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added optional 'block_on_transition' param for 'ensure' function that's called while a transition is in-process

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This commit is contained in:
Tom Nichols 2010-07-02 14:34:59 -04:00
parent 661cdd2018
commit 7968ca2892
1 changed files with 12 additions and 8 deletions
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20
sleekxmpp/xmlstream/statemachine.py
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@ -91,7 +91,6 @@ class StateMachine(object):
else: return False
try: # lock is acquired; all other threads will return false or wait until notify/timeout
self.notifier.clear()
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
@ -108,7 +107,8 @@ class StateMachine(object):
log.error( "StateMachine bug!! The lock should ensure this doesn't happen!" )
return False
finally:
self.notifier.set()
self.notifier.set() # notify any waiting threads that the state has changed.
self.notifier.clear()
self.lock.release()
@ -154,7 +154,7 @@ class StateMachine(object):
return self.ensure_any( (state,), wait=wait )
def ensure_any(self, states, wait=0.0):
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.
@ -173,11 +173,15 @@ class StateMachine(object):
if not state in self.__states:
raise ValueError( "StateMachine does not contain state '%s'" % state )
# Locking never really gained us anything here, since the lock was released
# before the function returned anyways. The only thing it _did_ do was
# increase the probability that this function would block for longer than
# intended if a `transition` function or context was running while holding
# the lock.
# 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.
# will return immediately if no transition is in process.
if block_on_transition: self.notifier.wait()
start = time.time()
while not self.__current_state in states:
# detect timeout: