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-rw-r--r--sleekxmpp/xmlstream/statemachine.py30
1 files changed, 25 insertions, 5 deletions
diff --git a/sleekxmpp/xmlstream/statemachine.py b/sleekxmpp/xmlstream/statemachine.py
index 065d5794..0c841a9f 100644
--- a/sleekxmpp/xmlstream/statemachine.py
+++ b/sleekxmpp/xmlstream/statemachine.py
@@ -10,6 +10,7 @@ import threading
import time
import logging
+
class StateMachine(object):
def __init__(self, states=[]):
@@ -27,7 +28,7 @@ class StateMachine(object):
self.__states.append( state )
- def transition(self, from_state, to_state, wait=0.0):
+ 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
@@ -47,12 +48,22 @@ class StateMachine(object):
if thread_should_exit: return
# perform actions here after successful transition
- This allows the thread to be interrupted by setting `thread_should_exit=True`
+ 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 )
+ 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):
+ 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`.
'''
@@ -73,10 +84,19 @@ class StateMachine(object):
self.lock.wait(wait)
if self.__current_state in from_states: # should always be True due to lock
+
+ return_val = True
+ # Note that func might throw an exception, but that's OK, it aborts the transition
+ if func is not None: return_val = func(*args,**kwargs)
+
+ # some 'false' value returned from func,
+ # indicating that transition should not occur:
+ if not return_val: return return_val
+
logging.debug(' ==== TRANSITION %s -> %s', self.__current_state, to_state)
self.__current_state = to_state
self.lock.notifyAll()
- return True
+ return return_val # some 'true' value returned by func or True if func was None
else:
logging.error( "StateMachine bug!! The lock should ensure this doesn't happen!" )
return False