64 lines
2.1 KiB
Python
64 lines
2.1 KiB
Python
# Copyright 2017 Mycroft AI Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# 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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"""Events with respect for montonic time.
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The MontonicEvent class defined here wraps the normal class ensuring that
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changes in system time are handled.
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"""
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from threading import Event
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from time import sleep, monotonic
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from mycroft.util.log import LOG
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class MonotonicEvent(Event):
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"""Event class with monotonic timeout.
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Normal Event doesn't do wait timeout in a monotonic manner and may be
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affected by changes in system time. This class wraps the Event class
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wait() method with logic guards ensuring monotonic operation.
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"""
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def wait_timeout(self, timeout):
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"""Handle timeouts in a monotonic way.
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Repeatingly wait as long the event hasn't been set and the
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monotonic time doesn't indicate a timeout.
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Args:
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timeout: timeout of wait in seconds
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Returns:
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True if Event has been set, False if timeout expired
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"""
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result = False
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end_time = monotonic() + timeout
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while not result and (monotonic() < end_time):
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# Wait however many seconds are left until the timeout has passed
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sleep(0.1) # Mainly a precaution to not busy wait
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remaining_time = end_time - monotonic()
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LOG.debug('Will wait for {} sec for Event'.format(remaining_time))
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result = super().wait(remaining_time)
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return result
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def wait(self, timeout=None):
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if timeout is None:
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ret = super().wait()
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else:
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ret = self.wait_timeout(timeout)
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return ret
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