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authorFlorent Le Coz <louiz@louiz.org>2014-07-17 14:19:04 +0200
committerFlorent Le Coz <louiz@louiz.org>2014-07-17 14:19:04 +0200
commit5ab77c745270d7d5c016c1dc7ef2a82533a4b16e (patch)
tree259377cc666f8b9c7954fc4e7b8f7a912bcfe101 /sleekxmpp/thirdparty/statemachine.py
parente5582694c07236e6830c20361840360a1dde37f3 (diff)
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Rename to slixmpp
Diffstat (limited to 'sleekxmpp/thirdparty/statemachine.py')
-rw-r--r--sleekxmpp/thirdparty/statemachine.py286
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diff --git a/sleekxmpp/thirdparty/statemachine.py b/sleekxmpp/thirdparty/statemachine.py
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-"""
- SleekXMPP: The Sleek XMPP Library
- Copyright (C) 2010 Nathanael C. Fritz
- This file is part of SleekXMPP.
-
- See the file LICENSE for copying permission.
-"""
-
-import threading
-import time
-import logging
-
-log = logging.getLogger(__name__)
-
-
-class StateMachine(object):
-
- def __init__(self, states=None):
- if not states: states = []
- self.lock = threading.Condition()
- self.__states = []
- self.addStates(states)
- self.__default_state = self.__states[0]
- self.__current_state = self.__default_state
-
- def addStates(self, states):
- self.lock.acquire()
- try:
- for state in states:
- if state in self.__states:
- raise IndexError("The state '%s' is already in the StateMachine." % state)
- self.__states.append(state)
- finally:
- self.lock.release()
-
-
- def transition(self, from_state, to_state, wait=0.0, func=None, args=[], kwargs={}):
- '''
- Transition from the given `from_state` to the given `to_state`.
- This method will return `True` if the state machine is now in `to_state`. It
- will return `False` if a timeout occurred the transition did not occur.
- If `wait` is 0 (the default,) this method returns immediately if the state machine
- is not in `from_state`.
-
- If you want the thread to block and transition once the state machine to enters
- `from_state`, set `wait` to a non-negative value. Note there is no 'block
- indefinitely' flag since this leads to deadlock. If you want to wait indefinitely,
- choose a reasonable value for `wait` (e.g. 20 seconds) and do so in a while loop like so:
-
- ::
-
- while not thread_should_exit and not state_machine.transition('disconnected', 'connecting', wait=20 ):
- pass # timeout will occur every 20s unless transition occurs
- if thread_should_exit: return
- # perform actions here after successful transition
-
- This allows the thread to be responsive by setting `thread_should_exit=True`.
-
- The optional `func` argument allows the user to pass a callable operation which occurs
- within the context of the state transition (e.g. while the state machine is locked.)
- If `func` returns a True value, the transition will occur. If `func` returns a non-
- True value or if an exception is thrown, the transition will not occur. Any thrown
- exception is not caught by the state machine and is the caller's responsibility to handle.
- If `func` completes normally, this method will return the value returned by `func.` If
- values for `args` and `kwargs` are provided, they are expanded and passed like so:
- `func( *args, **kwargs )`.
- '''
-
- return self.transition_any((from_state,), to_state, wait=wait,
- func=func, args=args, kwargs=kwargs)
-
-
- def transition_any(self, from_states, to_state, wait=0.0, func=None, args=[], kwargs={}):
- '''
- Transition from any of the given `from_states` to the given `to_state`.
- '''
-
- if not isinstance(from_states, (tuple, list, set)):
- raise ValueError("from_states should be a list, tuple, or set")
-
- for state in from_states:
- if not state in self.__states:
- raise ValueError("StateMachine does not contain from_state %s." % state)
- if not to_state in self.__states:
- raise ValueError("StateMachine does not contain to_state %s." % to_state)
-
- if self.__current_state == to_state:
- return True
-
- start = time.time()
- while not self.lock.acquire(False):
- time.sleep(.001)
- if (start + wait - time.time()) <= 0.0:
- log.debug("==== Could not acquire lock in %s sec: %s -> %s ", wait, self.__current_state, to_state)
- return False
-
- while not self.__current_state in from_states:
- # detect timeout:
- remainder = start + wait - time.time()
- if remainder > 0:
- self.lock.wait(remainder)
- else:
- log.debug("State was not ready")
- self.lock.release()
- return False
-
- try: # lock is acquired; all other threads will return false or wait until notify/timeout
- if self.__current_state in from_states: # should always be True due to lock
-
- # Note that func might throw an exception, but that's OK, it aborts the transition
- return_val = func(*args,**kwargs) if func is not None else True
-
- # some 'false' value returned from func,
- # indicating that transition should not occur:
- if not return_val:
- return return_val
-
- log.debug(' ==== TRANSITION %s -> %s', self.__current_state, to_state)
- self._set_state(to_state)
- return return_val # some 'true' value returned by func or True if func was None
- else:
- log.error("StateMachine bug!! The lock should ensure this doesn't happen!")
- return False
- finally:
- self.lock.notify_all()
- self.lock.release()
-
-
- def transition_ctx(self, from_state, to_state, wait=0.0):
- '''
- Use the state machine as a context manager. The transition occurs on /exit/ from
- the `with` context, so long as no exception is thrown. For example:
-
- ::
-
- with state_machine.transition_ctx('one','two', wait=5) as locked:
- if locked:
- # the state machine is currently locked in state 'one', and will
- # transition to 'two' when the 'with' statement ends, so long as
- # no exception is thrown.
- print 'Currently locked in state one: %s' % state_machine['one']
-
- else:
- # The 'wait' timed out, and no lock has been acquired
- print 'Timed out before entering state "one"'
-
- print 'Since no exception was thrown, we are now in state "two": %s' % state_machine['two']
-
-
- The other main difference between this method and `transition()` is that the
- state machine is locked for the duration of the `with` statement. Normally,
- after a `transition()` occurs, the state machine is immediately unlocked and
- available to another thread to call `transition()` again.
- '''
-
- if not from_state in self.__states:
- raise ValueError("StateMachine does not contain from_state %s." % from_state)
- if not to_state in self.__states:
- raise ValueError("StateMachine does not contain to_state %s." % to_state)
-
- return _StateCtx(self, from_state, to_state, wait)
-
-
- def ensure(self, state, wait=0.0, block_on_transition=False):
- '''
- Ensure the state machine is currently in `state`, or wait until it enters `state`.
- '''
- return self.ensure_any((state,), wait=wait, block_on_transition=block_on_transition)
-
-
- def ensure_any(self, states, wait=0.0, block_on_transition=False):
- '''
- Ensure we are currently in one of the given `states` or wait until
- we enter one of those states.
-
- Note that due to the nature of the function, you cannot guarantee that
- the entirety of some operation completes while you remain in a given
- state. That would require acquiring and holding a lock, which
- would mean no other threads could do the same. (You'd essentially
- be serializing all of the threads that are 'ensuring' their tasks
- occurred in some state.
- '''
- if not (isinstance(states,tuple) or isinstance(states,list)):
- raise ValueError('states arg should be a tuple or list')
-
- for state in states:
- if not state in self.__states:
- raise ValueError("StateMachine does not contain state '%s'" % state)
-
- # if we're in the middle of a transition, determine whether we should
- # 'fall back' to the 'current' state, or wait for the new state, in order to
- # avoid an operation occurring in the wrong state.
- # TODO another option would be an ensure_ctx that uses a semaphore to allow
- # threads to indicate they want to remain in a particular state.
- self.lock.acquire()
- start = time.time()
- while not self.__current_state in states:
- # detect timeout:
- remainder = start + wait - time.time()
- if remainder > 0:
- self.lock.wait(remainder)
- else:
- self.lock.release()
- return False
- self.lock.release()
- return True
-
- def reset(self):
- # TODO need to lock before calling this?
- self.transition(self.__current_state, self.__default_state)
-
- def _set_state(self, state): #unsynchronized, only call internally after lock is acquired
- self.__current_state = state
- return state
-
- def current_state(self):
- '''
- Return the current state name.
- '''
- return self.__current_state
-
- def __getitem__(self, state):
- '''
- Non-blocking, non-synchronized test to determine if we are in the given state.
- Use `StateMachine.ensure(state)` to wait until the machine enters a certain state.
- '''
- return self.__current_state == state
-
- def __str__(self):
- return "".join(("StateMachine(", ','.join(self.__states), "): ", self.__current_state))
-
-
-
-class _StateCtx:
-
- def __init__(self, state_machine, from_state, to_state, wait):
- self.state_machine = state_machine
- self.from_state = from_state
- self.to_state = to_state
- self.wait = wait
- self._locked = False
-
- def __enter__(self):
- start = time.time()
- while not self.state_machine[self.from_state] or not self.state_machine.lock.acquire(False):
- # detect timeout:
- remainder = start + self.wait - time.time()
- if remainder > 0:
- self.state_machine.lock.wait(remainder)
- else:
- log.debug('StateMachine timeout while waiting for state: %s', self.from_state)
- return False
-
- self._locked = True # lock has been acquired at this point
- self.state_machine.lock.clear()
- log.debug('StateMachine entered context in state: %s',
- self.state_machine.current_state())
- return True
-
- def __exit__(self, exc_type, exc_val, exc_tb):
- if exc_val is not None:
- log.exception("StateMachine exception in context, remaining in state: %s\n%s:%s",
- self.state_machine.current_state(), exc_type.__name__, exc_val)
-
- if self._locked:
- if exc_val is None:
- log.debug(' ==== TRANSITION %s -> %s',
- self.state_machine.current_state(), self.to_state)
- self.state_machine._set_state(self.to_state)
-
- self.state_machine.lock.notify_all()
- self.state_machine.lock.release()
-
- return False # re-raise any exception
-
-if __name__ == '__main__':
-
- def callback(s, s2):
- print((1, s.transition('on', 'off', wait=0.0, func=callback, args=[s,s2])))
- print((2, s2.transition('off', 'on', func=callback, args=[s,s2])))
- return True
-
- s = StateMachine(('off', 'on'))
- s2 = StateMachine(('off', 'on'))
- print((3, s.transition('off', 'on', wait=0.0, func=callback, args=[s,s2]),))
- print((s.current_state(), s2.current_state()))