142 lines
4.5 KiB
Python
142 lines
4.5 KiB
Python
# -*- coding: utf-8 -*-
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# *****************************************************************************
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#
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# This program is free software; you can redistribute it and/or modify it under
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# the terms of the GNU General Public License as published by the Free Software
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# Foundation; either version 2 of the License, or (at your option) any later
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# version.
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#
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# This program is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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# details.
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#
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# You should have received a copy of the GNU General Public License along with
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# this program; if not, write to the Free Software Foundation, Inc.,
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# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#
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# Module authors:
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# Markus Zolliker <markus.zolliker@psi.ch>
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#
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# *****************************************************************************
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import threading
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import time
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ETERNITY = 1e99
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class _SingleEvent:
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"""Single Event
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remark: :meth:`wait` is not implemented on purpose
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"""
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def __init__(self, multievent, timeout, name=None):
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self.multievent = multievent
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self.multievent.clear_(self)
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self.name = name
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if timeout is None:
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self.deadline = ETERNITY
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else:
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self.deadline = time.monotonic() + timeout
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def clear(self):
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self.multievent.clear_(self)
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def set(self):
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self.multievent.set_(self)
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def is_set(self):
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return self in self.multievent.events
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class MultiEvent(threading.Event):
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"""Class implementing multi event objects."""
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def __init__(self, default_timeout=None):
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self.events = set()
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self._lock = threading.Lock()
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self.default_timeout = default_timeout or None # treat 0 as None
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self.name = None # default event name
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self._actions = [] # actions to be executed on trigger
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super().__init__()
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def new(self, timeout=None, name=None):
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"""create a single event like object"""
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return _SingleEvent(self, timeout or self.default_timeout,
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name or self.name or '<unnamed>')
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def set(self):
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raise ValueError('a multievent must not be set directly')
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def clear(self):
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raise ValueError('a multievent must not be cleared directly')
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def is_set(self):
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return not self.events
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def set_(self, event):
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"""internal: remove event from the event list"""
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with self._lock:
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self.events.discard(event)
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if self.events:
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return
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try:
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for action in self._actions:
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action()
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except Exception:
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pass # we silently ignore errors here
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self._actions = []
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super().set()
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def clear_(self, event):
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"""internal: add event to the event list"""
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with self._lock:
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self.events.add(event)
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super().clear()
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def deadline(self):
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deadline = 0
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for event in self.events:
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deadline = max(event.deadline, deadline)
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return None if deadline == ETERNITY else deadline
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def wait(self, timeout=None):
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"""wait for all events being set or timed out"""
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if not self.events: # do not wait if events are empty
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return True
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deadline = self.deadline()
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if deadline is not None:
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deadline -= time.monotonic()
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timeout = deadline if timeout is None else min(deadline, timeout)
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if timeout <= 0:
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return False
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return super().wait(timeout)
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def waiting_for(self):
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return set(event.name for event in self.events)
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def get_trigger(self, timeout=None, name=None):
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"""create a new single event and return its set method
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as a convenience method
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"""
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return self.new(timeout, name).set
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def queue(self, action):
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"""add an action to the queue of actions to be executed at end
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:param action: a function, to be executed after the last event is triggered,
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and before the multievent is set
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- if no events are waiting, the actions are executed immediately
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- if an action raises an exception, it is silently ignore and further
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actions in the queue are skipped
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- if this is not desired, the action should handle errors by itself
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"""
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with self._lock:
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self._actions.append(action)
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if self.is_set():
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self.set_(None)
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