value
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